High-Performance Ni3P Catalyst for C═O Hydrogenation of Ethyl Levulinate: Niδ+ 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-xP/Al2O3 catalysts with different P/Ni molar ratios were prepared for the conversion of ethyl levulinate to γ-valerolactone. The developed Ni-0.38P/Al2O3 catalyst was 5.4 times more active than conventional Ni/Al2O3 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 Ni3P 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 Niδ+ sites. In situ FTIR for the surface reaction indicated that Niδ+ acted as a new active site to activate the C═O bond, which rendered the high intrinsic activity of Ni3P for the C═O hydrogenation of EL.