The electrochemical CO2 reduction reaction (CO2RR) to carbon monoxide (CO) offers a promising strategy for mitigating global warming while providing a valuable industrial feedstock. Polyoxometalates (POMs), anionic metal-oxo clusters, are attractive precursors for CO2RR catalysts owing to their structural and compositional tunability, as well as their versatility of their countercations. However, POM-based CO2RR catalysts often exhibit limited activity and require high overpotentials. Herein, we report a high performance CO2RR nanocatalyst derived from a Ba2+ salt of an Au-Ag alloy nanocluster incorporated in a POM framework, [Au8Ag26(P8W48O184)](24-) (AuAg), supported on a carbon black (Ba-AuAg/C). This system achieves a high current density (171 +/- 4 mA cm(-2)) and Faradaic efficiency (95.3 +/- 4.2%) for CO production at a low overpotential (-0.39 V-RHE), outperforming previously reported POM-based CO2RR catalysts. Postreaction analyses reveal the transformation of Ba-AuAg/C into small Au-Ag alloy nanoparticles with uniform elemental distribution, along with WOx nanoaggregates. Control experiments and detailed characterizations highlight the critical roles of the constituent elements, countercations, and catalyst structure in achieving superior catalytic performance. This work provides a new design strategy for the development of highly efficient and selective POM-based nanocatalysts for electrochemical CO2 conversion.

Developing efficient, high-performance intermetallic PtNiCo nanowire catalysts with precise diameter control is crucial for enabling the commercial deployment of proton exchange membrane fuel cells (PEMFCs).

In X-ray absorption fine structure (XAFS) measurements at undulator beamlines, it has been difficult to simultaneously achieve both spectral time resolution and high X-ray flux that fully utilizes the optical performance of the beamline. To overcome this challenge, we developed a synchronization architecture for undulator beamlines, in which the undulator gap serves as the master axis while a compact channel-cut monochromator follows a pre-calculated nonlinear trajectory. In contrast to conventional feedback approaches, in which the monochromator serves as the master, the undulator gap is used as the master axis, enabling fast and flexible nonlinear synchronization with the compact channel-cut monochromator. Transmission and fluorescence quick-XAFS (QXAFS) measurements were successfully performed at the Ni K edge in the extended X-ray absorption fine structure (EXAFS) region within 6.4 s. The incident photon flux was six times higher than that of conventional QXAFS using a tapered and fixed undulator gap at the same acquisition time, demonstrating that the proposed synchronization architecture enables high-flux EXAFS measurements that were previously difficult to achieve with undulator-based QXAFS.

To elucidate the correlation between the catalytic properties of metal nanoparticles used in polymer electrolyte fuel cells and the atomic arrangements of such nanoparticles, high-energy X-ray diffraction measurements were conducted. Using the measured data as a reference, Reverse Monte Carlo was performed on isolated finite-size spherical cluster models to visualize the atomic arrangements of Pt and Pt3Co nanoparticles. In the Pt3Co nanoparticles, the local composition of the nanoparticle center and the surface region differed. The tendency of Co atoms to be located closer to the surface rather than the center was confirmed. Furthermore, the atomic arrangements in the center of the Pt and Pt3Co nanoparticles were more disordered than those in the surface region. Thus, we clarified the difference in the distribution of atoms in the center and surface regions by creating a three-dimensional model of the atomic arrangement of the nanoparticles. The visualized structural model can contribute to the development and performance enhancement of nanoparticle catalysts.

