Boosting simultaneous catalytic removal of NOx and toluene via cooperation of Lewis acid and oxygen vacancies

MnOx-CeO2 supported on TiO2 nanotube (MnCe/TNT) were purposely tailored to concurrently lower toluene oxidation temperature and keep high N2 selectivity during simultaneous removal of NOx and toluene via low-temperature NH3-SCR (≤ 300 °C). Over 80% NO and toluene conversions were simultaneously achieved within 182–300 °C with N2 selectivity of more than 90%. Strong Lewis acidity and plentiful oxygen vacancies were synchronously generated as Mn3+ + Ce4+ shifted to Mn4+ + Ce3+, and this shift was enhanced by the TiO2 nanotube. Lewis acid and oxygen vacancies synergistically facilitated NH3-SCR and accelerated toluene adsorption/activation and ring opening, thus dramatically lowering toluene conversion temperature to match that of NH3-SCR. Gaseous NOx predominantly reacted with NH3 adsorbed on Lewis acid sites, following the Eley-Rideal mechanism to form N2. The consumption of adsorbed oxygen via toluene decomposition significantly suppressed the unfavorable catalytic NH3 oxidation and N2O formation, contributing to the high N2 selectivity.