Regulating Oxygen Species for Promoted Deep Oxidation of Toluene: A Comparative Study of Adsorbed Oxygen and Lattice Oxygen

Abstract

To explore effective way for the complete catalytic degradation of toluene at low temperature, catalysts with diverse activity of adsorbed oxygen (O_ads) and lattice oxygen (O_latt) are synthesized by introducing Sr²⁺ into the birnessite structure. Sr modification highly improved low-temperature catalytic activity and CO₂ selectivity of toluene oxidation under moist condition, especially on the BS-7.5 (Sr:Mn = 0.075) catalyst. A series of physiochemical characterizations and DFT calculations identified abundant O_latt with higher activity in Sr-doped birnessite and higher activity of O_ads in pure birnessite. In situ DRIFTS analysis further confirmed that activation of O_latt introduced by Sr replacement of Mn governed the reaction process towards continuous deep oxidation of toluene. These findings provide a deeper understanding of the mechanism of toluene degradation and strongly pave a way for improving the complete catalytic oxidation performance of VOCs at low temperature over MnO₂ catalysts from the aspect of regulating active oxygen-related properties.

Keywords: Birnessite, Alkaline metal doping, Toluene catalytic combustion, Lattice oxygen, Adsorbed oxygen