In-situ formation of electron-deficient Pd sites on AuPd alloy nanoparticles under irradiation enabled efficient photocatalytic Heck reaction

Abstract

Plasmonic metal nanoparticles have emerged as important candidates for photocatalysis. Numerous studies have shown that coupling of a plasmonic component (such as Au) as the light energy harvester with a catalytically active metal component (such as Pd) to form hybrid or alloy structures could achieve enhanced catalytic performance. However, the microscopic mechanism relative to the multicomponent plasmonic photocatalysis is still elusive. Here, we find that the electron-deficient Pd sites (Pdδ+) on AuPd alloy nanoparticle were formed under visible light irradiation, which play a decisive role in the AuPd alloy nanoparticle photocatalysis. The in-situ formed Pdδ+ under irradiation offers ideal platform for the catalytic reaction which is comparable to that under thermal heating conditions (>100 °C). The AuPd alloy nanoparticles show excellent conversion and selectivity for visible-light-driven Heck cross-coupling reaction under ambient conditions. The combination of experimental and density functional theory results suggest that the photocatalytic Heck reaction proceeds via a new radical-based single-electron transfer pathway on the AuPd alloy, and the in-situ formed Pdδ+ sites ideally provided efficient catalytic sites for the activation of reactant with much lower activation energy barrier under irradiation. The present work sheds light on the new mechanistic understandings of bimetallic plasmonic photocatalysis.