Continuous NO Upcycling into Ammonia Promoted by SO 2 in Flue Gas: Poison Can Be a Gift.

Although ammonia (NH 3 ) synthesis efficiency from the NO reduction reaction (NORR) is significantly promoted in recent years, one should note that NO is one of the major air pollutants in the flue gas. The limited NO conversion ratio is still the key challenge for the sustainable development of the NORR route, which potentially contributes more to contaminant emissions rather than its upcycling. Herein, we provide a simple but effective approach for continuous NO reduction into NH 3 , promoted by coexisting SO 2 poison as a gift in the flue gas. It is significant to discover that SO 2 plays a decisive role in elevating the capacity of NO absorption and reduction. A unique redox pair of SO 2 -NO is constructed, which contributes to the exceptionally high conversion ratio for both NO (97.59 ± 1.42%) and SO 2 (99.24 ± 0.49%) in a continuous flow. The ultrahigh selectivity for both NO-to-NH 3 upcycling (97.14 ± 0.55%) and SO 2 -to-SO 4 2- purification (92.44 ± 0.71%) is achieved synchronously, demonstrating strong practicability for the value-added conversion of air contaminants. The molecular mechanism is revealed by comprehensive in situ technologies to identify the essential contribution of SO 2 to NO upcycling. Besides, realistic practicality is realized by the efficient product recovery and resistance ability against various poisoning effects. The proposed strategy in this work not only achieves a milestone efficiency for NH 3 synthesis from the NORR but also raises great concerns about contaminant resourcing in realistic conditions.