Development of MgCo2O4–BaCO3 composites as microwave catalysts for the highly effective direct decomposition of NO under excess O2 at a low temperature

Abstract

The catalytic NO decomposition reaction is a hot research topic. However, it is still a huge challenge to achieve the NO decomposition reaction with high efficiency under excess O₂ at a low temperature. Herein, we developed MgCo₂O₄–BaCO₃ composites as novel microwave catalysts for the highly effective direct decomposition of NO by microwave catalysis under excess O₂ at a low temperature. Importantly, impressively high NO conversion of 99.6% and N₂ selectivity of 97.8% could be achieved over MgCo₂O₄–40%BaCO₃ at 250 °C under excess O₂; this NO conversion value was much higher than the highest NO conversion value reported over single MgCo₂O₄ (only 69.7%). Comparatively, the highest NO conversion and N₂ yield were only 29.5% and 15.1%, respectively, for MgCo₂O₄–40%BaCO₃ at 650 °C in the conventional reaction mode under identical conditions. O₂-TPD and XPS analyses of the catalysts were performed to demonstrate the possible reasons for such differences in catalytic activities. The apparent activation energies of MgCo₂O₄, MgCo₂O₄–20%BaCO₃, MgCo₂O₄–40%BaCO₃, and MgCo₂O₄–60%BaCO₃ were as low as 45.7, 26.4, 22.1, and 27.5 kJ mol⁻¹, respectively, indicating a significant microwave catalytic effect. In this work, we developed an attractive avenue for highly effective and environmentally friendly NO_x emission control and provided some guidelines for the rational design of outstanding microwave catalysts in microwave chemistry.