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

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_xcatalyst 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_xcatalyst in nominally pure aqueous H₂SO₄solutions. Moreover, this catalyst maintains robust operation at pH 0.3 and temperatures as high as 80 °C. Under these conditions, the [Ag + Bi]O_xcatalyst can deliver an OER rate of 100 mA cm^-2at 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_xsystem 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.