Enhanced Low-Temperature Activity of Toluene Oxidation over the Rod-like MnO₂/LaMnO₃ Perovskites with Alkaline Hydrothermal and Acid-Etching Treatment

Abstract

The MnO2/LaMnO3 catalyst with the rod-like morphology obtained by alkaline hydrothermal and acid etching treatment, performing 90% toluene conversion at 236 °C with a weight hourly space velocity of 60 000 mL·g–1·h–1. The alkaline hydrothermal strategy could modulate the morphology of LaMnO3 from block-like to rod-like, and A sites (La cations) were selectively dissolved upon subsequent acid etching treatment, constructing an enhanced porous structure. Compared with the bulk LaMnO3 perovskite, the MnO2/LaMnO3 catalyst possesses the increased ratio of Mn4+/Mn3+ on the surface, significantly improving the low-temperature catalytic activity and exhibiting a low apparent activation energy (Ea) of 38.6 kJ·mol–1. Moreover, the outcomes of XPS and O2-TPD display that the active surface oxygen species with the higher concentrations of lattice oxygen and increased surface oxygen vacancy density were endowed after alkali-acid treatments, accelerating the adsorption and reaction of toluene. This work develops a promising strategy to design MnO2/LaMnO3 catalysts with enhanced low-temperature activity for the removal of volatile organic compounds via high-efficient and low-cost treatment processes.