Borohydride oxidation-water reduction fuel cells advanced by local hydroxyl enrichment-inhibited borohydride hydrolysis on Cu(0) sites

Abstract

A promising fuel cell using the acidic hydrogen evolution reaction (HER) instead of kinetically sluggish oxygen reduction reaction to couple with the borohydride oxidation reaction (BOR) has been established. This BOR-HER fuel cell (BHFC) has achieved the concurrent electricity generation and hydrogen production. To catalyze HER/BOR, a copper (Cu)-doped cobalt phosphide nanosheet grown on Cu foam (Cu–CoP/CF) was developed, which exhibits significantly inhibited competitive NaBH₄ hydrolysis during BOR, along with excellent HER performance and stability over 700 h. Specifically, the Cu(0), in situ formed on the surface of Cu–CoP/CF, plays a decisive role in creating an OH⁻-enriched local environment, resulting in significantly inhibited borohydride hydrolysis but greatly enhanced BOR selectivity of up to 85%, as well as the reduced thermodynamic barrier of BOR. The assembled BHFC equipped with Cu–CoP/CF is capable of generating a high power density of 114 mW cm⁻² and concurrently producing hydrogen at a rate of at least 40 mol h⁻¹ m⁻² at cathode.