Designing oxygen evolution catalysts that are both active and durable under acidic conditions requires balancing the high activity of Ru oxides with the exceptional stability but limited abundance of Ir oxides. Here, we demonstrate that an optimized Ru0.875Ir0.125Ox-300 (annealing temperature (AT)) catalyst achieves an overpotential of 208 mV at 10 mA cm-2 and sustains stable operation for over 100 h, surpassing commercial IrO2 and RuO2 benchmarks. Despite extensive efforts, the structural and electronic evolution underlying the local-to-long-range ordering in mixed Ru-Ir oxides remains elusive because conventional X-ray diffraction (XRD) fails to resolve short-range structural motifs. Here, we combine atomic pair distribution function (PDF) analysis with operando multiedge X-ray absorption spectroscopy (XAS), including extended X-ray absorption fine structure (EXAFS) and high-energy-resolution fluorescence-detected X-ray absorption near-edge structure (HERFD-XANES) at the Ir L3 and Ru K edges, and surface-sensitive O K-edge spectroscopy, to track atomic and electronic transformations across composition and annealing temperature. Unlike conventional XRD or single-edge XAS, this combined approach enables direct correlation between short-/medium-range structural ordering and element-specific electronic responses under operando conditions. PDF analysis identifies the onset of rutile-like ordering near 300 °C (AT) in Ru-rich oxides, accompanied by cooperative Ir-O contraction and Ru-O expansion. Under anodic bias, Ir-O bonds contract further and accumulate 5d holes. In contrast, Ru-O bonds remain nearly invariant in the crystalline 300 °C (AT) phase but strongly shorten in the low-symmetry 250 °C (AT) state, reflecting the transition from a flexible to a rigid lattice. The combined fingerprints reveal that mixed-octahedra relaxation, Ir-O shortening coupled with moderated Ru-O response within a rutile-like framework, governs the activity-stability tradeoff, as revealed by operando EXAFS measurement. These findings establish lattice relaxation during the low-symmetry-to-rutile structural evolution as a mechanistic basis and design principle for durable, low-Ir acidic OER catalysts. This activity-stability balance is further supported by in a single-cell proton exchange membrane water electrolyzer, confirming relevance under membrane-electrode assembly (MEA) conditions.

Understanding the structural dynamics that govern the acidic oxygen evolution reaction (OER) is central to enabling durable, low-Ir proton-exchange-membrane water electrolysis. 1,2 Although Ir-based oxides remain the benchmark acidic OER catalysts, recent studies show that introducing small amounts of Ir into RuO₂ can stabilize Ru against over-oxidation and yield highly active, cost-efficient Ru–Ir mixed oxides. 3 However, the mechanistic origin of this stabilization—particularly the role of the amorphous-to-rutile transformation—remains poorly understood due to the lack of operando -resolved structural information. In this work, we developed a minimally Ir-containing Ru₀.₈₇₅Ir₀.₁₂₅Oₓ catalyst and tuned its short-range order through controlled thermal treatment at 250 °C (Ru₀.₈₇₅Ir₀.₁₂₅Oₓ-250) and 300 °C (Ru₀.₈₇₅Ir₀.₁₂₅Oₓ-300). The optimally treated material exhibits an overpotential of 208 mV at 10 mA cm⁻² and significantly improved durability. To directly visualize the atomic and electronic evolution associated with these thermal states, we employed a multi-modal operando approach combining atomic pair distribution function (PDF) analysis with operando hard/soft X-ray absorption spectroscopy—including EXAFS, HERFD-XANES at Ru and Ir edges, and O K-edge measurements. PDF and XAS analysis revealed that annealing from 250 °C to 300 °C induces cooperative lattice relaxation, involving Ir–O bond contraction and Ru–O bond expansion, while XANES and XPS confirmed progressive oxidation toward Ir⁴⁺ and Ru⁴⁺. Under operando OER conditions, both the 250 °C-derived and 300 °C-derived samples exhibit potential-driven Ir–O bond shortening and enhanced 5d-hole character, leading to highly covalent Ir centers associated with efficient O–O bond formation. These observations establish a direct connection between the thermal history of Ru–Ir oxides, their short-range structural motifs, and the emergence of catalytically active electronic configurations. Taken together, this study demonstrates that operando multi-edge XAS is indispensable for resolving the lattice relaxation and redox evolution underlying the low-symmetry-to-rutile transition in Ru–Ir mixed oxides. The insights gained here provide a mechanistic foundation for designing durable, ultra-low-Ir catalysts for acidic water electrolysis. Acknowledgment This work is based on results obtained from a project (JPNP14021) commissioned by the New Energy and Industrial Technology Development Organization (NEDO) of Japan. Reference: M. Retuerto, L. Pascual, J. Torrero, M. A. Salam, Á. Tolosana-Moranchel, D. Gianolio, P. Ferrer, P. Kayser, V. Wilke and S. Stiber, Nat. Mater. , 2022, 13 , 7935. N. Thakur, Y. Ren, M. Kumar, T. Uchiyama, M. Fujita, I. Arima, M. Ishida, Y. Wu, Y. Tsuji, H. Imai, M. Matsumoto, Y. Zhuang, K. Yamamoto, T. Matsunaga, K. Ohara, M. Matsumoto, Y. Orikasa, Y. Kuroda, S. Mitsushima and Y. Uchimoto, J. Am. Chem. Soc. , 2025, 147 , 30613-30625. W. Zhu, X. Song, F. Liao, H. Huang, Q. Shao, K. Feng, Y. Zhou, M. Ma, J. Wu and H. Yang, Nat. Mater. , 2023, 14 , 5365.

