Defect engineering and metal confinement on titanium dioxide enhances SO2/H2O tolerance in NOx reduction: Oxygen and metal vacancies

A desirable catalyst with excellent SO2/H2O tolerance at low temperatures is of great significance for NOx removal from actual flue gas. Defect engineering and metal confinement on metal oxide surfaces have emerged as effective strategies to enhance catalyst selectivity and activity. Herein, a Mn-based catalyst (CeCoMn/TiO2) with metal and oxygen vacancies was constructed by high-energy ball milling. The catalyst exhibited superior SO2/H2O tolerance stability (70.8 %) at 180 ℃ and 40000 h−1 than that prepared by the impregnation method (43.5 %). Metal vacancies can serve as anchor sites to generate well-dispersed active centers, and oxygen vacancies facilitate gas-phase oxygen replenishment and electron transfer. The synergistic effect of metal vacancies and oxygen vacancies improved the activity of the catalyst. In-situ infrared and theoretical calculations reveal that the reaction mechanism follows the Langmuir-Hinshelwood pathway. The catalyst prepared by ball milling has better SO2/H2O tolerance due to stronger acidity and interaction. The synergistic effect of dual-defect found in this study may guide the development of superior anti-poisoning catalysts.