Controlled Proton Transport via Self-Assembled Bimetallic Phosphate Nanotunnel Electrocatalyst

Electrochemical upgrading of 5-hydroxymethylfurfural (HMF) to 2,5-furandicarboxylic acid (FDCA) is limited by sluggish proton-coupled electron-transfer (PCET) kinetics and uncontrolled proton gradients. Herein, we report on a phytic acid-directed self-assembly design strategy for electrocatalysts that generates carbon-confined Cu/Ni/P nanotunnels, establishes proton-shuttling channels via Grotthuss-type hopping, and decouples potential-dependent adsorption from PCET to enable efficient oxidation of HMF. This precursor-selective approach differs fundamentally from conventional phosphorylation processes, allowing precise control over proton transport to decouple potential-dependent adsorption from PCET. The catalyst achieves near-quantitative performance, 100% HMF conversion with 99.9% FDCA yield and 98.2% FE at 1.47 V vs RHE, while sustaining 2 A cm –2 at 1.84 V up to 100 mM HMF. In situ Raman spectroscopy, DFT calculations and TOF reveal that phosphate moieties dynamically modulate Ni/Cu (oxy)hydroxide active sites and lower the rate-limiting dehydrogenation barriers by 0.73 eV through efficient proton relay and increase the TOF (0.06 s –1 to 1.09 s –1 ). A flow electrolyzer maintained stable operation for 120 h at 250 mA cm –2 with an FDCA productivity of 78 mg h –1 cm –2 . Techno-economic analysis confirms profitability at current densities as low as 100 mA cm –2 with 90% FE and electricity costs of 6–7 cents kW h –1 .