Synergistic visible light plasmonic photocatalysis of bi-metallic Gold-Palladium nanoparticles supported on graphene

Visible light photocatalysis using plasmonic nanoparticles is gaining currency due to the possibility of using freely available sun light to generate high energy 'hot' electrons. However, effective strategies have to be developed for the generation and stabilization of hot electrons and hot holes. In this work, nanoparticles of a plasmonic metal (Au) were combined with a highly active catalyst (Pd) nanoparticles along with a conductive catalyst support (few layered graphene, FLG). Nanoparticles having very small size could be prepared with the help of swollen liquid crystals as soft templates. The templates allowed entrapment of FLG along with a metal salt and yielded the nanocomposites on exposure to hydrazine vapor. Reduction of para-nitrophenol (p-NP) in presence of excess amount of sodium borohydride was used as a model reaction. Synergistic enhancement in photocatalytic activities could be observed with the Au-Pd/FLG being the best catalyst when compared to the nanoparticles of Au, Pd, Au-Pd and their nanocomposites with FLG (Au/FLG and Pd/FLG). Normalized rate constant (9.77 s−1 mg−1) of the Au-Pd/FLG was quite high compared to most other Au and Pd based nanomaterials that are reported in the literature. The enhanced photocatalytic activity of the Au-Pd/FLG nanocomposite could be correlated with its enhanced visible light activity. Moreover, enhanced adsorption of the reactant molecules and better charge transfer of the nanocomposite are also reasons for the observed photocatalytic activities of the Au-Pd/FLG nanocomposite.