▎ 摘　　要

Rational design and synthesis of efficient, stable and low-cost electrocatalysts for oxygen evolution reaction (OER) is critical for renewable energy conversion and storage. Herein, the reduction-engraved strategy was adopted to treat crystalline ferrite nanoparticles, which are highly dispersed on graphene oxide (GO) nanosheets. This reduction treatment generated abundant oxygen vacancies on the surface of nano-scale ferrites and dramatically enhanced their surface area, ensuring that the ferrite nanoparticles possess more accessible active sites for OER, and improve their electronic conductivity. Reduced cobalt/nickel ferrite (Co0.5Ni0.5Fe2O4, r-CNF), cobalt ferrite (CoFe2O4, r-CF) and nickel ferrite (NiFe2O4, r-NF) nanoparticles anchoring on the ultrathin GO nanosheets can act as highly active, stable and low-cost OER electrocatalysts in 1.0 M KOH solution. The r-CNF (Co : Ni = 1 : 1) on GO (r-CNFg) shows the best OER performance among the ferrite-based OER electrocatalysts, with an overpotential of 210 mV at 10 mA cm(-2) in 1.0 M KOH solution, much more efficient than that of a commercial benchmark catalyst IrO2 (230 mV). The catalytic current density of r-CNFg at 1.49 V vs. RHE is about 50 times higher than that of CNF and CNFg. Also, it exhibits prominent electrochemical stability over 500 h in 1.0 M KOH.