Dual sites modulating MoO2 nanospheres for synergistically enhanced electrocatalysis of water oxidation

Oxygen evolution reaction (OER) is of critical importance in the area of electrocatalysis as it is frequently involved in a diversity of electrochemical devices. Molybdenum-based materials, thanks to their metallic character induced high conductivity, have been widely studied as catalysts for a variety of reactions but few reports for oxygen evolution reaction (OER). Herein, we report a dual-sites modifying strategy to modulate electrocatalytic properties of metallic MoO2 nanospheres toward OER, which is implemented by a one-pot synthesis process to prepare nickel and iron co-doped molybdenum oxide (Mo0.9Ni0.05Fe0.05O2). The introduction of dual sites (i.e., Ni and Fe) on MoO2 nanospheres surface can tune the surface electronic structure and local-chemical environment with generation of high-valence Mo and hydroxyl-rich surface, synergistically contributing to the improved electrocatalytic performance in terms of stability and activity. Density functional theory (DFT) calculation indicates Fe-doping site favors for enhancing the turnover efficiency (TOF) while the Ni-doping site facilitates the first proton coupled electron transfer (PCET) upon electrocatalysis of OER. The Mo0.9Ni0.05Fe0.05O2 requires only 249 mV of overpotential to reach a current density of 10 mA cm-2 with excellent stability for 80 h. This study expands the research on molybdenum-based OER catalysts and gains insight into the origin of both the activity and stability of Ni/Fe-doping reactive sites.