Effect of the structure of CN/Silica composite support on the catalytic performances of Co3O4 for CO oxidation

- Carbon nitride/silica composites were first to be used as support for Co3O4 for CO oxidation.
- Full CO conversion was achieved by Co/CN/SBA-15, Co/CN/SBA-16 and Co/CN/MCF at 200 °C, 175 °C and 225 °C, respectively.
- CN promotes the dispersion of Co3O4 since it was decomposed in the preparation process of Co3O4.
- Pore size and structure of the silica materials affect the physicochemical properties of Co3O4.
- High activity of Co/CN/SBA-16 is due to stronger reducibility and higher Co3+/Co2+ molar ratio.

Noble metals are good catalysts for CO oxidation, but their limited reserves and high cost promote the finding of new and low-cost alternatives. In this paper, we systematically studied the effect of three kinds of carbon nitride/silica composite supports (CN/SBA-16, CN/SBA-15 and CN/MCF) on the catalytic oxidation of CO over Co3O4 catalyst. It was found that Co3O4 locates on the surface when CN/SBA-16 is used as support, while locates inside the pores if CN/SBA-15 and CN/MCF are used as supports. The Co3O4 located on the surface exhibits stronger reducibility and higher Co3+/Co2+ molar ratio than that located inside the pores. This can be that the Co3O4 which located inside the pores is stabilized by the silica, making the electrons hard to be excited. Catalytic tests showed that the Co3O4 supported on CN/SBA-16 composites (i.e., Co/CN/SBA-16) shows the best activity to the reaction, with full CO conversion obtained at 175 °C, which can be recycled for at least five times with no loss of activity, indicating the promising applications.

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