Anionic hexaniobate clusters [Nb6O19](8 -), which act as a superbase catalyst, could be synthesized by the microwave-assisted hydrothermal method at 180 degrees C within 10 min with high purity, whereas the conventional hydrothermal synthesis method requires a long reaction time (>24 h). In this study, the mechanism of synthesizing [Nb6O19](8-) by the microwave-assisted hydrothermal method was investigated by in situ quick-scan X-ray absorption fine structure and electrospray ionization time-of-flight mass spectroscopy. This revealed rapid [Nb6O19](8-) nucleation along with dissolution of Nb2O5 center dot nH(2)O accompanied by the formation of mononuclear Nb species at 160 degrees C. The unveiled mechanistic insights provide the controllability in products during microwave-assisted hydrothermal synthesis of polyoxoniobate clusters.

A new approach for hydrogen isotope separation using an unsaturated organometallic complex was proposed. Adsorption measurements of [Mn(dppe)2(CO)(N2)](BArF24) (Mn-dppe) (dppe = 1,2-bis(diphenylphosphino)ethane, BArF24 = B[C6H3(3,5-CF3)2]4) using H2 and D2 revealed a significant difference in the adsorption enthalpy of H2/D2 at much higher room temperatures than in previous studies, with D2 molecules being more strongly adsorbed on unsaturated metal sites. Mixed gas adsorption isotherms were calculated at each temperature using IAST, and it was predicted that D2 uptake was much larger than H2 uptake. Column chromatographic separation using the difference in adsorption enthalpy indicated that deuterium could be concentrated, and DFT calculations suggest that this difference in adsorption force is due to the difference in vibrational potentials involved in metal-dihydrogen bonding. This study introduces a new separation approach that could enable hydrogen isotope separation in the ambient temperature range.

The controlled supramolecular alignment of atomically precise metal nanoclusters is a promising method to unlock unprecedented properties and advanced functions beyond those of the individual monomeric nanoclusters. Conventional protocols for the construction of such assemblies require the use of two or more types of ligands for protecting and interconnecting the nanoclusters, respectively. Herein, a strategy is demonstrated for the hierarchical self‐assembly of an alkyne‐protected silver nanocluster into a 3D network in the crystalline lattice based on cooperative silver···acetylene coordination and silver···pyridyl coordination by a bifunctional ligand with a simple design. The bent ligand L produces a Cl@Ag14L12 monomer with a helical conformation resembling that of organic tripodal ligands, which assembles into a 3D network as evident from a single‐crystal X‐ray diffraction analysis. The monomeric and network structures are further characterized using grazing‐incidence small‐angle X‐ray scattering, atomic force microscopy, X‐ray photoelectron spectroscopy, and X‐ray absorption fine structure, in addition to photoluminescence with a microsecond lifetime in the solid state, exhibiting the success of the strategy toward the design of self‐assembled 3D supramolecular arrangements of atomically precise metal nanoclusters using a single, simple ligand.

