Interfacial Ru/RuO_x heterostructures on carbon support regulate selectivity in lignin hydrodeoxygenation

Constructing well-defined heterostructure interfaces in catalysts provides an approach to modulate scaling constraints and steer reaction pathways in biomass upgrading. Herein, we demonstrate that thermal restructuring of hydroxyl groups on carbon nanofibers (CNF) induces the formation of heterostructures of Ru/RuO_x, which function as bifunctional active sites for the one-pot hydrodeoxygenation (HDO) of lignin to liquid hydrocarbons. The optimized 5 wt% Ru/CNF catalyst delivers promising performance, achieving a mass/carbon yield of 49.1%/67.7%, with high selectivity toward saturated cycloalkanes. X-ray absorption spectroscopy and near-ambient pressure X-ray photoelectron spectroscopy confirm that thermal treatment of CNF tunes the oxidation state of Ru. DFT calculations reveal that O-rich Ru/CNF forms interfacial heterostructures of Ru/RuO_x polarized active sites, characterized by O^δ⁻···Ru^δ++···Ru^δ+ ensembles that heterolytically activate H₂ and strongly polarize C-O bonds in phenolic intermediates. The cooperative interplay between metallic Ru and partially oxidized RuO_x interfacial sites lowers the energy barriers for hydrogenation and deoxygenation reactions, enabling a cooperative‌ reaction pathway. These insights elucidate the molecular basis of tunable selectivity in lignin HDO and demonstrate that a polarized, oxygen-decorated metal-support interface provides general design principles for engineering next-generation catalysts for sustainable fuel production.