Surface Defect-Induced Site-Specific Dispersion of Pd Nanoclusters on TiO₂ Nanoparticles for Semihydrogenation of Phenyl Acetylene

Currently, the wide application of heterogeneous noble metal catalysts is greatly limited due to their high cost and scarcity in global reserves. Thus, an effective strategy is to design highly efficient and stable catalysts with low metal loadings. In this work, highly dispersed Pd nanoclusters supported on high-surface-area TiO2 with a large number of defective Ti3+-Ov structures (Ov: oxygen vacancy) were fabricated by our developed hydrogen bubble-assisted approach, which were applied for phenylacetylene semihydrogenation to produce styrene. As-constructed supported Pd catalysts bearing a Pd loading amount of 0.2 wt % afforded a superior catalytic performance to other Pd-based catalysts with higher Pd loading amounts and commercial TiO2-supported counterparts, along with a 99% yield of styrene and a quite high turnover frequency of ∼18,930 h–1 at room temperature and ambient hydrogen pressure. Comprehensive structural characterizations, comparative catalytic experiments, and density functional theory calculations based on a Pd4 cluster model system on a defective TiO2(101) surface emphatically revealed that surface defective structures could greatly facilitate the site-specific dispersion of single Pd atoms or nanoclusters, thereby leading to the formation of electron-rich Pd0 sites favoring the semihydrogenation of phenylacetylene.