Electrocatalytic C-C Coupled Oligomerization From Biomass Molecules Through Pd Single-Atom Interfacial Regulation.

Fossil-derived diesel raises sustainability and air-quality concerns, motivating biomass-based alternatives; however, current biodiesel routes suffer from food-fuel competition, poor fuel properties, and energy-intensive upgrading. Electrocatalytic C─C coupling of biomass molecules followed by hydrodeoxygenation (HDO) offers a cleaner pathway, yet has been limited to dimer formation. Here, we successfully resolved this longstanding bottleneck through construction of Pd1Cu single-atom alloy electrocatalyst, a trimer of 5-hydroxymethylfurfural is obtained with 44.7% selectivity. The combined oligomer (dimer and trimer) selectivity reaches 95.0% with 93.2% Faradaic efficiency, production rate achieves a record high of ∼50 g gcat -1 h-1. Subsequent HDO converts the oligomers into heteroatom-free n-dodecane and n-octadecane diesel blendstocks. Operando spectroscopy reveals a surface-confined ketyl-radical pathway in which isolated Pd atoms regulate hydrogen-atom supply and substrate adsorption, favoring C─C coupling over hydrogenation. This work establishes an electricity-driven route for controlled carbon-chain growth from biomass platforms.