MoO3 Doping Modulates CeO2/TiO2 Catalysts for Simultaneous NO x Reduction and Toluene Oxidation in Alkali-Rich Flue Gas: Unraveling the Microscopic Electronic Origin via DFT Calculations

CeO2/TiO2 catalysts are prone to severe deactivation in KCl-enriched flue gas environments derived from biomass or solid waste combustion during the removal of NO and toluene. While MoO3 doping significantly improves their resistance to KCl poisoning, the microscopic interaction mechanisms between surface components (MoO3, KCl, CeO2) and the reactants are still poorly understood. Herein, density functional theory (DFT) is applied to reveal the intrinsic insights into electron transfer, bonding, reactant adsorption, and activation characteristics. The results indicate that MoO3 doping weakens the charge transfer between KCl and active Ce sites, reduces the band gap, and enhances surface electron mobility. The introduction of MoO3 is capable of effectively suppressing the poisoning effect of KCl on catalysts for NO reduction and toluene oxidation. This modification strengthens NH3 adsorption and generates more active sites, thereby alleviating the inhibitory impact of KCl on NH3 activation. Furthermore, MoO3 restores the interfacial charge transfer that is depressed by KCl, diminishes the repulsive interaction toward toluene, and decreases the activation barrier for toluene oxidation, ultimately facilitating the progression of successive oxidation reactions. This study clarifies the electronic origin of the enhanced poisoning resistance achieved by MoO3 introduction and offers guidance for developing catalysts toward multipollutant synergistic purification under complex flue gas conditions.