CuO/Co₃O₄ Bifunctional Catalysts for Electrocatalytic 5-Hydroxymethylfurfural Oxidation Coupled Cathodic Ammonia Production

The electrochemical coupling of biomass oxidation and nitrogen conversion presents a potential strategy for high value-added chemicals and nitrogen cycling. Herein, in this work, CuO/Co₃O₄ with heterogeneous interface is successfully constructed as a bifunctional catalyst for the electrooxidation of 5-hydroxymethylfurfural to 2,5-furandicarboxylic acid and the electroreduction of nitrate to ammonia (NH₃). The open-circuit potential spontaneous experiment shows that more 5-hydroxymethylfurfural molecules are adsorbed in the Helmholtz layer of the CuO/Co₃O₄ composite, which certifies that the CuO/Co₃O₄ heterostructure is conducive to the kinetic adsorption of 5-hydroxymethylfurfural. In situ electrochemical impedance spectroscopy further shows that CuO/Co₃O₄ has faster reaction kinetics and lower reaction potential in oxygen evolution reaction and 5-hydroxymethylfurfural electrocatalytic oxidation. Moreover, CuO/Co₃O₄ also has a good reduction effect on NO₃^-. The ex-situ Raman spectroscopy shows that under the reduction potential, the metal oxide is reduced, and the generated Cu₂O can be used as a new active site for the reaction to promote the electrocatalytic conversion of NO₃^- to NH₃ synthesis. This work provides valuable guidance for the synthesis of value-added chemicals by 5-hydroxymethylfurfural electrocatalytic oxidation coupled with NO₃^- while efficiently producing NH₃.