Enhanced CO oxidation performance over hierarchical flower-like CoO based nanosheets via optimizing oxygen activation and CO chemisorption.

Enhancing low-temperature activity is a focus for carbon monoxide (CO) elimination by catalytic oxidation. In this work, the hierarchical flower-like silver (Ag) modified cobalt oxides (CoO) nanosheets were prepared by solvothermal method and applied into catalytic CO oxidation. The doped Ag species in the form of AgCoO induced the prolongated surface Co-O bond and weaker bond intensity. Consequently, the oxygen activation/migration ability and redox capacity of AgCo were enhanced with more oxygen vacancies. The chemisorbed CO was preferentially converted to CO but not carbonates. The inhibited carbonates accumulation could avoid the coverage of active sites. According to Density functional theory (DFT) calculations, the electron transfer from AgCoO to CoO promote electron donation ability of CoO layer, benefiting for oxygen activation. Moreover, the longer Co-C and C-O bond length suggest the weakened chemisorption strength and higher active of CO molecule. The Ag modified CoO exhibited more satisfactory activity at lower temperature. Typically, it realized 100% CO conversion at 90 °C, and displayed 6.3-fold higher reaction rate than pristine CoO at 40 °C. Moreover, the AgCo exhibited outstanding long-term stability and water resistance. In summary, the optimized oxygen activation, CO chemisorption and interfacial electron transfer synergistically boosted the CO oxidation activity on Ag modified CoO.