Radical-mediated electrocatalytic dimerization of furfural for bio-jet precursor over non-metallic catalysts with nitrogen-doped carbonaceous matrix

The electrocatalytic conversion of biomass-derived furfural (FF) into value-added chemicals represents a promising strategy for sustainable chemical synthesis. However, achieving high selectivity toward specific products, particularly C–C coupled dimers for bio-jet fuels, remains challenging due to competing hydrogen evolution and over-hydrogenation reactions. Herein, we developed a non-metallic catalyst derived from lignocellulosic biomass following a facile hydrothermal-pyrolysis process, where the hydrothermally combined heteroatoms by oxygen functionalities are in-situ fixation through high-temperature pyrolysis, together with a hierarchical porous structure that is beneficial for mass transfer. Controlled experiments revealed that pyrolysis temperature proved to be the most critical factor among all synthesis parameters, with 900°C yielding an optimal balance of nitrogen speciation and graphitic framework development that is essential for both activity and selectivity; under optimized conditions, the prepared catalyst (i.e. NC 900 ) achieves 98.7% FF conversion with 50.3% selectivity toward hydrofuroin (HDF) and a Faradaic efficiency of 45.2%. Furthermore, a series of in-situ techniques including the measurement of open circuit potential, hydrogen underpotential deposition, and electron paramagnetic resonance spectroscopy were conducted, which indicated that the electrocatalytic dimerization proceeds through a surface-catalyzed single-electron transfer followed by solution-phase radical coupling. More specifically, FF molecules are first adsorbed and protonated on the nitrogen-doped carbon surface, followed by single-electron reduction to generate carbon-centered radical intermediates, which then rapidly desorb and undergo homocoupling in the solution phase to form the HDF dimer. Nitrogen dopants enhance FF adsorption through electronic modification of the carbon surface, facilitate controlled single-electron transfer at appropriate redox potentials, and promote rapid radical desorption that favors solution-phase coupling over surface-bound side reactions. This work demonstrates the potential of rationally designed metal-free carbon catalysts for selective biomass electroconversion and provides mechanistic insights for developing sustainable C–C coupling strategies. The revealed radical-mediated coupling mechanism lays the foundation for designing mechanism-inspired metallic catalysts with enhanced performance and broadened substrate scope.