Surface Engineering in MgCo<sub>2</sub>O<sub>4</sub> Spinel Oxide for an Improved Oxygen Evolution Reaction
Ming Ya, Jianghao Wang, Guangshe Li, Guichen Gao, Xu Zhao, Jiawen Cui, Haijun Wu, Liping Li
Abstract
Spinel-type oxides exhibit great potential for the electrocatalytic oxygen evolution reaction (OER) due to their variable surficial composition and electronic structure. Herein, taking MgCo 2 O 4 as a prototype, we put forward a surface engineering procedure to tailor the surface composition and valence state of cobalt ions for enhancing the OER performance. We discovered that the calcination temperature can finely tailor the ratio of Co/Mg and Co 3+ /Co 2+ on the surface of MgCo 2 O 4 . MgCo 2 O 4 with the maximum ratio of Co 3+ /Co 2+ gives a current density of 10 mA cm –2 at a small overpotential of 283 mV. Such an overpotential is significantly lower than that of most cobalt-based spinel oxides ever reported. X-ray photoelectron spectra demonstrate that increasing the ratio of Co 3+ /Co 2+ plays key roles in improving the OER performance. This work furnishes an instructive idea in pursuit of spinel-type oxides with high OER catalytic activity and stability by surface engineering.