Abstract
To arrive to sustainable hydrogen-based energy solutions, the understanding of water-splitting catalysts plays the most crucial role. Herein, we combined state-of-the-art hypotheses on electrocatalytic active metal sites towards the oxygen evolution reaction (OER) to develop a highly efficient catalyst based on earth-abundant cobalt and zinc oxides. The precursor catalyst Zn 0.35 Co 0.65 O was synthesized via a fast microwave-assisted approach at low temperatures. Subsequent, it transformed in situ from the Wurtzite structure to the layered γ-Co(O)OH, while most of its zinc leaches out. This material shows outstanding catalytic performance and stability towards the OER in 1 M KOH (overpotential at 10 mA cm-2 η initial = 306 mV, η 98 h = 318 mV). By comparing the electrochemical results and ex situ analyses to today's literature, we were able to identify clear structure-activity correlations. Our findings suggest that coordinately unsaturated cobalt octahedra on the surface are indeed the active centers for the OER.