Sol-gel synthesis of silicon cobalt mixed oxide nanocomposites

Silicon cobalt mixed oxide samples, with three different composition: 10 (10Co), 20 (20Co) and 30 (30Co) cobalt wt %, were synthesized using a modified sol-gel method. The materials were characterized by TG/DTA, XRD, N2 adsorption techniques for their structural and textural properties. Redox and acidic properties were studied by TPR and FTIR of samples exposed to NO. Micropore and mesopore volumes were influenced by Co content The nature of cobalt oxide species and their interactions with silica matrix depended on the cobalt content. In 10Co sample no crystalline Co oxides were detected: the spinel Co3O4 was present as a segregated phase in the samples 20Co and 30Co. TPR measurements showed that cobalt species present in 10Co sample were hardly reducible. 20Co and 30Co showed TPR peaks due to the spinel Co3O4, and to Co2+ species strongly bonded to silica.. FT-IR spectra showed the presence of two type of weak acid Lewis sites due to surface Co2+ species