Direct visible photoexcitation on palladium nanocatalysts by chemisorption with distinct size dependence

Abstract

Direct photoexcitation of metal nanoparticles (NPs) can induce selective chemical reactions that are difficult to achieve with thermal energy. Here, we report that visible-light photoexcitation on palladium (Pd) NPs shows distinct particle size dependence; small Pd NPs (sub-3.0-nanometer) with low Pd loading (0.5 wt%) as a catalyst achieved excellent yield (100%) for Heck reaction. This is because (1) the light absorption of small Pd particles is more intensive than that of large Pd particles even if the Pd loadings are similar, and (2) the chemisorption of the reactants on the small Pd particles is stronger. The chemical adsorption can result in the hybridization of adsorbate orbitals and metal electronic states, and the photon absorption may directly excite the hybridized electronic states driving the reactions. This highly efficient visible-light-driven Pd nanocatalyst with low precious metal loading represents a promising step towards efficient cost-effective photocatalysis that operates under real-world conditions.