Abstract
This study aims to synthesize platinum-nickel mesoporous materials and nickel- or cobalt-loaded catalysts using platelet-like mesoporous SBA-15 silica as hard template. In the first part of the thesis, we found that highly dispersed and small nickel or cobalt nanoparticles could be formed during the thermal treatment in vacuum after impregnation of the molten salt precursor. The materials were characterized by transmission electron microscopy, and the reduction reaction was studied by in-situ X-ray diffraction, X-ray absorption spectroscopy and diffuse reflectance infrared Fourier transform spectroscopy. The second part of the thesis is the preparation of platinum-nickel replica and the electrocatalytic studies for the oxygen reduction reaction. The catalysts were made by impregnating large amount of nickel nitrate into SBA-15, reducing nickel by hydrogen, and finally replacing part of the metallic nickel by platinum by galvanic replacement during the removal of silica by hydrogen fluoride. We found that the two metals formed alloy, but the alloy nanoparticles did not show very good catalytic activity compared to commercial carbon-supported platinum. The results were probably associated to the decrease of exposed active surface area due to the aggregation of alloy nanoparticles during the catalysis.