Insights into the effects of surface properties of oxides on the catalytic activity of Pd for C–C coupling reactions

Abstract

Understanding the interaction between Pd nanocatalysts and metal oxide supports for heterogeneous C–C coupling reactions is still ambiguous since many factors influence the catalytic behavior of Pd nanocatalysts. Herein, three porous nanorods of CeO₂ with controllable surface properties were employed as supports for Pd nanocatalysts with similar dispersion, which avoided the impact of other factors including surface area, morphology and accessible active sites. It provides an ideal approach to probe synergetic catalytic behavior of metal nanoparticles on supports. The results obtained by studying three C–C coupling reactions (Ullman, Suzuki and Heck) indicate a strong correlation between the surface properties of supports and the catalytic activity of Pd nanocatalysts: supports with a strong basicity and a high concentration of oxygen vacancies result in a rich electron density of Pd and accelerate the first step of oxidative addition reaction for C–C coupling. The infrared spectroscopic study on ν[CO] of CO-treated catalysts and XPS analysis of the Pd(3d) core level provide strong evidence supporting the interaction of Pd/supports for C–C coupling reactions.