Pd Nanoclusters on TiO₂ for Photocatalytic Conversion of Phenylacetylene to Styrene

Selective hydrogenation of phenylacetylene is a crucial industrial reaction, yet developing catalysts with both high selectivity and activity remains challenging. Conventional hydrogenation catalysts often exhibit unevenly dispersed active metals, leading to agglomeration and reduced catalytic performance. Herein, with the aid of the ice-templating (ICT) strategy, we present TiO2-supported Pd nanocluster photocatalysts with ultralow Pd loading (0.1 wt %). The optimized Pd/TiO2–ICT catalyst achieves exceptional catalytic performance under ambient conditions (room temperature and atmospheric pressure) with methanol solvent and light irradiation, delivering 99% phenylacetylene conversion alongside 98% styrene selectivity. Advanced characterization reveals the catalyst’s superior structural features, including ultrasmall Pd clusters (1.2 nm diameter) and reduced Pd–Pd coordination number (6.3), which are significantly better than conventional counterparts. Systematic investigations establish a clear positive correlation between catalytic efficiency and critical structural parameters: smaller cluster dimensions and lower metal coordination numbers at equivalent Pd loadings. Mechanistic studies through comprehensive characterization elucidate that the photogenerated hydrogen radicals (•H) from methanol splitting directly drive the selective hydrogenation process. This study offers insights into both the application and structure–activity relationship of the ICT-based catalysts.