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. 2026 Jul 8;12(28):eaec8053. doi: 10.1126/sciadv.aec8053

Disordered vacancy-isolated Ce-Gd-O clusters achieve exceptional low-temperature oxygen-ion conductivity for fuel cells

Shengli Pang 1,2,*,†, Xudong He 1,†, Hao Lou 1, Kaijie Xu 1,3, Jintong Guan 1, Yi Zhuang 1, Xuyao Luo 1, Lianxu Xu 1, Qiangsheng Xiao 1, Yifei Gao 1, Peijie Zhang 1, Juan Yang 1,*, Yi Li 1, Chonglin Chen 2,4,*
PMCID: PMC13344376  PMID: 42418578

Abstract

Oxygen-ion conductors are central to clean energy technologies. Conventional long-range–ordered oxide-ion conductors require high operating temperatures, which increase cost and limit durability; overcoming the low temperature conductivity gap is a long-standing challenge. We created cerium (Ce)–gadolinium (Gd)–oxygen (O) clusters by thermal-shock exfoliation of fluorite Gd0.1Ce0.9O1.95 and examined their structure and ion transport. These disordered, vacancy-isolated clusters form percolative oxygen-ion pathways without long-range order, delivering exceptional conductivity of 2.14 ± 0.09 siemens per centimeter at 400°C—more than 320-fold higher than most previously reported oxide-ion conductors under comparable conditions. Used as a 0.5 weight % cathode additive in solid oxide fuel cells, they tripled the peak power density to 2.87 ± 0.04 watts per square centimeter at 750°C compared with the pristine Pr0.5Ba0.25Ca0.25CoO3–δ/Gd0.1Ce0.9O1.95 cathode and reversed degradation from −13.2 to +3.4% per 100 hours. These findings overturn the paradigm that high oxygen-ion conductivity requires long-range order and highlight Ce-Gd-O clusters as enablers for advanced energy technologies.

Oxygen ions move fast in oxide clusters at low temperatures, overturning conventional views and enabling energy device innovation.

INTRODUCTION

Ion transport underpins the operation of diverse electrochemical energy systems and catalytic processes. Lithium-ion conduction in liquid (1), gel-type (2), and solid (3) electrolytes drives the development of conventional, flexible, and all-solid–state lithium-ion batteries. Proton transport in perfluorosulfonic acid polymers (4) and ceramic oxides (5, 6) enables proton-exchange membrane fuel cells and protonic ceramic electrochemical cells. Oxide-ion conduction in solid oxides, first exploited in the mid-20th century, supports critical technologies such as solid oxide cells (SOCs) (7, 8), catalytic reactors (9, 10), oxygen separation membranes (11), and gas sensors (12). Among these, SOCs epitomize the transformative role of oxide-ion conductors, which function both as electrolytes for rapid ion transport and as electrode components that integrate ionic conduction with catalytic activity. This multifunctionality allows SOCs to deliver dispatchable power from renewable fuels and to produce value-added chemicals using green electricity, establishing them as a cornerstone of sustainable energy infrastructure.

Despite these advances, the intrinsically low oxide-ion conductivity of crystalline oxides remains a fundamental barrier. Existing materials rarely reach ≥0.01 S cm−1 below 400°C (13). Conventional understanding attributes efficient conduction to long-range–ordered crystalline frameworks, such as fluorite and perovskite derivatives, which provide well-defined diffusion pathways and maintain stable oxygen vacancy concentrations (8, 13–19). Decades of structural tailoring have improved conductivity, yet no crystalline oxide has met the target at low temperatures. This persistent gap severely limits the deployment of oxide-ion conductors in portable and intermediate-temperature energy systems.

