A macroporous carbon nanoframe for hosting Mott–Schottky Fe–Co/Mo2C sites as an outstanding bi-functional oxygen electrocatalyst

Abstract

Simultaneously optimizing the d-band center of the catalyst and the mass/charge transport processes during the oxygen catalytic reaction is an essential but arduous task in the pursuit of creating effective and long-lasting bifunctional oxygen catalysts. In this study, a Fe–Co/Mo₂C@N-doped carbon macroporous nanoframe was successfully synthesized via a facile “conformal coating and coordination capture” pyrolysis strategy. As expected, the resulting heterogeneous electrocatalyst exhibited excellent reversible oxygen electrocatalytic performance in an alkaline medium, as demonstrated by the small potential gap of 0.635 V between the operating potential of 1.507 V at 10 mA cm⁻² for the oxygen evolution reaction and the half-wave potential of 0.872 V towards the oxygen reduction reaction. Additionally, the developed Zn–air battery employing the macroporous nanoframe heterostructure displayed an impressive peak power density of 218 mW cm⁻², a noteworthy specific capacity of 694 mA h g_Zn⁻¹, and remarkable charging/discharging cycle durability. Theoretical calculations confirmed that the built-in electric field between the Fe–Co alloy and Mo₂C semiconductor could induce advantageous charge transport and redistribution at the heterointerface, contributing to the optimization of the d-band center of the nanohybrid and ultimately leading to a reduction in the reaction energy barrier during catalytic processes. The exquisite macroporous nanoframe facilitated the rapid transport of ions and charges, as well as the smooth access of oxygen to the internal active site. Thus, the presented unique electronic structure regulation and macroporous structure design show promising potential for the development of robust bifunctional oxygen electrodes.