To overcome this limitation, researchers designed atomically dispersed ruthenium-oxygen-chromium motifs that establish a protective mechanism designated as proximal oxidation damping. Through this proximity-dependent redox coupling, adjacent chromium sites dynamically buffer ruthenium against overoxidation, attenuating ruthenium oxidation while exhibiting synchronized, anticorrelated, and partially reversible chromium redox evolution. In proton exchange membrane water electrolysis operating at an industrial current density of one ampere per square centimeter, catalysts featuring these proximal ruthenium-chromium configurations demonstrated degradation rates that were six point eight times lower than conventional ruthenium single-atom catalysts and fourteen point four times lower than commercial ruthenium dioxide benchmarks. Furthermore, the proximal redox units delivered a fifty-five point seven-fold increase in resistance against oxidation-induced ruthenium dissolution compared with standard single-atom systems.
Fabrication of the heterogeneous diatomic catalyst relied on a one-pot hydrothermal method in which manganese dioxide host formation and dual-metal incorporation occurred concurrently. The synthesis began by dissolving zero point two three seven grams of potassium permanganate, representing one point five millimoles, in thirty-two milliliters of Milli-Q water under magnetic stirring for ten minutes. Subsequently, nineteen point six milligrams of ruthenium chloride trihydrate and twenty milligrams of chromium chloride hexahydrate were added to provide equimolar zero point zero seven five millimole metal precursor ratios, stirring for ten additional minutes. After mixing, one hundred and eighty-five microliters of concentrated thirty-seven weight percent hydrochloric acid was introduced, and agitation continued for another ten minutes. Substrates were prepared from AvCarb MGL370 carbon paper immersed in freshly prepared aqua regia containing hydrochloric and nitric acids in a three-to-one volume ratio for thirty minutes before being thoroughly rinsed with pure Milli-Q water.
The treated carbon paper substrate was suspended vertically inside a one hundred milliliter Teflon-lined stainless-steel autoclave above the vessel base to avoid collecting settled particulates or precipitated clusters. Hydrothermal reaction was performed at one hundred and twenty degrees Celsius for twelve hours. After natural cooling to room temperature, the catalyst-loaded carbon paper was rinsed repeatedly with absolute ethanol and Milli-Q water, dried at sixty degrees Celsius for two hours, and annealed in a furnace at two hundred degrees Celsius for one hour. Control formulations synthesized under equivalent conditions included isolated ruthenium single-atom catalysts without chromium chloride and unmodified manganese dioxide without metal salts. Additional synthetic controls evaluated nominal ruthenium loadings of two point five, ten, and twenty weight percent by adjusting precursor amounts to nine point eight, thirty-nine point two, and seventy-eight point four milligrams, alongside variable ruthenium-to-chromium ratios and annealing temperatures between two hundred and four hundred degrees Celsius.
To verify whether proximal redox coupling could be extended to alternative chemical systems, synthesis protocols were applied to related transition metals and lanthanides by replacing chromium with stoichiometric quantities of iron, cobalt, nickel, lanthanum, cerium, or erbium salts. Equimolar iridium analogues were also prepared using potassium hexachloroiridate precursors under identical processing steps. Microstructural morphology was examined by scanning electron microscopy on Hitachi SU8600 and Zeiss Gemini 560 instruments and transmission electron microscopy on a Thermo Fisher Scientific Talos F200S at two hundred kilovolts. High-resolution elemental distributions and atomic arrangements were resolved using a Thermo Fisher Scientific Spectra 300 aberration-corrected transmission electron microscope operating in high-angle annular dark-field imaging, integrated differential phase contrast, energy-dispersive X-ray spectroscopy, and electron energy-loss spectroscopy modes, with digital imaging datasets evaluated and processed through Gatan Microscopy Suite 3 software.
Atomic structure interpretations were complemented by multi-slice high-angle annular dark-field electron microscopy simulations using QSTEM software version two point fifty-one at an accelerating voltage of three hundred kilovolts. Simulations adopted a twenty-five milliradian convergence semi-angle, detector collection angles between seventy and two hundred milliradians for incoherent Z-contrast imaging, and frozen-phonon thermal diffuse scattering at three hundred Kelvin with fifty configurations across zero point five angstrom slices. Surface topography and phase characteristics were measured under ambient conditions using non-contact tapping-mode atomic force microscopy on a Park Systems NX10 with Arrow-NCR tips at scan rates of zero point two to zero point three hertz. Bulk crystallographic structures of the synthesized materials were characterized by X-ray diffraction on a Rigaku Smartlab diffractometer using copper K-alpha radiation across two-theta angles of ten to eighty degrees, with background-corrected patterns indexed using MDI Jade 6 software.
