Enhanced low temperature catalytic activity for toluene oxidation over core-shell LaMnO3@α-MnO2 catalyst with oxygen vacancies

Abstract

Engineering oxygen vacancies is an effective strategy to enhance the catalytic activity of MnO2 based composite oxides in heterogenous reactions, such as volatile organic compounds (VOCs) oxidation reaction. Core-shell structure LaMnO3@α-MnO2 catalysts were prepared by hydrothermal method via varying the concentrations of LaMnO3 and used in toluene oxidation reaction. Irregular core-shell structure L@M-10 catalyst exhibits excellent low temperature catalytic activity and stability, achieving 100% toluene removal efficiency at 200 °C. The light-off temperature (T50) and complete conversion temperature (T90) are 235 and 271 °C even after five repetitive cycles, respectively. The interfacial effect of L@M-10 sample promotes the generation of oxygen vacancies, facilitating the formation of active oxygen species. A possible oxidation reaction mechanism of toluene over L@M-10 catalyst was proposed in combination with the in-situ DRIFTS results. Fast ring-opening reaction and quick transformation of carboxylate or anhydride species into final products CO2 and H2O explains the superior catalytic property and stability of L@M-10 sample. This work highlights the effect of interface on the catalytic activity and stability of LaMnO3@α-MnO2 catalyst towards toluene oxidation and can offer a new insight into the utilization of interfacial effect in thermocatalytic reactions.