Nanostructuring offers a pathway to transcend these limits by tailoring defect configurations and migration pathways at the atomic scale (20–22). Interfaces, lattice distortions, and spatial confinement at the nanoscale can enhance vacancy concentrations and reduce migration barriers. Within this context, discrete metal oxide clusters—comprising only tens to hundreds of atoms—emerge as an unexplored class of ionic conductors. In this study, we synthesized structurally distinct Ce-Gd-O clusters through thermal-shock exfoliation of fluorite Gd0.1Ce0.9O1.95 (GDC). These clusters exhibit disordered, vacancy-isolated structures that support percolative transport without long-range order. As a result, they achieve an unprecedented oxide-ion conductivity of 2.14 ± 0.09 S cm−2 at 400°C, surpassing the critical application threshold by more than two orders of magnitude. This discovery establishes oxide nanoclusters as a platform for low-temperature ion transport and challenges the long-standing belief that high conductivity requires crystalline order.

RESULTS

Thermal-shock strain fragments fluorite GDC into Ce-Gd-O clusters

GDC is a benchmark oxide-ion conductor and serves as the parent phase for synthesizing Ce-Gd-O clusters. We engineered localized, high-magnitude lattice strain to detach targeted metal-oxygen units from the GDC framework and thereby fragment the fluorite lattice. To do so, we developed a scalable, contamination-free thermal-shock exfoliation that imposes abrupt thermal gradients across GDC (Fig. 1A). The thermal shock generates transient strain fields by exploiting differential thermal expansion between atomic planes held at distinct temperatures. Two intrinsic properties govern the microstructural response—thermal conductivity and fracture toughness. As benchmarks, metals combine high thermal conductivity and toughness, enabling millimeter-scale heat dissipation and dislocation-mediated stress relaxation (23). By contrast, Pr0.5Ba0.25Ca0.25CoO3–δ (PBCC), a representative oxide with compromised thermomechanical properties, develops nanoscale surface disorder, dislocations, and point defects under similar conditions (24). GDC exhibits a fracture toughness nearly 60% lower than that of PBCC together with ultralow thermal conductivity (figs. S1 and S2). These attributes confine thermal-shock effects to the outermost layer, establish steep thermal gradients, and concentrate lattice strain locally.

Fig. 1. Thermal-shock exfoliation fragments GDC into Ce-Gd-O clusters.

Fig. 1.

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(A) Schematic of GDC fragmentation during rapid quenching, highlighting strain-induced detachment of clusters. NPs, nanoparticles. (B) High-resolution transmission electron microscopy (TEM) of pristine GDC fluorite lattice [inset: fast Fourier transform (FFT) pattern; scale bar, 5 nm]. (C) TEM after exfoliation, revealing a nanoscale amorphous surface layer on GDC particles (yellow dashed outline; scale bar, 20 nm). (D) Magnified region from (C), showing liberated Ce-Gd-O clusters with corresponding FFT pattern (scale bar, 5 nm).

We quenched GDC from 1300°C into liquid nitrogen (≈−196°C) and directly observed catastrophic fragmentation of the brittle fluorite lattice into Ce-Gd-O clusters rather than undergoing plastic deformation (movie S1). High-resolution transmission electron microscopy (TEM) of pristine GDC confirms long-range fluorite order before treatment (Fig. 1B and fig. S3). Postexfoliation imaging reveals a nanoscale amorphous surface layer on GDC particles (Fig. 1C), and magnified views of this region display liberated Ce-Gd-O clusters with corresponding fast Fourier transform (FFT) patterns (Fig. 1D). These observations are consistent with strain-driven, near-surface fragmentation that produces discrete clusters while minimizing contamination and preserving scalability.

Atomic-scale disorder and dynamic oxygen coordination

We resolved the atomic configurations of Ce-Gd-O clusters using high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM). Figure 2A and fig. S4 reveal two dominant motifs: (i) disordered assemblies with short-range atomic correlations but no long-range periodicity (Fig. 2B), consistent with incipient exfoliation under steep thermal gradients; and (ii) crystalline clusters that maintain coherent ordering across multiple unit cells yet display pronounced local distortions (Fig. 2C and fig. S5). X-ray diffraction (XRD) corroborates these features, showing substantially broadened, asymmetrically distorted peaks for the cluster phase relative to the parent GDC (fig. S6), which indicates reduced long-range crystallinity and heterogeneous lattice strain—consistent with coexisting disordered assemblies and distorted crystalline domains seen by HAADF-STEM.

