Impact of Textural Properties of Mesoporous Porphyrinic Carbon Electrocatalysts on Oxygen Reduction Reaction Activity

Abstract

Transition-metal- and N-codoped carbon (M−N/C) catalysts have shown great promise as alternatives to Pt-based catalysts in the oxygen reduction reaction (ORR). The preparation of M−N/C catalysts by exploiting mesoporous silica templates is highly appealing as this method can generate catalysts with high surface areas, well-developed porosities, and abundant active sites. Herein, we report the relationship between the textural properties of mesoporous silica-templated Fe−N/C catalysts and their ORR activity. Iron-doped mesoporous porphyrinic carbons (Fe−MPCs) with varying textural properties were synthesized through nanocasting using mesoporous silicas as the templates and Fe porphyrin as the precursor. Fe−MPC catalysts showed excellent ORR activities with half-wave potentials reaching 0.82 V and 0.90 V (vs. reversible hydrogen electrode, RHE) in acidic and alkaline electrolytes, respectively. Fe−MPC catalysts with smaller particle sizes, larger mesopore sizes, and three dimensionally interconnected pore structures showed enhanced ORR activities.