Hydrogen Bridge-Mediated Efficient Electrooxidation of 5-Hydroxymethylfurfural on Ni(OH)─PO /Ni(PO) Heterojunctions.

Accelerating proton deintercalation and transfer on the catalyst surface is crucial for the electrochemical oxidation of 5-hydroxymethylfurfural (HMF) into the high-value 2,5-furanodicarboxylic acid (FDCA). Herein, we have constructed a Ni(OH)─PO /Ni(PO) heterojunction catalyst that demonstrates exceptional selectivity (97.16%), yield (94.16%), and Faraday efficiency (94.31%) in the selective oxidation of HMF toward FDCA. The incorporation of PO groups triggers the formation of hydrogen bridges and reconfigures the interfacial charge distribution, facilitating the activation and subsequent proton deintercalation of lattice-hydroxyl-groups to generate active Ni─O catalytic sites (PO ⋯H─O─Ni → HPO + Ni─O). Both density functional theory calculations and pH-dependent experiments emphasize the crucial function of these hydrogen bridges as proton ferries, effectively boosting the proton transfer efficiency during HMF oxidation. Theoretical studies unveil that the rate-controlling step for OH adsorption on Ni(OH)─PO occurs via the hydrogen bridge connecting the PO group with the α-C atom in *HMF-H intermediate (PO ⋯H─O⋯COR → PO ─H⋯O─COR), significantly reducing the energy barrier for HMF oxidation. This study introduces a novel hydrogen bridge-mediated electrooxidation mechanism that holds great potential for advancing biomass conversion technologies.