Fig. 2. Atomic-scale disorder and oxygen coordination dynamics in Ce-Gd-O clusters.

Fig. 2.

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(A) Atomic-resolution HAADF-STEM image of Ce-Gd-O clusters (scale bar, 2 nm). (B and C) Magnified regions illustrating dual motifs: (B) disordered assemblies with short-range correlations and no long-range periodicity; (C) crystalline clusters with multi–unit-cell ordering and local distortions. (D) Photographs of Ce-Gd-O clusters dispersed in anhydrous ethanol before and after brief manual agitation, demonstrating colloidal dispersibility. (E) Histogram of thickness and lateral-to-thickness aspect ratio distributions of Ce-Gd-O clusters obtained from AFM. (F) Time-resolved high-resolution TEM sequence (0 to 135 s) tracking electron-beam–induced directional migration on ultrathin carbon at 200 kV/110 μA (scale bar, 2 nm). (G) Normalized Ce L3-edge x-ray absorption near-edge structure (XANES) spectra for GDC and cluster samples. a.u., arbitrary units. (H and I) Wavelet transforms of extended x-ray absorption fine structure (EXAFS) spectra for (H) GDC and (I) clusters, highlighting differences in Ce-O coordination symmetry.

Distinct from conventional long-range–ordered oxide-ion conductors, Ce-Gd-O clusters form discrete nanostructures with ultrahigh specific surface area (Fig. 2, A to C). This fragmentation affords exceptional colloidal dispersibility: manual shaking in anhydrous ethanol produces homogeneous suspensions within ~1 s and requires no surfactant (Fig. 2D and movie S2). For industrial-scale production, high-shear dispersion vessels or equivalent equipment can be used to achieve uniform bulk dispersion of Ce-Gd-O clusters in anhydrous ethanol. Atomic force microscopy (AFM) of air-dried clusters on mica confirms that the solid-state dispersion persists, with no interparticle coalescence and no agglomerates exceeding ~8 nm in high-resolution topography (fig. S7). The preserved discrete morphology demonstrates intrinsic resistance to coalescence. Further analysis indicates that the Ce-Gd-O clusters have a thickness as low as 0.63 ± 0.02 nm and an aspect ratio up to 10.40 ± 0.23, demonstrating an ultrathin nanosheet structure.

To probe interclusters coupling, we performed in situ TEM by drop casting concentrated ethanol suspensions onto ultrathin carbon films. High-resolution imaging shows uniformly dispersed individual clusters without resolvable aggregation (Fig. 2F and fig. S8). Under controlled electron-beam irradiation, the clusters exhibit synchronized, directional migration toward support features (Fig. 2F and movie S3). This collective kinematic response evidences dynamic interparticle coupling that is consistent with short-range electrostatic/dipolar interactions arising from undercoordinated surface sites and enhanced curvature. These interactions can facilitate percolative oxygen-ion exchange between neighboring clusters, supporting conductivity in the absence of long-range crystallinity.

We further examined the local chemical environment by Ce L3-edge x-ray absorption near-edge structure (XANES) spectroscopy (Fig. 2G). Compared with fluorite GDC, the clusters display enhanced absorption intensity, suggesting reduced Ce 5d occupancy associated with disrupted long-range order and increased electron localization (25). Wavelet-transform analysis of extended x-ray absorption fine structure (EXAFS) (Fig. 2, H and I) shows that the average Ce─O bond length relaxes from 2.25 ± 0.01 Å in GDC to 2.30 ± 0.01 Å in the clusters. This elongation is consistent with weakened metal-oxygen orbital hybridization and reduced bond energy in the cluster phase. Together, the electronic-structure evolution and coordination changes provide atomic-scale evidence for enhanced oxygen reactivity, clarifying how structural reorganization enables superior oxygen-ion transport.

