Rational Regulation of High-Entropy Perovskite Oxides through Hole Doping for Efficient Oxygen Electrocatalysis

Due to the high configuration entropy, unique atomic arrangement, and electronic structures, high-entropy materials are being actively pursued as bifunctional catalysts for both the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) in rechargeable zinc-air batteries (ZABs). However, a relevant strategy to enhance the catalytic activity of high-entropy materials is still lacking. Herein, a hole doping strategy has been employed to enable the high-entropy perovskite La(Cr_0.2Mn_0.2Fe_0.2Co_0.2Ni_0.2)O₃ to effectively catalyze the ORR and OER. Hole doping experiments rely on the substitution of Sr²⁺ for La³⁺. The optimized La_0.7Sr_0.3(Cr_0.2Mn_0.2Fe_0.2Co_0.2Ni_0.2)O₃ displays remarkable activity for the ORR and the OER, with a low potential difference of 0.880 V between the half-wave potential of the ORR and the OER potential at 10 mA cm^-2, exceeding the majority of perovskite bifunctional catalysts. Further analysis of the electronic structures reveals that hole doping could regulate the e_g-orbital filling of the transition-metal cations in high-entropy perovskites to an ideal position and thereby generate many highly active sites to promote the redox activity of oxygen. The assembled rechargeable ZAB with the targeted high-entropy perovskite as the cathode affords a specific capacity of 774.5 mAh g_Zn^-1 under 10 mA cm^-2 and durability for a period of 300 cycles, comparable to that of the 20%Pt/C + RuO₂ ZAB. This work offers an important approach for the advancement of efficient high-entropy perovskites for ZABs.