Self-assembly of graphene quantum dots into 2D textile-derived Janus Fe/FeOx@C for oxygen electrocatalysis

Abstract

Carbons play a significant role in the electrocatalytic oxygen reduction reaction (ORR) owing to the strong interaction between carbon and loaded electroactive centers, which usually requires a high degree of graphitization and uniform heteroatom (e.g., N, S, and O)-doping on carbon. Herein, we propose a self-assembly strategy to synthesize graphene quantum dot (GQD)-based 2D textile as a substrate for metal ion loading, which was further pyrolyzed into Fe/FeO_x particles covered by a nitrogen-doped carbon shell (Fe/FeO_x@C). Benefiting from the periphery amino and hydroxyl groups in GQDs, the coordination of Fe with N and O in the assembly leads to the formation of metallic Fe–N and FeO_x to form highly dispersed Janus Fe/FeO_x particles, while the graphitic sp² domain of GQDs improves the degree of graphitization during pyrolysis. Remarkably, the resulting Fe/FeO_x@C exhibits superior electrocatalytic performance toward both the ORR and OER, with a half-wave potential of 0.85 V vs. RHE and an overpotential of 350 mV to deliver a current density of 10 mA cm⁻² for the OER, which further facilitates bifunctional oxygen electrocatalysis with a gap of 0.73 V between the OER potential (10 mA cm⁻²) and the ORR half-wave potential. This work provides new insight into the rational design of carbon substrates with high-degree graphitization and uniform heteroatom distribution for the ORR.