Enhanced low-temperature NH3-SCR performance via acid-modified CuCeO catalysts with balanced redox and acidity

Abstract

Nitrogen oxide (NO_x) is one of the major sources of air pollution, and the development of efficient and stable catalysts for low-temperature selective catalytic reduction (SCR) of NO_x is still a major challenge. In this paper, we prepared acid-treated CuCeO catalysts by precipitation and wet impregnation methods. The experimental results showed that although the sulfuric acid treatment led to a decrease in the number of oxygen vacancies of the CuCeO catalyst and hindered the adsorption of NO, the quantity and intensity of the Brønsted acid sites of the catalyst were significantly enhanced, and the balance between the redox capacity and the acidity allowed the H₂SO₄-treated CuCeO catalysts to exhibit a 100 % NO_x conversion and N₂ selectivity. Meanwhile, sulfuric acid treatment attenuated the peroxidation of NH₃, resulting in improved both high-temperature catalytic performance and selectivity. Additionally, in situ DRIFTS results showed that the H₂SO₄-treated CuCeO catalysts primarily operated via the L-H mechanism at lower temperatures, whereas at higher temperatures, they followed the E-R mechanism. This research offers both experimental findings and theoretical perspectives that contribute to the advancement of high-performance CuCe-based catalysts for NH₃-SCR applications.