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. 2026 Mar 29;19(7):e202600014. doi: 10.1002/cssc.202600014

Insight Into the Porphyrin‐Modulated Interfacial Charge Transfer Kinetics Behavior of Molybdenum Disulfide Nanostructures by Scanning Photoelectrochemical Microscopy

Ze Wang 1, Tingchuan Li 1, Xingming Ning 1, Kunlin Hai 1, Shengya Zhang 1, Tingjun Zhang 1, Hui Xiao 1, Yanjun Feng 1, Jing Chen 1, Xiaoquan Lu 1,✉
PMCID: PMC13449621  PMID: 41904959

Abstract

Hydrogen generation through electrocatalytic water decomposition using semiconductor electrocatalysts is considered a promising approach, which is expected to replace fossil fuel. Transition metal dichalcogenides, especially MoS2‐based catalysts, have been considered as the state‐of‐the‐art hydrogen evolution reaction electrocatalysts due to favorable catalytic activity. However, obtaining metastable phase MoS2 nanomaterials with high purity remains a great challenge. Additionally, since most of the generally prepared MoS2 is a mixed phase, it often fails to exhibit any type of superior catalytic performance. Herein, 5, 10, 15, 20‐Tetrakis (4‐hydroxyphenyl) porphyrin (THPP) was used as an electron donor to modify semiconducting phase 2H–MoS2. After the modification, the catalytic properties of 2H–MoS2 are shifted toward those of metallic phase 1T–MoS2. We investigated charge transfer kinetic behavior from a microscopic point of view with the help of in situ scanning photoelectrochemical microscopy (SPECM). It is found that 2H–MoS2/NiS2/THPP exhibits significantly higher charge transfer rate constant of 0.35 × 10−2 cm s−1, which is more than three times that of 2H–MoS2/NiS2. The enhanced charge transfer kinetics is attributed to the introduction of the porphyrin acting as a charge transporting mediator, which accelerates rapid charge transfer, thereby inhibiting charge carrier recombination and enhancing charge separation.

Keywords: charge transfer, microinterface, porphyrin, rate constant, scanning photoelectrochemical microscopy

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1. Introduction

Hydrogen (H2) is considered as a promising alternative to fossil fuels. 2D nanomaterials have demonstrated efficient electrocatalytic capabilities to promote the hydrogen evolution reaction (HER). In particular, phase engineering of 2D nanomaterials opens up a new research field to impart 2D nanostructures with superior properties for intensive application in catalyzing HER [1, 2, 3]. Transition metal dichalcogenides (TMDCs) have engaged extensive research attention due to their 2D stacked molecular structures and their chemical and physical properties. Among the various TMDCs materials, 2H‐phase single‐crystal molybdenum disulfide (MoS2) nanosheets form basic unit of multifarious bulk MoS2 and crystalline MoS2 nanostructures, which show excellent catalytic activities with edge sites and planar sulfur vacancies, e.g., sites with very low Gibbs free energies for hydrogen adsorption (analogous to those of the most efficient Pt as well as other noble metals) [4, 5]. Controlling the phase structures of catalysts is of considerable significance for electrochemical applications. Especially in electrocatalysis, the binding state of catalysts with different phases directly affects their catalytic activity [6]. The introduction of interacting substances or the application of mechanical strain could induce phase transformation due to structural distortions and different filling of the Mo–d bands. Thus, different arrangements of atoms in MoS2 lead to different electronic structures, which influence the electrocatalytic properties [7, 8, 9]. Therefore, phase engineering has been recognized as an excellent and effective strategy for tuning the intrinsic chemical property of nanomaterials and achieving precise preparation of efficient electrocatalysts. The very interesting structures and properties resulting from phase engineering of 2D nanomaterials open up new space for electrochemical HER applications [10, 11, 12].

