Countercation Manipulation Enables Selective Electrochemical CO2‐to‐Formate Conversion Over Bi‐Polyoxometalate‐Derived Catalysts

Kimitake Kawakami; Kentaro Yonesato; Shimon Akino; Soichi Kikkawa; Seiji Yamazoe; Takuma Kaneko; Tomoya Uruga; Fumiaki Amano; Yoshiaki Honjo; Takaki Hatsui; Koji Harano; Kazuya Yamaguchi; Kosuke Suzuki

doi:10.1002/chem.71437

. 2026 Jul 22;32(40):e71437. doi: 10.1002/chem.71437

Countercation Manipulation Enables Selective Electrochemical CO₂‐to‐Formate Conversion Over Bi‐Polyoxometalate‐Derived Catalysts

Kimitake Kawakami ¹, Kentaro Yonesato ^1,², Shimon Akino ¹, Soichi Kikkawa ³, Seiji Yamazoe ³, Takuma Kaneko ⁴, Tomoya Uruga ⁴, Fumiaki Amano ⁵, Yoshiaki Honjo ⁶, Takaki Hatsui ⁶, Koji Harano ^7,⁸, Kazuya Yamaguchi ¹, Kosuke Suzuki ^1,^2,^✉

PMCID: PMC13716004 PMID: 42485582

ABSTRACT

Electrochemical conversion of CO₂ into formate (HCOO⁻) represents a promising strategy for mitigating global warming while producing an industrially important chemical. Polyoxometalates (POMs), anionic molecular metal‐oxo clusters, offer unique opportunities as catalysts and catalyst precursors for the electrochemical CO₂ reduction reaction (CO₂RR) owing to their structural diversity, compositional tunability, and flexibility in countercation selection. Despite these advantages, effective strategies for developing POM‐based CO₂RR catalysts with high selectivity toward HCOO⁻ remain limited. In this study, we demonstrate countercation manipulation as a powerful approach to achieving selective HCOO⁻ production using a bismuth (Bi)‐incorporated POM, [Bi₄O(γ‐SiW₁₀O₃₆)₂(OAc)]⁷⁻ (Bi4). Under gas‐diffusion CO₂RR conditions with a 2 M KHCO₃ aqueous electrolyte, the Ba²⁺ salt of Bi4 immobilized on carbon (Ba‐Bi4/C) exhibited high HCOO⁻ selectivity with a Faradaic efficiency of 84.3% at −0.79 V_RHE, whereas the corresponding tetra‐n‐butylammonium (TBA⁺) salt (TBA‐Bi4/C) exhibited substantially lower selectivity (26.6% at −0.79 V_RHE). Post‐reaction analyses revealed that both catalysts transformed into highly dispersed Bi species protected by WO _x nanoaggregates. Control experiments and detailed characterizations indicated that the countercations, in conjunction with the POM‐derived catalyst structure, play a crucial role in governing CO₂RR performance.

Keywords: bismuth, electrochemical CO₂ reduction reaction, electrode catalysts, nanocatalysts, polyoxometalates

Ba²⁺ salt of Bi‐incorporated polyoxometalate (POM), Bi4 ([Bi₄O(γ‐SiW₁₀O₃₆)₂(OAc)]⁷⁻), immobilized on a carbon support (Ba‐Bi4/C) functioned as a formate (HCOO⁻)‐selective catalyst for electrochemical CO₂ reduction reaction (CO₂RR). The incorporation of Ba²⁺ and the formation of highly dispersed Bi species were the key factors for Ba‐Bi4/C to achieve efficient HCOO⁻ production.

graphic file with name CHEM-32-e71437-g004.webp

1. Introduction

Recent global warming, caused primarily by anthropogenic emissions of carbon dioxide (CO₂), poses a serious threat to modern society [1]. To mitigate this climate crisis, considerable efforts have been devoted to developing technologies that utilize CO₂ as a chemical feedstock. Among the various CO₂ utilization strategies, electrochemical CO₂ reduction reaction (CO₂RR) is particularly attractive because it enables the conversion of CO₂ into value‐added chemicals and fuels under mild conditions using renewable electricity [2, 3]. Among the possible CO₂RR products, formic acid (HCOOH) and its conjugate base, formate (HCOO⁻), are especially appealing. HCOOH is an important industrial chemical widely used in agriculture, leather processing, food preservation, and pharmaceutical industries [4], and has recently attracted attention as a promising hydrogen carrier owing to its high stability, low toxicity, low flammability, and moderate volumetric energy density. Notably, the decomposition of HCOOH/HCOO⁻ produces only CO₂ as a by‐product, enabling a closed carbon cycle in which CO₂ can be recycled to regenerate HCOOH—a feature that is often difficult to achieve with other hydrogen carriers [5]. In addition, techno‐economic analyses suggest that CO₂RR‐based production of HCOOH is considered economically viable [6]. Therefore, the development of efficient CO₂RR systems for HCOOH/HCOO⁻ production is highly desirable.

The catalytic performance of CO₂RR is strongly governed by both the catalyst material and the electrolyte composition. Among various metals, bismuth (Bi)‐based catalysts are known to exhibit high selectivity toward HCOO⁻ while effectively suppressing the competing hydrogen (H₂) evolution reaction owing to their high overpotential for H₂ production [7, 8]. In parallel, the identity of electrolyte cations plays a crucial role in determining CO₂RR activity and selectivity. Larger alkali metal cations, such as Cs⁺ and K⁺, have been reported to enhance CO₂RR performance by modulating the interfacial electric field, local pH, and stabilization of key reaction intermediates [9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20]. Although the effects of alkali metal cations have been extensively studied, considerably fewer investigations have focused on multivalent cations, such as alkaline earth metal cations [13, 15, 17, 20, 21], despite both experimental and theoretical indications that Ba²⁺ can outperform smaller divalent cations such as Ca²⁺ [13, 17, 20, 21]. However, the use of alkaline earth metal cations at high concentration in CO₂RR electrolytes—particularly in gas‐diffusion electrode systems—remains challenging, as the formation of insoluble carbonate or hydroxide species can hinder CO₂ transport to the catalyst surface [15]. These insights suggest that combining Bi‐based catalysts with cations possessing large ionic radii represents a promising approach for selective CO₂RR. Recently, Chang and coworkers investigated cation effects using Bi nanosheets and demonstrated that larger cations, such as Cs⁺ and Ba²⁺, enhance HCOOH productivity and selectivity in acidic electrolytes (pH 2) [20]. Nevertheless, a fundamental understanding of cation effects on Bi‐based CO₂RR catalysts remains limited, and strategies to systematically exploit these effects are still at an early stage.

Polyoxometalates (POMs), anionic molecular metal‐oxo clusters composed of multiple {MO _x } units (M = W, Mo, V, etc.), are characterized by their structural diversity, compositional tunability, and flexibility in countercation selection, as well as unique physicochemical properties such as acid‐base property and multielectron redox property [22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35]. In particular, metal‐incorporated POMs enable atomic‐level control over active metal species and have emerged as promising (pre)catalysts for CO₂RR as well as components of CO₂RR catalysts [36, 37, 38, 39]. Our group has recently demonstrated that the catalytic performance of POM‐derived CO₂RR catalysts is highly sensitive to the identity of countercations, with Ba²⁺ significantly enhancing activity and selectivity for carbon monoxide (CO) production [40, 41]. Despite these advances, POM‐based CO₂RR catalysts that efficiently produce HCOOH/HCOO⁻ remain scarcely explored (Tables 1 and S1) [42, 43, 44, 45].

TABLE 1.

Summary of POM‐based CO₂RR catalysts exhibiting large FE_{HCOOH/HCOO−} (> 50%).

Catalyst	Electrolyte	Potential	FE_{HCOOH/HCOO−} (%)	j _{HCOOH/HCOO−} (mA cm⁻²)	Reference
Ba‐Bi4/C	2 M KHCO₃	−0.79 V_RHE	84.3	33.5	This work
Ba‐Bi4/C	2 M KHCO₃	−0.87 V_RHE	68.3	63.9	This work
Bi‐PMo nanosheets	0.5 M NaHCO₃	−0.86 V_RHE	93 ± 2	ca. 31	[42]
Bi‐PMo nanosheets	0.5 M NaHCO₃	−1.16 V_RHE	ca. 67	ca. 39	[42]
Indium sheet	0.1 M Na₂SO₄ containing 2 mM SiW₉V₃	−1.2 V_Ag/AgCl (−0.76 V_RHE)	<5	<0.2	[43]
		−1.6 V_Ag/AgCl	56.82	ca. 1.9
		−1.7 V_Ag/AgCl	ca. 42	ca. 2.6
Cu₉S₅ single‐unit‐cell nanowires ^a	0.1 M KHCO₃	−0.8 V_RHE	82.0	ca. 2.5	[44]
Cu₉S₅ single‐unit‐cell nanowires ^a	0.1 M KHCO₃	−0.9 V_RHE	57.1	3.20	[44]
TBA₃H[(Ru(dmbpy)(ppt)Cl)₂P₂W₁₇O₅₇] ^b	0.1 M TBAPF₆‐acetonitrile containing acetic acid	−1.56 V_NHE	67	—	[45]

Open in a new tab

^{^a}

Nanowires composed of Cu₉S₅ unit cell and PW12.

^{^b}

dmbpy = 4,4'‐dimethyl‐2,2'‐dipyridyl, ppt = 4'‐(4‐phosphonophenyl)‐2,2':6',2''‐terpyridine.

In this work, we demonstrate that the rational combination of a Bi‐incorporated POM and a Ba²⁺ countercation provides an effective strategy for constructing HCOO⁻‐selective CO₂RR catalysts (Figure 1). A Bi‐incorporated POM, Bi4 ([Bi₄O(γ‐SiW₁₀O₃₆)₂(OAc)]⁷⁻, Figure 1a) [46], was synthesized by incorporating Bi³⁺ ions into a divacant lacunary POM, SiW10 ([γ‐SiW₁₀O₃₄(H₂O)₂]⁴⁻) and subsequently immobilized on a carbon support (Figure 1b). The effect of countercation identity was investigated by comparing tetra‐n‐butylammonium (TBA⁺), Cs⁺, Mg²⁺, and Ba²⁺ salts. CO₂RR experiments using a gas‐fed electrolyzer revealed that the Ba²⁺‐containing catalyst exhibited markedly enhanced HCOO⁻ production compared with its TBA⁺ analogue (Figure 1b). Through a combination of electrochemical analyses, x‐ray absorption fine structure analyses, and electron microscopy, we show that the Bi‐incorporated POM serves as a molecular precursor that undergoes in situ transformation under CO₂RR conditions to generate highly dispersed Bi species stabilized by WO _x nanoaggregates, while the Ba²⁺ countercation plays a crucial role in directing the reaction selectivity. This study establishes countercation manipulation as a powerful approach for achieving efficient and selective electrochemical HCOO⁻ production.

Preparation of POM‐derived Bi catalysts and their application in CO₂RR. (a) Synthetic method and the structure of **Bi4** ([Bi₄O(γ‐SiW₁₀O₃₆)₂(OAc)]⁷⁻). (b) Schematic illustration of the catalyst preparation and CO₂RR using TBA‐**Bi4**/C and Ba‐**Bi4**/C.

2. Results and Discussion

2.1. Preparation and Characterization of the Catalysts

Carbon‐supported Bi‐incorporated POM catalysts were prepared by adapting a previously reported impregnation method for POM‐derived electrocatalysts [41]. TBA‐Bi4 (Figure 1a) [46] was first immobilized on a carbon support (Vulcan XC 72R), affording TBA‐Bi4/C (Figure 1b). Subsequently, the countercation of Bi4 was exchanged from TBA⁺ to Ba²⁺, Mg²⁺, or Cs⁺ by vigorously stirring TBA‐Bi4/C in an acetone solution containing trifluoromethanesulfonate salts of Ba²⁺, Mg²⁺, or Cs⁺, yielding Ba‐Bi4/C, Mg‐Bi4/C, or Cs‐Bi4/C, respectively (Figure 1b).

To investigate the structure of Bi4 after immobilization and cation exchange, Bi and W L₃‐edge x‐ray absorption fine structure (XAFS) measurements were performed (Figure 2). At the Bi L₃‐edge, both TBA‐Bi4/C and Ba‐Bi4/C exhibited extended x‐ray absorption fine structure (EXAFS) oscillation patterns similar to that of TBA‐Bi4, indicating preservation of the Bi coordination environment (Figure 2a). Notably, the Fourier‐transformed EXAFS spectrum of TBA‐Bi4/C displayed an increased peak intensity at approximately 1.7 Å (Bi─O bond) relative to that of TBA‐Bi4, whereas Ba‐Bi4/C exhibited a slightly lower peak intensity than TBA‐Bi4/C (Figure 2b). Similarly, at the W L₃‐edge, the EXAFS oscillation patterns of TBA‐Bi4/C and Ba‐Bi4/C closely resembled those of TBA‐Bi4 (Figure 2c). While TBA‐Bi4 and TBA‐Bi4/C showed similar Fourier‐transformed EXAFS spectra, Ba‐Bi4/C showed a higher intensity for the peak at approximately 1.3 Å (terminal W═O bond) [47] and a lower intensity for the peak at approximately 1.7 Å (W─O(─W) bond) [47] compared with those of TBA‐Bi4/C (Figure 2d). These results indicated that immobilization and cation exchange induce only minor perturbations in the local coordination environment of Bi and W, while the overall Bi4 structure remains largely intact in both TBA‐Bi4/C and Ba‐Bi4/C.

