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

A desirable catalyst with excellent SO₂/H₂O tolerance at low temperatures is of great significance for NO_x 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.