The dye sensitization is referred to as a promising approach to improve the photoresponse property of semiconductors. Among these common dyes, including erythrosine B, rose Bengal and prophyrin, the porphyrin is used for the remarkable coefficient material to embellish the semiconductors as a result of good chemical stability as well as visible‐light response compared to other dyes [13, 14]. In the field of photoelectrocatalysis, most porphyrins are commonly used as photosensitizer or building blocks of metal‐organic frameworks and covalent organic frameworks [15, 16, 17], while their potential as catalysts for constructing interfacial electric fields at the interface remains relatively unexplored. Among various nonprecious metal‐based catalysts, porphyrin has attracted widespread attention as low‐cost electrocatalysts for HER. Porphyrins have π‐conjugated aromatic macrocycles and thus can coordinate a variety of metal ions, while having high extinction coefficients in visible light range of electromagnetic spectrum. During the HER process, H2O can bind to the center of the porphyrin axially vacant coordination site. Then, H2O is reduced to H2 after accepting electrons on the MoS2 conduction band. Grafting porphyrin catalysts onto suitable carriers, such as 2D nanomaterials MoS2, is a promising tactic to enhance the electronic conductivity and stability of the catalysts and to prevent them from degradation and aggregation during the HER process [18, 19, 20]. Porphyrin loading may lead to distortion of the MoS2 crystals, which adjusts the electronic structure, further improves the electrical conductivity, and generates a large number of active sites, which likewise effectively reduces the H‐binding free energy of HER. Therefore, the loading of porphyrin catalysts will effectively improve the HER electrocatalytic activity of MoS2 [21, 22]. The substantial increase in the HER catalytic activity may be due to the combined effect of generation of new active sites through porphyrin doping and the 2H‐to‐1T phase transformation. Based on this idea, we rationally design loaded porphyrins as synergistic catalysts, which leads to the tuning of the electronic structure and the generation of a large number of active sites.

Inspired by the above motivation, we designed a state‐of‐the‐art MoS2‐based HER catalyst. In stark contrast, the 2H–MoS2/NiS2/THPP heterostructure exhibits exceptional HER activity, comparable to that of the 1T–MoS2/NiS2 catalyst. The THPP modification significantly reduces charge transfer resistance, simultaneously passivating surface defects in 2H–MoS2/NiS2 and optimizing interfacial charge transfer kinetics. The intensity‐modulated photocurrent spectroscopy (IMPS) measurement further shows that the porphyrin effectively promotes the charge transfer in the catalytic system as compared to the porphyrin‐free 2H–MoS2/NiS2. In addition, local charge transfer dynamics of different electrodes under light illumination were also investigated in situ using scanning photoelectrochemical microscopy (SPECM). 2H–MoS2/NiS2/THPP shows the higher charge transfer rate constants, which further demonstrates the stepped‐up charge transfer behavior of the porphyrin charge transfer mediator. Meanwhile, the catalytic properties of the semiconducting phase 2H–MoS2/NiS2 shift toward those of the metallic phase 1T–MoS2 after electron doping. More importantly, this study provides an effective method for the development of efficient and excellent MoS2‐based HER catalysts.

