Continuous NO Upcycling into Ammonia Promoted by SO₂ in Flue Gas: Poison Can Be a Gift

Abstract

Although ammonia (NH3) 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 NH3, promoted by coexisting SO2 poison as a gift in the flue gas. It is significant to discover that SO2 plays a decisive role in elevating the capacity of NO absorption and reduction. A unique redox pair of SO2–NO is constructed, which contributes to the exceptionally high conversion ratio for both NO (97.59 ± 1.42%) and SO2 (99.24 ± 0.49%) in a continuous flow. The ultrahigh selectivity for both NO-to-NH3 upcycling (97.14 ± 0.55%) and SO2-to-SO4 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 SO2 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 NH3 synthesis from the NORR but also raises great concerns about contaminant resourcing in realistic conditions.

Dual built-in spontaneous electric fields in an S-scheme heterojunction for enhanced photocatalytic H2O2 production

“…Thus, it was clearly found that the MnOOH cocatalyst is located on the BiVO 4 /Cu 2 O S-scheme heterojunction. 39…”

Photocatalytic NOx removal and recovery: progress, challenges and future perspectives

“…The chemical redox pair of SO 2 -Fe(III) is illustrated in eqn ( 21)- (23). 114 Fe(II) / Fe(III) (spontaneous oxidation) (21)…”

“…Furthermore, the on-site coupled system demonstrated the synergistic removal and recycling of NO and SO 2 without the need for scavengers. 114 The formation of the SO 2 –NO redox pair facilitates high conversion rates of both NO and SO 2 in continuous flow. Achieving a remarkable selectivity for both NO-to-NH 3 upcycling (97%) and SO 2 -to-SO 4 2− purification (92%) simultaneously underscores the practicability of value-added conversion of air pollutants ( Fig.…”

“…7a and b ). 114 Maintaining the efficiency of NO conversion and reduction crucially depends on preventing the oxidation of Fe( ii ) to Fe( iii ) in Fe( ii ) EDTA. Through verified in situ ATR-FTIR experiments, it was revealed that SO 2 exhibited a promoting effect on Fe( ii ) maintenance, while no interaction was observed between SO 2 and EDTA ( Fig.…”

Selective Electrocatalytic Conversion of Nitric Oxide to High Value‐Added Chemicals

“…[7][8][9] Notably, the combustion of fossil fuels and emissions from vehicle exhaust have significantly increased the concentration of nitric oxide (NO) in the atmosphere. [10][11][12] This rapid rise in NO level has severely impacted the environment (e.g., photochemical smog, ozone layer depletion, and acid rain) and human health. [13,14] Currently, the predominant method for NO removal is selective catalytic reduction (SCR) technology, which typically requires the utilization of valuable reducing agents such as ammonia (NH 3 ) or urea.…”