Efficient carbon-supported Ag-MFe2O4 (MÂ =Â Co, Mn) core-shell catalysts for oxygen reduction reactions in alkaline media

Nanoparticles with core-shell or hollow interiors have immense potential for catalysis. Herein, Ag@MxFe3−xO4 (M = Co, Mn) core-shell nanoparticles were firstly synthesized through a seed-mediated method. These particles were then loaded onto carbon catalyst supports to form Ag@MxFe3−xO4/C. Then, hollow-MxFe3−xO4/C was prepared with the diffusion of Ag from Ag@MxFe3−xO4/C in saturated NaCl solution at room temperature. As a result, Ag@MnFe2O4/C demonstrates better oxygen reduction reaction (ORR) activity than Ag@CoFe2O4/C and other Ag@MnxFe3−xO4/C with various Mn/Fe ratios. Moreover, Ag@MFe2O4/C shows superior ORR catalytic activities over hollow-MFe2O4/C, which can be due to electronic coupling between Ag core and MFe2O4 shell. Furthermore, Ag@MnFe2O4/C catalysts demonstrate high durability for the ORR in alkaline media and insensitivity to methanol. These findings will provide helpful guidance for design and fabrication of carbon-supported core-shell catalysts for ORR in the future.