Theoretical insight into H 2 O impact on V 2 O 5 /TiO 2 catalysts for selective catalytic reduction of NO x .

H 2 O in flue gas causes the deactivation of V 2 O 5 /TiO 2 catalysts for selective catalytic reduction (SCR) of NO x with NH 3 at low temperatures. Developing water resistance requires understanding the theoretical mechanism of H 2 O impact on the catalysts. The aim of this work was to clarify the adsorption process of H 2 O and the deactivation mechanism induced by H 2 O through density functional theory (DFT). The process of H 2 O adsorption was studied based on a modeled V 2 O 5 /TiO 2 catalyst surface. It was found that H 2 O had a strong interaction with exposed titanium atoms. Water adsorption on the catalyst surface significantly alters the electronic structure of VO x sites, transforming Lewis acid sites into Brønsted acid sites. Exposed titanium sites contribute to the decrease of Lewis acidity via adsorbed water. Ab initio thermodynamic calculations show that H 2 O adsorption on V 2 O 5 /TiO 2 is stable at low coverage but less favorable at high coverage. Adsorption of NH 3 is the most critical step for the SCR of NO x , and the adsorption of H 2 O can hinder this process. The H 2 O coverage below 15% of adsorption sites could enhance the NH 3 adsorption rate and have a limited effect on the acidity, while higher coverage impeded the adsorption ability of VO x sites. This work provided electron-scale insight into the adsorption impact of H 2 O on the surface of V 2 O 5 /TiO 2 catalysts, presented thermodynamic analysis of the adsorption of H 2 O and NH 3 , paving the way for the exploration of V 2 O 5 /TiO 2 catalysts with improved water resistance.