▎ 摘　　要

Heterogeneous nanopartides with synergistic effects between different composites are potential catalysts with bifunctional catalytic activity for oxygen reduction (ORR) and oxygen evolution reaction (OER). Herein, heteroatoms such as N and S are doped into graphene substrates to improve catalytic activity and structural stability of Ag-MnFe2O4 nanoparticles, Interestingly, these particles keep a primarily heterogeneous structure for their assembly on N, S-codoped graphene (NSG), while Ag domains shrink on S-doped graphene (SG) or N-doped graphene (NG). Subsequently, Ag-MnFe2O4 /NSG shows the best bifunctional catalytic activity due to the improved stability of Ag-MnFe2O4 NPs on NSG and enhanced bonding energy between supports and particles. The Koutecky-Levich plots confirm a major four-electron reaction pathway for the ORRs on Ag-MnFe2O4/NSG. Meanwhile, Ag-MnFe2O4/NSG exhibits higher stability and better methanol tolerance than commercial Pt/C. Therefore, Ag-MnFe2O4/NSG with bi functional catalytic activity for ORR and OER is a promising non-Pt catalyst candidate. (C) 2020 Elsevier B.V. All rights reserved.