First-principles insights into the adsorption and interaction mechanism of selenium on selective catalytic reduction...

Selenium (Se) species can deposit in selective catalytic reduction (SCR) system during the denitrification process, which is harmful to the catalyst. To improve the Se-poisoning resistance of SCR catalysts, the influence mechanism of Se species on vanadium-titanium-based catalysts should be elucidated from an atomic scale. In this paper, theoretical calculations were conducted to reveal the adsorption and interaction mechanism of Se species on V₂O₅-WO₃(MoO₃)/TiO₂ surface based on the first-principles. The impact of Se species on the electronic structure of the catalyst was investigated from electron transfer, bond formation, and VO site activity. The results show that the adsorption of elementary Se (Se⁰) belongs to chemisorption, while SeO₂ can undergo both physisorption and chemisorption. For the chemisorption of Se species, obvious charge transfer with the catalyst is observed and Se-O bond is formed, which enhances the oxidation activity of the catalyst, triggers the reaction of Se⁰ and SeO₂ with the catalyst components to generate SeVO_x and SeW(Mo)O_x. The active sites are thereby damaged and the SCR performance is reduced. The above conclusions are mutually confirmed with the previous experimental research. By studying the correlation with the adsorption energies of Se species, descriptors manifesting the Se species adsorption were initially investigated to unveil the relationship between the electronic structure and the adsorption energy. Finally, the influence of temperature on Se adsorption was investigated. The adsorption can only proceed spontaneously below 500 K and is inhibited at high temperatures.