Oxygen Evolution on Metal‐oxy‐hydroxides: Beneficial Role of Mixing Fe, Co, Ni Explained via Bifunctional Edge/acceptor Route

Oxygen evolution reaction (OER) via mixed metal oxy hydroxides [M(O)(OH)] may take place on a large variety of possible active sites on the actual catalyst. A single site computational description assumes a 4‐step electrochemical mechanism with coupled H + /e − transfers between 4 intermediates (M‐*, M‐OH, M=O, M‐OOH). We also consider bifunctional routes, in which an unstable M‐OOH species converts via a proton shuttling pathway to a thermodynamically more favourable bare M‐* site, O 2 and a hydrogenated acceptor site; the acceptor site takes up the proton forming a hydrogenated acceptor site after recombination with an electron from the catalyst material. Here, we combine pure metal γ‐M(O)(OH) edge sites (M=Fe, Co, Ni) with as proton‐acceptor sites different threefold coordinated oxygens on β‐(M,M’)(O)(OH) terraces (M,M’=Fe, Co, Ni). The acceptor sites on these terraces have of a M’ 2 MO motif. Our combinatorial study results in a ranking of the bifunctional OER activity on a 3D‐volcano plot. By studying various bi‐ and tri‐metallic oxy hydroxide combinations, we show that their excellent experimental OER activity results from bifunctionality and provide a roadmap to construct innovative low overpotential OER catalysts.