A study on the NH3-SCR performance and reaction mechanism of a cost-effective and environment-friendly black TiO2 catalyst

Abstract

In this paper, black TiO₂ without adding active components was developed for NH₃-SCR-DeNO_x. The catalytic activity tests showed that the NO removal efficiency of black TiO₂ was always greater than 90% at 330–390 °C, which almost reached that of the commercial NH₃-SCR-DeNO_x catalyst. XRD, UV-vis, TG, EPR, XPS, H₂-TPR, DFT and NH₃-TPD analyses were carried out to study the structure–effectiveness relationship. We found that a large number of oxygen vacancies were formed over the black TiO₂ surface. It was not only promoted the adsorption of NH₃via direct (oxygen vacancies as Lewis acid sites for NH₃ adsorption) and indirect (oxygen vacancies promote the formation of surface hydroxyl groups, which are Brønsted acid sites for NH₃ adsorption) forms, but also improved the redox properties by promoting the reduction of Ti⁴⁺ to Ti³⁺. These changes lead to the superior catalytic activity of black TiO₂ for NH₃-SCR-DeNO_x. Additionally, an in situ DRIFT study demonstrated that the NH₃-SCR-DeNO_x reaction over black TiO₂ occurred via the Eley–Rideal (E–R) mechanism. Finally, the catalytic stability and resistance to H₂O and SO₂ of the black TiO₂ catalyst were studied, and it showed good performances. This study offered new and important insights into the understanding of the role of oxygen vacancies in determining the physical and chemical properties of catalysts.