Optimizing Alkyne Hydrogenation Performance of Pd on Carbon in Situ Decorated with Oxygen-Deficient TiO₂ by Integrating the Reaction and Diffusion

Abstract

The reaction/diffusion kinetics are fundamentally determined by the electronic properties of supported Pd catalysts and further govern the catalytic activity and selectivity in the partial hydrogenation of alkynes. However, how the electronic metal–support interactions and the tradeoff between reaction and diffusion affect the catalytic performance still remain elusive. Here, the optimized catalyst Pd supported on carbon decorated with oxygen-deficient TiO2(Pd/TiO2-VO@C) features a remarkable enhancement in performance for semihydrogenation of 2-methyl-3-butyn-2-ol with a TOF 31-fold higher than that of Lindlar catalyst. The improved performance of Pd/TiO2-VO@C benefits from the fact that TiO2-VO@C subtly modulates the electronic properties of Pd, and an appropriate amount of TiO2-VO allows a decrease in the reaction barrier and C promotes the diffusion ability of the catalyst, achieving the balance between reaction and diffusion. By using microkinetic modeling, the reactivity difference of various catalysts is quantitatively predicted and the calculated turnover frequency volcano curve is rationalized as a function of reaction barrier and diffusion ability, which agrees well with the experimental results. The quantitative regulation of catalytic performance by tuning the support properties is a general strategy, which provides a basis to design robust catalysts for diverse reactions.