XAFS measurements of TBA‐**Bi4**/C and Ba‐**Bi4**/C. (a) k ³‐weighted Bi L₃‐edge EXAFS oscillation. (b) Fourier‐transformed Bi L₃‐edge EXAFS spectra (k = 3–11 Å⁻¹). (c) k ³‐weighted W L₃‐edge EXAFS oscillation. (d) Fourier‐transformed W L₃‐edge EXAFS spectra (k = 3–13 Å⁻¹).

Infrared (IR) spectroscopy was further employed to assess the structural integrity of Bi4 in TBA‐Bi4/C and Ba‐Bi4/C. However, due to strong absorption from the carbon support, the characteristic IR absorption bands of Bi4 could not be observed for TBA‐Bi4/C and Ba‐Bi4/C. Therefore, IR spectra of unsupported TBA‐Bi4 and Ba‐Bi4 were measured. As shown in Figure S1, Ba‐Bi4 exhibited characteristic absorption bands in the range of 300–1000 cm⁻¹ that closely resemble those of TBA‐Bi4. Importantly, no bands attributable to TBA⁺ were observed for Ba‐Bi4 in the range of 1350–1500 cm⁻¹, indicating successful countercation exchange without significant structural change to Bi4. Because Ba‐Bi4 was prepared using the same protocol as Ba‐Bi4/C, these results support effective replacement of TBA⁺ with Ba²⁺ in the supported catalyst.

Elemental analysis further confirmed these findings (Table S2). Both TBA‐Bi4/C and Ba‐Bi4/C exhibited Bi:W ratios close to 4:20, consistent with the molecular composition of Bi4 ([Bi₄O(γ‐SiW₁₀O₃₆)₂(OAc)]⁷⁻). Moreover, Ba‐Bi4/C showed a Ba:W ratio of 3.5:20. Considering the heptaanionic charge of Bi4 and the divalent charge of Ba²⁺, this ratio supports nearly complete exchange of TBA⁺ with Ba²⁺.

2.2. CO₂RR Study

The CO₂RR performance of the catalysts was evaluated using a gas‐fed electrolyzer equipped with a gas‐diffusion electrode (Figure S2). In addition to the Bi4‐derived catalysts, a Ba²⁺ salt of SiW10 ([γ‐SiW₁₀O₃₄(H₂O)₂]⁴⁻, a precursor of Bi4) supported on carbon (Ba‐SiW10/C) was prepared as a control sample (see Figure S3 and Table S2 for characterization). The catalyst‐loaded electrodes were fabricated by drop‐casting catalyst inks onto carbon fiber‐based gas‐diffusion layer (Sigracet 39 BB, see Supporting Information for detailed methods).

CO₂ electrolysis was conducted at approximately −0.8 V_RHE (iR‐corrected) for 1 h under 80 mL min⁻¹ CO₂ flow with 2 M KHCO₃ aqueous solution. Gaseous products (CO and H₂) and the water‐soluble product (HCOO⁻) in the catholyte were quantified by gas chromatography and ¹H NMR, respectively. As summarized in Figures 3a and S4a, and Table S3, Ba‐Bi4/C exhibited the highest partial current density (j _HCOO− = 33.5 mA cm⁻²) and Faradaic efficiency (FE_HCOO− = 84.3%) for HCOO⁻ production among all catalysts tested. No CO or HCOO⁻ was detected when the bare carbon support was used or when electrolysis was performed under an Ar atmosphere using Ba‐Bi4/C (Table S4), confirming that these products originate from CO₂RR. Notably, Ba‐Bi4/C exhibited a j _HCOO−value comparable to or higher than those of previously reported POM‐based CO₂RR catalysts at similar applied potentials (Table 1). In contrast, Mg‐Bi4/C, Cs‐Bi4/C, and TBA‐Bi4/C exhibited lower CO₂RR performance, with TBA‐Bi4/C predominantly producing H₂ and showing significantly lower HCOO⁻ productivity and selectivity (j _HCOO− = 9.6 mA cm⁻², FE_HCOO− = 26.6%), highlighting the importance of selecting appropriate countercations to achieve superior CO₂RR performance. Bismuth(III) acetate (Bi(OAc)₃), a precursor of Bi4, exhibited an even lower j _HCOO− value of 6.1 mA cm⁻², although its FE_HCOO− was moderate (70.4%) (Figures 3b and S4b and Table S3). In addition, a physical mixture of Bi(OAc)₃ and Ba‐SiW10/C (Ba‐SiW10/C+Bi(OAc)₃) showed low CO₂RR performance. We also evaluated the CO₂RR performance of monolayer bismuth tungstate (Bi₂WO₆), known for efficiently producing HCOO⁻ [48], and bulk Bi₂WO₆ [49], but both samples exhibited substantially lower productivity and selectivity for HCOO⁻ production (Figures 3b and S4b and Table S3). These results underscore the critical role of Bi incorporation into the POM framework in achieving high HCOO⁻‐selective CO₂RR performance.

CO₂RR performance of POM‐derived catalyst‐loaded electrodes with 2 M KHCO₃ flow: FE (left axis) and j _HCOO− (right axis). (a) **Bi4**/C possessing various countercations at a constant potential around −0.8 V_RHE for 1 h. (b) Ba‐**Bi4**/C and other benchmark catalysts at a constant potential around −0.8 V_RHE for 1 h. (c) Ba‐**Bi4**/C at different potentials for 1 h. (d) Ba‐**Bi4**/C at −0.82 V_RHE for 9 h. All potentials were iR‐corrected.

Potential‐dependent measurements revealed a volcano‐type relationship between HCOO⁻ selectivity and the applied potential for Ba‐Bi4/C (Figures 3c and S4c and Table S5), with a maximum FE_HCOO− of 84.3% observed at −0.79 V_RHE. At more negative potentials, the j _HCOO− increased further, reaching 63.9 mA cm⁻² at −0.87 V_RHE, representing the highest value reported to date for POM‐based CO₂RR catalysts (Table 1). Tafel analysis revealed that the Tafel slope values in the low overpotential region were 55, 54, 63, and 66 mV dec⁻¹ for Ba‐Bi4/C, TBA‐Bi4/C, Ba‐SiW10/C+Bi(OAc)₃, and Bi(OAc)₃, respectively (Figure S5). Notably, these values are close to the theoretical value of 59 mV dec⁻¹, indicating that the protonation of *CO₂ ⁻ to form *OCHO is the rate‐limiting step across these samples [42, 50, 51, 52]. This kinetic similarity suggested that the enhanced HCOO⁻ productivity of Ba‐Bi4/C cannot be attributed to a change in the rate‐limiting step but to other factors (as discussed in detail in the following sections). Subsequently, long‐term CO₂RR electrolysis was conducted at −0.82 V_RHE for 9 h using Ba‐Bi4/C (Figures 3d and S4d,e and Table S6). Although the selectivity to H₂ gradually increased during the prolonged electrolysis, the FE_HCOO− remained above 70% even after 9 h, and the j _HCOO− remained nearly constant throughout the experiment. In addition, although the slight fluctuations were observed during the initial 4 h, the total current density stabilized at approximately 40 mA cm⁻² thereafter, demonstrating the robust electrochemical stability of the catalyst.

2.3. Characterization of a Ba‐Bi4/C‐Loaded Electrode After CO₂RR

Based on the above results, we next discuss the structural evolution of Ba‐Bi4/C under CO₂RR conditions.

We first performed XAFS measurements on Ba‐Bi4/C electrodes before and after immersion in the catholyte (2 M KHCO₃) for 1 h to examine the effect of catholyte contact on the electronic state and the structure of Bi4. As displayed in Figure 4, both electrodes exhibited x‐ray absorption near edge structure (XANES) spectra (Figure 4a) and EXAFS oscillation patterns that closely resemble those of pristine Ba‐Bi4/C (Figure 4b,d), although slight variations in the peak intensities associated with the Bi─O bond (peak around 1.7 Å, Figure 4c), the terminal W═O bond (peak around 1.3 Å, Figure 4e) [47], and the W─O(─W) bond (peak around 1.7 Å, Figure 4e) [47] were observed. These results suggest that, although minor perturbations occurred during electrode fabrication and catholyte contact, the overall electronic state and the molecular structure of Bi4 were largely retained.

XAFS measurements of Ba‐**Bi4**/C‐loaded electrodes. (a) Bi L₃‐edge XANES spectra. (b) k ³‐weighted Bi L₃‐edge EXAFS oscillation. (c) Fourier‐transformed Bi L₃‐edge EXAFS spectra (k = 3–11 Å⁻¹). (d) k ³‐weighted W L₃‐edge EXAFS oscillation. (e) Fourier‐transformed W L₃‐edge EXAFS spectra (k = 3–13 Å⁻¹).

To identify the catalytically active Bi species generated under CO₂RR conditions, cyclic voltammetry (CV) of the Ba‐Bi4/C electrode after CO₂RR at −0.8 V_RHE for 1 h was conducted (Figure S6). A single cathodic peak appeared in the range of 0.1–0.2 V_RHE, which can be assigned to the reduction of Bi³⁺ to Bi⁰ [53]. Given that CO₂RR was conducted at much more negative potentials (approximately −0.8 V_RHE), Bi⁰ species were likely generated during electrolysis and served as the truly catalytically active sites.

Further insight into the post‐reaction catalyst structure was obtained by XAFS measurements of the Ba‐Bi4/C electrode after CO₂RR (Figure 4). The Bi L₃‐edge XANES spectrum of the post‐reaction electrode closely overlapped with those of pristine Ba‐Bi4/C and the electrode before the reaction, indicating that Bi was predominantly present as Bi³⁺ after the reaction (Figure 4a). This observation does not contradict the CV results, as the ex situ XAFS measurements were performed after exposure of the electrode to air, which can readily oxidize metallic Bi. At the W L₃‐edge, the EXAFS oscillation pattern of the electrode after CO₂RR more closely resembled that of WO₃ than that of the electrode before the reaction; however, clear differences were observed in the k range of 7–9 Å⁻¹ and in the Fourier‐transformed spectra around 3–4 Å (Figure 4d,e). These features suggest the formation of WO _x species distinct from bulk WO₃ during CO₂RR.

To further elucidate the nanoscale structure of the catalyst after CO₂RR, electron microscopy analysis was performed. We initially carried out atomic‐resolution transmission electron microscopy (TEM) observation of the Ba‐Bi4/C electrode after a 1 h CO₂RR (Figure S7). However, the detailed analysis of catalyst morphology was difficult due to the low contrast between the carbon support and the catalyst. High‐angle annular dark‐field scanning transmission electron microscopy (HAADF‐STEM) image (Figure 5a) and the corresponding STEM energy‐dispersive X‐ray spectroscopy (EDS) mappings (Figure 5b–e) suggest the formation of WO _x nanoaggregates within which Bi species are highly dispersed. Although some Bi species formed nanoparticles within WO _x nanoaggregates (Figure S8), low‐magnification STEM images also verified that most of the Bi species were highly dispersed (Figure S9). Liu and coworkers reported that, under CO₂RR conditions, monolayer bismuth tungstate (Bi₂WO₆) reconstructs to form metallic Bi stabilized by tungsten oxide species, as revealed by in situ characterization techniques [48]. In light of this report, it is reasonable to conclude that, in the present system, Bi species are likewise stabilized by WO _x nanoaggregates.

STEM images of Ba‐**Bi4**/C‐loaded electrode after a 1 h CO₂RR. (a) HAADF‐STEM image and (b–e) STEM‐EDS mappings (Bi, magenta; W, cyan; Ba, yellow).

Taken together, the CV, XAFS, and STEM results demonstrate that Ba‐Bi4/C is transformed into highly dispersed Bi species protected by WO _x nanoaggregates under CO₂RR conditions.

2.4. Effect of Countercations on CO₂RR Performance

As shown in the former section, TBA‐Bi4/C exhibited substantially lower CO₂RR performance than Ba‐Bi4/C. In this section, we discuss the role of countercation in determining the CO₂RR performance.

