The catalytic activity of reduced graphene aerogel anchored with CoFe2O4 spinel via self-assembly technique for enhanced oxygen evolution reaction

The development of low-cost and highly active oxygen evolution reaction (OER) electrocatalysts is of significant importance for the advancement of sustainable new clean energy and storage systems. Herein, reduced graphene oxide (rGO) anchored with spinel CoFe2O4 (rGO/CoFe2O4) is prepared by hydrothermal synthesis, combined with freeze-drying and heat treatment processes. The effects of different spinel types, the loading amount of CoFe2O4 and heat treatment temperatures on the OER performance are investigated. The resulting possesses a typical mesoporous structure composed of CoFe2O4 nanoparticles with 20-50 nm and the lamellar rGO, leading to a large BET specific surface area. The as-prepared rGO/CoFe2O4 has an overpotential of 325 mV, a low Tafel slope (63.02 mV/dec) at a current density of 10 mA cm-2, and shows excellent stability with no significant current decay. Based on Density Functional Theory (DFT) calculations, the transition from *O to *OOH has the highest Gibbs free energy, which is the rate-determining step of the entire catalytic process. The Fe site on the (100) crystal plane of CoFe2O4 is most likely the reactive site for the OER process, improving the OER activity by decreasing the binding strength between the catalytic surface and adsorbed *O intermediates.