Hydrogenolysis of Lignin Model Compounds on Ni Nanoparticles Surrounding the Oxygen Vacancy of CeO2

Thecleavage of C-O bonds presents the crucial step forrealizing the depolymerization of lignin. Herein, we report that Ninanoparticles (NiNPs) supported on CeO2 with oxygen vacancies(O-v) show high activity and selectivity in hydrogenolysisof C-O bonds of diphenyl ether (DPE, a lignin model compound),while single-site Ni (SSNi) is nearly inactive in the reaction. Temperature-programmeddesorption (TPD) demonstrates that both DPE and H-2 canbe adsorbed and activated on NiNPs. Density functional theory (DFT)calculation further indicates that the NiNPs are more reactive forH(2) and DPE because the O-v at the interface betweenNiNPs and CeO2 can greatly enhance the adsorption of DPE,but no adsorption of DPE on SSNi was observed. It is identified thatthe Ni atoms of NiNPs neighboring the O-v of CeO2 are the catalytic sites of the Ni/CeO2 catalyst for theefficient cleavage of C-O bonds in lignin model compounds.This work highlights that the Ni sites neighboring the O-v of CeO2 can act as efficient active sites for rupturingthe C-O bonds in lignin models, which can be conducive to therational design of metal-supported catalysts, especially for the hydrogenolysisof C-O bonds in biomass conversion.