Abstract: The development of cost-effective and efficient bifunctional electrocatalysts remains a major challenge in coupling biomass-derived platform molecules, such as 5-hydroxymethylfurfural (HMF), with green hydrogen production. In this study, a P-doped Co₃S₄/NF electrocatalyst with excellent catalytic activity was successfully synthesized using a novel plasma-assisted doping technique. Electrochemical evaluations demonstrated outstanding performance, achieving a low potential of 1.21 V vs. RHE at 100 mA cm^-2 in 1 M KOH containing 20 mM HMF. Anion exchange membrane (AEM) simulations under industrial operating conditions confirmed that the catalyst exhibited long-term electrochemical stability at elevated temperatures while effectively coupling the hydrogen evolution reaction (HER) with the HMF oxidation reaction (HMFOR). In situ Raman spectroscopy revealed the dynamic evolution of sulfur and phosphorus species on the surface of the P-Co₃S₄/NF electrode. These findings indicate that the active species synergistically enhance HMFOR activity through electro-oxidation, dissolution, and re-adsorption processes, contributing to sustained stability. Furthermore, theoretical calculations showed that phosphorus doping optimizes the adsorption of *OOH intermediates, lowering the reaction energy barrier and enabling highly efficient conversion of HMF into 2,5-furandicarboxylic acid (FDCA). This unique plasma-assisted doping strategy offers valuable insights for the rational design of high-performance transition-metal-based electrocatalysts for integrated biomass conversion and hydrogen production.

Key words: Biomass upgrading, HMF electro-oxidation, Green chemistry, Plasma-assisted doping, AEM