Facilitated catalytic surface engineering of MnCo₂O₄ electrocatalyst towards enhanced oxygen evolution reaction

The overall conversion efficiency of water electrolysis is primarily restricted by the sluggish kinetics of the oxygen evolution reaction (OER). To overcome the OER bottleneck, fundamental scientific attention is keenly directed toward the development of durable, cost-effective, and highly efficient catalysts, and therefore, the focus of current research. Herein, we report the facile fabrication of promising noble–metal–free oxygen defects engineered MnCo₂O₄ (O_d-MnCo₂O₄) catalyst as a highly efficient OER water electrocatalyst in an alkaline KOH medium. The MnCo₂O₄ nanosheet is directly grown on the nickel foam and dramatically changes to a crumpled sphere after NaBH₄ treatment, which results in increased oxygen defects (O_d). The engineered O_d in MnCo₂O₄ might modify their electronic structure effectively, which results in improved electrical conductivity and a large quantity of electrochemically accessible active surface area. The O_d-MnCo₂O₄ catalyst demonstrates an outstanding OER activity and exhibits a small overpotential of 250 and 316 mV at a current density of 10 and 100 mA cm⁻², respectively, with a modest Tafel slope of 64 mV dec^–1. The O_d-MnCo₂O₄ catalyst also demonstrates excellent perseverance till 60 h upon continuous chronopotentiometric test even at 100 mA cm⁻² and further reveals a static potential response at low and high rates. The excellent OER performance is ascribed to enhanced electrochemically active sites and improved electronic conductivity aroused from the NaBH₄ reduction.