Effect of reduction on NO plus CO reaction performance of CuO-Co3O4 symbiotic oxide porous nanosheet and DFT calculation

As an ideal substitute for the precious metals in the selective catalytic reduction of NO by CO, transition metal oxides perform very well. Thus, a series of CuO - Co3O4 symbiotic oxide porous nanosheet catalysts are prepared with a CTAB-assisted hydrothermal method. Cu5 with the ratio of Cu and Co is 5 : 10, has the best activity on the premise of maintaining the nanosheet structure. Reduction pretreatment of Cu5 with H-2 is carried out, and the surface will be rapidly oxidized in air. In this period, Cu, CuO and Co3O4 were produced and coexisted on surface. Cu5-re-163 exhibits greatly higher N-2 selectivity but a little inferior NO conversion. Further DFT calculation and characterizations proved that [N] free radicals exist during the reaction. The reaction on Cu5 and Cu-re-163 follow L-H and E-R mechanism respectively. [N] radicals on the latter are much easier to desorb, so that they are easy to combine with each other to form N-2 rather than with NO to generate N2O, as the reason why Cu5-re163 has better selectivity.