Electrochemical hydrogenation of furfural for synthesis of furfuryl alcohol over copper oxide catalytic electrode.

Furfural (FF) is a biomass-derived platform molecule characterized by an aldehyde group attached to a furan ring. The selective electrochemical hydrogenation (ECH) of the aldehyde group into hydroxymethyl offers a sustainable approach for converting FF into valuable furfuryl alcohol (FA) chemical. Efficient catalyst that balances active hydrogen (H*) generation and FF adsorption is crucial for electrochemical FF-to-FA conversion. Herein, a self-supported copper oxide (CuO) with mixed Cu oxidation values was fabricated onto Cu foam substrate (CuO/CF) via facile electrodeposition and was investigated as a catalytic electrode for ECH of FF to FA. Under optimal condition, the electrocatalytic system achieved a maximized faradaic efficiency (FE) of 83 % and a selectivity of 95 % for FA synthesis at a cathodic current density (J) of -20 mA cm. Electrochemical in situ Raman spectroscopy, H* detection, and thiol passivation experiments revealed the ECH pathway for FF conversion. In this progress, the H* generated via water dissociation reacts with adsorbed FF to afford FA with high FE and selectivity over CuO/CF. In situ X-ray diffraction (XRD) characterizations evidenced that the reductive reconstruction of CuO active layer into Cu metal under negative potential, which enhances the generation of H* and facilitates the ECH of adsorbed FF to FA. Furthermore, pairing the cathodic ECH of FF with anodic magnesium (Mg) oxidation reaction constituted a Mg-FF battery, which enabled electricity output at a high power density (3.7 mW cm) during FA electrosynthesis. This work offers essential instruction for electrochemical valorization of biomass-derived FF molecule, and showcases a viable paradigm for construction of metal-organic battery to concurrently generate electricity and value-added chemicals.