Phosphorus and Fluorine Co-Doping Induced Enhancement of Oxygen Evolution Reaction in Bimetallic Nitride Nanorods Arrays: Ionic Liquid-Driven and Mechanism Clarification

Electrocatalytic splitting of water is becoming increasingly crucial for renewable energy and device technologies. As one of the most important half-reactions for water splitting reactions, the oxygen evolution reaction (OER) is a kinetically sluggish process that will greatly affect the energy conversion efficiency. Therefore, exploring a highly efficient and durable catalyst to boost the OER is of great urgency. In this work, we develop a facile strategy for the synthesis of well-defined phosphorus and fluorine co-doped Ni_1.5 Co_1.5 N hybrid nanorods (HNs) by using ionic liquids (ILs; 1-butyl-3-methylimidazolium hexafluorophosphate). In comparison to the IrO₂ catalyst, the as-obtained PF/Ni_1.5 Co_1.5 N HNs manifests a low overpotential of 280 mV at 10 mA cm^-2 , Tafel slope of 66.1 mV dec^-1 , and excellent durability in 1.0 m KOH solution. Furthermore, the iR-corrected electrochemical results indicate it could achieve a current density of 100 mA cm^-2 at an overpotential of 350 mV. The combination of cobalt and nickel elements, 1D mesoporous nanostructure, heteroatom incorporation, and ionic liquid-assisted nitridation, which result in faster charge transfer capability and more active surface sites, can facilitate the release of oxygen bubbles from the catalyst surface. Our findings confirm that surface heteroatom doping in bimetallic nitrides could serve as a new class of OER catalyst with excellent catalytic activity.