Phosphate-Mediated Proton-Shuttling Interfacial Microenvironment for Efficient 5-Hydroxymethylfurfural Electrooxidation

Engineering a phosphate-anchored proton-shuttling interfacial microenvironment on NiCo hydroxides. • Reversible PO 4 3− /HPO 4 2− interconversion accelerates the kinetics of hydrogen transfer process. • Achieving near-quantitative FDCA yield and robust stability in an MEA electrolyzer. • Validating the proton-shuttling strategy for oxidative upgrading of diverse biomass substrates. The rational design of interfacial microenvironments that regulate proton transfer is crucial for overcoming the kinetic bottleneck of proton-coupled electron transfer (PCET) in electrocatalytic biomass oxidation. Herein, we propose a phytic acid (PA)-derived phosphate modification strategy to construct a phosphate-mediated proton-transfer-regulated interface in NiCo(OH) x -PA for efficient 5-hydroxymethylfurfural (HMF) electrooxidation. Unlike conventional static ligand modification and active-site regulation strategies, phosphate groups utilize their Lewis basicity to regulate interfacial proton-transfer kinetics through reversible PO 4 3 ⁻/HPO 4 2 ⁻ interconversion, thereby promoting the Ni 2+ /Ni 3+ redox cycle during HMFOR. Operando spectroscopic characterization and theoretical calculations reveal that phosphate groups serve as dynamic proton relays to facilitate proton-transfer coupling between Ni 2+ -OH activation and HMF dehydrogenation, lowering the energy barrier of key reaction steps and enhancing HMFOR selectivity over the competing OER pathway. Consequently, the optimized NiCo(OH) x -PA catalyst achieves nearly quantitative FDCA Faradaic efficiency and excellent stability over 55 consecutive cycles. This phosphate-mediated proton-transfer-regulated interface provides a new strategy for designing efficient electrocatalytic biomass upgrading systems. Download: Download high-res image (168KB) Download: Download full-size image A phytic acid (PA)-induced surface reconstruction strategy is developed to accelerate proton-coupled electron transfer (PCET) during HMF electrooxidation. Surface-anchored phosphate groups act as proton shuttles, facilitating rapid deprotonation and boosting HMF-to-FDCA conversion with nearly 100% yield and Faradaic efficiency. This work provides a ligand-engineering paradigm for designing high-performance biomass-upgrading electrocatalysts.