Chemical oxidation states and surface bonding configurations were investigated through X-ray photoelectron spectroscopy using a SPECS PHOIBOS 150 hemispherical analyzer with an aluminum K-alpha source, calibrated against the carbon one-s peak at two hundred and eighty-four point five electron volts. Bulk elemental ruthenium loadings and trace metal dissolution rates were quantified using an Agilent 7800 inductively coupled plasma mass spectrometer and a PerkinElmer Optima 8300 optical emission spectrometer. Vibrational structures were recorded on a Renishaw spectrometer with five hundred and thirty-two and seven hundred and eighty-five nanometer lasers. In situ Raman spectra were gathered in zero point five molar sulfuric acid using an immersion objective and a platinum counter electrode at ten percent laser power with thirty accumulations. Working electrodes comprised catalyst loadings of zero point six four milligrams per square centimeter for the ruthenium-chromium catalyst and zero point six eight milligrams per square centimeter for the single-atom ruthenium control on carbon paper.
Synchrotron X-ray absorption spectroscopy performed at the BESSY II facility in Berlin tracked dynamic electronic transitions and atomic coordination environments during acidic electrolysis. Chromium and manganese K-edge along with iridium L3-edge spectra were collected at the KMC-3 beamline across specified energy windows, while ruthenium K-edge spectra were measured in fluorescence mode at the BAMline using a passivated detector. Operando spectra acquired in sulfuric acid revealed attenuated ruthenium oxidation coupled with anticorrelated and partially reversible chromium redox evolution, confirming that proximal redox buffering is accompanied by bounded and partially reversible changes in local metal-oxygen coordination. Quantitative fine-structure fitting performed with Bessy_47b and SimXLite using FEFF8 scattering paths confirmed metal-oxygen nearest-neighbor shells across defined momentum and radial ranges.
Electrochemical oxygen evolution reaction measurements were carried out in an Autolab M204 workstation in zero point five molar sulfuric acid for acidic testing and one molar potassium hydroxide for alkaline testing. A three-electrode cell configuration utilized a graphite rod counter electrode, a saturated potassium chloride silver-silver chloride reference electrode, and catalyst-coated carbon paper across a one square centimeter geometric area. Linear sweep voltammetry sweeps from one point two to one point nine volts versus the reversible hydrogen electrode were executed at five millivolts per second. Chronopotentiometry was evaluated in a sealed CorrTest CS932S H-type cell partitioned by a Nafion 117 membrane containing forty milliliters of electrolyte per compartment. Active surface areas were evaluated using cyclic voltammetry at scan rates between twenty and one hundred millivolts per second, while Faradaic efficiency toward oxygen generation was confirmed under argon purging at ten milliamperes per square centimeter via gas chromatography.
Device-level performance was assessed in a proton exchange membrane water electrolyzer featuring a four square centimeter active cell area. Anode inks consisting of catalyst powder and Nafion ionomer dispersed in ethanol and water were sprayed onto platinum-coated titanium porous transport layers to achieve an anode catalyst loading of approximately one milligram per square centimeter, delivering roughly fifty micrograms of ruthenium per square centimeter. Cathodes were fabricated by spray-coating platinum on carbon onto Nafion 117 membranes at eighty degrees Celsius at zero point four milligrams per square centimeter, alongside comparative commercial ruthenium dioxide anodes at two milligrams per square centimeter. Following hot-pressing at one hundred and thirty degrees Celsius, the electrolyzer was operated at eighty degrees Celsius with pure water flow at twenty-five milliliters per minute, showing stable operation and significantly reduced cell voltage degradation during durability testing at one ampere per square centimeter, alongside daily sampling of anode effluent for inductively coupled plasma metal dissolution testing.
Complementary first-principles density functional theory within the Vienna Ab initio Simulation Package employed projector augmented wave potentials, Perdew-Burke-Ernzerhof functionals, and Hubbard U corrections of three point zero six electron volts for manganese, two point seventy-nine electron volts for ruthenium, and two point four electron volts for chromium. The four-electron oxygen evolution pathway was computed across adsorbed intermediate states with vibrational free-energy corrections. Stepwise dissolution pathways modeled surface ruthenium oxidation through ruthenium dioxide dihydroxide and ruthenium trioxide hydroxide intermediates before aqueous ruthenium tetroxide release and vacancy formation.
Subject of Research: Oxidation damping in atomically dispersed electrocatalysts for water electrolysis
Article Title: Proximal redox coupling enables oxidation damping for stable water electrolysis
Article References: Chen, T., Wang, K., Xia, L., Jiang, W., Ferreira Gomes, B., Yang, L., Zhao, K., Huang, H., Lobo, C. M. S., Ram, R., Chen, J., He, R., Garzón Manjón, A., Gupta, K., Zhu, Z., Dimitropoulos, M., Golovanova, V., Gimenes Vernasqui, L., Hörnig, S., … García de Arquer, F. P. (2026). Proximal redox coupling enables oxidation damping for stable water electrolysis. Nature Materials. https://doi.org/10.1038/s41563-026-02783-4
Image Credits: AI Generated
DOI: 10.1038/s41563-026-02783-4
Keywords: water electrolysis, oxygen evolution reaction, single-atom catalysts, heterogeneous diatomic catalysts, ruthenium dissolution, proton exchange membrane water electrolysis, oxidation damping, redox coupling, X-ray absorption spectroscopy, extended X-ray absorption fine structure, manganese dioxide host, density functional theory, anion exchange membrane water electrolysis, differential electrochemical mass spectrometry, electrochemical impedance spectroscopy, in situ Raman spectroscopy, aberration-corrected STEM, Faradaic efficiency