2. Results and Discussion

The crystalline structure of the materials was determined by X‐ray diffraction (XRD) analysis, and the XRD image of the Ni(OH)2‐x –[Mo7O24 6‐] x/6 (Figure S1) clearly shows peaks consistent with Ni(OH)2. On the other hand, whether the Mo7O24 6‐ anion in the precursor was successfully intercalated or not was further verified by Fourier transform infrared (FT‐IR) spectroscopy (Figure S2). As shown, the FT‐IR spectra of Ni(OH)2‐x –[Mo7O24 6‐] x/6 show significant peaks of Mo7O24 6‐ ions at 696, 868 cm−1 as well as peaks of MoO4 2‐ ions at 813 cm−1 which are relatively weak. The FT‐IR spectral data further corroborate the successful insertion of Mo7O24 6‐ into the Ni(OH)2 interlayer. Afterward, 1T–MoS2/NiS2 was obtained by sulfidation of the previously obtained precursor. As shown in Figure S1, the XRD results of the material obtained after the sulfidation of the precursor show that the material possesses NiS2 and MoS2 phases, and both phases are less crystalline. In addition, the (002) crystal plane of MoS2 is significantly broadened, representing the presence of MoS2 in the form of thin layers with relatively large interlayer spacing. In order to further determine the structure and composition of the samples, morphological characterization was carried out. Figure 1a,b, and c shows scanning electron microscopy (SEM) images of the synthesized materials. Specifically, Figure 1a shows the morphology of the precursor Ni(OH)2‐x –[Mo7O24 6‐] x/6. In order to realize the transformation of the material phases, the synthesized 1T–MoS2/NiS2 was allowed to anneal in an argon atmosphere at 300°C for 3 h. As a result, the 1T–MoS2/NiS2 was successfully transformed into 2H–MoS2/NiS2. 1T–MoS2/NiS2 nanosheets and 2H–MoS2/NiS2 nanosheets are shown in Figure 1b and c, respectively. Similar to the 1T–MoS2/NiS2 flakes, the 2H–MoS2/NiS2 nanosheets exhibit a good nanoflower‐like structure with a tendency to form aggregated bundles.

FIGURE 1.

FIGURE 1

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SEM of (a) Ni(OH)2‐x –[Mo7O24 6‐] x/6, (b) 1T–MoS2/NiS2, (c) 2H–MoS2/NiS2. (d) TEM and (e) HRTEM of 2H–MoS2/NiS2/THPP. (f) Elemental mapping of the 2H–MoS2/NiS2/THPP. HRTEM = High‐resolution transmission electron microscopy; SEM = scanning electron microscopy; TEM = transmission electron microscopy.

Figure 1d shows a flake‐like morphology of the synthesized material 2H–MoS2/NiS2/THPP in the transmission electron microscopy (TEM) image. High‐resolution transmission electron microscopy (HRTEM) demonstrates clearly the (002) and (211) lattice facets of the 2H–MoS2 and NiS2 (Figure 1e), which is in accordance with the XRD results. In addition, Figure 1f shows the energy‐dispersive X‐ray spectra of the 2H–MoS2/NiS2/THPP composites, which reveals the uniform distribution of the elements of S, Ni, O, N, and Mo, indicating a relatively homogeneous and sufficient Mo7O24 6‐ intercalation in the precursor and a relatively complete sulfidation of the precursor. Meanwhile, THPP (Figure S3) was uniformly loaded on the surface of 2H–MoS2/NiS2, which also indicates the successful preparation of 2H–MoS2/NiS2/THPP composites.

X‐ray photoelectron spectroscopy (XPS) analyses were carried out to further investigate the chemical composition of 2H–MoS2/NiS2/THPP. As shown in Figure 2a, the full‐scale XPS spectrum of 2H–MoS2/NiS2/THPP confirms the presence of Ni, N, O, S, and Mo as the dominant elements. As shown in Figure 2b, the two prominent peaks at 232.9 and 235.6 eV correspond to Mo 3d5/2 and Mo 3d3/2, respectively. The S 2p spectrum (Figure 2c) displays two doublets at binding energies of 162.4 eV (2p3/2) and 163.3 eV (2p1/2), which are assigned to 2H–MoS2. The binding energies at 856.6 eV (Ni 2p3/2) and 874.1 eV (Ni 2p1/2) in Figure 2d confirm the presence of Ni. At 531.2 eV in the O 1s spectrum (Figure 2e), the peak can be attributed to oxygen species chemisorbed at the metal surface. This indicates that an interaction may exist between THPP and 2H–MoS2/NiS2. Deconvolution of the heterojunction's N 1s spectrum yields three peaks (Figure 2f) at binding energies of 397.5 eV (sp2‐bonded nitrogen), 399.9 eV (tertiary nitrogen), and 402.6 eV (amino groups). These results demonstrate the successful synthesis of 2H–MoS2/NiS2/THPP heterojunctions featuring robust interfacial bonding. Furthermore, Raman spectroscopy was employed to confirm the crystalline phase of MoS2 (Figure S4). It exhibits peaks at 148, 237, and 336 cm−1, which perfectly match the J1, J2, and J3 peaks characteristic of 1T–MoS2.

