Theoretical Investigation of the Alkali Metal Poisoning Tolerance Mechanism of CeO2-Containing Fe and H2SO4 Additives

Development of selective catalytic reduction (SCR) with alkali tolerance is an essential task to remove air pollution. The previously developed Fe- and H2SO4-induced CeO2 exhibited high alkali tolerance while maintaining a high nitrogen oxide conversion (Khan, M.N.; Han, L.: Wang. P.; and Zhang, D. iScience, 2020. 23(6), 101173). In this work, we focused on understanding the influence of induced Fe and H2SO4 in the continuous development and improvement of alkali tolerance catalysts. The roles of Fe and H2SO4 in preventing alkali poisoning were investigated by using density functional theory calculations. Our results showed that a potassium species hindered the formation of Bronsted acid sites by occupying the lattice oxygen sites on the CeO2 surface and inhibited the adsorption of the reductant, NH3. The induced Fe and H2SO4 promoted the formation of oxygen vacancies and generated characteristic adsorption sites (SO4/Fe_CeO2_V-o) for the accumulation of multiple potassium atoms. Hence, the synergistic effect of Fe and H2SO4 protects NH3 adsorption sites on the CeO2 surface from potassium poisoning of the catalyst. These findings can also give insight into understanding the similar ability of metal oxide-based catalysts with sulfate ion against alkali poisoning and open new ways in facilitating the tailored design of alkali tolerance catalysts for NH3-SCR.

Automated summary

In this study, the role of induced Fe and H2SO4 in preventing alkali poisoning was investigated. The results showed that Fe and H2SO4 can promote the formation of oxygen vacancies and generate characteristic adsorption sites, protecting NH3 adsorption sites on the catalyst surface from potassium poisoning. These findings are important for understanding the ability of metal oxide-based catalysts with sulfate ion against alkali poisoning and facilitating the tailored design of alkali tolerance catalysts.