Cobalt oxide confined in mesoporous SiO2 as effective catalyst for CO oxidation

Ordered mesoporous SiO2 samples (SBA-15) with different pore sizes were prepared as carriers, and a series of catalysts (CoOx@SBA-15(X)) were synthesized to confine CoOx in SBA-15 through the solid-state grinding method for CO oxidation. The characterization results showed that the aggregation of CoOx in the pores of the carrier SBA-15 was effectively inhibited by the confinement effect, which further facilitated the formation of the main catalytic site Co(III) species. The results of the density-functional theory calculations further confirmed that Co(III) was the important catalytic site for CO oxidation. Compared with the catalyst prepared through the impregnation method, catalysts CoOx@SBA-15(X) exhibited a lower CO conversion temperature and activation energy for CO oxidation. In addition, the pore size of the carrier SBA-15 had a significant impact on the catalytic activity of CoOx, and the catalyst prepared with a larger pore size SBA-15 as carrier exhibited a higher catalytic activity. This result was mainly attributed to the fact that the confinement effect could effectively enhance the defect formation in metal oxides. Furthermore, the catalyst with a larger pore size SBA-15 as a carrier presented a higher content of Co(III) species, which significantly enhanced the catalytic activity of CoOx for CO oxidation. The results demonstrated that the pore structure of SBA-15 could affect the formation of the metal oxide (CoOx) species, which further significantly affected the catalytic activity of CoOx for CO oxidation. The results are expected to provide a strategy to synthesize efficient catalysts for CO oxidation by using ordered mesoporous materials.

Automated summary

The confinement effect of ordered mesoporous SiO2 was found to effectively inhibit the aggregation of CoOx, promoting the formation of Co(III) species and enhancing the catalytic activity for CO oxidation. Additionally, the pore size of the carrier SBA-15 played a significant role in the catalytic activity of CoOx.