FIGURE 2.

FIGURE 2

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XPS of (a) survey spectrum, (b) Mo 3d, (c) S 2p, (d) Ni 2p, (e) O 1s, and (f) N 1s of the 2H–MoS2/NiS2/THPP. XPS = X‐ray photoelectron spectroscopy.

To evaluate the HER catalytic activity of MoS2, electrocatalytic performance was measured for 2H–MoS2/NiS2 and 1T–MoS2/NiS2 by using a standard three‐electrode system in 1.0 M KOH. All polarization curves were IR corrected. Linear sweep voltammetry revealed a high overpotential of 241 mV versus RHE for 2H–MoS2/NiS2 at 10 mA cm−2. Notably, 1T–MoS2/NiS2 demonstrated significantly enhanced HER activity with an overpotential of 118 mV versus RHE at 10 mA cm−2 (Figure 3a). To elucidate the HER mechanism, Tafel plots were analyzed (Figure 3b). The 1T–MoS2/NiS2 heterostructure catalyst exhibits a low Tafel slope of 73 mV dec−1, suggesting a Volmer–Heyrovsky pathway with electrochemical hydrogen desorption as the rate‐determining step. In contrast, the 2H–MoS2/NiS2 displays significantly higher Tafel slopes of 82 mV dec−1. The UV–visible diffuse reflectance spectra (Figure S5) show that the 1T–MoS2/NiS2 and 2H–MoS2/NiS2 nanosheets have a negligible effect on the light trapping, implying that the enhanced catalytic performance is mainly attributed to the charge transfer. Electrochemical impedance spectroscopy (EIS) measurements (Figure S9) were conducted and analyzed using equivalent circuit modeling to elucidate the interfacial charge transfer dynamics. The Nyquist plots (Figure 3c) reveal a significant reduction in the arc radius for the 1T–MoS2/NiS2 compared to 2H–MoS2/NiS2, indicating lower charge transfer resistance. This demonstrates their superior electrical conductivity and enhanced interfacial charge transport efficiency, which is consistent with cyclic voltammetry (CV) results (Figure S6). The charge carrier lifetime extension effect of 1T–MoS2/NiS2 was further confirmed by time‐resolved photoluminescence measurements (Figure 3d and Table S1). The 1T–MoS2/NiS2 composite exhibits an extended charge lifetime of 3.58 ns, which enhances the probability of charge carriers participating in catalytic reactions. This improvement is attributed to more efficient charge separation and migration.

FIGURE 3.

FIGURE 3

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(a) Polarization curves, (b) Tafel plots, (c) EIS, and (d) time‐resolved transient photoluminescence of 2H–MoS2/NiS2 and 1T–MoS2/NiS2. EIS = Electrochemical impedance spectroscopy.

We propose employing SPECM for direct detection of photogenerated charge carriers and real‐time monitoring of their transfer kinetics behavior near MoS2‐based photoelectrodes. As an established scanning probe technique (Figure S10), SPECM utilizes a precisely positioned microelectrode tip to perform localized electrochemical characterization through controlled surface scanning or approach measurements (Figures S11 and S12). This method has proven to be particularly valuable for investigating heterogeneous charge transfer processes [23, 24, 25, 26]. Figure 4a shows the probe approach curves (PACs) for various photoelectrodes (1T–MoS2/NiS2 and 2H–MoS2/NiS2) under the illumination and dark conditions. Illumination induces positive feedback behavior, characterized by increasing probe current near the substrate, while negative feedback (decreasing current) occurs in the dark. Fitting the data to a theoretical model reveals kinetic rate constants (K eff; Figure 4b) [27, 28, 29], with the 1T–MoS2/NiS2 substrate showing the higher K eff (0.56 × 10−2 cm s−1)—5.1‐fold greater than 2H–MoS2/NiS2 (Table 1). These results consistently indicate that the 1T–MoS2 markedly enhances interfacial charge transfer between 1T–MoS2 and NiS2, while simultaneously promoting the spatial separation of photogenerated charges.

