Toluene Unexpectedly Promotes Low-Temperature NO x Reduction by Inducing Peroxide Oxygen on Ce–Ti Catalysts

Abstract

Volatile organic compounds (VOCs) are widely considered to inhibit NH3–SCR by competing with NH3 for surface sites and blocking redox centers, yet industrial flue gases frequently contain both VOCs and NOx. Here we show that toluene unexpectedly promotes low-temperature DeNOx over Ce–Ti catalysts, with the hollow nanotube-structured CeTiNTs exhibiting outstanding performance, achieving >90% conversion of both NOx and toluene at 200 °C with high CO2 selectivity and near-unity N2 selectivity. Mechanistically, toluene acts as an electron donor to surface Ce sites, increasing the Ce3+ fraction and oxygen-vacancy-associated adsorbed oxygen. In situ near-ambient-pressure XPS and Raman spectroscopy reveal the toluene-triggered formation of surface peroxide (O22–), which accelerates NO oxidation to NO2 and thus initiates the fast-SCR pathway, while simultaneously enabling deep oxidation of toluene. Density functional theory corroborates preferential adsorption of toluene on Ce sites and reduced oxygen-vacancy formation energies at specific lattice positions. These results establish a reaction-coupling route in which toluene exhibits dual effects, involving competitive adsorption that partially inhibits certain NH3–SCR steps, while predominantly promoting low-temperature fast-SCR via peroxide-enabled NO oxidation through enhanced oxygen activation, offering a mechanistic basis for rational catalyst design for multipollutant abatement.