Vacancy Engineering Strategy Releases the Electrocatalytic Oxygen Evolution Reaction Activity of High-Entropy Oxides.

The sluggish kinetics of oxygen evolution reaction (OER) poses a great challenge to the industrial promotion of electrocatalytic water splitting and zinc-air battery. Herein, we demonstrate that the kinetic limitation of the OER imposed by a conventional adsorbate evolution mechanism can be successfully overcome through activating lattice oxygen in the electrocatalyst. For example, incorporating aluminum (Al) into high-entropy oxides (HEO) remarkably enhances the oxygen vacancy concentration, facilitates the generation of reactive oxygen species, and promotes the deprotonation during the electrochemical OER process, thereby boosting the kinetic reaction. This defect engineering strategy effectively decreases the energy barrier associated with the lattice oxygen oxidation and optimizes the configurational entropy of HEO, resulting in remarkable structural stability. Consequently, the developed HEO decorated with Al (HEO-Al) achieves an overpotential of ∼206 mV at 10 mA cm in water electrolysis and a power density (∼20 mW cm) in rechargeable zinc-air battery, with long-term stability of 100 h, realizing an optimal balance between electrocatalytic activity and stability. More importantly, the performances of HEO-Al are significantly superior to those of the HEO counterpart (∼260 mV, ∼1.5 mW cm) and commercial ruthenium oxide (∼359 mV, ∼5 mW cm), showing great competitiveness and application prospect. These results offer essential inspiration for other electrochemical applications dominated by the OER at the same time.