Accessibility of Co3O4 particles patterned in SBA-15

Abstract

Crystalline Co3O4 nanoparticles were patterned in the pores of SBA-15 silicas using the "two solvents" technique (Co/Si atomic ratios between 0.10 and 0.35, pore sizes: 5.1, 5.6 and 7.3 nm). Normalized surface areas, calculated from N2 sorption experiments, reveal a partial plugging of the pores which, for a given Co/Si atomic ratio, increases when the pore size decreases. The CO oxidation catalytic reactivity of the Co3O4 particles either embedded or extracted from silica confirms that the Co3O4 particles are partially accessible to reagents. Despite accessibility limitations, the reactivity of the patterned Co3O4 particles compares favorably with the very few data available in the literature. Unexpectedly low activation energies are even measured. Finally, H2-TPR experiments reveal that accessibility limitations are correlated with the formation of hardly reducible Co silicate species.