High-entropy spinel oxides as efficient ORR catalysts towards enhanced kinetics for zinc-air batteries

Abstract

Efficient oxygen electrocatalysts for the oxygen reduction reaction (ORR) are vital for energy conversion and storage devices, but slow kinetics remain a significant challenge. There is an urgent need to develop a new electrocatalyst with high active sites. Here, we report the synthesis of high-entropy spinel oxide ((FeMnNiCuCr)₃O₄) loaded onto reduced graphene oxide (rGO) via a co-precipitation hydrothermal method. The multi-elemental mechanism of high-entropy spinel oxide and the role of rGO in enhancing catalytic activity are elucidated. The prepared electrocatalyst demonstrates efficient ORR catalytic performance (E_1/2 = 0.83 V) and reaction kinetics (100.2 mV dec^-1). It exhibits excellent catalytic activity in a liquid zinc-air battery (ZAB) with a low gap voltage (∼0.75 V) and long cycle stability (1162 h). This catalytic performance can be attributed to the cooperative mechanism of high-entropy-driven polymetallic elements, wherein Cr³⁺ regulates the electronic structure of Fe²⁺ at the tetrahedral site, serving as the primary ORR active site, while rGO facilitates electron transfer, thereby enhancing ORR catalytic activity. This study presents a feasible approach to improving the slow ORR kinetics in ZABs using a high-entropy strategy.