Flower-Like Ag-Supported Ce-Doped Mn3O4 Nanosheets Heterostructure for Highly Efficient Oxygen Reduction Reaction: Roles of Metal Oxides in Ag Surface States

Tuning Ag surface states by metal oxides is a feasible method to enhance oxygen reduction reaction (ORR) performance of Ag-based catalysts. Herein, we develop a heterostructural electrocatalyst of the flower-like Ag-supported nanosheets of metal oxides (Mn3O4 and Ce-doped Mn3O4) by a facile two-step solution method for highly-efficient alkaline ORR. Not only does Mn3O4/Ag exhibit a comparable activity to commercial Pt/C, but also small amounts of Ce3+ (2~5 mol.%) doped into Mn3O4 make ORR activity and stability outperform those of Pt/C. The roles of the adjustment for Ag surface states induced by the supported Mn3O4 and Ce doping in the enhanced ORR performance were studied. The strong electrons transfer from Ag substrates to Mn3O4 makes the d-center of Ag shift up, accelerating the kinetics of O-O bond split on Ag surfaces (increasing the activity of active sites for O-O bond dissociation). Additionally, 5% Ce3+ doping further tunes Ag surface electronic structures to improve ORR performance of Mn3O4/Ag....