Sintering and redispersion of platinum catalysts supported on tin oxide

CO oxidation activities of platinum/tin oxide catalysts prepared by impregnation have been investigated in relation with their nano-structural changes in various reduction–oxidation treatments. Variously treated Pt/SnO2 catalysts were characterized by XRD, XPS, and TEM. In 1 wt.% Pt/SnO2 catalyst calcined at 400 °C, crystallized fine particles of Pt were highly dispersed on SnO2 due to strong chemical interaction between two components. After the heat-treatment in a reducing atmosphere, the sintered Pt particles with grown size were frequently observed. Furthermore, unique texture of particles with core–shell structure was produced in the catalyst exposed in air after the reduction treatment at 400 °C. These large particles with the peculiar shape were re-dispersed by the reoxidation treatment at 400 °C to fine particle with similar size to the as-calcined catalysts. The reversibility of the microstructural changes between growth and redispersion of deposited particles was confirmed after the several reduction–oxidation cycles. It was revealed that the structural changes on the interface of Pt/SnO2 catalysts were closely related to the catalytic activity for CO oxidation.