Oxygen vacancies engineered self-supported B doped Co3O4 nanowires as an efficient multifunctional catalyst for electrochemical water splitting and hydrolysis of sodium borohydride

Developing earth abundant electrocatalyst is imperative to large-scale hydrogen production for transforming current fossil fuel-based economy into future renewable energy economy. In this paper, we report the synthesis of self-supported VOB-Co3O4/NF nanowire arrays directly grown on Ni foam, which can serve as a trifunctional catalyst for producing hydrogen and oxygen by electrolyzing water in alkaline media or producing hydrogen via hydrolyzing alkaline NaBH4 solution. The engineered boron and oxygen defects in Co3O4 nanowires prove to effectively modulate their electronic structure leading to the increased electrical conductivity and create a large quantity of electroactive sites. The resulting self-supported VOB-Co3O4/NF electrode delivers a current density of 50 mA cm−2 at overpotentials of 184 mV for hydrogen evolution reaction (HER) and 315 mV for oxygen evolution reaction (OER) in 1.0 M KOH with excellent stability and durability. The VOB-Co3O4/NF as both cathode and anode requires 1.67 V to achieve a current density of 10 mA cm−2 for overall water splitting reaction. Besides, VOB-Co3O4/NF presents much higher hydrogen generation rate (HGR) of 7055 mL min−1 gcatalyst−1 with activation energy (Ea) of ca. 29.7 kJ mol−1. for hydrolytic dehydrogenation of alkaline NaBH4 solution, outperforming most of the reported non-noble metal-based catalysts and even precious metal catalysts.