Vacancy-mediated oxygen-ion transport at exceptional conductivity

We quantified oxygen-ion conduction of Ce-Gd-O clusters in air using a dedicated two-electrode platform (Fig. 3, A to C). Two parallel platinum (Pt) electrodes patterned on a single-crystal yttria-stabilized zirconia (YSZ; 10 mm by 10 mm by 0.5) formed the test electrodes (Fig. 3A). By repeatedly drop casting and drying the ethanol suspension (Fig. 2D), a Ce-Gd-O cluster nanolayer 2.1 to 2.5 nm thick was formed on the YSZ single-crystal substrate between the two Pt electrodes (Fig. 3B and fig. S9). The electrochemical impedance spectra (EIS) were measured at different temperatures in air using a Solartron 1260 + 1287 workstation. Typical results are shown in Fig. 3C, from which the total ohmic resistance RΩ,total originating primarily from the Ce-Gd-O clusters was obtained. To ensure reliability, we measured three independent samples (fig. S10). By subtracting the system resistance RΩ,system from cables, Pt leads, and electrodes (fig. S11) and the contribution from oxygen-ion conduction in the YSZ substrate RΩ,YSZ (fig. S12), the intrinsic ohmic resistance of the Ce-Gd-O clusters RΩ,Ce-Gd-O was determined (fig. S13). The activation energy of RΩ,Ce-Gd-O from 400° to 800°C was 1.13 ± 0.06 eV (fig. S13), well above typical values for electronic conduction (<0.2 eV) (26), indicating oxygen-ion–dominated transport. We further confirmed the ionic mechanism by open-circuit voltage (OCV) tests in a solid oxide fuel cell (SOFC) button cell: A cluster-modified cell (dip coated from ethanol suspension; fig. S14A) sustained an OCV of 1.11 to 1.13 V at 400° to 750°C, close to the Nernst value (fig. S14, B and C), thereby excluding electronic short circuiting. Density functional theory calculations of the Ce-Gd-O cluster projected density of states indicated a bandgap of 4.7 eV, providing further support for the absence of electronic conduction (fig. S15).

Fig. 3. Exceptional oxygen-ion conductivity and vacancy-mediated transport in Ce-Gd-O clusters.

Fig. 3.

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(A) EIS platform with parallel Pt electrodes and (B) a Ce-Gd-O cluster layer ~2.5 nm thick on a single-crystal YSZ substrate. (C) Typical Nyquist plots at 600°C for the configurations shown in (A). (D) Temperature-dependent conductivity of Ce-Gd-O clusters benchmarked against Bi1.9Te0.1LuO4.05Cl (8), Ba7Nb3.8Mo1.2O20.1 (7), Ba7Ta3.7Mo1.3O20.15 (19), GDC (14), La0.8Sr0.2Ga0.83Mg0.17O2.815 (15), Bi3.9Sr0.1NbO8-δCl (16), YSZ (13), and Ba3MoNbO8.5 (18). (E) In situ Raman spectra of GDC in air (50° to 600°C). (F) In situ Raman spectra of Ce-Gd-O clusters in air (50° to 600°C), highlighting disorder-enhanced low-frequency modes (<300 cm−1), red-shifted F2g vibration (~465 cm−1), and intensified oxygen-vacancy bands (550 to 600 cm−1).

Using the Fig. 3A geometry, we extracted the oxygen-ion conductivity of Ce-Gd-O clusters in air and benchmarked it against state-of-the-art conductors (Fig. 3D (7, 8, 13–16, 18, 19). The clusters reach 2.14 ± 0.09 S cm−1 at 400°C, surpassing conventional materials by orders of magnitude: ~1400× higher than GDC (1.5 × 10−3 S cm−1) (14), ~3900× higher than La0.8Sr0.2Ga0.83Mg0.17O2.815 (5.4 × 10−4 S cm−1) (15), and ~18,000× higher than YSZ (1.2 × 10−4 S cm−1) (13). It also exceeds the prior best oxide-ion conductor Bi1.9Te0.1LuO4.05Cl (6.5 × 10−3 S cm−1) (8) by >320×, establishing exceptional low-temperature conductivity.

