Chemical etching to boost medium-entropy metal oxide for oxygen evolution reaction in alkaline

It is crucial to improve the catalytic activity of medium-entropy materials by adjusting the surface electronic structure of medium-entropy materials. In this research, we utilize a chemical etching method for synthesizing a medium-entropy metal oxide E-FeCoNiZn with abundant defects. Owing to the etching of Zn, a special form of electron-transfer by means of electron-accepting-donating is introduced, which greatly optimizes OER activity. The E-FeCoNiZn displays a superior OER activity with a low overpotential of 259 mV at 10 mA cm -2 and a small Tafel slope of 37.1 mV dec -1 in 1 M KOH solution, outperforming the performance of FeCoNiZn and Ni-foam, while maintaining excellent stability over 48 h. Theoretical calculations demonstrate that the introduction of defects regulates the surface electronic structure of the E-FeCoNiZn via modifying the number of electrons transferred and then optimize the OER activity. This work provides a new strategy for designing medium-entropy materials possessing high catalytic activity.