FIGURE 4.

FIGURE 4

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(a) PACs of different materials under the dark and light condition, (b) charge transfer rate constant (K eff) of materials, (c) IMPS responses, and (d) transit times of different materials. PACs = Probe approach curves.

TABLE 1.

Charge transfer rate constants (K eff) of different samples.

Sample 1T–MoS2/NiS2 2H–MoS2/NiS2
K eff (10−2·cm s−1) 0.56 0.11
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The IMPS was employed to examine charge transport properties [30, 31, 32, 33]. Using the methodology established by Peter et al., we systematically investigated how charge transport molecules and semiconductors influence interface‐charge modulation in operational photoelectrochemical (PEC) systems. Comparative IMPS analysis of various integrated electrodes enables evaluation of charge recombination (K rec) and transfer (K trans) kinetics at the MoS2/electrolyte interface [34, 35]. The typical IMPS response of each material is shown in Figure 4c. The larger semicircle radii observed for 1T–MoS2/NiS2 compared to 2H–MoS2/NiS2 electrodes demonstrate that 1T–MoS2 effectively suppresses charge recombination. Consistent with previous work, the transient duration (τ d) for each photoelectrode was calculated using τ d = (2π f min)−1 [36, 37], where f min represents the minimum frequency at the low point (Figure 4c). Figure 4d shows a distinct decrease in τ d (2H–MoS2/NiS2 > 1T–MoS2/NiS2), demonstrating that the incorporation of 1T–MoS2/NiS2 leads to enhanced charge transfer dynamics.

Polarization curves of 2H–MoS2/NiS2/THPP heterostructure and reference catalyst (2H–MoS2/NiS2) were acquired in 1.0 M KOH electrolyte (Figure 5a). The 2H–MoS2/NiS2 exhibits inert HER activity in alkaline media, likely owing to insufficient active sites. In stark contrast, the 2H–MoS2/NiS2/THPP heterostructure demonstrates exceptional HER performance, requiring only 160 mV overpotential to achieve 10 mA cm−2. This activity approaches that of the 1T–MoS2/NiS2 catalyst. Furthermore, THPP layer modification lowers the charge transfer resistance (Figure 5b), demonstrating its ability to both passivate 2H–MoS2/NiS2 surface defects and optimize charge transfer kinetics at the interface. However, THPP incorporation significantly increases the PL lifetime (Figure S7 and Table S1), demonstrating its crucial role in facilitating efficient charge transfer from 2H–MoS2/NiS2 to the catalyst surface. Subsequent incorporation of THPP molecule further increases the semicircle size compared to 2H–MoS2/NiS2(Figure 5c), indicating substantially enhanced charge transfer kinetics and more effective recombination inhibition. As shown in Figure 5d and Table S2, the τ d values for the 2H–MoS2/NiS2/THPP and 2H–MoS2/NiS2 are determined to be 1.10 and 1.32 ms, respectively. The significantly lower (83%) τ d value observed for 2H–MoS2/NiS2/THPP suggests more quick charge transport rate. The observed positive feedback suggests efficient charge transfer from 2H–MoS2 to THPP through their interface (Figure 5e,f and Table S3), consistent with EIS results (Figure 5b). This demonstrates THPP's role in interfacial activation and kinetic enhancement at the 2H–MoS2/NiS2/THPP junction.

FIGURE 5.

FIGURE 5

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(a) Polarization curves. (b) EIS. (c) IMPS responses. (d) Transit time of different materials. (e) PACs and (f) Rate constant (K eff). EIS = Electrochemical impedance spectroscopy; IMPS = intensity‐modulated photocurrent spectroscopy; PACs = probe approach curves.