To probe the atomic-scale origin of this performance, we conducted in situ Raman spectroscopy on GDC and Ce-Gd-O clusters from 50° to 600°C (Fig. 3, E and F). In the low-frequency region (<300 cm−1), clusters exhibit intensified multiplet features rather than the single broad band of GDC, consistent with distorted nanocluster configurations observed by HAADF-STEM (Fig. 2A) (27). The fluorite-like F2g mode (~465 cm−1), which reflects symmetric breathing of lattice oxygen, redshifts in clusters, indicating weakened M─O bonding, in line with synchrotron analyses (Fig. 2, G to I). Notably, oxygen-vacancy–associated bands (550 to 600 cm−1) redshift and increase by ~3× in intensity relative to GDC, consistent with reduced vacancy-formation energies and elevated vacancy concentrations. Unlike crystalline oxides, where excessive vacancies aggregate and raise migration barriers via Coulomb repulsion and strain, the clusters show no Raman signatures of vacancy aggregation (800 to 1000 cm−1). We attribute the maintained population of isolated vacancies and low migration barriers to disordered coordination environments that disrupt vacancy ordering through randomized strain fields and Coulomb screening. By preventing vacancy clustering while maximizing mobile-vacancy density, Ce-Gd-O clusters sustain percolative oxygen-ion transport without long-range crystallinity, suggesting a design principle for next-generation oxide-ion conductors.

Multifunctional cluster platforms for energy devices

The coupled attributes of Ce-Gd-O clusters—low-temperature oxygen-ion conductivity, exceptionally high densities of free oxygen vacancies, nanoscale dimensions, and colloidal stability—motivate their use as versatile building blocks for next-generation energy technologies. Their conductivity and dispersibility enable integration with polymer matrices to form flexible solid-state electrolyte membranes, which may reduce manufacturing cost and thermal constraints in SOCs while allowing mechanically robust operation at ≤400°C (28, 29). In parallel, the combination of high vacancy density, ultrahigh surface area, and uniform dispersion motivates evaluation as catalytic platforms for processes that benefit from vacancy-mediated activation and maximal active-site exposure, including sustainable ammonia synthesis/decomposition, green alcohol production, biomass reforming, and electrocatalytic water splitting (9, 10, 30, 31).

To demonstrate practical viability, we engineered an SOFC cathode by integrating Ce-Gd-O clusters with PBCC, a conventional cathode material with known activity and stability limitations (32). Simple blending of PBCC powder (99.5 wt %) with 0.5 wt % clusters in deionized water produced conformal nanoscale coatings on PBCC particles (movie S4 and fig. S16). The homogeneous coverage arises from electrostatically driven, self-limiting assembly that leverages colloidal stability, nanoscale dimensions, and complementary zeta potentials between clusters and PBCC (Fig. 4A and fig. S17).

Fig. 4. Ce-Gd-O clusters as effective modifiers for SOFC cathodes.

Fig. 4.

