Preparation And Electrocatalytic Performance Of Silver-Manganese Ferrate Nanocomposites Supported On Doped-Graphenes

Fuel cell is a new energy conversion and storage device with low pollution,high power density and high energy conversion efficiency.In order to promote oxygen reduction reaction?ORR?at cathode,transition metal oxide/doped graphene nanocomposites are prepared and analyzed for their electrocatalytic activity.Effects of the content/species of doped atoms in graphene supports on the structural stability and electrocatalytic activity of Ag-MnFe₂O₄ nanoparticles are systematically studied.Nitrogen doped graphene?NG?,sulfur doped graphene?SG?and nitrogen-sulfur codoped graphene?NSG?are synthesized with high temperature calcination.Through comparative analyses,it is found that the type of doped atoms has great influence on the electrocatalytic performance of ORR.NG has the best ORR electrocatalytic performance.In addition,the amount of nitrogen source?melamine?is critical to the electrocatalytic performance of NG.Ag-MnFe₂O₄ nanoparticles have been prepared with solvothermal method and deposited on doped graphenes.Interestingly,these particles keep primarily heterogeneous structure for the assembly on NSG,while Ag domains shrink a lot on S-dopedgraphene?SG?andN-dopedgraphene?NG?.Subsequently,Ag-MnFe₂O₄/NSG shows the best oxygen reduction reaction?ORR?and oxygen evolution reaction?OER?activities 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 candidate.Phosphorus doped graphene?PG?,nitrogen-phosphorus codoped graphene?NPG?,sulfur-phosphorus codoped graphene?SPG?and nitrogen-sulfur-phosphorus tridoped graphene?NSPG?supporters are prepared by calcination at high temperature.These doped graphenes are utilized as supports for Ag-MnFe₂O₄ nanoparticles.Results show that the calcination temperature will affect the ORR catalytic performance of PG,and the synergistic effect between NSPG and Ag-MnFe₂O₄ improve the electrocatalytic performance of the Ag-MnFe₂O₄/NSPG nanocomposite.Finally,the electrocatalytic performance of Ag-MnFe₂O₄/NSPG is better than Ag-MnFe₂O₄/NPG and Ag-MnFe₂O₄/SPG.In addition,Ag-MnFe₂O₄/NSPG has better OER performance,higher stability and better methanol tolerance than commercial Pt/C.