Abstract
High-performance non-precious metal catalysts exhibit high electrocatalytic activity for the oxygen-reduction reaction (ORR), which is indispensable for facilitating the development of multifarious renewable energy systems. In this work; N-doped carbon-encapsulated Fe(3)C nanosphere ORR catalysts were prepared through simple carbonization of iron precursors loaded with polyacrylamide microspheres. The effect of iron precursors loading on the electrocatalytic activity for ORR was investigated in detail. The electrochemical measurements revealed that the N-doped carbon-encapsulated Fe(3)C nanospheres exhibited outstanding electrocatalytic activity for ORR in alkaline solutions. The optimized catalyst possessed more positive onset potential (0.94 V vs. reversible hydrogen electrode (RHE)), higher diffusion limiting current (5.78 mA cm(-2)), better selectivity (the transferred electron number n > 3.98 at 0.19 V vs. RHE) and higher durability towards ORR than a commercial Pt/C catalyst. The efficient electrocatalytic performance towards ORR can be attributed to the synergistic effect between N-doped carbon and Fe(3)C as catalytic active sites; and the excellent stability results from the core-shell structure of the catalysts.