Cobalt/silica nanocomposite via thermal calcination-reduction of gel precursors

Well dispersed and thermally stable Co/SiO2 nanocomposite powders have been synthesized successfully via thermal calcination-reduction process of the prepared gel precursors. Co-gelation method for the cobalt and silica sources in the same solution mixture was found to be the best way to prepare these materials. Single (Co3O4) and (Co) phase formation could be confirmed by XRD and FTIR techniques for the products after calcination and reduction stages at the optimum process conditions, respectively. Surface analysis and TEM investigations of the reduced sample containing 25 wt.% Co revealed that highly dispersed cobalt nanoparticles embedded in a mesoporous inorganic polymeric silica matrix could be obtained. The silica matrix played a key role in protecting metallic cobalt nanoparticles from oxidation upon heating in air up to 400 °C. Addition of ethylene glycol to the gel mixture during gelation resulted in the formation of an additional organic polymeric protective layer. This layer promotes the formation of a regular pore structure upon its removal through calcinations and reduction steps. The current study could help in understanding the parameters affecting the dispersion and phase formation of cobalt species in silica matrix which indeed affect the activity of Co/SiO2 nanocomposite as a catalyst in different processes and reactions.