Acidic enol electrooxidation-coupled hydrogen production with ampere-level current density.

Hydrogen production coupled with biomass upgrading is vital for future sustainable energy developments. However, most biomass electrooxidation reactions suffer from high working voltage and low current density, which substantially hinder large-scale industrial applications. Herein, we report an acidic hydrogen production system that combined anodic ascorbic acid electrooxidation with cathodic hydrogen evolution. Unlike C-H and O-H bonds cleavage with slow kinetics in conventional organic oxidation, the highly active enol structure in ascorbic acid allows for an ultralow overpotential of only 12 mV@10 mA/cm 2 using Fe single-atom catalysts, and reaches 1 A/cm 2 at only 0.75 V (versus reversible hydrogen electrode) with approximately 100% Faraday efficiency for hydrogen production. Furthermore, the fabricated two-electrode membrane-free electrolyser delivers an industrial current density of 2 A/cm 2 @1.1 V at 60 °C (2.63 kWh/Nm 3  H 2 ), which requires half of the electricity consumption in conventional water electrolysis (~5 kWh/Nm 3  H 2 ). This work provides a new avenue for achieving industrial-scale hydrogen production from biomass.