Energy-efficient monosaccharides electrooxidation coupled with green hydrogen production by bifunctional Co9S8/Ni3S2 electrode

•Coupling electrochemical HER with xylose electrooxidation using a bifunctional Co9S8/Ni3S2 electrocatalyst.•Electrochemically generated Co2+/Co3+, Co3+/Co4+, Ni2+/Ni3+, and Ni3+/Ni4+ redox promote the monosaccharide oxidation.•Monosaccharide electrooxidation upgrading to value-added commodity along with green H2 production.•The xylose oxidation reduced the overall energy consumption with respect to the water electrolysis. Water electrolysis is a sustainable strategy for renewable energy conversion and storage that can be replenished by intermittent electricity sources. Despite the decades-long progress, the commercialization of water electrolysis remains fraught with difficulties owing to its high electricity consumption. We couple the hydrogen evolution reaction with the electrooxidation of xylose obtained from regenerated hemicellulose to organic acids, utilizing a bifunctional electrode consisting of Co9S8/Ni3S2. The electrochemically activated anodic sites, including Co2+/Co3+, Co3+/Co4+, Ni2+/Ni3+, and Ni3+/Ni4+ redox species, are responsible for xylose electrooxidation, with the required potential reduced by 290 mV at 100 mA cm−2 compared with water oxidation. Moreover, the process yields over 60% towards formic acid at the anode, is accompanied by the production of hydrogen at the cathode. Xylose oxidation is kinetically and thermodynamically more favorable than water oxidation, significantly reducing the overall energy consumption relative to conventional water electrolysis. This study provides a promising strategy for the scalable and energy-efficient process of biomass electrooxidation coupled with hydrogen production.