Interfacial electron transfer promotes photo-catalytic reduction of 4-nitrophenol by Au/Ag₂O nanoparticles confined in dendritic mesoporous silica nanospheres

Manipulating the electron transfer in composite metals or/and metal oxides on the nanoscale is crucial for the development of improved heterogeneous catalysts. However, how the interactions between multiple active components affect and even dominate the unusual catalytic properties has long remained elusive. Here, using dendritic mesoporous silica nanospheres (DMSNs) with unique open 3D porous networks as a silica matrix, a highly dispersed Au/Ag bimetallic catalyst with a uniform size of less than 3.0 nm is fabricated by a multi-step in situ nanocrystal seeding-induced-growth (SIG) strategy. The obtained Au/Ag bimetallic catalysts show an exceptional superior photocatalytic activity for the reduction of 4-nitrophenol (4-NP), surpassing most reported noble metal nanoparticle catalysts. Experimental observations and a photo-irradiation enhanced electron transfer (PIEET) model based on semiconductor energy band theory and the work function principle reveal that the unusual photocatalytic activity originates from the optimized combination of dual metal components and the enhanced electron transfer ability of the double active centres confirmed by UV-vis absorption and XPS measurements, which synergistically promote the reduction kinetics of the reduction of 4-NP.