Enhancing Activity of Ni₂P‑Based Catalysts by a Yolk–Shell Structure and Transition Metal-Doping for Catalytic Transfer Hydrogenation of Vanillin

Catalytic transfer hydrogenation (CTH) is regarded as a promising technology for upgrading biomass to fuels and valuable chemicals in the presence of heterogeneous catalysts. In this work, three Ni₂P-based catalysts, such as Ni₂P@YSS with a yolk–shell structure, Ni₂P@SiO₂ with a core–shell structure, and Ni₂P/SiO₂ with a simple surface-loading structure, were prepared using different synthesis strategies, and were used in the CTH of vanillin in an ethanol environment. The Ni₂P@YSS catalyst exhibited the highest conversion (85.6%) and a selectivity of 2-methoxy-4-methylphenol of 76.2% at 180 °C for 5 h among a series of Ni₂P-based catalysts, which are closely related to the higher specific surface area (462 m² g^–1), acidic site density (2.31 mmol g^–1), and stronger metal–support interactions of the Ni₂P@YSS catalyst. Besides, transition metals (Zr and La) were introduced to the Ni₂P@YSS catalyst to increase the oxygen vacancy and improve the H dissociation ability, thereby enhancing the catalytic performance of the Ni₂P-based catalysts.