Modulating the electronic configuration of Co species in MOF/MXene nanosheet derived Co-based mixed spinel oxides for an efficient oxygen evolution reaction

Abstract

The electronic configuration of Co cations at octahedral (Oct) sites plays a crucial role in the catalytic activity of Co₃O₄-based spinel oxides toward the oxygen evolution reaction (OER). However, there are few reports on modulating the electronic configuration of partial Co_Oct³⁺ (t⁶_2ge⁰_g) to Co_Oct²⁺ (t⁶_2ge¹_g) for further promoting their OER performances. Herein, a metal–organic framework (MOF)/MXene composite material pyrolysis–reorganization strategy is developed to obtain heterogeneous Co-based mixed spinel oxides, Co₃O₄/Co₂TiO₄. By regulating the pyrolysis temperature, the mesoporous structures and the electronic configuration of Co_Oct cations of mixed spinel oxides can be simultaneously optimized, leading to exceptional OER performances with low overpotentials of 280 mV on a glassy carbon electrode and 260 mV on Ni foam at 10 mA cm⁻² as well as good stability in alkaline solution. The synergistic catalytic effect between Co_Oct³⁺ in Co₃O₄ and Co_Oct²⁺ in Co₂TiO₄ is shown to be crucial for improving the OER activity. This finding will provide a new pathway for promoting the OER activity of Co-based spinel oxides.