Engineering the Mechanically Mixed BaMnO3-CeO2 Catalyst for NO Direct Decomposition: Effect of Thermal Treatment on Catalytic Activity

A 5 wt% BaMnO3-CeO2 composite catalyst prepared by the one-pot method exhibits extraordinary catalytic performance for nitrogen monoxide (NO) direct decomposition into N-2 and O-2; however, the reasons for the high activity remain to be explored. Here, the catalyst was prepared by mechanical mixing and then subjected to thermal treatment at different temperatures (600-800 degrees C) to explore the underlying reasons. The thermal pre-treatment at temperatures higher than 600 degrees C can improve the catalytic activity of the mechanically mixed samples. The 700 degrees C-treated 5%BaMnO3-CeO2 sample shows the highest activity, with NO conversion to N-2 of 13.4%, 40.6% and 57.1% at 600, 700, and 800 degrees C, respectively. Comparative activity study with different supports (ZrO2, TiO2, SiO2, Al2O3) reveals that CeO2 is indispensable for the high performance of a BaMnO3-CeO2 composite catalyst. The Ce species (mainly Ce3+) in CeO2 components diffuse into the lattice of BaMnO3, generating oxide ion vacancy in both components as evidenced by X-ray photoelectron spectroscopy and Raman spectra, which accelerates the rate-determining step and thus higher activity. The chemisorption results show that the interaction between BaMnO3 and CeO2 leads to higher redox activity and mobility of lattice oxygen. This work demonstrates that engineering the oxide ion vacancy, e.g., by thermal treatment, is an effective strategy to enhance the catalytic activity towards NO direct decomposition, which is expected to be applicable to other heterogeneous catalysts involving oxide ion vacancy.

Automated summary

Thermal treatment can improve the catalytic activity of the 5 wt% BaMnO3-CeO2 composite catalyst for NO decomposition. The diffusion of Ce species from CeO2 to BaMnO3 lattice generates oxide ion vacancy, accelerating the rate-determining step and enhancing the catalytic activity.