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(A) Self-limiting electrostatic assembly of Ce-Gd-O clusters on PBCC particles. (B) Stability at 750°C under 0.7 V: Cluster-modified cathode shows +3.4% per 100 hours versus pristine PBCC/GDC at −13.2% per 100 hours over 200 hours. (C) Current-voltage-power characteristics after durability testing. (D) Benchmarking at 750°C: peak power density (vertical) versus degradation rate (horizontal) for PBCC/GDC, PBCC/Ce-Gd-O, and literature cathodes—(Pr0.4Sr0.6)0.95Co0.2Fe0.7Ni0.1O (33), Sr0.95Ti0.3Fe0.6Ni0.1O3–δ (34), Sr-(La0.6Sr0.4)0.95Co0.2Fe0.8O3−δ (35), LaBaCo2O5+δ (36), Ce0.025Sm0.475Sr0.5CoO3±δ (37), (Pr1/6Nd1/6Sm1/6Ba1/6Sr1/6)6/7(Mn1/6Co)6/7O3–δ (38), Pr0.2Sm0.2Nd0.2Gd0.2La0.2BaCo2O5+δ (39), Pr0.4La0.4Ba0.4Sr0.4Ca0.4Fe2O5+δ (40), (Mg0.2Fe0.2Co0.2Ni0.2Cu0.2)Fe2O4/GDC (41), PrBaCo2O5+δ/GDC (42), Nd0.9BaCo2O5+δ/BaCo1–yBixO3–x (43), SrFe0.93Mo0.07O3–δ/GDC (44), (La0.6Sr0.4)0.9Cr0.8Fe0.1Ni0.1O3–δ/Ce0.8Gd0.1Ni0.05Fe0.05O2–δ (45), and PrBaCo2O5+δ/SmBa0.5Ca0.5CoCuO5+δ (46). PPD, peak power density.

Electrochemical testing of anode-supported cells (fig. S18) shows substantial performance gains. At 750°C under 0.7-V constant bias, the cluster-modified cathode shifts from −13.2% per 100 hours of degradation to +3.4% per 100 hours over 200 hours (Fig. 4B). The peak power density reaches 2.87 ± 0.04 W cm−2 (versus 0.81 ± 0.01 W cm−2 for PBCC/GDC) (figs. S19 and S20), and operation at 0.7 V attains 2.14 W cm−2 (Fig. 4C). These improvements are consistent with abundant surface vacancies and high ionic conductivity in the clusters coating, which together establish efficient oxygen-reduction pathways at the cathode-gas interface. Furthermore, the Ce-Gd-O clusters form a nanoscale surface layer on PBCC that likely provides a flexible interface, which under operational conditions can modulate the electronic structure and particle orientation, suppress surface segregation of Ba and other cations, and facilitate oxygen reduction reactions while reducing cathode polarization resistance (fig. S19).

Benchmarking at 750°C places the cluster-modified PBCC among the best-performing cathodes, combining high power density with favorable degradation kinetics (Fig. 4D) (33–46). Notably, the amorphization of GDC elevates PBCC/GDC from baseline to benchmark-level performance, identifying Ce-Gd-O clusters as effective, low-dosage modifiers for next-generation SOFC cathodes.

DISCUSSION

Our findings show that thermal-shock exfoliation of fluorite GDC yields Ce-Gd-O nanoclusters that sustain fast oxygen-ion transport at 400°C (2.14 ± 0.09 S cm−1). Microscopy and spectroscopy together indicate disordered, vacancy-isolated coordination environments with elongated Ce─O bonds, while in situ Raman reveals enhanced vacancy signatures without evidence of vacancy aggregation. We interpret the high conductivity as arising from percolative exchange of oxide ions across interacting clusters, enabled by abundant, isolated vacancies and short-range electrostatic/dipolar coupling rather than long-range crystallinity. This mechanism challenges the prevailing view that efficient oxide-ion conduction requires ordered vacancy channels in crystalline frameworks.

Beyond the transport physics, the clusters attributes—nanoscale dimensions, colloidal stability, and compatibility with oxide surfaces—offer a practical route to interface engineering. As a proof of concept, trace loadings on a conventional PBCC cathode improved both activity and durability under SOFC operating conditions, consistent with an increase in near-surface ionic pathways at the gas-cathode interface. More broadly, the ability to decouple high vacancy density from vacancy clustering suggests design principles for low-temperature ion conductors: favor locally disordered coordination that screens Coulomb interactions, maximize isolated mobile-vacancy populations, and exploit interparticle coupling to establish percolative networks across heterogeneous interfaces.

