An unexpected reversal: The smart performance of hydrogen chloride on SbCe catalysts for NH3-SCR reaction

ABSTRACT

Understanding the influence of HCl on the NH₃-selective catalytic reduction reaction mechanism is crucial for designing highly efficient denitrification catalysts. The formation of chlorate species on the surface of the synthesized SbCeO_x catalyst, induced by HCl, significantly enhances low-temperature activity, as evidenced by a 30% increase in NO conversion at 155 °C. Furthermore, it improves N₂ selectivity at high temperatures, with a notable 17% increase observed at 405 °C. Both experimental results and density functional theory calculations confirm that chlorate species form at Ce sites. This formation facilitates the creation of oxygen vacancies, boosting the oxygen exchange capacity. It also increases NH₃ adsorption at the Ce sites, promotes the formation of Sb-OH, and reduces competitive OH adsorption on these sites. Notably, compared with the reaction mechanism without HCl, the presence of chlorate species enhances NH₃ adsorption and activation, which is vital for subsequent catalytic reactions.