Synergetic effects of surface free Co3O4 species on catalytic oxidation of NO over cerium-cobalt solid solution

The xCo3O4/Ce0.85Co0.15-3xO2-δ catalyst was prepared by a sol-gel method for selective catalytic oxidation of NO. The experimental results showed that the highest catalytic activity reached 60.2% at 300 °C. In addition, the Raman spectra and XPS results confirmed that the Ce-Co catalyst contained surface free Co3O4 species and Co ions in the Ce0.85Co0.15-3xO2-δ solid solution. Surface free Co3O4 species could be removed by hydrochloric acid, leading to decrease of the catalyst activity. For the xCo3O4/Ce0.85Co0.15-3xO2-δ catalyst, the surface free Co3O4 species and the Ce0.85Co0.15-3xO2-δ solid solution enhanced catalytic performance, and the former provided the adsorption sites of NO and the latter promoted the activation of oxygen. This research studied the synergetic effects of Co3O4 species and Ce0.85Co0.15-3xO2-δ solid solution on the process of NO oxidation. For the xCo3O4/Ce0.85Co0.15-3xO2-δ catalyst, the enhanced catalytic performance was due to the synergy between the surface Co3O4 species and the Ce0.85Co0.15-3xO2-δ solid solution, as the former provided the sites for NO chemisorption and the latter promoted the activation of oxygen.