A PGM-free NOx adsorber + selective catalytic reduction catalyst system (AdSCR) for trapping and reducing NOx in lean exhaust streams at low temperatureElectronic supplementary information (ESI) available. See DOI: 10.1039/c8cy00343b

Low-temperature operation of urea/NH 3 -SCR converters, required by recent emission regulations, is challenging due to technological limits related to poor catalytic activity, difficult urea decomposition and undesired ammonium nitrate formation. Herein, we present a novel concept of a catalytic device, which adds a NO x storage functionality to a typical SCR catalyst. This enables capture and storage of NO x in lean exhaust streams already at room temperature, with significant efficiencies under dry conditions, as well as direct reduction of the stored NO x at higher temperatures. The proposed system (AdSCR = adsorption + selective catalytic reduction) is intrinsically different from the well-known existing NO x storage reduction (LNT) + SCR systems. In fact, it is free of PGM materials and does not require lean-rich cycling, being operated just like an SCR catalyst. It has therefore potential advantages both in terms of costs and flexibility of the aftertreatment configuration: in principle, it can be integrated into conventional SCR converters, leading to improved deNO x efficiencies without additional modifications of the aftertreatment architecture. Novel AdSCR systems are able to trap and reduce NO x in lean exhausts at low temperature.