Insights into the effect of cobalt substitution into copper-manganese oxides on enhanced benzene oxidation activity

Co-substituted Cu-Mn spinel oxides were synthesized, characterized, and catalytic performance for benzene oxidation was evaluated. Spinel phases, and the substitution of Mn sites by Co were confirmed for the ternary oxides. Co0.2Cu0.8MnOy showed the highest activities with the lowest apparent activation energy among the ternary oxides. The improved catalytic properties due to Co substitution are attributed to more activated lattice oxygen, stronger adsorption of benzene, and a larger specific surface area. Density functional theory simulations also revealed that the Co substitution enhanced the reactivity of the lattice oxygen. Adsorbed and activated benzene reacted with lattice oxygen to form abundant oxygen defects, which promoted O2 adsorption and dissociation, contributing to enhanced catalytic activity. The effect of water vapor on the catalytic benzene oxidation was also clarified.