Photochemical Route for Accessing Amorphous Metal Oxide Materials for Water Oxidation Catalysis

TLDR

Large‑scale water electrolysis for hydrogen production needs catalysts that lower OER kinetic barriers, and while most catalysts are crystalline mixed‑metal oxides, amorphous phases can also achieve high activity. The study demonstrates that photochemical metal‑organic deposition at low temperature can produce amorphous mixed‑metal oxide films for OER catalysis. The authors use photochemical metal‑organic deposition, a low‑temperature process, to synthesize amorphous mixed‑metal oxide films, addressing the challenge that conventional amorphous‑material methods are not amenable to mixed‑metal compositions. The resulting films exhibit a homogeneous, composition‑controlled metal distribution, and amorphous iron oxide outperforms hematite while a‑Fe(100‑y‑z)Co(y)Ni(z)O(x) matches the performance of commercial noble‑metal oxide electrolyzer catalysts.

Abstract

Large-scale electrolysis of water for hydrogen generation requires better catalysts to lower the kinetic barriers associated with the oxygen evolution reaction (OER). Although most OER catalysts are based on crystalline mixed-metal oxides, high activities can also be achieved with amorphous phases. Methods for producing amorphous materials, however, are not typically amenable to mixed-metal compositions. We demonstrate that a low-temperature process, photochemical metal-organic deposition, can produce amorphous (mixed) metal oxide films for OER catalysis. The films contain a homogeneous distribution of metals with compositions that can be accurately controlled. The catalytic properties of amorphous iron oxide prepared with this technique are superior to those of hematite, whereas the catalytic properties of a-Fe(100-y-z)Co(y)Ni(z)O(x) are comparable to those of noble metal oxide catalysts currently used in commercial electrolyzers.