High-Performance Ni 3 P Catalyst for C═O Hydrogenation of Ethyl Levulinate: Ni δ+ as Outstanding Adsorption Sites

It is important but challenging to develop non-noble metal catalysts with high activity and selectivity for biomass conversion. The activation of C═O bond is a crucial step in biomass upgradation. Herein, a series of Ni- x P/Al 2 O 3 catalysts with different P/Ni molar ratios were prepared for the conversion of ethyl levulinate to γ-valerolactone. The developed Ni-0.38P/Al 2 O 3 catalyst was 5.4 times more active than conventional Ni/Al 2 O 3 based on turnover frequency and significantly outperformed the state-of-the-art non-noble metal catalysts. The unique catalytic performance was ascribed to the formation of Ni 3 P phase, which was identified by several characterizations. The results of DFT calculation and characterization by XPS and CO-FTIR revealed that electron was transferred from Ni to P with the formation of Ni δ+ sites. In situ FTIR for the surface reaction indicated that Ni δ+ acted as a new active site to activate the C═O bond, which rendered the high intrinsic activity of Ni 3 P for the C═O hydrogenation of EL.