Targeting Euro 7 and Forthcoming China 7 Emission Standard: Progress of Ammonia and Nitrous Oxide Purification Catalysts

Abstract

To address the stringent ammonia (NH3) and nitrous oxide (N2O) emission limits set by Euro 7 and the upcoming China 7 emission standards, this study first examines the formation pathways of NH3 and N2O in vehicle exhaust after-treatment system. Subsequently, a detailed overview of representative catalytic technologies for NH3 and N2O removal was presented, including passive selective catalytic reduction (pSCR), selective catalytic oxidation of ammonia (NH3-SCO) catalysts and direct catalytic N2O decomposition catalysts, and discusses the reaction mechanisms of these catalysts. Given that the downstream region of exhaust after-treatment system typically operates at relatively low temperatures, research on NH3 and N2O emission control has primarily focused on the development of efficient low-temperature catalysts, and noble metal catalysts have demonstrated excellent low-temperature performance. Therefore, this review systematically summarizes recent advances in mainstream catalysts, including Cu-based catalysts for pSCR, Ag-, Pt-, and Pd-based catalysts for NH3-SCO, and Rh-based catalysts for direct catalytic N2O decomposition. Finally, this review outlines future research directions and remaining challenges, offering insights into potential advancements in NH3 and N2O emission reduction for vehicles.