#### Article
Some authors report very low NO\({}_{\rm x}\) emissions using a combination of LNT (Lean NO\({}_{\rm x}\) Trap), SCR, and an ammonia slip catalyst under demanding urban driving conditions [4]; others propose the use of a type of non-hybrid 2.0 L D-segment vehicle in combination with LNT, catalyzed DPF, and down-stream SCR [5]. Very recent studies demonstrate that LNT and SCR coated filters offer further cold start emission reduction, and that the innovative diesel mild hybrids can offer synergistic gains for lower NO\({}_{\rm x}\) as well as CO\({}_{2}\) improvements [2]. Taking these premises into account, LNTs are still an interesting technology in the framework of a combined diesel or lean-burn engine strategy for efficient NO\({}_{\rm x}\) removal; lean combustion would need a complete rework of exhaust aftertreatment systems on gasoline engines, which traditional three-way catalysts (TWC) could not operate. Under these multiple contexts, LNT catalysts should be able to store NO\({}_{\rm x}\) in a temperature window between 150 \({}^{\circ}\)C and 350 \({}^{\circ}\)C under lean conditions, and subsequently reduce them under rich conditions; during this step, together with N\({}_{2}\), some NH\({}_{3}\) can be formed that could assist the downstream SCR device. However, several catalyst formulations, mainly based on zeolite doped with noble metals like Pd, could permit the storage of NO\({}_{\rm x}\) at low temperatures, subsequently releasing them at a higher temperature for the proper operation of the downstream SCR element [2]. All these actions can yield a lot of benefits and create a complex interplay in the design of new generation after-treatment strategies. An investigation of the influence of the various components forming these catalysts deserves special attention. LNT catalysts operate under cyclic conditions. In the first step, under lean conditions (that is, in excess of oxygen), NO\({}_{\rm x}\) is stored onto the catalyst's surface in the form of nitrites and/or nitrates depending on the storage temperature, while in the second step, the stored NO\({}_{\rm x}\) is reduced under rich conditions, with N\({}_{2}\) as a main product [6; 7; 8; 9; 10; 11; 12; 13; 14; 15; 16]. Nevertheless, some other products might be formed, such as NO, NO\({}_{2}\), NH\({}_{3}\), or N\({}_{2}\)O, because of an inefficient reduction or thermal decomposition. Typically, LNT catalysts are constituted of noble metals (Pt, Pd, Rh), which efficiently oxidize NO to NO\({}_{2}\) under O\({}_{2}\) and favor the generation of reduced N-products during the rich phase; they are also comprised of alkaline or alkaline earth metal oxides (Ba, K) as the storage component [10; 13; 15; 17; 18; 19]. The catalytic NO oxidation to NO\({}_{2}\) is a critical point due to the relevance of the NO\({}_{2}\) presence in different degullution technologies [20; 21; 22; 23]; indeed, not only can NO\({}_{2}\) be effectively retained onto catalytic NSR storage components, thus increasing the NO\({}_{\rm x}\) removal capacity of these systems, but it can also be very active in soot oxidation, being more oxidant than O\({}_{2}\). Thus, NO\({}_{2}\)-assisted soot combustion processes are interesting for the proper regeneration of diesel particulate filters (DPF), as well as in diesel particulate-NO\({}_{\rm x}\) reduction systems (DPNR) for the simultaneous removal of both contaminants [24; 25; 26; 27]. Ceria is a common component in several traditional automotive catalytic systems, such as three-way catalysts (TWCs) [6; 7], due to its unique properties. First of all, its oxygen storage capacity (OSC), which allows for the regulation of oxygen partial pressure under atmosphere changes. Cerium-based oxides, combined with Zr or Pr, are frequently used as redox catalysts in a number of applications [28; 29; 30; 31]; cerium oxide is also present in significant amounts in LNT catalyst formulations [32] to increase thermal stability and add OSC functionality [11].