To further validate the above conclusion, localized PEC behavior was characterized using SPECM. Figure S8a and Figure S8b show photocurrent mapping of the 2H–MoS2/NiS2/THPP photoelectrode under dark and illuminated conditions, respectively. The measured photocurrents during illumination (4.6–4.8 nA) significantly exceed those in darkness (2.0–2.7 nA), indicating enhanced utilization of photogenerated charges for surface catalytic reactions at constant height. This observation aligns with the PAC curve analysis, confirming consistent charge transfer behavior.

In addition to outstanding catalytic performance, the 2H–MoS2/NiS2/THPP photoelectrode exhibits remarkable stability over extended testing periods. The catalytic stability of the 2H–MoS2/NiS2/THPP photoelectrode was evaluated via SPECM imaging under visible light irradiation (Figure 6) [38, 39, 40]. In constant‐height mode, two SPECM images were acquired by fine‐scale scanning of the 2H–MoS2/NiS2/THPP film. After 3 h of continuous illumination, the photocurrent response exhibits negligible change, demonstrating exceptional photoelectric stability. This enhanced photostability originates from robust adsorption and efficient interfacial charge transfer between the 2H–MoS2 substrate and the THPP molecule.

FIGURE 6.

FIGURE 6

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Stability test results of 2H–MoS2/NiS2/THPP using SPECM map (100 × 100 μm). SPECM = Scanning photoelectrochemical microscopy.

We aim to gain deeper insight into the relationship between the aforementioned properties and molecular structure. We employed density functional theory to calculate the lowest unoccupied molecular orbital, highest occupied molecular orbital, and energy gap (ΔE) of porphyrin molecules. As shown in Figure 7a, the energy gaps of the two porphyrin molecules exhibit no significant difference. However, to further investigate the charge distribution characteristics, we conducted an additional analysis of the material's electrostatic potential (ESP). As shown in Figure 7b, compared to TCPP, THPP exhibits significantly enhanced electrostatic potential regions. This heightened potential more effectively attracts and stabilizes charges, thereby establishing a directional charge transport pathway at the interface. Consequently, the higher electrostatic potential of THPP optimizes charge migration pathways at the interface, effectively suppressing nonradiative recombination processes and promoting efficient charge separation and transfer.

FIGURE 7.

FIGURE 7

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(a) Frontier molecular orbitals and energy gap of TCPP and THPP. (b) The ESP distribution maps of TCPP and THPP. ESP = Electrostatic potential.

3. Conclusion

In conclusion, we have investigated the mechanism of porphyrin‐modified MoS2 and the charge transfer kinetics from a microinterfacial point of view, using the MoS2 system as a prototype. Through in situ SPECM, IMPS and conventional electrochemical measurements show that the improved catalytic performance mainly stems from faster charge transfer kinetics. In particular, the charge transfer kinetics rate constant of 0.35 × 10−2 cm s−1 for 2H–MoS2/NiS2/THPP is 3.2 times higher than that of 2H–MoS2/NiS2 (0.11 × 10−2 cm s−1) in the designed doping system. As expected, the 2H–MoS2/NiS2/THPP obtained after electron doping possesses catalytic properties comparable to those of the metallic phase 1T–MoS2, along with excellent stability. These findings not only offer new insights into the mechanism of charge transfer, but also guide the design of efficient MoS2‐based HER catalysts for electrocatalytic water decomposition.

