Electronic modulation with heterointerface engineering of CoNiB/g-C₃N₄ for enhanced bifunctional electrocatalysis of oxygen evolution and hydrogen evolution reactions

This work synthesizes and uses a cobalt/nickel boride–graphitic carbon nitride (CoNiB/g-C₃N₄) heterostructure as a bifunctional electrocatalyst for the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER). With overpotentials of 89 mV for HER and 280 mV for OER at 10 mA cm⁻², and corresponding Tafel slopes of 108 and 41 mV dec⁻¹, the heterostructure demonstrates a remarkable activity. The heterostructure performs better than pure CoNiB and g-C₃N₄ because of its strong electronic coupling, more exposed active sites, reduced charge-transfer resistance, and long-term durability. Density functional theory (DFT) calculations confirm that cobalt sites (Co-sites) of the CoNiB/g-C₃N₄ heterostructure are primary active sites, with an optimized electronic structure that enhances OER kinetics and nearly has optimum hydrogen adsorption energy (ΔG_H∗). This study presents a cost-effective approach for designing transition metal boride-based heterostructures as high-performance bifunctional electrocatalysts for water splitting as well as for energy conversion and storage systems.