Cobalt- and iron-coordinated graphitic carbon nitride on reduced graphene oxide: A nonprecious bimetallic M–N_x–C analogue electrocatalyst for efficient oxygen reduction reaction in acidic media

The electrocatalytic oxygen reduction reaction (ORR) in acidic media is quite strenuous. Although platinum (Pt)-based materials are considered state-of-the-art ORR catalysts, their high cost and poor durability greatly impede their extensive application in polymer electrolyte membrane fuel cells and direct methanol fuel cells. Here, we report a bimetallic M–N_x–C-class electrocatalyst comprising Co- and Fe-coordinated graphitic carbon nitride ((Co,Fe)–CN) and reduced graphene oxide (RGO) as an effective substitute for expensive Pt-based catalysts for the ORR in acidic media. The fabricated (Co,Fe)–CN/RGO catalyst exhibits a high surface area, high porosity, fast charge-transfer kinetics at the (Co,Fe)–CN/RGO 2D/2D interface, and abundant Co–N_x–C and Fe–N_x–C active sites. Because of these favorable properties, the optimized (Co,Fe)–CN/RGO catalyst displayed extraordinary electrocatalytic ORR activity, with an onset potential of 875 mV, which is only 41 mV more negative than that of a commercial Pt/C, and follows an efficient four-electron reaction pathway in acidic media. Notably, the fabricated catalyst demonstrated excellent methanol tolerance and long-term stability compared with the reference Pt/C. Therefore, this work provides a rational design approach to fabricating graphitic-C₃N₄-based nonprecious bimetallic electrocatalysts with M–N_x–C active sites for enhanced ORR activity in fuel-cell applications.