Beyond active sites: interfacial water engineering with single-atom Ni-WC _<i>x</i> for concurrent energy storage and biomass conversion

Coupling biomass valorization with rechargeable metal-air batteries offers a promising strategy to address energy storage and sustainable synthesis challenges. However, it demands highly active bifunctional catalysts capable of replacing the sluggish oxygen evolution reaction (OER) with value-added biomass electrooxidation. We report here a single-atom nickel-decorated tungsten carbide (Ni-WC _<i>x</i> ) catalyst that demonstrates exceptional bifunctional activity for both the oxidation of 5-hydroxymethylfurfural (HMF) and the oxygen reduction reaction (ORR). The catalyst achieves near-quantitative conversion of HMF to furandicarboxylic acid (FDCA) with 99% selectivity and shows excellent ORR performance, featuring a half-wave potential (<i>E</i> _1/2) of 0.855 V. Through <i>in situ</i> spectroscopic analysis and multiscale simulations, we reveal a dual role of the atomically dispersed Ni ^<i>δ</i>+ sites: serving as intrinsic active centers and reconstructing the interfacial hydrogen-bond network to facilitate mass transport of bulky HMF molecules. When applied in an HMF-assisted Zn-air battery, the catalyst enables an ultralow charge-discharge voltage gap of 0.71 V at 20 mA cm^-2 and remarkable cycling stability. This work proposes a new design strategy for electrocatalysts, emphasizing interfacial solvent engineering as a critical route to advanced hybrid energy-chemical systems.