The Energy Level Regulation of CoMo Carbonate Hydroxide for the Enhanced Oxygen Evolution Reaction Activity

The oxygen evolution reaction (OER) accompanied by multistep proton-coupled electron transfer is the decisive step of electrochemical water splitting due to the sluggish kinetics process. Enhancing the efficiency of water splitting indispensably requires stable and high-efficiency electrocatalysts for OER. The OER activity of electrocatalysts can be largely heightened by well adjusting their energy level and active sites. Herein, the amorphous iron cobalt molybdenum carbonate hydroxide core–shell microspheres (FeCoMo/CoMo) offer significant opportunities to improve the OER activity in both thermodynamics and kinetics due to the appropriate matching of the energy level with the equilibrium potential of OER and the abundant active sites.The well-designed Fe_0.25–CoMoCH/NF sample exhibits prominent activity toward OER with an overpotential as low as 232 mV to deliver a current density of 10 mA cm^–2, a small Tafel slope of 46 mV dec^–1, and excellent stability in alkaline solution. Mechanistic studies using a rotating ring-disk electrode confirm the four-electron pathway with high faradaic efficiency (97.7%) toward OER. This research provides a model system so as to tune the inherent catalytic activity of electrocatalysts.