Steering adsorption behavior of 5-hydroxymethylfurfural at CuAu alloys for one-electron dehydrogenation electrocatalysis pairing anodic 5-hydroxymethyl-2-furancarboxylic acid and bipolar hydrogen production

Selective electrocatalytic 5-hydroxymethylfurfural (HMF) oxidation reaction (HMFOR) is believed to be highly dependent on the surface adsorption behaviors. Herein, a series of CuAu alloys with various metallic compositions and steered surface adsorption behaviors were prepared by a one-step electrodeposition method. By optimizing the Cu molar ratios, a superior electrocatalytic performance for HMFOR via one-electron dehydrogenation could be observed over Cu_0.25Au_0.75, reaching a current density of 84.8 mA cm–2 at 0.4 V vs. RHE, with 94.5% 5-hydroxymethyl-2-furancarboxylic acid (HMFCA) yield, 98.6% HMFCA faradaic efficiency (FE) and 94.6% H₂ FE. Remarkably, with Cu_0.25Au_0.75 as the anode and Pt/C as the cathode, the integrated membrane electrode assembly electrolyzer could operate at a low cell voltage of 0.45 V for simultaneous HMFOR and bipolar H₂ production, with 94.5% HMFCA FE and ~200% H₂ FE. Experimental investigations and theoretical calculations demonstrate that the alloying induced charge redistribution between Cu and Au could modulate the d-band centers, and then steer the surface adsorption behaviors to balance HMF adsorption and HMFCA desorption at surface, ensuring the active site availability for one-electron dehydrogenation HMFOR. This work presents a facile strategy for designing efficient electrocatalysts for ultralow-potential HMFOR, with fundamental surface adsorption behaviors deepened for biomass electrooxidation.