Revised Oxygen Evolution Reaction Activity Trends for First-Row Transition-Metal (Oxy)hydroxides in Alkaline Media.

First-row transition-metal oxides and (oxy)hydroxides catalyze the oxygen evolution reaction (OER) in alkaline media. Understanding the intrinsic catalytic activity provides insight into improved catalyst design. Experimental and computationally predicted activity trends, however, have varied substantially. Here we describe a new OER activity trend for nominally oxyhydroxide thin films of Ni(Fe)O(x)H(y) > Co(Fe)O(x)H(y) > FeO(x)H(y)-AuO(x) > FeO(x)H(y) > CoO(x)H(y) > NiO(x)H(y) > MnO(x)H(y). This intrinsic trend has been previously obscured by electrolyte impurities, potential-dependent electrical conductivity, and difficulty in correcting for surface-area or mass-loading differences. A quartz-crystal microbalance was used to monitor mass in situ and X-ray photoelectron spectroscopy to measure composition and impurity levels. These new results provide a basis for comparison to theory and help guide the design of improved catalyst systems.