Translating these principles could proceed along two complementary tracks. On the materials side, systematic compositional tuning of rare-earth/ceria-based clusters and controlled modulation of size, surface charge (ζ-potential), and ligand-free dispersion may allow rational control of vacancy populations and intercluster coupling. On the device side, scalable deposition (dip coating, spray, or ink processing) and self-limiting assembly on porous electrodes/electrolytes can be optimized to place clusters where ionic bottlenecks dominate, with percolation models guiding target coverages and geometries. These steps may enable lower-temperature operation, reduced ohmic and polarization losses, and compatibility with flexible or polymer-supported architectures.

Limitations: At present, the laboratory-scale production of Ce-Gd-O nanoclusters is only about 5 to 10 mg per batch. In industrial-scale production, a fully continuous process can be realized by top-stage continuous feeding of GDC powder via spraying, mid-stage continuous heating in a vertical high-temperature zone, and bottom-stage in situ collection through liquid-nitrogen quenching, enabling scalable and continuous fabrication of these nanoclusters. The concentration and distribution of isolated oxygen vacancies were inferred from indirect spectroscopic signatures; while our Raman/x-ray absorption spectroscopy evidence is consistent with this interpretation, direct quantification of vacancy density in nanoclusters systems remains challenging, and conventional isotope-exchange or long-range diffusion approaches may not be applicable. Last, device demonstrations were restricted to one cathode chemistry and high-temperature testing; broader validation across different electrode/electrolyte families and operation closer to 400°C will be important for application.

Together, the results identify vacancy-isolated, disordered oxide nanoclusters as a viable platform for percolative oxygen-ion transport and interface activation. By coupling locally disordered coordination with intercluster coupling, this approach offers a complementary route to ion conduction that can be integrated by low-dose surface modification. With quantitative transport partitioning, durability mapping, and scale-up of controlled assembly, these clusters may help enable efficient, lower-temperature electrochemical energy systems.

MATERIALS AND METHODS

Synthesis of Ce-Gd-O clusters

Submicrometer, crystalline GDC powder was equilibrated at 1300°C for 2 hours in ambient air and then quenched in liquid nitrogen (≈−196°C) to induce thermal shock. The resulting powder was dispersed in anhydrous ethanol (99.99%; Sigma-Aldrich) and ultrasonicated for 30 min. Suspensions were centrifuged at 5000g (20°C) to collect exfoliated clusters. Approximately 5 wt % of GDC is converted into Ce-Gd-O clusters and collected. Unless otherwise stated, stock dispersions were ~ 0.1 mg ml−1 in ethanol.

Structural and morphological characterization

TEM (FEI Tecnai F20; 200 kV) and aberration-corrected HAADF-STEM (FEI Titan Themis G3; 300 kV) were used to resolve clusters structures. Samples were drop cast onto carbon-film TEM grids. XRD used Cu Kα radiation (λ = 1.5406 Å) over 2θ = 20° to 80° with lattice refinements using FullProf.

X-ray absorption spectroscopy

Ce L3-edge XANES and EXAFS spectra were collected at National Synchrotron Radiation Center beamline TLS07A1. Samples were prepared as uniform films on Kapton tape. Spectra were calibrated against CeO2 (Alfa Aesar; 99.99%). Data reduction used Demeter (ATHENA, ARTEMIS) including wavelet-transform analysis.

Intercluster interactions

AFM (Bruker Dimension Icon) was performed on cluster drop cast on mica substrates. In situ TEM was conducted on ethanol suspensions deposited on ultrathin carbon-film grids, with time-resolved imaging under 200 kV for ~3 min.

