Mixed Silver–Bismuth Oxides: A Robust Oxygen Evolution Catalyst Operating at Low pH and Elevated Temperatures

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Development of catalysts for the oxygen evolution reaction (OER) that are capable of robust operation at low pH and elevated temperatures, but do not contain scarce ruthenium and iridium, presents a challenging yet very attractive strategy in decreasing the high cost of efficient water electrolyzers paired with proton-exchange electrolytes. Toward this aim, combinations of both catalytically active and acid-stable components offer an appealing approach to cost-effective anode catalysis for low-pH water electrolysis. The current work presents an oxygen-evolving [Ag + Bi]O x catalyst based on intermixed silver and bismuth oxides, prepared by a simple anodic electrodeposition. We demonstrate that numerous electrode substrates can be functionalized and operate stably with the [Ag + Bi]O x catalyst in nominally pure aqueous H 2 SO 4 solutions. Moreover, this catalyst maintains robust operation at pH 0.3 and temperatures as high as 80 °C. Under these conditions, the [Ag + Bi]O x catalyst can deliver an OER rate of 100 mA cm –2 at an overpotential of 0.70 ± 0.02 V vs reversible hydrogen electrode (RHE). In situ X-ray absorption spectroscopic and Fourier transformed alternating current cyclic voltammetric studies of the [Ag + Bi]O x system demonstrate the stabilizing role of the bismuth oxide matrix that facilitates the transformation of silver into a highly oxidized state catalyzing the acidic water electrooxidation.