Ultrathin reticulated carbon material as a metal-free electrocatalyst for oxygen reduction reaction

Abstract

Development of excellent oxygen reduction reaction (ORR) electrocatalysts for fuel cell cathodes is critical for sustainable commercialization. However, transition metal catalysts produce H2O2 during ORR catalysis, promoting the Fenton reaction, and Pt-based catalysts are expensive and prone to poisoning and inactivation. Therefore, developing metal-free ORR catalysts is critical. Herein, a N, F, and S triple-doped metal-free ORR electrocatalyst, T1P1-950, was synthesized using thiourea and polytetrafluoroethylene via a one-step heat treatment method. T1P1-950 exhibited a graphene-like reticulated structure, and its ORR half-wave potential (E1/2) was 16 mV higher than that of Pt/C in an alkaline medium (0.861 V vs. 0.845 V). In acidic media, the ORR E1/2 of T1P1-950 was 80 mV lower than that of Pt/C (E1/2: 0.751 V vs. 0.831 V). In addition, T1P1-950 was superior to Pt/C in terms of methanol resistance and durability. This can be attributed to the following factors: (1) The catalyst has a network structure similar to that of graphene, which is conducive to the transport of reactive particles in the ORR; (2) the synergistic effect of N, F, and S doping enhances the ORR efficiency of the active sites; and (3) the catalyst has high active functional group and N contents of 6.1% and 7.1%, respectively, which is conducive to the formation of more active sites. In addition, the assembled zinc-air battery also proves that the T1P1-950 has excellent oxygen electrocatalytic performance in practical operation. This study offers a universal technique for producing a broad range of heteroatom-doped ultrathin reticulated carbon materials.