High loading of atomically exposed edge nickel sites embedded in hollow porous carbon nanofibers for enhanced methanol electrooxidation in direct methanol fuel cells

Abstract

The enhancement of catalytic activity and durability for atomically dispersed metal-nitrogen-carbon (M–N–C) catalysts in methanol oxidation reaction (MOR) anodes within direct methanol fuel cells presents a significant challenge. Here, we developed hollow porous nanofiber catalysts featuring edge Ni–N₄ atomic sites through coaxial electrostatic spinning with domain-restricted Ni atoms embedded within a zeolitic imidazolium ester backbone, thereby increasing the exposure of accessible active sites (Ni: 4.96 %). The distinctive hollow porous fiber morphology and hierarchical structure facilitate convenient electronic conductivity and mass transport of reactants. Theoretical findings indicate that the surface adsorption of methanol at the edge Ni–N₄ atomic sites exhibits negative free energy, promoting the adsorption and activation of reactants. Furthermore, the initial dehydrogenation step demonstrates a low free energy change, favoring reaction kinetics. The membrane electrode assembly achieved a power density of 42.2 mW cm⁻² in single-cell application tests while displaying improved durability. This research provides valuable insights for future advancements in single-atom catalyst development for fuel cells or other energy applications.