Size-dependence on Electrochemical Performance of Fe-N-C Catalysts for Oxygen Reduction and Cathodes of Direct Methanol Fuel Cells

Comprehension of the structure-activity relationship is of great importance for the rational design of electrocatalysts for oxygen reduction reaction (ORR). Herein, Fe-N-C catalysts derived from zeolitic imidazolate framework-8 (ZIF-8) with tunable size ranging from 30 to 400 nm are precisely synthesized. Structural investigation indicates that the catalyst with smaller size possesses higher proportion of mesopore originated from particles stacking, which leads to enhanced catalyst utilization and accelerated mass transport. The size effect of catalyst on ORR activity is systematically investigated by rotation disk electrode (RDE) and direct methanol fuel cell (DMFC) tests. The electrochemical performance of the Fe-N-C catalyst is found increased with the reduction of its particle size. The correlation among size, mesoporosity and catalyst performance is discussed, giving new inspiration for the rational design strategies of the non-precious metal catalysts.