Post‐reaction characterization of the TBA‐Bi4/C electrode after CO₂RR at −0.8 V_RHE was first conducted. CV measurement revealed a cathodic peak in the range of 0.1–0.2 V_RHE corresponding to the reduction of Bi³⁺ to Bi⁰, indicating that Bi⁰ is also generated as the active species under CO₂RR conditions (Figure S6). XAFS analysis further clarified that the Bi L₃‐edge XANES spectra and W L₃‐edge EXAFS oscillation patterns of TBA‐Bi4/C and Ba‐Bi4/C electrodes after the reaction were largely comparable, with only minor differences observed in the Fourier‐transformed W L₃‐edge EXAFS spectra (Figure S10). Consistent with these results, STEM analysis revealed the formation of highly dispersed Bi species protected by WO _x nanoaggregates on the TBA‐Bi4/C electrode after the reaction (Figure S11). These observations suggest that both catalysts underwent similar structural transformations during CO₂RR. Elemental analysis was performed to quantify the Bi content remaining on the electrodes after reaction. As summarized in Table S7, although initial Bi loadings were nearly identical for both samples, the Ba‐Bi4/C electrode after the reaction exhibited a slightly lower Bi loading than the TBA‐Bi4/C electrode after the reaction. This result suggests that differences in Bi loading are unlikely to be the primary origin of the large performance difference.

It has been reported that electron‐rich Bi‐based CO₂RR catalysts tend to exhibit higher CO₂RR performance, as electron‐rich Bi sites facilitate either the reduction of *OCHO intermediates or the formation of *CO₂ ⁻ intermediates [54, 55]. To assess the electronic state of Bi, CV measurements were performed on TBA‐Bi4/C and Ba‐Bi4/C electrodes after the reaction (Figure S6). Notably, the reduction peak of Bi³⁺ for the TBA‐Bi4/C electrode appeared at a potential approximately 10 mV more negative than that for the Ba‐Bi4/C electrode. Chen and coworkers reported a correlation among the reduction potential of Bi³⁺, the electronic state of Bi, and the CO₂RR performance, demonstrating that more electron‐rich Bi species exhibit more negative reduction potentials and higher CO₂RR activity [54]. Accordingly, TBA‐Bi4/C appears to generate slightly more electron‐rich Bi species, consistent with our previous report [40]. This difference may originate from countercation‐dependent electron‐donating properties of the WO _x nanoaggregates.

Importantly, despite possessing slightly more electron‐rich species, TBA‐Bi4/C exhibited inferior CO₂RR performance. This finding indicates that electronic effects cannot account for the enhanced CO₂RR performance of Ba‐Bi4/C. We therefore attribute the superior performance of Ba‐Bi4/C primarily to cation effects. Although the origin of cation effects in CO₂RR remains under debate, three main contributions have been proposed: (a) modulation of the electric field near the electrode surface; (b) buffering of the local pH near the electrode surface; and (c) stabilization of reaction intermediates [56, 57, 58, 59]. While it is difficult to unambiguously identify the dominant factor in the present system, it is reasonable to conclude that Ba²⁺‐induced cation effects play a critical role in enhancing the CO₂RR performance of Ba‐Bi4/C.

2.5. Effect of Catalyst Structure on CO₂RR Performance

As described in the CO₂RR Study Section, Bi(OAc)₃ exhibited significantly lower CO₂RR performance than Ba‐Bi4/C. In this section, we discuss the influence of the catalyst structure on CO₂RR performance.

After CO₂RR at −0.8 V_RHE for 1 h, CV analysis of the Bi(OAc)₃‐derived electrode revealed a reduction peak corresponding to the conversion of Bi³⁺ to Bi⁰ in the range of 0.0–0.3 V_RHE, indicating that Bi⁰ species also serve as the active species in this system (Figure S6). Ex situ XAFS measurement suggested that in situ‐generated Bi⁰ species were fully oxidized to Bi³⁺ after the reaction (Figure S12). TEM analysis further revealed the formation of Bi nanoparticles with an average diameter of 2.9 ± 1.2 nm after the reaction (Figure S13). These outcomes all suggest that Bi(OAc)₃ is transformed into small Bi nanoparticles during the reaction. Elemental analysis (Table S7) showed that the Bi content remaining on the Bi(OAc)₃ electrode after CO₂RR was approximately twice that on the Ba‐Bi4/C electrode after the reaction, suggesting that the inferior CO₂RR performance observed for Bi(OAc)₃ may not stem from lower Bi loading.

CV measurements comparing the electronic states of Bi species formed on Bi(OAc)₃ and Ba‐Bi4/C electrodes after reaction showed that the reduction peak for Ba‐Bi4/C shifted by approximately 10 mV to a more negative potential, suggesting the formation of slightly more electron‐rich Bi species (Figure S6). However, given the small magnitude of this shift, electronic effects are unlikely to be the dominant factor governing the observed performance difference. Instead, we attribute the superior performance of Ba‐Bi4/C primarily to its ability to generate and stabilize highly dispersed Bi species. The electrochemical impedance spectroscopy at −0.8 V_RHE revealed that the catalyst derived from Ba‐Bi4/C exhibited significantly lower charge transfer resistance than that derived from Bi(OAc)₃ (Figure S14). The close proximity between Bi and {WO₆} units in Ba‐Bi4/C facilitates the formation of isolated or highly dispersed Bi species stabilized by WO _x nanoaggregates, whereas Bi(OAc)₃, lacking such protection by WO _x species, readily aggregates into Bi nanoparticles. As a consequence, Ba‐Bi4/C showed faster electron transfer kinetics and higher CO₂RR performance.

3. Conclusion

In this study, we demonstrated that countercation manipulation provides a facile and powerful strategy for tuning the performance of POM‐based electrocatalysts for CO₂RR. A bismuth (Bi)‐incorporated POM, [Bi₄O(γ‐SiW₁₀O₃₆)₂(OAc)]⁷⁻ (Bi4), was immobilized on a carbon support via an impregnation method to afford TBA‐Bi4/C, followed by countercation exchange with Ba²⁺ to yield Ba‐Bi4/C. When evaluated as gas‐diffusion electrodes in a gas‐fed CO₂ electrolyzer using 2 M KHCO₃ aqueous electrolyte, Ba‐Bi4/C exhibited markedly enhanced formate (HCOO⁻) production, achieving a high partial current density (j _HCOO− = 33.5 mA cm⁻²) and Faradaic efficiency (FE_HCOO− = 84.3%) at −0.79 V_RHE. In contrast, TBA‐Bi4/C showed significantly lower HCOO⁻ selectivity (FE_HCOO− = 26.6% at −0.79 V_RHE), while Bi(OAc)₃, a precursor of Bi4, exhibited lower HCOO⁻ productivity (j _HCOO− = 6.1 mA cm⁻²). Post‐reaction analyses revealed that both Ba‐Bi4/C and TBA‐Bi4/C underwent in situ structural reconstruction during CO₂RR to form highly dispersed Bi species stabilized by WO _x nanoaggregates, whereas Bi(OAc)₃ was transformed into aggregated Bi nanoparticles. Systematic control experiments and characterizations highlighted the critical roles of both countercation identity and molecular structure of the precatalyst in achieving high CO₂RR performance, underscoring countercation manipulation as a key design parameter.

Given that HCOO⁻‐selective POM‐based CO₂RR catalysts remain scarce and the role of cations in Bi‐based CO₂RR catalysis is still not fully understood, this work provides new insights into cation effects and establishes a generalizable strategy for designing efficient POM‐based CO₂RR catalysts. We anticipate that the concept of countercation engineering demonstrated here will inspire further development of molecularly defined electrocatalysts for selective and efficient CO₂ conversion.

Funding

Japan Science and Technology Agency. Japan Society for the Promotion of Science

Conflicts of Interest

The authors declare no conflicts of interest.

Supporting information

Supporting File 1: chem71437‐sup‐0001‐SuppMat.pdf The authors have cited additional references within the Supporting Information [60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96]. The Supporting Information includes experimental section and supplementary figures and tables.

CHEM-32-e71437-s001.pdf^{(12.6MB, pdf)}

Acknowledgments

This work was financially supported by the JSPS KAKENHI (Grant JP24K01448, JP24H00463, JP24H02210, JP24H02217, JP22H04971, JP23H04874) and the JST FOREST (JPMJFR213M). A part of this work was supported by Advanced Research Infrastructure for Materials and Nanotechnology in Japan (ARIM) (JPMXP1225NM0211, JPMXP12 25UT0269) of the Ministry of Education, Culture, Sports, Science and Technology (MEXT). A part of this study was supported by Advanced Engineering and Services Division in National Institute for Materials Science (NIMS). The authors thank Dr. Fumihiko Uesugi (NIMS), Mr. Kouichi Okudaira (NIMS), Mr. Hiroyuki Oshikawa (The University of Tokyo), and Ms. Mari Morita (The University of Tokyo) for the assistance with TEM, HAADF‐STEM, and EDS analyses. XAFS measurements using a CITIUS detector were performed at BL36XU in SPring‐8 under an approved SACLA/SPring‐8 Basic Development Program proposal (No. 202407 and No. 202505).

Data Availability Statement

The data that support the findings of this study are available in the Supporting Information of this article.

