Constructing amorphous/amorphous heterointerfaces in nickel borate/boride composites for efficient electrocatalytic methanol oxidation

Abstract

Owing to the inherently torpid kinetics involving an intricate multi-electron redox process, the methanol oxidation reaction (MOR) severely restrains the efficiency of direct methanol fuel cells (DMFCs). Herein, we put forward a room-temperature liquid-phase reaction strategy to construct an amorphous/amorphous heterojunction structure in a nickel borate/boride composite. It is found that the two sides of the heterointerface are composed of amorphous nickel boride (a-Ni_xB) nanoparticles and amorphous nickel borate (a-Ni-B_i) ultrathin nanosheets. Experimental measurements reveal that the amorphous/amorphous heterostructure endows the catalyst with enhanced charge transport capacity and stepped-up formation of electroactive NiOOH species, both of which contribute considerably to optimizing the catalytic kinetics for the MOR. As a result of the highly exposed active area and better intrinsic reactivity of catalytic sites, the amorphous Ni-B_i/Ni_xB (a-Ni-B_i/Ni_xB) hybrid catalyst exhibits outstanding electrocatalytic MOR activity with a low onset potential of 0.38 V vs. Ag/AgCl and a large current density of 213 mA cm⁻² at a potential of 0.6 V vs. Ag/AgCl, which can be comparable to the best MOR performance of highly active Ni-based catalysts to date. This work opens new opportunities to design and synthesize efficient MOR electrocatalysts.