Synergistic effect of Ag-doped Mn3O4 and AgCl composite as a regenerable and high-performance catalyst for the oxygen reduction reaction

Abstract

The rational development of efficient electrocatalysts to augment the sluggish oxygen reduction reaction (ORR) is essential for energy conversion and storage. Silver-based electrocatalysts have shown good performance towards ORR among the potential alternatives to commercial Pt electrocatalysts. Mixed transition metal oxides (MTMO) have also proven to be efficient towards ORR. This work demonstrates the excellent ORR activity of an Ag-doped Mn₃O₄ and AgCl composite synthesized in a single-step coprecipitation method. Compared to Pt/C, the composite exhibited outstanding methanol tolerance and stability. The superior activity of the composite is attributed to the synergistic contribution of the upshift of the d band center of Ag in AgCl and the presence of Mn²⁺, and Mn³⁺/Mn⁴⁺ redox centers in Mn₃O₄. A slight reduction in ORR activity was observed after stability cycles due to the electrochemical conversion of AgCl to nanoporous Ag; nonetheless, the performance can be restored by regenerating AgCl through gentle treatment with HCl. This work provides insights into developing cost-effective, methanol-tolerant, and stable electrocatalysts for ORR.