References

1. Masson‐Delmotte V., Zhai P., Pirani A., et al., IPCC “ Climate Change 2021: The Physical Science Basis ,” Contribution of Working Group I to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change, (Cambridge University Press; ): 2021. [Google Scholar]
2. Sun Z., Ma T., Tao H., Fan Q., and Han B., “Fundamentals and Challenges of Electrochemical CO₂ Reduction Using Two‐Dimensional Materials,” Chem 3 (2017): 560, 10.1016/j.chempr.2017.09.009. [DOI] [Google Scholar]
3. Nitopi S., Bertheussen E., Scott S. B., et al., “Progress and Perspectives of Electrochemical CO₂ Reduction on Copper in Aqueous Electrolyte,” Chemical Reviews 119 (2019): 7610, 10.1021/acs.chemrev.8b00705. [DOI] [PubMed] [Google Scholar]
4. Hietala J., Vuori A., Johnsson P., Pollari I., Reutemann W., and Kieczka H., Formic Acid, Ullmann's Encyclopedia of Industrial Chemistry (Wiley‐VCH Verlag, 2016), 10.1002/14356007.a12_013.pub3. [DOI] [Google Scholar]
5. Zhong H., Iguchi M., Chatterjee M., Himeda Y., Xu Q., and Kawanami H., “Formic Acid‐Based Liquid Organic Hydrogen Carrier System With Heterogeneous Catalysts,” Advanced Sustainable Systems 2 (2018): 1700161, 10.1002/adsu.201700161. [DOI] [Google Scholar]
6. Jouny M., Luc W., and Jiao F., “General Techno‐Economic Analysis of CO₂ Electrolysis Systems,” Industrial & Engineering Chemistry Research 57 (2018): 2165, 10.1021/acs.iecr.7b03514. [DOI] [Google Scholar]
7. Xia D., Yu H., Xie H., et al., “Recent Progress of Bi‐Based Electrocatalysts for Electrocatalytic CO₂ Reduction,” Nanoscale 14 (2022): 7957, 10.1039/D2NR01900K. [DOI] [PubMed] [Google Scholar]
8. Liang X.‐D., Tian N., Hu S.‐N., Zhou Z.‐Y., and Sun S.‐G., “Recent Advances of Bismuth‐Based Electrocatalysts for CO₂ Reduction: Strategies, Mechanism and Applications,” Materials Reports Energy 3 (2023): 100191, 10.1016/j.matre.2023.100191. [DOI] [Google Scholar]
9. Murata A. and Hori Y., “Product Selectivity Affected by Cationic Species in Electrochemical Reduction of CO₂ and CO at a Cu Electrode,” Bulletin of the Chemical Society of Japan 64 (1991): 123, 10.1246/bcsj.64.123. [DOI] [Google Scholar]
10. Thorson M. R., Siil K. I., and Kenis P. J. A., “Effect of Cations on the Electrochemical Conversion of CO₂ to CO,” Journal of the Electrochemical Society 160 (2012): F69, 10.1149/2.052301jes. [DOI] [Google Scholar]
11. Singh M. R., Kwon Y., Lum Y., Ager J. W., and Bell A. T., “Hydrolysis of Electrolyte Cations Enhances the Electrochemical Reduction of CO₂ Over Ag and Cu,” Journal of the American Chemical Society 138 (2016): 13006, 10.1021/jacs.6b07612. [DOI] [PubMed] [Google Scholar]
12. Resasco J., Chen L. D., Clark E., et al., “Promoter Effects of Alkali Metal Cations on the Electrochemical Reduction of Carbon Dioxide,” Journal of the American Chemical Society 139 (2017): 11277, 10.1021/jacs.7b06765. [DOI] [PubMed] [Google Scholar]
13. Ringe S., Clark E. L., Resasco J., et al., “Understanding Cation Effects in Electrochemical CO₂ Reduction,” Energy & Environmental Science 12 (2019): 3001, 10.1039/C9EE01341E. [DOI] [Google Scholar]
14. Malkani A. S., Anibal J., and Xu B., “Cation Effect on Interfacial CO₂ Concentration in the Electrochemical CO₂ Reduction Reaction,” ACS Catalysis 10 (2020): 14871, 10.1021/acscatal.0c03553. [DOI] [Google Scholar]
15. Bhargava S. S., Cofell E. R., Chumble P., Azmoodeh D., Someshwar S., and Kenis P. J. A., “Exploring Multivalent Cations‐Based Electrolytes for CO₂ Electroreduction,” Electrochimica Acta 394 (2021): 139055, 10.1016/j.electacta.2021.139055. [DOI] [Google Scholar]
16. Monteiro M. C. O., Dattila F., Hagedoorn B., García‐Muelas R., López N., and Koper M. T. M., “Absence of CO₂ Electroreduction on Copper, Gold and Silver Electrodes Without Metal Cations in Solution,” Nature Catalysis 4 (2021): 654, 10.1038/s41929-021-00655-5. [DOI] [Google Scholar]
17. Monteiro M. C. O., Dattila F., López N., and Koper M. T. M., “The Role of Cation Acidity on the Competition Between Hydrogen Evolution and CO₂ Reduction on Gold Electrodes,” Journal of the American Chemical Society 144 (2022): 1589, 10.1021/jacs.1c10171. [DOI] [PMC free article] [PubMed] [Google Scholar]
18. Gu J., Liu S., Ni W., Ren W., Haussener S., and Hu X., “Modulating Electric Field Distribution by Alkali Cations for CO₂ Electroreduction in Strongly Acidic Medium,” Nature Catalysis 5 (2022): 268, 10.1038/s41929-022-00761-y. [DOI] [Google Scholar]
19. Jiang T.‐W., Wang S.‐S., Qin X., et al., “Uncovering the Cation Effects on the Electroreduction of CO₂ on Pd/C Catalysts − An SEIRAS Study,” Journal of Catalysis 434 (2024): 115520, 10.1016/j.jcat.2024.115520. [DOI] [Google Scholar]
20. Chang Y., Tan Z., Han J., et al., “Effect of Alkali and Alkaline Earth Metal Cations on the HCOOH Selectivity of the CO₂ Electrochemical Reduction Reaction on Bi Electrodes in Acidic media,” Journal of Alloys and Compounds 1035 (2025): 181524, 10.1016/j.jallcom.2025.181524. [DOI] [Google Scholar]
21. Schizodimou A. and Kyriacou G., “Acceleration of the Reduction of Carbon Dioxide in the Presence of Multivalent Cations,” Electrochimica Acta 78 (2012): 171, 10.1016/j.electacta.2012.05.118. [DOI] [Google Scholar]
22. Pope M. T., Heteropoly and Isopoly Oxometalates (Springer, 1983), https://link.springer.com/book/9783662120064. [Google Scholar]
23. Hill C. L. and Prosser‐McCartha C. M., “Homogeneous Catalysis by Transition Metal Oxygen Anion Clusters,” Coordination Chemistry Reviews 143 (1995): 407, 10.1016/0010-8545(95)01141-B. [DOI] [Google Scholar]
24. Kozhevnikov I. V., “Catalysis by Heteropoly Acids and Multicomponent Polyoxometalates in Liquid‐Phase Reactions,” Chemical Reviews 98 (1998): 171, 10.1021/cr960400y. [DOI] [PubMed] [Google Scholar]
25. Mizuno N. and Misono M., “Heterogeneous Catalysis,” Chemical Reviews 98 (1998): 199, 10.1021/cr960401q. [DOI] [PubMed] [Google Scholar]
26. Dolbecq A., Dumas E., Mayer C. R., and Mialane P., “Hybrid Organic−Inorganic Polyoxometalate Compounds: From Structural Diversity to Applications,” Chemical Reviews 110 (2010): 6009, 10.1021/cr1000578. [DOI] [PubMed] [Google Scholar]
27. Wang S.‐S. and Yang G.‐Y., “Recent Advances in Polyoxometalate‐Catalyzed Reactions,” Chemical Reviews 115 (2015): 4893, 10.1021/cr500390v. [DOI] [PubMed] [Google Scholar]
28. Vilà‐Nadal L. and Cronin L., “Design and Synthesis of Polyoxometalate‐Framework Materials From Cluster Precursors,” Nature Reviews Materials 2 (2017): 17054, 10.1038/natrevmats.2017.54. [DOI] [Google Scholar]
29. Gumerova N. I. and Rompel A., “Synthesis, Structures and Applications of Electron‐Rich Polyoxometalates,” Nature Reviews Chemistry 2 (2018): 0112, 10.1038/s41570-018-0112. [DOI] [Google Scholar]
30. Suzuki K., Mizuno N., and Yamaguchi K., “Polyoxometalate Photocatalysis for Liquid‐Phase Selective Organic Functional Group Transformations,” ACS Catalysis 8 (2018): 10809, 10.1021/acscatal.8b03498. [DOI] [Google Scholar]
31. Misra A., Kozma K., Streb C., and Nyman M., “Beyond Charge Balance: Counter‐Cations in Polyoxometalate Chemistry,” Angewandte Chemie International Edition 59 (2020): 596, 10.1002/anie.201905600. [DOI] [PMC free article] [PubMed] [Google Scholar]
32. Fabre B., Falaise C., and Cadot E., “Polyoxometalates‐Functionalized Electrodes for (Photo)Electrocatalytic Applications: Recent Advances and Prospects,” ACS Catalysis 12 (2022): 12055, 10.1021/acscatal.2c01847. [DOI] [Google Scholar]
33. Kruse J.‐H., Langer M., Romanenko I., et al., “Polyoxometalate‐Soft Matter Composite Materials: Design Strategies, Applications, and Future Directions,” Advanced Functional Materials 32 (2022): 2208428, 10.1002/adfm.202208428. [DOI] [Google Scholar]
34. Cameron J. M., Guillemot G., Galambos T., et al., “Supramolecular Assemblies of Organo‐Functionalised Hybrid Polyoxometalates: From Functional Building Blocks to Hierarchical Nanomaterials,” Chemical Society Reviews 51 (2022): 293, 10.1039/D1CS00832C. [DOI] [PubMed] [Google Scholar]
35. Falaise C., “Super‐Reduced Polyoxometalates in Aqueous Solution: Historical Perspectives and Current Challenges,” European Journal of Inorganic Chemistry 28 (2025): e202400827, 10.1002/ejic.202400827. [DOI] [Google Scholar]
36. Azaiza‐Dabbah D., Vogt C., Wang F., et al., “Molecular Transition Metal Oxide Electrocatalysts for the Reversible Carbon Dioxide–Carbon Monoxide Transformation,” Angewandte Chemie International Edition 61 (2022): e202112915, 10.1002/anie.202112915. [DOI] [PubMed] [Google Scholar]
37. Azaiza‐Dabbah D., Wang F., Haddad E., et al., “Heterometallic Transition Metal Oxides Containing Lewis Acids as Molecular Catalysts for the Reduction of Carbon Dioxide to Carbon Monoxide With Bimodal Activity,” Journal of the American Chemical Society 146 (2024): 27871, 10.1021/jacs.4c10412. [DOI] [PMC free article] [PubMed] [Google Scholar]
38. Sun M.‐L., Wang Y.‐R., He W.‐W., et al., “Efficient Electron Transfer From Electron‐Sponge Polyoxometalate to Single‐Metal Site Metal–Organic Frameworks for Highly Selective Electroreduction of Carbon Dioxide,” Small 17 (2021): 2100762, 10.1002/smll.202100762. [DOI] [PubMed] [Google Scholar]
39. Li C., Zhang Y., Shu L., Teng Y.‐L., Wang Y.‐R., and Dong B.‐X., “Boosting Electrochemical Reduction of CO₂ to CO via Fixation Keggin‐Type Polyoxoanions XW₁₁Co (X = Si, P, Co) Into ZIF‐8 Cavities: Pivotal Role of Central Atoms in Catalytic Performance,” Polyoxometalates 4 (2025): 9140097, 10.26599/POM.2025.9140097. [DOI] [Google Scholar]
40. Kawakami K., Yabe T., Amano F., Yamaguchi K., and Suzuki K., “Pd‐incorporated Polyoxometalate Catalysts for Electrochemical CO₂ Reduction,” Chemical Science 15 (2024): 14829, 10.1039/D4SC04304A. [DOI] [PMC free article] [PubMed] [Google Scholar]
41. Kawakami K., Yonesato K., Kikkawa S., et al., “Polyoxometalate‐Based Au–Ag Alloy Nanocatalysts for Efficient Electrochemical CO₂ Reduction Reaction,” ChemCatChem 18 (2026): e01423, 10.1002/cctc.202501423. [DOI] [Google Scholar]
42. Guo S.‐X., Zhang Y., Zhang X., Easton C. D., MacFarlane D. R., and Zhang J., “Phosphomolybdic Acid‐Assisted Growth of Ultrathin Bismuth Nanosheets for Enhanced Electrocatalytic Reduction of CO₂ to Formate,” ChemSusChem 12 (2019): 1091, 10.1002/cssc.201802409. [DOI] [PubMed] [Google Scholar]
43. Zha B., Li C., and Li J., “Efficient Electrochemical Reduction of CO₂ Into Formate and Acetate in Polyoxometalate Catholyte With Indium Catalyst,” Journal of Catalysis 382 (2020): 69, 10.1016/j.jcat.2019.12.010. [DOI] [Google Scholar]
44. Yang D., Zuo S., Yang H., and Wang X., “Single‐Unit‐Cell Catalysis of CO₂ Electroreduction Over Sub‐1 Nm Cu₉S₅ Nanowires,” Advanced Energy Materials 11 (2021): 2100272, 10.1002/aenm.202100272. [DOI] [Google Scholar]
45. Kuramochi S., Cameron J. M., Fukui T., et al., “Selective Electrochemical CO₂ Conversion With a Hybrid Polyoxometalate,” Chemical Communications 59 (2023): 10801, 10.1039/D3CC02138F. [DOI] [PubMed] [Google Scholar]
46. Hanaya T., Suzuki K., Sato R., Yamaguchi K., and Mizuno N., “Creation of Bismuth–Tungsten Oxide Nanoclusters Using Lacunary Polyoxometalates,” Dalton Transactions 46 (2017): 7384, 10.1039/C7DT01587A. [DOI] [PubMed] [Google Scholar]
47. Evans J., Pillinger M., and Rummey J. M., “Applications of Extended X‐Ray Absorption Fine Structure Spectroscopy to the Study of Polyoxometalates,” Journal of the Chemical Society, Dalton Transactions25 (1996): 2951, 10.1039/DT9960002951. [DOI] [Google Scholar]
48. Liu S., Wang C., Wu J., et al., “Efficient CO₂ Electroreduction With a Monolayer Bi₂WO₆ Through a Metallic Intermediate Surface State,” ACS Catalysis 11 (2021): 12476, 10.1021/acscatal.1c02495. [DOI] [Google Scholar]
49. Hori H., Takase M., Amano F., and Ohtani B., “Mechanism of the Formation of Hierarchical‐Structured Bismuth Tungstate Photocatalyst Particles Through Counter‐Flow Supply of Bismuth and Tungsten Sources,” Chemistry Letters 44 (2015): 1723, 10.1246/cl.150893. [DOI] [Google Scholar]
50. Zhang X., Sun X., Guo S.‐X., Bond A. M., and Zhang J., “Formation of Lattice‐Dislocated Bismuth Nanowires on Copper Foam for Enhanced Electrocatalytic CO₂ Reduction at Low Overpotential,” Energy & Environmental Science 12 (2019): 1334, 10.1039/C9EE00018F. [DOI] [Google Scholar]
