Anion-cation co-substitution activation of spinel CoMoO4 for efficient oxygen evolution reaction

Developing an efficient earth-abundant catalyst able to accelerate oxygen evolution reaction (OER) is crucial for realizing the scalable application of electrochemical water splitting. Spinel transition metal oxides represent a promising catalyst for this reaction, but to data, their catalytic performance is still further improved to satisfy the practical application. Being different from previous nanostructure engineering and hybridization strategy, herein, we reported an anion-cation co-substitution activation of CoMoO4 for OER through a facile solvothermal treatment of FeCo-Prussian blue analogue (PBA) nanocube in the presence of thiourea and ammonium molybdate. The combination of experimental results with theoretical analysis uncovered that anion-cation cosubstitution allowed the formation of ultrathin porous nanosheet structure with more accessible active sites, enhanced charge and mass transfer ability and optimized adsorption free energy towards oxygen-containing intermediates. As a result, the Fe and S co-substituted CoMoO4 (Fe0.5Co0.5MoO4-xSx) nanoflowers assembled by nanosheets exhibited a drastically improved OER catalytic activity with an overpotential as low as 263 mV to afford a current density of 10 mA cm(-2) and a small Tafel slope of 87 mV dec(-1), superior to the state-of-the-art IrO2/C and most reported binary transition metal oxide-based electrocatalysts.