In-situ fabrication of porous-silica-microsphere-supported platinum nanocluster catalyst by γ-ray radiation

Abstract The synthesis and stable loading of metal nanoclusters have always been a hot and difficult topic in the field of nano-metal catalysts. In this work, micron-sized inverse opal SiO2 microspheres (IO-SiO2) are firstly prepared as the carrier of platinum nanoclusters (PtNCs) through a sol-gel process of tetraethyl orthosilicate (TEOS) on sacrificed polystyrene (PS) colloidal crystal microspheres template. After the IO-SiO2 carriers are dispersed into the aqueous solution of H2PtCl6 and irradiated by 60Co γ-ray radiation for a certain absorbed dose in a deoxygenized atmosphere, PtNCs with a size of less than 2 nm are in situ synthesized based on a redox equilibrium of Pt(0)/Pt(IV) induced by effect of the reductive species (eaq-, H•) and oxidizing radicals (HO•) produced by the radiolysis of water, and immobilized on IO-SiO2 without the help of any stabilizer. Due to the large pore volume of the IO-SiO2, the loading capacity of PtNCs can reach as high as 18.63 μg/mgmicrosphere. The prepared IO-SiO2-supported PtNCs (PtNCs@IO-SiO2) show excellent catalytic activity and recyclability for the reduction of o-nitroaniline by NaBH4 as the model reaction. This work offers a new route to prepare stable and high-performance metal nanocluster catalysts loaded on porous microspheres using γ-ray radiation technique.