Oxygen-ion conductivity measurements

Two parallel Pt electrodes were patterned on YSZ single-crystal substrates (100, 10 × 10 × 0.5 mm). A uniform nanolayer was formed on the YSZ surface by repeatedly drop casting and naturally drying the anhydrous Ce-Gd-O cluster ethanol suspension. EIS measurements were performed using a Solartron 1260 + 1287 workstation before and after the formation of the Ce-Gd-O cluster nanolayer over the temperature range of 400° to 800°C, along with measurements of the system ohmic resistance from cables, Pt leads, and electrodes. Conductivity extraction procedures are detailed in the Supplementary Materials.

Electrochemical cell fabrication and testing

PBCC powders were blended with 0.5 wt % Ce-Gd-O clusters (movie S4) or 0.5 wt % GDC powders to prepare the cathode composites PBCC/Ce-Gd-O and PBCC/GDC, respectively. PBCC/Ce-Gd-O and PBCC/GDC were mixed with ethyl cellulose and terpineol through ball milling to obtain the corresponding cathode inks. The cathode inks were deposited onto anode-supported half-cells by screen printing, followed by drying at 120°C for 4 hours and sintering at 950°C for 2 hours to form porous cathode layers with a diameter of ~4 mm and a thickness of ~18 μm (fig. S18). The single cells were assembled into the SOFC testing system using a 100-mesh gold grid as the electronic current collector, with humidified H2 supplied to the anode and ambient air to the cathode (47). Current-voltage, power density–time, and EIS measurements were collected using a Solartron 1260 + 1287 workstation.

In situ Raman spectroscopy

Raman spectra (WITec alpha300R) were collected in air from 50° to 600°C (heating rate of 5°C min−1 with 10-min stabilization). A 633-nm laser (15 mW) was used with ~1-cm−1 resolution.

Zeta potential and posttest microscopy

Zeta potentials of clusters and PBCC powders were measured with a Zetasizer Nano ZS. Posttest microstructures were characterized by field-emission scanning electron microscopy (FEI Quanta 250 FEG) with Energy Dispersive Spectroscopy mapping.

Acknowledgments

C.C. would like to thank the Distinguished Visiting Professorship from the DoE Los Alamos National Laboratories.

Funding:

This work was supported by the National Key R&D Program of China (2024YFB3815302 to S.P.) and the National Natural Science Foundation of China (U2032157 to S.P.).

Author contributions:

Conceptualization: S.P., J.Y., and C.C. Methodology: S.P. and C.C. Software: J.G. Validation: S.P., X.H., Y.Z., and C.C. Formal analysis: X.H., H.L., K.J.X., Q.X., Y.G., P.Z., J.Y., and Y.L. Investigation: X.H., H.L., K.J.X., J.G., Y.Z., X.L., L.X., Q.X., Y.G., P.Z., and J.Y. Resources: S.P. and J.Y. Data curation: S.P. and J.Y. Writing—original draft: X.H. Writing—review and editing: S.P., Y.L., and C.C. Visualization: S.P. and X.H. Supervision: S.P., J.Y., and C.C. Project administration: S.P., J.Y., and C.C. Funding acquisition: S.P. and C.C.

Competing interests:

S.P., X.H., J.Y., H.L., and Y.L. are coinventors on a patent filed by Jiangsu University on 16 July 2025 (Patent No. ZL202510975996.6, granted in China) related, in part, to the work described herein. All other authors declare that they have no competing interests.

Data, code, and materials availability:

All data and code needed to evaluate and reproduce the results in the paper are present in the paper and/or the Supplementary Materials. This study did not generate new materials.

Supplementary Materials

The PDF file includes:

Supplementary Text

Figs. S1 to S20

Legends for movies S1 to S4

References

sciadv.aec8053_sm.pdf (7.3MB, pdf)

Other Supplementary Material for this manuscript includes the following:

Movies S1 to S4

sciadv.aec8053_movies_s1_to_s4.zip (27.5MB, zip)

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Supplementary Materials

Supplementary Text

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References

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Movies S1 to S4

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Data Availability Statement

All data and code needed to evaluate and reproduce the results in the paper are present in the paper and/or the Supplementary Materials. This study did not generate new materials.

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