51. Fan T., Ma W., Xie M., et al., “Achieving High Current Density for Electrocatalytic Reduction of CO₂ to Formate on Bismuth‐Based Catalysts,” Cell Reports Physical Science 2 (2021): 100353, 10.1016/j.xcrp.2021.100353. [DOI] [Google Scholar]
52. Sui P.‐F., Gao M.‐R., Zhu M.‐N., et al., “Unlocking Nanotubular Bismuth Oxyiodide Toward Carbon‐Neutral Electrosynthesis,” EES Catalysis 1 (2023): 290, 10.1039/D3EY00034F. [DOI] [Google Scholar]
53. Huang X., Han X., Tang R., et al., “Anion‐Mediated In Situ Reconstruction of the Bi₂MoO₆ Precatalyst for Enhanced Electrochemical CO₂ Reduction Over a Wide Potential Window,” ACS Applied Materials & Interfaces 16 (2024): 742, 10.1021/acsami.3c14930. [DOI] [PubMed] [Google Scholar]
54. Chen X., Chen H., Zhou W., et al., “Boron Dopant Induced Electron‐Rich Bismuth for Electrochemical CO₂ Reduction With High Solar Energy Conversion Efficiency,” Small 17 (2021): 2101128, 10.1002/smll.202101128. [DOI] [PubMed] [Google Scholar]
55. Li Z., Sun B., Xiao D., et al., “Electron‐Rich Bi Nanosheets Promote CO₂ ^·− Formation for High‐Performance and pH‐Universal Electrocatalytic CO₂ Reduction,” Angewandte Chemie International Edition 62 (2023): e202217569, 10.1002/anie.202217569. [DOI] [PubMed] [Google Scholar]
56. Moura de Salles Pupo M. and Kortlever R., “Electrolyte Effects on the Electrochemical Reduction of CO₂ ,” ChemPhysChem 20 (2019): 2926, 10.1002/cphc.201900680. [DOI] [PMC free article] [PubMed] [Google Scholar]
57. Marcandalli G., Monteiro M. C. O., Goyal A., and Koper M. T. M., “Electrolyte Effects on CO₂ Electrochemical Reduction to CO,” Accounts of Chemical Research 55 (2022): 1900, 10.1021/acs.accounts.2c00080. [DOI] [PMC free article] [PubMed] [Google Scholar]
58. Deng B., Huang M., Zhao X., Mou S., and Dong F., “Interfacial Electrolyte Effects on Electrocatalytic CO₂ Reduction,” ACS Catalysis 12 (2022): 331, 10.1021/acscatal.1c03501. [DOI] [Google Scholar]
59. Khani H., Puente Santiago A. R., and He T., “An Interfacial View of Cation Effects on Electrocatalysis Systems,” Angewandte Chemie International Edition 62 (2023): e202306103, 10.1002/anie.202306103. [DOI] [PubMed] [Google Scholar]
60. Kuhl K. P., Cave E. R., Abram D. N., and Jaramillo T. F., “New Insights Into the Electrochemical Reduction of Carbon Dioxide on Metallic Copper Surfaces,” Energy & Environmental Science 5 (2012): 7050, 10.1039/C2EE21234J. [DOI] [Google Scholar]
61. Kamata K., Yonehara K., Sumida Y., Yamaguchi K., Hikichi S., and Mizuno N., “Efficient Epoxidation of Olefins With ≥99% Selectivity and Use of Hydrogen Peroxide,” Science 300 (2003): 964, 10.1126/science.1083176. [DOI] [PubMed] [Google Scholar]
62. Suzuki T., Yabe T., Wachi K., Yonesato K., Suzuki K., and Yamaguchi K., “Creation of Highly Dispersed Supported Polyoxometalate Cesium Salts via Cation Exchange From Alkylammonium Salts on Supports,” ChemNanoMat 9 (2023): e202200428, 10.1002/cnma.202200428. [DOI] [Google Scholar]
63. Gonglach S., Paul S., Haas M., et al., “Molecular Cobalt Corrole Complex for the Heterogeneous Electrocatalytic Reduction of Carbon Dioxide,” Nature Communications 10 (2019): 3864, 10.1038/s41467-019-11868-5. [DOI] [PMC free article] [PubMed] [Google Scholar]
64. Takahashi Y., Abe M., Uematsu H., et al., “High‐Resolution and High‐Sensitivity X‐Ray Ptychographic Coherent Diffraction Imaging Using the CITIUS Detector,” Journal of Synchrotron Radiation 30 (2023): 989, 10.1107/S1600577523004897. [DOI] [PMC free article] [PubMed] [Google Scholar]
65. García M., Aguirre M. J., Canzi G., Kubiak C. P., Ohlbaum M., and Isaacs M., “Electro and Photoelectrochemical Reduction of Carbon Dioxide on Multimetallic Porphyrins/Polyoxotungstate Modified Electrodes,” Electrochimica Acta 115 (2014): 146, 10.1016/j.electacta.2013.10.142. [DOI] [Google Scholar]
66. Girardi M., Blanchard S., Griveau S., et al., “Electro‐Assisted Reduction of CO₂ to CO and Formaldehyde by (TOA)₆[α‐SiW₁₁O₃₉Co(_)] Polyoxometalate,” European Journal of Inorganic Chemistry (2015): 3642, 10.1002/ejic.201500389. [DOI] [Google Scholar]
67. Guo S.‐X., MacFarlane D. R., and Zhang J., “Bioinspired Electrocatalytic CO₂ Reduction by Bovine Serum Albumin‐Capped Silver Nanoclusters Mediated by [α‐SiW₁₂O₄₀]⁴⁻ ,” ChemSusChem 9 (2016): 80, 10.1002/cssc.201501343. [DOI] [PubMed] [Google Scholar]
68. Guo S.‐X., Li F., Chen L., MacFarlane D. R., and Zhang J., “Polyoxometalate‐Promoted Electrocatalytic CO₂ Reduction at Nanostructured Silver in Dimethylformamide,” ACS Applied Materials & Interfaces 10 (2018): 12690, 10.1021/acsami.8b01042. [DOI] [PubMed] [Google Scholar]
69. Wang Y.‐R., Huang Q., He C.‐T., et al., “Oriented Electron Transmission in Polyoxometalate‐Metalloporphyrin Organic Framework for Highly Selective Electroreduction of CO₂ ,” Nature Communications 9 (2018): 4466, 10.1038/s41467-018-06938-z. [DOI] [PMC free article] [PubMed] [Google Scholar]
70. Girardi M., Platzer D., Griveau S., et al., “Assessing the Electrocatalytic Properties of the {Cp*Rh^III}²⁺‐Polyoxometalate Derivative [H₂PW₁₁O₃₉{Rh^IIICp*(OH₂)}]^3– Towards CO₂ Reduction,” European Journal of Inorganic Chemistry (2019): 387, 10.1002/ejic.201800454. [DOI] [Google Scholar]
71. Du J., Lang Z.‐L., Ma Y.‐Y., et al., “Polyoxometalate‐based Electron Transfer Modulation for Efficient Electrocatalytic Carbon Dioxide Reduction,” Chemical Science 11 (2020): 3007, 10.1039/C9SC05392A. [DOI] [PMC free article] [PubMed] [Google Scholar]
72. Liu Y.‐J., Shao P., Gao M.‐Y., Fang W.‐H., and Zhang J., “Synthesis of Ag‐Doped Polyoxotitanium Nanoclusters for Efficient Electrocatalytic CO₂ Reduction,” Inorganic Chemistry 59 (2020): 11442, 10.1021/acs.inorgchem.0c01245. [DOI] [PubMed] [Google Scholar]
73. Li C., Zha B., and Li J., “A SiW₁₁Mn‐Assisted Indium Electrocatalyst for Carbon Dioxide Reduction Into Formate and Acetate,” Journal of CO2 Utilisation 38 (2020): 299, 10.1016/j.jcou.2020.02.008. [DOI] [Google Scholar]
74. Zang D., Li Q., Dai G., Zeng M., Huang Y., and Wei Y., “Interface Engineering of Mo₈/Cu Heterostructures Toward Highly Selective Electrochemical Reduction of Carbon Dioxide Into Acetate,” Applied Catalysis B 281 (2021): 119426, 10.1016/j.apcatb.2020.119426. [DOI] [Google Scholar]
75. Yang H., Yang D., Zhou Y., and Wang X., “Polyoxometalate Interlayered Zinc–Metallophthalocyanine Molecular Layer Sandwich as Photocoupled Electrocatalytic CO₂ Reduction Catalyst,” Journal of the American Chemical Society 143 (2021): 13721, 10.1021/jacs.1c05580. [DOI] [PubMed] [Google Scholar]
76. Ying J., Zhang B., Tian A., and Wang X., “A Series of A‐ and B‐type Anderson Compounds With Al, Te and Cr as Centers by Tuning Different Ligands: Syntheses, Electrochemical, Photocatalytic and CO₂RR Properties,” CrystEngComm 23 (2021): 2572, 10.1039/D1CE00185J. [DOI] [Google Scholar]
77. Yu H., Ying J., Tian Y., and Tian A., “Synthesis, Structure and Properties of a Three‐Dimensional Polyoxometalate‐Based Compound Modified by Two Organic Ligands,” Inorganic Chemistry Communications 123 (2021): 108338, 10.1016/j.inoche.2020.108338. [DOI] [Google Scholar]
78. Zhang B., Ying J., Zhang X., Wang C., and Tian A., “Electrocatalytic, Photocatalytic, Fluorescence Sensing and CO₂RR Properties of a Series of Homopolymolybdate Hybrid Coordination Polymers,” New Journal of Chemistry 45 (2021): 13340, 10.1039/D1NJ02283K. [DOI] [Google Scholar]
79. Liu J., Wang S., Liu N., et al., “Au‐Polyoxometalates A‐B‐A‐B Type Copolymer‐Analogue Sub‐1 Nm Nanowires,” Small 17 (2021): 2006260, 10.1002/smll.202006260. [DOI] [PubMed] [Google Scholar]
80. Sun W., Li C., and Zhao H., “The Targeted Multi‐Electrons Transfer for Acetic Acid and Ethanol Obtained With (n‐Bu₄N)₃SVW₁₁O₄₀ and in Synergetic Catalysis in CO₂ Electroreduction,” Journal of Power Sources 517 (2022): 230665, 10.1016/j.jpowsour.2021.230665. [DOI] [Google Scholar]
81. Huang Q., Niu Q., Li X.‐F., et al., “Demystifying the Roles of Single Metal Site and Cluster in CO₂ Reduction via Light and Electric Dual‐Responsive Polyoxometalate‐Based Metal‐Organic Frameworks,” Science Advances 8 (2022): eadd5598, 10.1126/sciadv.add5598. [DOI] [PMC free article] [PubMed] [Google Scholar]
82. Li S.‐Q., Dai L.‐F., Tian Y.‐Q., Yi Y.‐X., Yan J., and Liu C., “Polymolybdate‐Guided Assembly of a Thiacalix[4]Arene‐Protected Ag Nanocluster for Electrocatalytic CO₂ Reduction,” Chemical Communications 59 (2023): 575, 10.1039/D2CC05692E. [DOI] [PubMed] [Google Scholar]
83. Peng M.‐T., Chen C., Zhang Y., Xu J.‐Y., Teng Y.‐L., and Dong B.‐X., “Exploring the Role of Sandwich‐Type Polyoxometalates in {K₁₀(PW₉O₃₄)₂M₄(H₂O)₂}@PCN‐222 (M = Mn, Ni, Zn) for Electroreduction of CO₂ to CO,” Dalton Transactions 52 (2023): 10737, 10.1039/D3DT01535A. [DOI] [PubMed] [Google Scholar]
84. Sun W., Tai Y., Tian W., Zhou L., and Li C., “Electrochemical CO₂ Reduction to Ethanol: Synergism of (n‐Bu₄N)₃SVMo₁₁O₄₀ and an In Catalyst,” Electrochimica Acta 445 (2023): 142067, 10.1016/j.electacta.2023.142067. [DOI] [Google Scholar]
85. Tubul‐Sterin T., Baranov M., Gan‐Or G., Leffler N., Neyman A., and Weinstock I. A., “Polyoxometalate‐Complexed Indium Hydroxide: Atomically Homogeneous Impregnation via Countercation Exchange,” Inorganic Chemistry 62 (2023): 1804, 10.1021/acs.inorgchem.1c03857. [DOI] [PubMed] [Google Scholar]
86. Sun W., Yao D., Tai Y., et al., “Efficient Electrocatalytic CO₂ Reduction to Ethanol Through the Proton Coupled Electron Transfer Process of PV_nMo_(12‐n) (n = 1, 2, 3) Over Indium Electrode,” Journal of Colloid & Interface Science 650 (2023): 121, 10.1016/j.jcis.2023.06.167. [DOI] [PubMed] [Google Scholar]
87. Sun W., Zhou L., Tian W., Li S., Yang M., and Li C., “Selective CO₂ to Proportionally Tunable Syngas at Lower Onset Potential Enabled by Bimetallic Chalcogenides in Polyoxometalate Medium,” Applied Catalysis B 356 (2024): 124206, 10.1016/j.apcatb.2024.124206. [DOI] [Google Scholar]
88. Shu L., Li C., Peng M.‐T., Liu M.‐J., Teng Y.‐L., and Dong B.‐X., “Heterogenization of a Sandwich [(PW₉O₃₄)₂Co₄(H₂O)₂]¹⁰⁻ in PCN‐222/PCN‐222(M): Exploring the Electron Transfer for Electrocatalytic CO₂ Reduction,” European Journal of Inorganic Chemistry 27 (2024): e202400485, 10.1002/ejic.202400485. [DOI] [Google Scholar]
89. Zhang Y., Li C., Shu L., Teng Y.‐L., and Dong B.‐X., “Research on the Construction of a Series of Transition Metal‐Substituted Keggin‐Type TMSPOMs@PCN‐224 Composites Through the Encapsulation Method and Their Electron Transfer Mechanism in CO₂RR,” Inorganic Chemistry 63 (2024): 11592, 10.1021/acs.inorgchem.4c00840. [DOI] [PubMed] [Google Scholar]
90. Liang J.‐J., Zhang Y.‐C., Chang Z.‐H., et al., “Two New 6‐nitrobenzimidazole Ligand‐Modified Polymolybdate‐Based Metal–Organic Complexes With Excellent Capacitive and Electrocatalytic Performances,” New Journal of Chemistry 48 (2024): 1248, 10.1039/D3NJ04841A. [DOI] [Google Scholar]
91. Tai Y., Sun W., Yao D., et al., “Keggin‐Type P‐W‐Mo‐V Polyoxometalates in Electrocatalyzed CO₂ Reduction Using Indium Electrodes,” Polyoxometalates 3 (2024): 9140051, 10.26599/POM.2023.9140051. [DOI] [Google Scholar]
92. Zhang P., Shi W.‐X., Yin H.‐Q., et al., “W₁₀ Single‐Cluster‐Mediated Syngas Electrosynthesis in Single‐Sandwich‐Layer ZnAl‐Layered Double Hydroxide Catalysts,” ACS Nano 19 (2025): 37206, 10.1021/acsnano.5c11814. [DOI] [PubMed] [Google Scholar]
93. Liu C., Song L., Wu W., Li H., Dang D., and Bai Y., “Photo‐coupled Electrocatalytic Conversion of CO₂ to CO Over Cobalt Phthalocyanine‐Modified POM‐K₈Ta₆O₁₉ Z‐Scheme Photocathodes,” Green Chemistry 27 (2025): 15607, 10.1039/D5GC04093K. [DOI] [Google Scholar]
94. Sun W., Li C., Tai Y., Zhou L., Tian W., and Li S., “Selective Proton‐Coupled Electron Transfer Engineering Between Cu_xIn_y Alloy and Polyoxometalate Medium for Efficient CO₂ Electroreduction to CO,” Journal of Catalysis 450 (2025): 116254, 10.1016/j.jcat.2025.116254. [DOI] [Google Scholar]
95. Sun W., Li C., Zhou L., Tian W., Li S., and Yang M., “Engineering the Interface Charge Redistribution and Boosted Kinetics via Polyoxometalate for Efficient Carbon Dioxide Electroreduction in Acidic Medium,” Journal of Colloid & Interface Science 697 (2025): 137912, 10.1016/j.jcis.2025.137912. [DOI] [PubMed] [Google Scholar]
96. Xia K., Yatabe T., Yonesato K., et al., “Structural Engineering of Au─Ag Heterometallic Nanoparticles Using Multidentate Polyoxometalate Ligands,” Small 22 (2026): e14728, 10.1002/smll.202514728. [DOI] [PubMed] [Google Scholar]