This study presents an operando analysis of Pt nanoparticle (NP) electrocatalysts in a polymer electrolyte fuel cell (PEFC) under cyclic voltammetry (CV), utilizing a multimodal system combining high-energy resolution fluorescence detected X-ray absorption near-edge structure (HERFD-XANES), resonant inelastic X-ray scattering (RIXS), X-ray diffraction (XRD), and quick X-ray absorption fine structure (QXAFS) techniques. The developed multi-analysis provides insight into the voltage-dependent adsorption structures and bonding states of active oxygen species on Pt NPs. CV-synchronized HERFD-XANES spectra reveal the evolution of Pt electronic states, highlighting shifts in bonding characteristics associated with changes in the applied voltage. In the anodic scan, oxygen species adsorb on Pt NPs at specific voltages, inducing structural changes that can be detected via XRD and QXAFS analysis. Density functional theory (DFT) calculations combined with finite difference method near-edge structure (FDMNES) simulations predict the stability and binding configurations of adsorbed oxygen species, emphasizing the role of edge sites of Pt NPs in the oxygen reduction reaction (ORR) activity. Additionally, the study evaluates degradation effects through accelerated durability tests (ADT), showing how Pt NP coarsening impacts adsorption dynamics and the electronic structure under ADT cycling. The CV processes were visualized by operando HERFD-XANES and RIXS spectroscopies. The findings demonstrate the potential of CV-synchronized HERFD-XANES and RIXS to provide atomistic insights into catalytic mechanisms on Pt NPs, supporting the optimization of Pt-based electrocatalysts for improved performance and durability in PEFC applications.

The dynamics of CeO2-supported 1.5 nm Pt nanoparticles (Pt/CeO2) during catalysis for CO oxidation at 50 degrees C were observed. High-energy resolution fluorescence-detected (HERFD) Pt L3-edge X-ray absorption near-edge structure (XANES) spectroscopy with millisecond time resolution was used for this observation. A series of time-resolved spectra of Pt/CeO2 during CO oxidation were fitted by linear combinations of spectra corresponding to bare, CO-adsorbed, and surface-oxidised Pt nanoparticles. The analysis revealed that after O2 pulse injection into CO-adsorbed Pt nanoparticles, all adsorbed CO was oxidised within 0.5 s, forming a bare Pt surface. Subsequently, the bare Pt surface was oxidised at a much slower rate, approximately 10 s, compared with the oxidation of adsorbed CO. These findings demonstrate the utility of time-resolved HERFD-XANES spectroscopy in studying catalytic processes. This reveals variations in the Pt surface state and the kinetics of CO and Pt oxidation on Pt/CeO2 during the CO oxidation reaction.

There is a large gap between the performances indicated by rotating disk electrode (RDE) results in acidic media and the actual performances obtained in membrane-electrode assemblies (MEAs) composed of the same electrocatalysts. It is unclear whether the intrinsic kinetic reactivity of the available surface Pt sites of Pt-based cathode electrocatalysts is similar or different at RDE and in MEA. To address this, we used an operando element-selective time-resolved Pt LIII-edge quick X-ray absorption fine structure (QXAFS) technique to determine transient response profiles and rate constants, k d(WL), k d(CNPt-O), and k d(CNPt-Pt), corresponding to changes in the oxidation states [white line (WL) intensity] and local structures (coordination numbers of Pt-O and Pt-Pt bonds) at Pt sites for nine representative Pt-based cathode electrocatalysts under transient voltage operations, aiming to understand the oxygen reduction reaction (ORR) performance gap between RDE and MEA. For the first time, the transient kinetics and reactivity of electrocatalyst themselves in MEA, characterized by the operando QXAFS analysis technique, were systematically compared with the electrochemical activity [mass activity (I mass) and surface specific activity (I specific)] of the electrocatalysts in MEA and at RDE. The operando time-resolved QXAFS analysis revealed that the ORR activities of available surface Pt sites at RDEs of the electrocatalysts, including notably structured electrocatalysts (concave octahedral PtNi x /C and Pt nanowire/C), were kinetically reflected at good levels of k d(WL) and k d(CNPt-O) in MEA performances, despite large RDE-MEA gaps observed in the electrochemically determined I mass and I specific. As the I mass and I specific of MEA increased, the relaxation time k d(CNPt-Pt) -1, which indicates long-term durability, decreased, reflecting a dilemma in the development of remarkable Pt-based electrocatalysts, while the k d(CNPt-Pt) -1 was almost independent of ECSA. The differences and similarities in the kinetic reactivity and durability of the Pt surface between RDE and MEA were examined using operando QXAFS transient kinetics and electrochemical performance measurements to elucidate the underlying factors contributing to the performance gap between RDE and MEA. The insights gained aim to support the development of next-generation polymer electrolyte fuel cells with enhanced performance and durability by leveraging the operando time-resolved QXAFS technique under the transient kinetic-response operation.

