Cobalt, nickel and ruthenium-silica based materials synthesized by the sol–gel method

The physical and chemical characteristics of silica based materials and doped with different metals (Ni, Co and Ru) synthesized by the sol–gel method were investigated. The used techniques were: temperature programmed reduction, thermogravimetric analysis, specific surface area measurements, X-ray diffraction and Photoacoustic Spectroscopy. After calcination, higher surface areas were obtained, with the larger value for Ru–SiO2 (550 m2/g), followed by Ni–SiO2 (337 m2/g) and Co–SiO2 (298 m2/g). For Ni–SiO2, the nickel oxide is present at the surface in two different forms. This also happens for the Co–SiO2 material, which showed two reduction peaks, probably attributed to the CoIII⇒CoIICoIII⇒CoII and CoII⇒Co0CoII⇒Co0 reaction. However, for Ru–SiO2 only one peak reduction was observed. The X-ray diffraction data revealed the existence of an amorphous structure, while thermogravimetric analysis showed that the calcination procedure decomposes the organic residues adsorbed at the material surface.