Dynamic Restructuring of Carbon Nanotube-Supported High-Entropy Alloys Enabling Efficient Oxygen Electrocatalysis

Oxygen electrocatalysis, mainly including the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER), is a cornerstone in rechargeable metal–air batteries. However, these reactions are sluggish due to the four-electron transfer process and the linear scaling relationship of the intermediate binding strength. Herein, we have rationally developed a hybrid composite consisting of high-entropy alloy nanoparticles (NPs) encapsulated in carbon nanotubes (CNTs) to significantly improve the electrocatalytic performance. In situ spectroscopy investigations and theoretical calculations disclose that high-entropy alloys undergo dynamic reconstruction to form MOOH and M–OH (M represents metallic elements) as the authentic active species in the ORR and OER processes, respectively. Specifically, Fe, Co, Mn, and Cu regulate the charge transfer between the Ni–O bonds in MOOH for the OER, while the high-entropy effect and surface-absorbed OH groups coregulate the d-band center of surface Co for the efficient ORR. Accordingly, the as-developed FeCoNiMnCu@CNTs exhibits activity for both ORR and OER, with an ultralow voltage gap of 0.626 V between the half-wave potential of ORR and the OER potential at 10 mA cm –2 . Moreover, Zn–air batteries with FeCoNiMnCu@CNTs exhibit a power density of 131.3 mW cm –2 and robust stability.