Associated Data

This section collects any data citations, data availability statements, or supplementary materials included in this article.

Supplementary Materials

CHEM-32-e71437-s001.pdf^{(12.6MB, pdf)}

Data Availability Statement

The data that support the findings of this study are available in the Supporting Information of this article.

[chem71437-bib-0001] 1. Masson‐Delmotte V., Zhai P., Pirani A., et al., IPCC “ Climate Change 2021: The Physical Science Basis ,” Contribution of Working Group I to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change, (Cambridge University Press; ): 2021. [Google Scholar]

[chem71437-bib-0002] 2. Sun Z., Ma T., Tao H., Fan Q., and Han B., “Fundamentals and Challenges of Electrochemical CO₂ Reduction Using Two‐Dimensional Materials,” Chem 3 (2017): 560, 10.1016/j.chempr.2017.09.009. [DOI] [Google Scholar]

[chem71437-bib-0003] 3. Nitopi S., Bertheussen E., Scott S. B., et al., “Progress and Perspectives of Electrochemical CO₂ Reduction on Copper in Aqueous Electrolyte,” Chemical Reviews 119 (2019): 7610, 10.1021/acs.chemrev.8b00705. [DOI] [PubMed] [Google Scholar]

[chem71437-bib-0004] 4. Hietala J., Vuori A., Johnsson P., Pollari I., Reutemann W., and Kieczka H., Formic Acid, Ullmann's Encyclopedia of Industrial Chemistry (Wiley‐VCH Verlag, 2016), 10.1002/14356007.a12_013.pub3. [DOI] [Google Scholar]

[chem71437-bib-0005] 5. Zhong H., Iguchi M., Chatterjee M., Himeda Y., Xu Q., and Kawanami H., “Formic Acid‐Based Liquid Organic Hydrogen Carrier System With Heterogeneous Catalysts,” Advanced Sustainable Systems 2 (2018): 1700161, 10.1002/adsu.201700161. [DOI] [Google Scholar]

[chem71437-bib-0006] 6. Jouny M., Luc W., and Jiao F., “General Techno‐Economic Analysis of CO₂ Electrolysis Systems,” Industrial & Engineering Chemistry Research 57 (2018): 2165, 10.1021/acs.iecr.7b03514. [DOI] [Google Scholar]

[chem71437-bib-0007] 7. Xia D., Yu H., Xie H., et al., “Recent Progress of Bi‐Based Electrocatalysts for Electrocatalytic CO₂ Reduction,” Nanoscale 14 (2022): 7957, 10.1039/D2NR01900K. [DOI] [PubMed] [Google Scholar]

[chem71437-bib-0008] 8. Liang X.‐D., Tian N., Hu S.‐N., Zhou Z.‐Y., and Sun S.‐G., “Recent Advances of Bismuth‐Based Electrocatalysts for CO₂ Reduction: Strategies, Mechanism and Applications,” Materials Reports Energy 3 (2023): 100191, 10.1016/j.matre.2023.100191. [DOI] [Google Scholar]

[chem71437-bib-0009] 9. Murata A. and Hori Y., “Product Selectivity Affected by Cationic Species in Electrochemical Reduction of CO₂ and CO at a Cu Electrode,” Bulletin of the Chemical Society of Japan 64 (1991): 123, 10.1246/bcsj.64.123. [DOI] [Google Scholar]

[chem71437-bib-0010] 10. Thorson M. R., Siil K. I., and Kenis P. J. A., “Effect of Cations on the Electrochemical Conversion of CO₂ to CO,” Journal of the Electrochemical Society 160 (2012): F69, 10.1149/2.052301jes. [DOI] [Google Scholar]

[chem71437-bib-0011] 11. Singh M. R., Kwon Y., Lum Y., Ager J. W., and Bell A. T., “Hydrolysis of Electrolyte Cations Enhances the Electrochemical Reduction of CO₂ Over Ag and Cu,” Journal of the American Chemical Society 138 (2016): 13006, 10.1021/jacs.6b07612. [DOI] [PubMed] [Google Scholar]

[chem71437-bib-0012] 12. Resasco J., Chen L. D., Clark E., et al., “Promoter Effects of Alkali Metal Cations on the Electrochemical Reduction of Carbon Dioxide,” Journal of the American Chemical Society 139 (2017): 11277, 10.1021/jacs.7b06765. [DOI] [PubMed] [Google Scholar]

[chem71437-bib-0013] 13. Ringe S., Clark E. L., Resasco J., et al., “Understanding Cation Effects in Electrochemical CO₂ Reduction,” Energy & Environmental Science 12 (2019): 3001, 10.1039/C9EE01341E. [DOI] [Google Scholar]

[chem71437-bib-0014] 14. Malkani A. S., Anibal J., and Xu B., “Cation Effect on Interfacial CO₂ Concentration in the Electrochemical CO₂ Reduction Reaction,” ACS Catalysis 10 (2020): 14871, 10.1021/acscatal.0c03553. [DOI] [Google Scholar]

[chem71437-bib-0015] 15. Bhargava S. S., Cofell E. R., Chumble P., Azmoodeh D., Someshwar S., and Kenis P. J. A., “Exploring Multivalent Cations‐Based Electrolytes for CO₂ Electroreduction,” Electrochimica Acta 394 (2021): 139055, 10.1016/j.electacta.2021.139055. [DOI] [Google Scholar]

[chem71437-bib-0016] 16. Monteiro M. C. O., Dattila F., Hagedoorn B., García‐Muelas R., López N., and Koper M. T. M., “Absence of CO₂ Electroreduction on Copper, Gold and Silver Electrodes Without Metal Cations in Solution,” Nature Catalysis 4 (2021): 654, 10.1038/s41929-021-00655-5. [DOI] [Google Scholar]

[chem71437-bib-0017] 17. Monteiro M. C. O., Dattila F., López N., and Koper M. T. M., “The Role of Cation Acidity on the Competition Between Hydrogen Evolution and CO₂ Reduction on Gold Electrodes,” Journal of the American Chemical Society 144 (2022): 1589, 10.1021/jacs.1c10171. [DOI] [PMC free article] [PubMed] [Google Scholar]

[chem71437-bib-0018] 18. Gu J., Liu S., Ni W., Ren W., Haussener S., and Hu X., “Modulating Electric Field Distribution by Alkali Cations for CO₂ Electroreduction in Strongly Acidic Medium,” Nature Catalysis 5 (2022): 268, 10.1038/s41929-022-00761-y. [DOI] [Google Scholar]

[chem71437-bib-0019] 19. Jiang T.‐W., Wang S.‐S., Qin X., et al., “Uncovering the Cation Effects on the Electroreduction of CO₂ on Pd/C Catalysts − An SEIRAS Study,” Journal of Catalysis 434 (2024): 115520, 10.1016/j.jcat.2024.115520. [DOI] [Google Scholar]

[chem71437-bib-0020] 20. Chang Y., Tan Z., Han J., et al., “Effect of Alkali and Alkaline Earth Metal Cations on the HCOOH Selectivity of the CO₂ Electrochemical Reduction Reaction on Bi Electrodes in Acidic media,” Journal of Alloys and Compounds 1035 (2025): 181524, 10.1016/j.jallcom.2025.181524. [DOI] [Google Scholar]

[chem71437-bib-0021] 21. Schizodimou A. and Kyriacou G., “Acceleration of the Reduction of Carbon Dioxide in the Presence of Multivalent Cations,” Electrochimica Acta 78 (2012): 171, 10.1016/j.electacta.2012.05.118. [DOI] [Google Scholar]

[chem71437-bib-0022] 22. Pope M. T., Heteropoly and Isopoly Oxometalates (Springer, 1983), https://link.springer.com/book/9783662120064. [Google Scholar]

[chem71437-bib-0023] 23. Hill C. L. and Prosser‐McCartha C. M., “Homogeneous Catalysis by Transition Metal Oxygen Anion Clusters,” Coordination Chemistry Reviews 143 (1995): 407, 10.1016/0010-8545(95)01141-B. [DOI] [Google Scholar]

[chem71437-bib-0024] 24. Kozhevnikov I. V., “Catalysis by Heteropoly Acids and Multicomponent Polyoxometalates in Liquid‐Phase Reactions,” Chemical Reviews 98 (1998): 171, 10.1021/cr960400y. [DOI] [PubMed] [Google Scholar]

[chem71437-bib-0025] 25. Mizuno N. and Misono M., “Heterogeneous Catalysis,” Chemical Reviews 98 (1998): 199, 10.1021/cr960401q. [DOI] [PubMed] [Google Scholar]

[chem71437-bib-0026] 26. Dolbecq A., Dumas E., Mayer C. R., and Mialane P., “Hybrid Organic−Inorganic Polyoxometalate Compounds: From Structural Diversity to Applications,” Chemical Reviews 110 (2010): 6009, 10.1021/cr1000578. [DOI] [PubMed] [Google Scholar]

[chem71437-bib-0027] 27. Wang S.‐S. and Yang G.‐Y., “Recent Advances in Polyoxometalate‐Catalyzed Reactions,” Chemical Reviews 115 (2015): 4893, 10.1021/cr500390v. [DOI] [PubMed] [Google Scholar]

[chem71437-bib-0028] 28. Vilà‐Nadal L. and Cronin L., “Design and Synthesis of Polyoxometalate‐Framework Materials From Cluster Precursors,” Nature Reviews Materials 2 (2017): 17054, 10.1038/natrevmats.2017.54. [DOI] [Google Scholar]

[chem71437-bib-0029] 29. Gumerova N. I. and Rompel A., “Synthesis, Structures and Applications of Electron‐Rich Polyoxometalates,” Nature Reviews Chemistry 2 (2018): 0112, 10.1038/s41570-018-0112. [DOI] [Google Scholar]

[chem71437-bib-0030] 30. Suzuki K., Mizuno N., and Yamaguchi K., “Polyoxometalate Photocatalysis for Liquid‐Phase Selective Organic Functional Group Transformations,” ACS Catalysis 8 (2018): 10809, 10.1021/acscatal.8b03498. [DOI] [Google Scholar]

[chem71437-bib-0031] 31. Misra A., Kozma K., Streb C., and Nyman M., “Beyond Charge Balance: Counter‐Cations in Polyoxometalate Chemistry,” Angewandte Chemie International Edition 59 (2020): 596, 10.1002/anie.201905600. [DOI] [PMC free article] [PubMed] [Google Scholar]

[chem71437-bib-0032] 32. Fabre B., Falaise C., and Cadot E., “Polyoxometalates‐Functionalized Electrodes for (Photo)Electrocatalytic Applications: Recent Advances and Prospects,” ACS Catalysis 12 (2022): 12055, 10.1021/acscatal.2c01847. [DOI] [Google Scholar]

[chem71437-bib-0033] 33. Kruse J.‐H., Langer M., Romanenko I., et al., “Polyoxometalate‐Soft Matter Composite Materials: Design Strategies, Applications, and Future Directions,” Advanced Functional Materials 32 (2022): 2208428, 10.1002/adfm.202208428. [DOI] [Google Scholar]

[chem71437-bib-0034] 34. Cameron J. M., Guillemot G., Galambos T., et al., “Supramolecular Assemblies of Organo‐Functionalised Hybrid Polyoxometalates: From Functional Building Blocks to Hierarchical Nanomaterials,” Chemical Society Reviews 51 (2022): 293, 10.1039/D1CS00832C. [DOI] [PubMed] [Google Scholar]

