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

The cleavage of C–O bonds presents the crucial step for realizing the depolymerization of lignin. Herein, we report that Ni nanoparticles (NiNPs) supported on CeO2 with oxygen vacancies (Ov) show high activity and selectivity in hydrogenolysis of C–O bonds of diphenyl ether (DPE, a lignin model compound), while single-site Ni (SSNi) is nearly inactive in the reaction. Temperature-programmed desorption (TPD) demonstrates that both DPE and H2 can be adsorbed and activated on NiNPs. Density functional theory (DFT) calculation further indicates that the NiNPs are more reactive for H2 and DPE because the Ov at the interface between NiNPs and CeO2 can greatly enhance the adsorption of DPE, but no adsorption of DPE on SSNi was observed. It is identified that the Ni atoms of NiNPs neighboring the Ov of CeO2 are the catalytic sites of the Ni/CeO2 catalyst for the efficient cleavage of C–O bonds in lignin model compounds. This work highlights that the Ni sites neighboring the Ov of CeO2 can act as efficient active sites for rupturing the C–O bonds in lignin models, which can be conducive to the rational design of metal-supported catalysts, especially for the hydrogenolysis of C–O bonds in biomass conversion.