4. Experimental Section

4.1. Preparation of Ni(OH)2‐x –[Mo7O24] x/6, 1T–MoS2/NiS2, and 2H–MoS2/NiS2 Materials

Ni(OH)2‐x –[Mo7O24] x/6 was synthesized via a modified hydrothermal method based on literature procedures [41]. Typically, 4 mL of aqueous Ni(NO3)2 · 6H2O (0.5 M), 12 mL of hexamethylenetetramine (HMT, 1.0 M), 4 mL of (NH4)6Mo7O24·4H2O (0.1 M), and 4 mL of trisodium citrate dihydrate (0.2 M) were combined in 100 mL of Milli‐Q water. The mixture was magnetically stirred (600 rpm) in a glass beaker for 10 min to achieve homogeneity, then transferred to a 200 mL Teflon‐lined autoclave. The sealed reactor was heated to 120°C and maintained for 24 h. After cooling to room temperature, the product was collected by centrifugation (10,000 rpm, 10 min), washed sequentially with deionized (DI) water and ethanol (6 cycles), and vacuum‐dried at ambient temperature for 12 h. 1T–MoS2/NiS2 was synthesized via hydrothermal treatment. Typically, 0.1 g of Ni(OH)2‐x –[Mo7O24] x/6 precursor, 2.2 g thioacetamide (TAA), and 35 mL DI water were combined in a glass beaker. The mixture was vigorously stirred for 30 min, followed by 10 min ultrasonication. The resulting suspension was transferred to a 50 mL Teflon‐lined stainless steel autoclave, sealed, and heated to 220°C for 24 h. After cooling to room temperature, the product was collected by centrifugation (10,000 rpm, 10 min), washed alternately with DI water and absolute ethanol (six cycles each), and vacuum‐dried at ambient temperature overnight. The 1T–MoS2/NiS2 samples obtained from the above preparation were laid flat in a 3 × 1 cm porcelain boat, which was placed under the thermocouple in the tube furnace, and heat‐treated with Ar gas (100 sccm). The temperature was raised to 300°C at a rate of 5°C/min and held at 300°C for 3 h and then cooled down to room temperature with the furnace to obtain the 2H–MoS2/NiS2 complexes.

4.2. Preparation of 2H–MoS2/NiS2/THPP Photoelectrode

The 2H–MoS2/NiS2/THPP photoelectrode was fabricated using spin coating. 0.2 mL of 0.05 mM THPP ethanol solution was deposited onto the 2H–MoS2/NiS2 substrate, followed by calcination in a muffle furnace at 100°C for 60 min.

4.3. Photoelectrochemical Measurements

PEC performance of the all MoS2‐based photoelectrodes was conducted utilizing an electrochemical workstation (AUTOLAB, Switzerland, Metrohm) using a typical three‐electrode cell configuration in 0.2 M of Na2SO4 with a scan rate of 50 mV s−1, MoS2‐based photoelectrodes (1.0 × 1.0 cm) served as the working electrode, a platinum as the auxiliary electrode, and a Ag/AgCl/saturated KCl electrode as the reference electrode. AM 1.5G (light intensity 100 mW/cm2) solar simulator (300 W Xenon arc lamp, Beijing Perfectlight Technology Co. Ltd., PLS‐SXE300+) was used as the visible light source. The lamp was 20 cm away from the MoS2‐based photoelectrode. The applied potential versus Ag/AgCl was converted to the RHE scale by using Equation: E (RHE) = E (Ag/AgCl) + 0.197 + 0.0591pH. The EIS (10 KHz–0.05 Hz) was carried out by applying an additional alternating voltage of 10 mV in 0.2 M Na2SO4 at open‐circuit potential.

4.4. Scanning Photoelectrochemical Microscopy Measurements

The classical feedback mode has been diffusely used to explore charge transfer kinetics, the current I T = i T /i T,∞ is plotted against the distance L = d/a, where i T is the real‐time current during the probe approaching to the substrate MoS2‐based photoelectrodes, and i T,∞ is a steady‐state current reached when the tip is far from the substrate MoS2‐based photoelectrode. However, d is the real‐time distance between tip and substrate MoS2‐based photoelectrode, and a is probe radius. For a defined photoelectrode, the charge transfer kinetics rate constant (K eff) can be calculated from a experimental simulation by our previous works. Typically, a four‐electrode cell was used in SPECM measurements, using the SPECM tip with 25 µm diameter (RG ≈ 3, RG is the ratio of the overall electrode radius over the platinum disk radius) as working electrode 1, a platinum wire as an auxiliary electrode, an Ag/AgCl as the reference electrode, and substrate film electrode sample was regarded as working electrode 2, respectively. An AM 1.5 G filter (100 mW/cm2, 300W Xenon lamp) was used as the light source, with a wavelength range spanning from 200 to 1200 nm. 1 mM K3Fe(CN)6 in 100 mM KCl was used as probe molecule to study the PEC properties. The mappings were obtained according to the above method in constant height mode in a small scale (100 × 100 μm).

