Controlled gold–palladium cores in ceria hollow spheres as nanoreactor for plasmon-enhanced catalysis under visible light irradiation

Visible-light-driven organic transformations boosting by localized surface plasmon resonance (LSPR) have been attracting considerable interests. Gold-palladium (Au-Pd) bimetallic nanoparticles (NPs) are considered as ideal plasmonic catalysts realizing efficient light-driven catalysis. Nevertheless, stability and adjustability of plasmonic Au-Pd NPs remain to be a challenging task. Herein, we designed the controlled Au-Pd cores in ceria (CeO2) hollow spheres (Au-Pd@h-CeO2) as nanoreactor for Suzuki cross-coupling reactions. Under visible light irradiation, the Au-Pd@h-CeO2 exhibited remarkable photocatalytic performance with a turnover frequency (TOF) value as high as 797 h-1. More impressively, the coupling reactions of aryl chlorides bearing electron-withdrawing groups proceeded better and afforded the corresponding desired products in good yields. Detailed structural, optical and photoelectrochemical characterizations unraveled that the enhanced photocatalytic efficiency of Au-Pd@h-CeO2 was attributed to the LSPR effect of controllable Au-Pd cores and their synergetic effect of hollow CeO2 shells. The merits of this hollow sphere architecture lied on as followed: (I) Incident light could be reflected and refracted between the inner cores and outer shells, which extended the trapping of incident light, and then enhanced the light harvesting efficiency; (II) the mesoporous architecture of CeO2 hollow spheres provided a huge specific surface area and numerous mesoporous channels, which could enhance the absorption of reactants and provided more active sites; (III) LSPR excitation of Au-Pd NPs and band-gap excitation of CeO2 simultaneously occurred under visible light illumination, inducing a more efficient separation and transfer of charge carriers. Furthermore, due to the confinment effect of CeO2 shells, the Au-Pd@h-CeO2 exhibited an excellent reusability after six cycles without significant deactivation of yield. Our findings provided a facile way to design highly efficient plasmonic-enhanced photocatalysts utilized for catalytic organic reactions.