Unveiling the poisoning mechanism of thallium on the catalytic performance of commercial V2O5/TiO2 SCR catalyst

V 2 O 5 /TiO 2 has been wide used in the selective catalytic reduction of NO x by NH 3 (NH 3 -SCR). However, the poisoning mechanism of thallium (Tl) on the catalytic performance of commercial V 2 O 5 /TiO 2 catalyst has remained unclear. Herein, we have systematically investigated the poisoning effect of Tl based on the different characterizations and DFT calculations. It was found that the strong interaction between V and Tl exists, resulting in the transformation of V from monomeric VO x to polymeric and crystalline VO x , the formation of V-O-Tl species, a decrease in the active V 5+ sites, and the inhibition of the adsorption and activation of NH 3 on both Brønsted and Lewis acid sites. Mechanistic studies further confirmed that inactive nitrate intermediate species gradually accumulated over V 2 O 5 /TiO 2 catalyst surface due to the presence of Tl. A combination of factors ultimately led to the deactivation of the V 2 O 5 /TiO 2 catalyst. This study unveils the poisoning mechanism of Tl on V-based catalysts and shed light on the design of Tl-tolerant NH 3 -SCR catalysts.