A progressive review on NO purification from diesel vehicle exhaust: From technology development to material active sites analysis

Despite of the main techniques like Passive NOx adsorbers (PNAs), NOx Storage and Reduction (NSR), and Selective Catalytic Reduction (SCR), newly coupling technologies, such as the PNA-SCR system, NSR-SCR system, dual SCR system, etc., have been greatly developed to meet the more and more strict emission limit of NOx from diesel vehicle. This work firstly presents a macro-systematic review of new and traditional technologies for NOx purification of diesel vehicle exhaust from the aspects of technique characteristics, purification mechanisms, material types, and the coupling forms of new techniques. Then, the functional sites including adsorption sites, and catalytic sites as well as their functional continuity of PNAs, SCR, NSR materials and coupling materials were illustrated from the microscopic points of view. Finally, the factors affecting the formation of single or composite sites were clarified in detail, based on which the future directions for the research of coupling material composite sites were proposed. It was hoped that this review could provide some knowledge and enlightenment for designing highly efficient materials for NOx purification from diesel vehicle exhaust.