[chem71437-bib-0035] 35. Falaise C., “Super‐Reduced Polyoxometalates in Aqueous Solution: Historical Perspectives and Current Challenges,” European Journal of Inorganic Chemistry 28 (2025): e202400827, 10.1002/ejic.202400827. [DOI] [Google Scholar]

[chem71437-bib-0036] 36. Azaiza‐Dabbah D., Vogt C., Wang F., et al., “Molecular Transition Metal Oxide Electrocatalysts for the Reversible Carbon Dioxide–Carbon Monoxide Transformation,” Angewandte Chemie International Edition 61 (2022): e202112915, 10.1002/anie.202112915. [DOI] [PubMed] [Google Scholar]

[chem71437-bib-0037] 37. Azaiza‐Dabbah D., Wang F., Haddad E., et al., “Heterometallic Transition Metal Oxides Containing Lewis Acids as Molecular Catalysts for the Reduction of Carbon Dioxide to Carbon Monoxide With Bimodal Activity,” Journal of the American Chemical Society 146 (2024): 27871, 10.1021/jacs.4c10412. [DOI] [PMC free article] [PubMed] [Google Scholar]

[chem71437-bib-0038] 38. Sun M.‐L., Wang Y.‐R., He W.‐W., et al., “Efficient Electron Transfer From Electron‐Sponge Polyoxometalate to Single‐Metal Site Metal–Organic Frameworks for Highly Selective Electroreduction of Carbon Dioxide,” Small 17 (2021): 2100762, 10.1002/smll.202100762. [DOI] [PubMed] [Google Scholar]

[chem71437-bib-0039] 39. Li C., Zhang Y., Shu L., Teng Y.‐L., Wang Y.‐R., and Dong B.‐X., “Boosting Electrochemical Reduction of CO₂ to CO via Fixation Keggin‐Type Polyoxoanions XW₁₁Co (X = Si, P, Co) Into ZIF‐8 Cavities: Pivotal Role of Central Atoms in Catalytic Performance,” Polyoxometalates 4 (2025): 9140097, 10.26599/POM.2025.9140097. [DOI] [Google Scholar]

[chem71437-bib-0040] 40. Kawakami K., Yabe T., Amano F., Yamaguchi K., and Suzuki K., “Pd‐incorporated Polyoxometalate Catalysts for Electrochemical CO₂ Reduction,” Chemical Science 15 (2024): 14829, 10.1039/D4SC04304A. [DOI] [PMC free article] [PubMed] [Google Scholar]

[chem71437-bib-0041] 41. Kawakami K., Yonesato K., Kikkawa S., et al., “Polyoxometalate‐Based Au–Ag Alloy Nanocatalysts for Efficient Electrochemical CO₂ Reduction Reaction,” ChemCatChem 18 (2026): e01423, 10.1002/cctc.202501423. [DOI] [Google Scholar]

[chem71437-bib-0042] 42. Guo S.‐X., Zhang Y., Zhang X., Easton C. D., MacFarlane D. R., and Zhang J., “Phosphomolybdic Acid‐Assisted Growth of Ultrathin Bismuth Nanosheets for Enhanced Electrocatalytic Reduction of CO₂ to Formate,” ChemSusChem 12 (2019): 1091, 10.1002/cssc.201802409. [DOI] [PubMed] [Google Scholar]

[chem71437-bib-0043] 43. Zha B., Li C., and Li J., “Efficient Electrochemical Reduction of CO₂ Into Formate and Acetate in Polyoxometalate Catholyte With Indium Catalyst,” Journal of Catalysis 382 (2020): 69, 10.1016/j.jcat.2019.12.010. [DOI] [Google Scholar]

[chem71437-bib-0044] 44. Yang D., Zuo S., Yang H., and Wang X., “Single‐Unit‐Cell Catalysis of CO₂ Electroreduction Over Sub‐1 Nm Cu₉S₅ Nanowires,” Advanced Energy Materials 11 (2021): 2100272, 10.1002/aenm.202100272. [DOI] [Google Scholar]

[chem71437-bib-0045] 45. Kuramochi S., Cameron J. M., Fukui T., et al., “Selective Electrochemical CO₂ Conversion With a Hybrid Polyoxometalate,” Chemical Communications 59 (2023): 10801, 10.1039/D3CC02138F. [DOI] [PubMed] [Google Scholar]

[chem71437-bib-0046] 46. Hanaya T., Suzuki K., Sato R., Yamaguchi K., and Mizuno N., “Creation of Bismuth–Tungsten Oxide Nanoclusters Using Lacunary Polyoxometalates,” Dalton Transactions 46 (2017): 7384, 10.1039/C7DT01587A. [DOI] [PubMed] [Google Scholar]

[chem71437-bib-0047] 47. Evans J., Pillinger M., and Rummey J. M., “Applications of Extended X‐Ray Absorption Fine Structure Spectroscopy to the Study of Polyoxometalates,” Journal of the Chemical Society, Dalton Transactions25 (1996): 2951, 10.1039/DT9960002951. [DOI] [Google Scholar]

[chem71437-bib-0048] 48. Liu S., Wang C., Wu J., et al., “Efficient CO₂ Electroreduction With a Monolayer Bi₂WO₆ Through a Metallic Intermediate Surface State,” ACS Catalysis 11 (2021): 12476, 10.1021/acscatal.1c02495. [DOI] [Google Scholar]

[chem71437-bib-0049] 49. Hori H., Takase M., Amano F., and Ohtani B., “Mechanism of the Formation of Hierarchical‐Structured Bismuth Tungstate Photocatalyst Particles Through Counter‐Flow Supply of Bismuth and Tungsten Sources,” Chemistry Letters 44 (2015): 1723, 10.1246/cl.150893. [DOI] [Google Scholar]

[chem71437-bib-0050] 50. Zhang X., Sun X., Guo S.‐X., Bond A. M., and Zhang J., “Formation of Lattice‐Dislocated Bismuth Nanowires on Copper Foam for Enhanced Electrocatalytic CO₂ Reduction at Low Overpotential,” Energy & Environmental Science 12 (2019): 1334, 10.1039/C9EE00018F. [DOI] [Google Scholar]

[chem71437-bib-0051] 51. Fan T., Ma W., Xie M., et al., “Achieving High Current Density for Electrocatalytic Reduction of CO₂ to Formate on Bismuth‐Based Catalysts,” Cell Reports Physical Science 2 (2021): 100353, 10.1016/j.xcrp.2021.100353. [DOI] [Google Scholar]

[chem71437-bib-0052] 52. Sui P.‐F., Gao M.‐R., Zhu M.‐N., et al., “Unlocking Nanotubular Bismuth Oxyiodide Toward Carbon‐Neutral Electrosynthesis,” EES Catalysis 1 (2023): 290, 10.1039/D3EY00034F. [DOI] [Google Scholar]

[chem71437-bib-0053] 53. Huang X., Han X., Tang R., et al., “Anion‐Mediated In Situ Reconstruction of the Bi₂MoO₆ Precatalyst for Enhanced Electrochemical CO₂ Reduction Over a Wide Potential Window,” ACS Applied Materials & Interfaces 16 (2024): 742, 10.1021/acsami.3c14930. [DOI] [PubMed] [Google Scholar]

[chem71437-bib-0054] 54. Chen X., Chen H., Zhou W., et al., “Boron Dopant Induced Electron‐Rich Bismuth for Electrochemical CO₂ Reduction With High Solar Energy Conversion Efficiency,” Small 17 (2021): 2101128, 10.1002/smll.202101128. [DOI] [PubMed] [Google Scholar]

[chem71437-bib-0055] 55. Li Z., Sun B., Xiao D., et al., “Electron‐Rich Bi Nanosheets Promote CO₂ ^·− Formation for High‐Performance and pH‐Universal Electrocatalytic CO₂ Reduction,” Angewandte Chemie International Edition 62 (2023): e202217569, 10.1002/anie.202217569. [DOI] [PubMed] [Google Scholar]

[chem71437-bib-0056] 56. Moura de Salles Pupo M. and Kortlever R., “Electrolyte Effects on the Electrochemical Reduction of CO₂ ,” ChemPhysChem 20 (2019): 2926, 10.1002/cphc.201900680. [DOI] [PMC free article] [PubMed] [Google Scholar]

[chem71437-bib-0057] 57. Marcandalli G., Monteiro M. C. O., Goyal A., and Koper M. T. M., “Electrolyte Effects on CO₂ Electrochemical Reduction to CO,” Accounts of Chemical Research 55 (2022): 1900, 10.1021/acs.accounts.2c00080. [DOI] [PMC free article] [PubMed] [Google Scholar]

[chem71437-bib-0058] 58. Deng B., Huang M., Zhao X., Mou S., and Dong F., “Interfacial Electrolyte Effects on Electrocatalytic CO₂ Reduction,” ACS Catalysis 12 (2022): 331, 10.1021/acscatal.1c03501. [DOI] [Google Scholar]

[chem71437-bib-0059] 59. Khani H., Puente Santiago A. R., and He T., “An Interfacial View of Cation Effects on Electrocatalysis Systems,” Angewandte Chemie International Edition 62 (2023): e202306103, 10.1002/anie.202306103. [DOI] [PubMed] [Google Scholar]

[chem71437-bib-0060] 60. Kuhl K. P., Cave E. R., Abram D. N., and Jaramillo T. F., “New Insights Into the Electrochemical Reduction of Carbon Dioxide on Metallic Copper Surfaces,” Energy & Environmental Science 5 (2012): 7050, 10.1039/C2EE21234J. [DOI] [Google Scholar]

[chem71437-bib-0061] 61. Kamata K., Yonehara K., Sumida Y., Yamaguchi K., Hikichi S., and Mizuno N., “Efficient Epoxidation of Olefins With ≥99% Selectivity and Use of Hydrogen Peroxide,” Science 300 (2003): 964, 10.1126/science.1083176. [DOI] [PubMed] [Google Scholar]

[chem71437-bib-0062] 62. Suzuki T., Yabe T., Wachi K., Yonesato K., Suzuki K., and Yamaguchi K., “Creation of Highly Dispersed Supported Polyoxometalate Cesium Salts via Cation Exchange From Alkylammonium Salts on Supports,” ChemNanoMat 9 (2023): e202200428, 10.1002/cnma.202200428. [DOI] [Google Scholar]

[chem71437-bib-0063] 63. Gonglach S., Paul S., Haas M., et al., “Molecular Cobalt Corrole Complex for the Heterogeneous Electrocatalytic Reduction of Carbon Dioxide,” Nature Communications 10 (2019): 3864, 10.1038/s41467-019-11868-5. [DOI] [PMC free article] [PubMed] [Google Scholar]

[chem71437-bib-0064] 64. Takahashi Y., Abe M., Uematsu H., et al., “High‐Resolution and High‐Sensitivity X‐Ray Ptychographic Coherent Diffraction Imaging Using the CITIUS Detector,” Journal of Synchrotron Radiation 30 (2023): 989, 10.1107/S1600577523004897. [DOI] [PMC free article] [PubMed] [Google Scholar]

[chem71437-bib-0065] 65. García M., Aguirre M. J., Canzi G., Kubiak C. P., Ohlbaum M., and Isaacs M., “Electro and Photoelectrochemical Reduction of Carbon Dioxide on Multimetallic Porphyrins/Polyoxotungstate Modified Electrodes,” Electrochimica Acta 115 (2014): 146, 10.1016/j.electacta.2013.10.142. [DOI] [Google Scholar]

[chem71437-bib-0066] 66. Girardi M., Blanchard S., Griveau S., et al., “Electro‐Assisted Reduction of CO₂ to CO and Formaldehyde by (TOA)₆[α‐SiW₁₁O₃₉Co(_)] Polyoxometalate,” European Journal of Inorganic Chemistry (2015): 3642, 10.1002/ejic.201500389. [DOI] [Google Scholar]

[chem71437-bib-0067] 67. Guo S.‐X., MacFarlane D. R., and Zhang J., “Bioinspired Electrocatalytic CO₂ Reduction by Bovine Serum Albumin‐Capped Silver Nanoclusters Mediated by [α‐SiW₁₂O₄₀]⁴⁻ ,” ChemSusChem 9 (2016): 80, 10.1002/cssc.201501343. [DOI] [PubMed] [Google Scholar]

[chem71437-bib-0068] 68. Guo S.‐X., Li F., Chen L., MacFarlane D. R., and Zhang J., “Polyoxometalate‐Promoted Electrocatalytic CO₂ Reduction at Nanostructured Silver in Dimethylformamide,” ACS Applied Materials & Interfaces 10 (2018): 12690, 10.1021/acsami.8b01042. [DOI] [PubMed] [Google Scholar]

[chem71437-bib-0069] 69. Wang Y.‐R., Huang Q., He C.‐T., et al., “Oriented Electron Transmission in Polyoxometalate‐Metalloporphyrin Organic Framework for Highly Selective Electroreduction of CO₂ ,” Nature Communications 9 (2018): 4466, 10.1038/s41467-018-06938-z. [DOI] [PMC free article] [PubMed] [Google Scholar]

