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

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.