Unlocking concerted proton-electron transfer in cobalt oxyhydroxide for industrial-current biomass upgrading and integrated hydrogen production

Abstract

Cobalt oxyhydroxide (CoOOH) is a promising catalyst for biomass electrooxidation, yet its reaction mechanism remains contentious regarding its competition with the oxygen evolution reaction (OER) at high overpotentials. Herein, we resolve this controversy by identifying a key intermediate that triggers a switch from the lattice oxygen mechanism (LOM) for OER to a concerted proton–electron transfer (CPET) mechanism for the glucose oxidation reaction (GOR). Operando spectroscopy and isotope-labeling experiments reveal that the electrochemically generated O–Co4+(O*)–O site preferentially extracts protons from glucose via CPET, which effectively suppresses O─O coupling and parasitic oxygen evolution. This mechanism enables CoOOH to achieve a high GOR current density of 100 mA cm−2 at only 1.23 V vs. RHE with a formate Faradaic efficiency of 97.0%. Moreover, the two-electrode flow electrolyzer integrating GOR with hydrogen evolution reaction achieves a current of 2.7 A (300 mA cm−2) at a low cell voltage of 1.70 V, co-producing formate and hydrogen with high Faradaic efficiencies (87.5% and 98.4%, respectively), and maintaining stable operation for over 100 h. This work not only clarifies the CPET-dominated mechanism in biomass electrooxidation but also proposes a scalable strategy for energy‑saving coproduction of valuable chemicals and green hydrogen