Ordered intermetallic PtCo alloys are promising candidates for next-generation low-Pt catalysts in proton exchange membrane fuel cells (PEMFCs) due to their high activity and stability originating from ligand and strain effects. However, the influence of the ordered phase on the surface structure, especially after Pt-rich shell formation, remains poorly understood. In this study, we systematically investigated the structural and electrochemical properties of PtCo catalysts with varying degrees of ordering, prepared by controlling the annealing temperature and time. We combined X-ray diffraction (XRD), X-ray absorption spectroscopy (XAS), scanning transmission electron microscopy (STEM), and pair distribution function (PDF) analysis to elucidate the correlation between the ordering degree, the atomic structure, and the electrochemical performance. For the first time, our detailed X-ray total scattering measurements revealed the true structural characteristics of PtCo alloys, indicating that the phase types and their relative contents vary significantly with the ordering degree. The ordered PtCo catalysts develop a Pt-rich surface layer with anisotropic strain, featuring contracted Pt-Pt distances along the surface and elongated distances across the surface, which likely contributes to its enhanced ORR activity and stability compared to their disordered counterparts. The electrochemical studies and PDF analysis suggested that the ordering transition occurs concurrently with particle growth, leading to an abrupt increase in the ORR activity at 350 °C before forming a long-range ordered phase, suggesting that local structural changes at the particle surface play a crucial role in enhancing the ORR activity. Further, operando XAS studies confirm lesser Pt-oxidation and Pt-OH formation for ordered structures than disordered ones. We believe that our findings provide new insights into the relationship between the ordering degree, particle growth, and catalytic properties of PtCo catalysts, offering guidance for the design of high-performance electrocatalysts with optimized surface structures.

Protonic solid oxide electrolysis cells are pivotal for environmentally sustainable hydrogen production via water splitting but suffer from efficiency losses due to partial hole conductivity. Here, we introduce a device architecture based on a hydride-ion (H-)/proton (H+) bipolar electrolyte, which exploits electrochemical rectification at a heteroionic interface to overcome this limitation. The perovskite-type BaZr0.5In0.5O2.75 electrolyte undergoes an in situ transformation under electrolysis conditions, forming an H+-conducting hydrate layer adjacent to the anode and an H--conducting oxyhydride layer near the cathode, governed by competitive thermodynamic equilibria of hydration and hydrogenation. This bipolar configuration enables high Faradaic currents through the superior H-ion conductivity of the oxyhydride phase, stabilized by cathodic potentials, while facilitating continuous H+/H-interconversion at the interface. Furthermore, electrochemical hydrogenation generates an electron-depleted interfacial layer that effectively suppresses hole conduction. Consequently, the cells achieve efficiencies of '95% at 1.0 A cm-2, surpassing conventional H+ unipolar designs.

