Ag-enhanced Catalytic Performance of Ordered Mesoporous Fe-N-Graphitic Carbons for Oxygen Electroreduction

Mesoporous Fe-N-C supported Ag nanoparticles (AgNPs) with different metal loadings (Fe-N-C/AgNPs-n, n = 1, 2, 3) were prepared by a facile method. The as-prepared Fe-N-C/AgNPs-n catalysts were demonstrated to be the excellent electrocatalysts for oxygen reduction reaction (ORR) in alkaline media. The Fe-N-C/AgNPs-2 exhibited the highest electrocatalytic activity with onset potential of 1.03 V and half-wave potential of 0.88 V for ORR, which were higher than commercial Pt/C (20 wt%) and Fe-N-C catalysts reported in the literature. Moreover, the prepared Fe-N-C/AgNPs-2 material possessed intrinsic long-time stability and the excellent methanol resistance toward the ORR in alkaline media. The Tafel slope and Tafel curve shape for ORR on Fe-N-C/AgNPs-n and Fe-N-C and the decrease of N's binding energy in the Fe-N-C/AgNPs-n testify that the active sites for ORR in Fe-N-C/AgNPs-n are on Fe-N-C rather than on AgNPs. The AgNPs enhance the electrocatalytic activity of Fe-N-C for ORR as cocatalyst by inducing a more negative charge on the adjacent N to C, which may be the important reason for improving ORR performance of Fe-N-C.