Enhanced CO oxidation performance over hierarchical flower-like Co₃O₄ based nanosheets via optimizing oxygen...

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 (Co₃O₄) nanosheets were prepared by solvothermal method and applied into catalytic CO oxidation. The doped Ag species in the form of AgCoO₂ induced the prolongated surface Co-O bond and weaker bond intensity. Consequently, the oxygen activation/migration ability and redox capacity of Ag_0.02Co were enhanced with more oxygen vacancies. The chemisorbed CO was preferentially converted to CO₂ 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 AgCoO₂ to Co₃O₄ promote electron donation ability of Co₃O₄ 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 Co₃O₄ 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 Co₃O₄ at 40 °C. Moreover, the Ag_0.02Co 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 Co₃O₄.