Synergy effect of CuO on CuCo₂O₄ for methane catalytic combustion

Spinel oxides (AB₂O₄) have been widely studied as catalysts for methane combustion. Increasing attention was focused on the catalysis properties of the [B₂O₃] octahedron; however, the role of the [AO] tetrahedron in the catalytic activity was seldom discussed. Herein, a series of (CuO) -CuCo₂O₄ (x = 0, 0.1, 0.2) composite oxides were synthesized by a solvothermal method. The structure, morphology, and physicochemical properties of the as-synthesized samples were characterized by the XRD, SEM, BET, and XPS techniques. The results of the catalytic activity tests showed that the coexistence of CuO with CuCo₂O₄ can improve the catalytic activity. The XPS results demonstrated that there were remarkable Cu⁺ ions present in the composite oxides, which can cause increases in the number of oxygen vacancies on the surface of the catalysts. In addition, the redox of Cu⁺ and Cu²⁺ may improve the oxygen exchange capacity for methane oxidation.