[chem71437-bib-0070] 70. Girardi M., Platzer D., Griveau S., et al., “Assessing the Electrocatalytic Properties of the {Cp*Rh^III}²⁺‐Polyoxometalate Derivative [H₂PW₁₁O₃₉{Rh^IIICp*(OH₂)}]^3– Towards CO₂ Reduction,” European Journal of Inorganic Chemistry (2019): 387, 10.1002/ejic.201800454. [DOI] [Google Scholar]

[chem71437-bib-0071] 71. Du J., Lang Z.‐L., Ma Y.‐Y., et al., “Polyoxometalate‐based Electron Transfer Modulation for Efficient Electrocatalytic Carbon Dioxide Reduction,” Chemical Science 11 (2020): 3007, 10.1039/C9SC05392A. [DOI] [PMC free article] [PubMed] [Google Scholar]

[chem71437-bib-0072] 72. Liu Y.‐J., Shao P., Gao M.‐Y., Fang W.‐H., and Zhang J., “Synthesis of Ag‐Doped Polyoxotitanium Nanoclusters for Efficient Electrocatalytic CO₂ Reduction,” Inorganic Chemistry 59 (2020): 11442, 10.1021/acs.inorgchem.0c01245. [DOI] [PubMed] [Google Scholar]

[chem71437-bib-0073] 73. Li C., Zha B., and Li J., “A SiW₁₁Mn‐Assisted Indium Electrocatalyst for Carbon Dioxide Reduction Into Formate and Acetate,” Journal of CO2 Utilisation 38 (2020): 299, 10.1016/j.jcou.2020.02.008. [DOI] [Google Scholar]

[chem71437-bib-0074] 74. Zang D., Li Q., Dai G., Zeng M., Huang Y., and Wei Y., “Interface Engineering of Mo₈/Cu Heterostructures Toward Highly Selective Electrochemical Reduction of Carbon Dioxide Into Acetate,” Applied Catalysis B 281 (2021): 119426, 10.1016/j.apcatb.2020.119426. [DOI] [Google Scholar]

[chem71437-bib-0075] 75. Yang H., Yang D., Zhou Y., and Wang X., “Polyoxometalate Interlayered Zinc–Metallophthalocyanine Molecular Layer Sandwich as Photocoupled Electrocatalytic CO₂ Reduction Catalyst,” Journal of the American Chemical Society 143 (2021): 13721, 10.1021/jacs.1c05580. [DOI] [PubMed] [Google Scholar]

[chem71437-bib-0076] 76. Ying J., Zhang B., Tian A., and Wang X., “A Series of A‐ and B‐type Anderson Compounds With Al, Te and Cr as Centers by Tuning Different Ligands: Syntheses, Electrochemical, Photocatalytic and CO₂RR Properties,” CrystEngComm 23 (2021): 2572, 10.1039/D1CE00185J. [DOI] [Google Scholar]

[chem71437-bib-0077] 77. Yu H., Ying J., Tian Y., and Tian A., “Synthesis, Structure and Properties of a Three‐Dimensional Polyoxometalate‐Based Compound Modified by Two Organic Ligands,” Inorganic Chemistry Communications 123 (2021): 108338, 10.1016/j.inoche.2020.108338. [DOI] [Google Scholar]

[chem71437-bib-0078] 78. Zhang B., Ying J., Zhang X., Wang C., and Tian A., “Electrocatalytic, Photocatalytic, Fluorescence Sensing and CO₂RR Properties of a Series of Homopolymolybdate Hybrid Coordination Polymers,” New Journal of Chemistry 45 (2021): 13340, 10.1039/D1NJ02283K. [DOI] [Google Scholar]

[chem71437-bib-0079] 79. Liu J., Wang S., Liu N., et al., “Au‐Polyoxometalates A‐B‐A‐B Type Copolymer‐Analogue Sub‐1 Nm Nanowires,” Small 17 (2021): 2006260, 10.1002/smll.202006260. [DOI] [PubMed] [Google Scholar]

[chem71437-bib-0080] 80. Sun W., Li C., and Zhao H., “The Targeted Multi‐Electrons Transfer for Acetic Acid and Ethanol Obtained With (n‐Bu₄N)₃SVW₁₁O₄₀ and in Synergetic Catalysis in CO₂ Electroreduction,” Journal of Power Sources 517 (2022): 230665, 10.1016/j.jpowsour.2021.230665. [DOI] [Google Scholar]

[chem71437-bib-0081] 81. Huang Q., Niu Q., Li X.‐F., et al., “Demystifying the Roles of Single Metal Site and Cluster in CO₂ Reduction via Light and Electric Dual‐Responsive Polyoxometalate‐Based Metal‐Organic Frameworks,” Science Advances 8 (2022): eadd5598, 10.1126/sciadv.add5598. [DOI] [PMC free article] [PubMed] [Google Scholar]

[chem71437-bib-0082] 82. Li S.‐Q., Dai L.‐F., Tian Y.‐Q., Yi Y.‐X., Yan J., and Liu C., “Polymolybdate‐Guided Assembly of a Thiacalix[4]Arene‐Protected Ag Nanocluster for Electrocatalytic CO₂ Reduction,” Chemical Communications 59 (2023): 575, 10.1039/D2CC05692E. [DOI] [PubMed] [Google Scholar]

[chem71437-bib-0083] 83. Peng M.‐T., Chen C., Zhang Y., Xu J.‐Y., Teng Y.‐L., and Dong B.‐X., “Exploring the Role of Sandwich‐Type Polyoxometalates in {K₁₀(PW₉O₃₄)₂M₄(H₂O)₂}@PCN‐222 (M = Mn, Ni, Zn) for Electroreduction of CO₂ to CO,” Dalton Transactions 52 (2023): 10737, 10.1039/D3DT01535A. [DOI] [PubMed] [Google Scholar]

[chem71437-bib-0084] 84. Sun W., Tai Y., Tian W., Zhou L., and Li C., “Electrochemical CO₂ Reduction to Ethanol: Synergism of (n‐Bu₄N)₃SVMo₁₁O₄₀ and an In Catalyst,” Electrochimica Acta 445 (2023): 142067, 10.1016/j.electacta.2023.142067. [DOI] [Google Scholar]

[chem71437-bib-0085] 85. Tubul‐Sterin T., Baranov M., Gan‐Or G., Leffler N., Neyman A., and Weinstock I. A., “Polyoxometalate‐Complexed Indium Hydroxide: Atomically Homogeneous Impregnation via Countercation Exchange,” Inorganic Chemistry 62 (2023): 1804, 10.1021/acs.inorgchem.1c03857. [DOI] [PubMed] [Google Scholar]

[chem71437-bib-0086] 86. Sun W., Yao D., Tai Y., et al., “Efficient Electrocatalytic CO₂ Reduction to Ethanol Through the Proton Coupled Electron Transfer Process of PV_nMo_(12‐n) (n = 1, 2, 3) Over Indium Electrode,” Journal of Colloid & Interface Science 650 (2023): 121, 10.1016/j.jcis.2023.06.167. [DOI] [PubMed] [Google Scholar]

[chem71437-bib-0087] 87. Sun W., Zhou L., Tian W., Li S., Yang M., and Li C., “Selective CO₂ to Proportionally Tunable Syngas at Lower Onset Potential Enabled by Bimetallic Chalcogenides in Polyoxometalate Medium,” Applied Catalysis B 356 (2024): 124206, 10.1016/j.apcatb.2024.124206. [DOI] [Google Scholar]

[chem71437-bib-0088] 88. Shu L., Li C., Peng M.‐T., Liu M.‐J., Teng Y.‐L., and Dong B.‐X., “Heterogenization of a Sandwich [(PW₉O₃₄)₂Co₄(H₂O)₂]¹⁰⁻ in PCN‐222/PCN‐222(M): Exploring the Electron Transfer for Electrocatalytic CO₂ Reduction,” European Journal of Inorganic Chemistry 27 (2024): e202400485, 10.1002/ejic.202400485. [DOI] [Google Scholar]

[chem71437-bib-0089] 89. Zhang Y., Li C., Shu L., Teng Y.‐L., and Dong B.‐X., “Research on the Construction of a Series of Transition Metal‐Substituted Keggin‐Type TMSPOMs@PCN‐224 Composites Through the Encapsulation Method and Their Electron Transfer Mechanism in CO₂RR,” Inorganic Chemistry 63 (2024): 11592, 10.1021/acs.inorgchem.4c00840. [DOI] [PubMed] [Google Scholar]

[chem71437-bib-0090] 90. Liang J.‐J., Zhang Y.‐C., Chang Z.‐H., et al., “Two New 6‐nitrobenzimidazole Ligand‐Modified Polymolybdate‐Based Metal–Organic Complexes With Excellent Capacitive and Electrocatalytic Performances,” New Journal of Chemistry 48 (2024): 1248, 10.1039/D3NJ04841A. [DOI] [Google Scholar]

[chem71437-bib-0091] 91. Tai Y., Sun W., Yao D., et al., “Keggin‐Type P‐W‐Mo‐V Polyoxometalates in Electrocatalyzed CO₂ Reduction Using Indium Electrodes,” Polyoxometalates 3 (2024): 9140051, 10.26599/POM.2023.9140051. [DOI] [Google Scholar]

[chem71437-bib-0092] 92. Zhang P., Shi W.‐X., Yin H.‐Q., et al., “W₁₀ Single‐Cluster‐Mediated Syngas Electrosynthesis in Single‐Sandwich‐Layer ZnAl‐Layered Double Hydroxide Catalysts,” ACS Nano 19 (2025): 37206, 10.1021/acsnano.5c11814. [DOI] [PubMed] [Google Scholar]

[chem71437-bib-0093] 93. Liu C., Song L., Wu W., Li H., Dang D., and Bai Y., “Photo‐coupled Electrocatalytic Conversion of CO₂ to CO Over Cobalt Phthalocyanine‐Modified POM‐K₈Ta₆O₁₉ Z‐Scheme Photocathodes,” Green Chemistry 27 (2025): 15607, 10.1039/D5GC04093K. [DOI] [Google Scholar]

[chem71437-bib-0094] 94. Sun W., Li C., Tai Y., Zhou L., Tian W., and Li S., “Selective Proton‐Coupled Electron Transfer Engineering Between Cu_xIn_y Alloy and Polyoxometalate Medium for Efficient CO₂ Electroreduction to CO,” Journal of Catalysis 450 (2025): 116254, 10.1016/j.jcat.2025.116254. [DOI] [Google Scholar]

[chem71437-bib-0095] 95. Sun W., Li C., Zhou L., Tian W., Li S., and Yang M., “Engineering the Interface Charge Redistribution and Boosted Kinetics via Polyoxometalate for Efficient Carbon Dioxide Electroreduction in Acidic Medium,” Journal of Colloid & Interface Science 697 (2025): 137912, 10.1016/j.jcis.2025.137912. [DOI] [PubMed] [Google Scholar]

[chem71437-bib-0096] 96. Xia K., Yatabe T., Yonesato K., et al., “Structural Engineering of Au─Ag Heterometallic Nanoparticles Using Multidentate Polyoxometalate Ligands,” Small 22 (2026): e14728, 10.1002/smll.202514728. [DOI] [PubMed] [Google Scholar]

PERMALINK

Countercation Manipulation Enables Selective Electrochemical CO2‐to‐Formate Conversion Over Bi‐Polyoxometalate‐Derived Catalysts

Kimitake Kawakami

Kentaro Yonesato

Shimon Akino

Soichi Kikkawa

Seiji Yamazoe

Takuma Kaneko

Tomoya Uruga

Fumiaki Amano

Yoshiaki Honjo

Takaki Hatsui

Koji Harano

Kazuya Yamaguchi

Kosuke Suzuki

ABSTRACT

1. Introduction

TABLE 1.

FIGURE 1.

2. Results and Discussion

2.1. Preparation and Characterization of the Catalysts

FIGURE 2.

2.2. CO2RR Study

FIGURE 3.

2.3. Characterization of a Ba‐Bi4/C‐Loaded Electrode After CO2RR

FIGURE 4.

FIGURE 5.

2.4. Effect of Countercations on CO2RR Performance

2.5. Effect of Catalyst Structure on CO2RR Performance

3. Conclusion

Funding

Conflicts of Interest

Supporting information

Acknowledgments

Data Availability Statement

References

Associated Data

Supplementary Materials

Data Availability Statement

ACTIONS

PERMALINK

RESOURCES

Similar articles

Cited by other articles

Links to NCBI Databases

Countercation Manipulation Enables Selective Electrochemical CO₂‐to‐Formate Conversion Over Bi‐Polyoxometalate‐Derived Catalysts

2.2. CO₂RR Study

2.3. Characterization of a Ba‐Bi4/C‐Loaded Electrode After CO₂RR

2.4. Effect of Countercations on CO₂RR Performance

2.5. Effect of Catalyst Structure on CO₂RR Performance