The hydrogenation of CO2 to methanol is a promising route for carbon capture and utilization, however achieving high selectivity and productivity remains a challenge. This study presents a novel catalyst synthesized by pyrolyzing a zirconium-based metal-organic framework impregnated with indium, yielding ultrafine In2O3 nanoparticles uniformly embedded within a ZrO2 and carbon matrix. The resulting In2O3/ZrO2 heterojunction exhibited abundant oxygen vacancies at the interface, which is crucial for enhancing the catalytic performance. Under gas-phase conditions, the catalyst achieves an exceptional methanol selectivity of 81% with a record-high productivity of 2.64 gMeOH·gcat⁻¹·h⁻¹ at mild reaction conditions, while in liquid-phase hydrogenation, methanol selectivity reaches 96%. Comprehensive structural characterizations confirmed that oxygen vacancies and the heterointerface served as active sites, facilitating CO2 activation and methanol stabilization. Mechanistic insights from in-situ DRIFTS and ATR-IR spectroscopy revealed that methanol formation proceeds via the formate pathway, further supported by in-situ ambient-pressure X-ray photoelectron spectroscopy, demonstrating electronic structural modulation and an increased concentration of oxygen vacancies. These findings underscore the critical role of defect engineering in optimizing CO2 hydrogenation catalysts and provide a pathway for designing highly efficient systems for sustainable methanol production.

The chemical state of radiocesium (RCs) was determined using X-ray absorption near-edge structure (XANES) in fluorescence mode and microbeam X-ray fluorescence (μ-XRF) mapping for the cesium (Cs) incorporated in a radiocesium-bearing silica microparticle (CsMP) that was released during the Fukushima Dai-ichi Nuclear Power Plant accident in 2011. The sample investigated here was classified as a CsMP emitted from Unit 1 (diameter: approximately 500 µm; Cs weight concentration: approximately 50 µg/g). The Cs Lα emission from this Type-B CsMP with a much lower Cs concentration than those of calcium and titanium was difficult to detect using a silicon drift detector, severely decreasing the signal-to-background ratio of the Cs Lα emission. In this study, a high-energy-resolution energy-dispersive transition-edge sensor was used for X-ray spectroscopic analysis, which enabled the measurement of Cs LIII-edge XANES for RCs in the Type-B CsMP. The results revealed the presence of two distinct RCs species in CsMPs. Bulk XANES analysis indicated that one species consists of RCs dissolved in the silicate matrix. Additionally, μ-XRF-XANES revealed that the RCs species were heterogeneously distributed within the CsMP with enrichment observed on the surfaces of internal voids, suggesting that the gaseous RCs species, such as CsCl, adhered to these surfaces during the cooling process of the molten silicate. The speciation and μm-scale mapping of RCs provide further insights into (i) the formation process of spherical Type-B CsMP and (ii) the incorporation and internal distribution processes of RCs within the particle. (239 words).

This review is focused on FC-BENTEN, an advanced synchrotron X-ray experimental database developed at SPring-8 with support from Japan’s New Energy and Industrial Technology Development Organization (NEDO). Designed to advance polymer electrolyte fuel cells (PEFCs) research, FC-BENTEN addresses challenges in improving efficiency, durability, and cost-effectiveness through data-driven approaches informed by materials informatics (MI). Through standardization of protocols for sample preparation, data acquisition, analysis, and formatting, the database ensures high-quality, reproducible data essential for reliable scientific outcomes. FC-BENTEN streamlines metadata creation using automated processes and template-based tools, enhancing data management, accessibility, and interoperability. Security measures include two-factor authentication, safeguarding sensitive information and maintaining controlled user access. Planned integration with MI platforms will broaden data cross-referencing capabilities, facilitate PEFC applications expansion, and guide future research. This review discusses FC-BENTEN’s architectural framework, metadata standardization efforts, and role in advancing PEFC research through a high-throughput experimental workflow. It illustrates how data-driven methods and standardized practices contribute to innovation, underscoring databases’ potential to accelerate next-generation PEFC technologies development.