Mn doping for regulating the electronic structure of Co3O4 to construct dual active sites for oxygen electrocatalysis

Abstract

Efficient bifunctional catalysts for the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER) are crucial for rechargeable Zn–air batteries (ZABs). However, these catalysts often suffer from poor O₂ conversion efficiency and a lack of dual active sites for oxygen reactions. Regulating the electronic structure through elemental doping is an efficient strategy for constructing dual active sites of catalysts. Nevertheless, the mechanisms of O₂ adsorption/activation, the nature of the reaction active sites, and the associated energy barriers remain poorly understood. Herein, we report a Mn-doped Co₃O₄ (MnCo₂O₄) bimetallic oxide. The impact of Mn doping on the ORR/OER performance of Co₃O₄ is investigated using both density functional theory (DFT) calculations and experimental methods. The DFT findings indicate that Mn doping modifies the electronic structure, activates Co sites in Co₃O₄, and introduces new Mn active sites, resulting in dual active sites for the OER/ORR. As predicted, MnCo₂O₄ exhibits remarkable ORR/OER performance, with a potential difference (ΔE) as low as 0.87 V, which is 0.11 V smaller than that of Co₃O₄. Furthermore, a rechargeable ZAB delivers a narrow discharge–charge voltage gap (0.76 V), high cycling stability over long periods (90 h), and a peak power density of up to 97 mW cm⁻² in a liquid system. Such excellent results demonstrate that Mn–Co bimetallic synergistic catalysis is an effective strategy for improving ORR/OER selectivity.