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

Abstract

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/cm2 using Fe single-atom catalysts, and reaches 1 A/cm2 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/cm2@1.1 V at 60 °C (2.63 kWh/Nm3 H2), which requires half of the electricity consumption in conventional water electrolysis (~5 kWh/Nm3 H2). This work provides a new avenue for achieving industrial-scale hydrogen production from biomass.