Author Contributions

Ze Wang: conceptualization (lead), data curation (lead), methodology (lead), software (lead), writing – original draft (lead). Tingchuan Li: investigation (equal), software (equal). Xingming Ning: conceptualization (equal), investigation (equal). Kunlin Hai: data curation (equal), software (equal). Shengya Zhang: data curation (lead), validation (equal). Tingjun Zhang: data curation (equal), investigation (equal). Hui Xiao: software (equal), validation (equal). Yanjun Feng: data curation (equal), formal analysis (equal). Jing Chen: software (equal), visualization (equal). Xiaoquan Lu: conceptualization (lead), funding acquisition (lead), project administration (lead), supervision (lead), writing – review & editing (lead).

Supporting Information

Additional supporting information can be found online in the Supporting Information section. Supporting Fig. S1: XRD of different samples. Supporting Fig. S2: FT‐IR spectra of different samples. Supporting Fig. S3: UV–Vis absorption spectra for THPP. Supporting Fig. S4: Raman spectra of 2H–MoS2/NiS2/THPP. Supporting Fig. S5: UV–visible diffuse reflectance spectroscopy of 1T–MoS2/NiS2 and 2H–MoS2/NiS2. Supporting Fig. S6: The CV curves of 1T–MoS2/NiS2 and 2H–MoS2/NiS2. Supporting Fig. S7: Time‐resolved transient photoluminescence of different samples. Supporting Fig. S8: SPECM mapping of 2H–MoS2/NiS2/THPP film in the (a) dark and (b) light. Supporting Fig. S9: The scheme of the PEC setup. Supporting Fig. S10: The diagram of the SPECM experimental setup. Supporting Fig. S11: The image of ultramicroelectrode (UME) (RG ≈ 3). Supporting Fig. S12: CVs of UME measured in 1.0 mM K3Fe(CN)6 containing 0.1 M KCl with a scan rate of 10 mV s−1. Supporting Table S1: The average fluorescence lifetimes of 2H–MoS2/NiS2, 2H–MoS2/NiS2/THPP and 1T‐MoS2/NiS2. Supporting Table S2: Transit times (t d) of different samples. Supporting Table S3: Kinetic rate constants (K eff) of different film samples.

Funding

This study was supported by National Natural Science Foundation of China (22127803, 22174110, 22374121), Key Program of Natural Science Foundation of Gansu Province (24JRRA779), Gansu Provincial Innovation Group Project (26JRRA002), Major Cultivation Project of University Scientific Research Innovation Platform in Gansu Province (2024CXPT‐05), Joint Funds of the National Natural Science Foundation of China (U25A20579).

Conflicts of Interest

The authors declare no conflicts of interest.

Supporting information

Supplementary Material

CSSC-19-e202600014-s001.pdf (1.1MB, pdf)

Acknowledgments

This work was supported by the National Natural Science Foundation of China (grant no. 22127803, 22174110, 22374121), the Joint Funds of the National Natural Science Foundation of China (U25A20579), the Key Program of Natural Science Foundation of Gansu Province (24JRRA779), Gansu Provincial Innovation Group Project (26JRRA002) and the Major Cultivation Project of University Scientific Research Innovation Platform in Gansu Province (grant no. 2024CXPT‐05). This research was also supported by the Engineering Laboratory of Electrochemical Technology and Nanodevice of Gansu Province.

Data Availability Statement

The data that support the findings of this study are available from the corresponding author upon reasonable request.

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Associated Data

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

Supplementary Materials

Supplementary Material

CSSC-19-e202600014-s001.pdf (1.1MB, pdf)

Data Availability Statement

The data that support the findings of this study are available from the corresponding author upon reasonable request.

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