Effect of different oxygen species on the oxidative coupling of methane over TiO2 catalysts

Abstract

TiO2 is widely used in oxidative coupling of methane (OCM) reaction because of its low cost, reducibility and nontoxicity, but pure TiO2 has poor activity on methane activation. Density functional theory with an additional Hubbard-like parameter (DFT + U) was used to research OCM reaction on Ir/TiO2(001), Pt/TiO2(001) and Mn/TiO2(001) catalysts to explore catalysts with high activity and C2 hydrocarbon selectivity. The results indicate that Ir, Pt and Mn doping can significantly improve the activity of lattice oxygen and reduce the activation energy of methane dissociation. Additionally, the evolution of oxygen species on Ir/TiO2(001) Pt/TiO2(001) and Mn/TiO2(001) catalysts show that the lattice oxygen species and peroxide species have the strongest activity to activate methane. However, the superoxide species has the worst activity. Furthermore, the formation paths of ethane and ethylene were researched on Ir/TiO2(001), Pt/TiO2(001) and Mn/TiO2(001) surfaces. And we expect that Ir/TiO2(001) is effective for catalyzing OCM reaction.