Iron-Doped Nickel Molybdate with Enhanced Oxygen Evolution Kinetics

Electrochemical water splitting is one of the potential approaches for making renewable energy production and storage viable. The oxygen evolution reaction (OER), as a sluggish four-electron electrochemical reaction, has to overcome high overpotential to accomplish overall water splitting. Therefore, developing low-cost and highly active OER catalysts is the key for achieving efficient and economical water electrolysis. In this work, Fe-doped NiMoO₄ was synthesized and evaluated as the OER catalyst in alkaline medium. Fe³⁺ doping helps to regulate the electronic structure of Ni centers in NiMoO₄, which consequently promotes the catalytic activity of NiMoO₄. The overpotential to reach a current density of 10 mA cm⁻² is 299 mV in 1 m KOH for the optimal Ni_0.9Fe_0.1MoO₄, which is 65 mV lower than that for NiMoO₄. Further, the catalyst also shows exceptional performance stability during a 2 h chronopotentiometry testing. Moreover, the real catalytically active center of Ni_0.9Fe_0.1MoO₄ is also unraveled based on the ex situ characterizations. These results provide new alternatives for precious-metal-free catalysts for alkaline OER and also expand the Fe-doping-induced synergistic effect towards performance enhancement to new catalyst systems.