Electrocatalytic Reactive Capture of NO from O2-Containing Simulated Flue Gas Using Highly O2-Resistant Fe2+-(salen-SO3) for NH3 Synthesis

Abstract

Efficient removal of nitric oxide (NO) from flue gases remains a significant environmental challenge due to its low concentration, poor water solubility, and the presence of oxygen, which deactivates traditional NO absorbents such as Fe2+-EDTA. Herein, we present an electrochemistry-based reactive NO capture system using SO3-functionalized Fe2+-salen as an NO absorbent with outstanding oxygen resistance. The unique tetracoordinate structure of the salen-SO3 ligand reduces the electron density at the Fe2+ center, preventing its oxidation to Fe3+ under air exposure. Coupled with highly porous NiMo electrocatalysts, the system achieves an NH3 production rate of 2.0 mmol h-1 cm-2 geo with 97% Faraday efficiency under 100% NO. This continuous NO capture and conversion into NH3 was maintained under air-exposed conditions at 60% of the performance level under 100% NO, with stability over 160 h. Mechanistic studies reveal that Fe2+ is the critical active site for NO reduction and elucidate complete reaction pathways for NH3 synthesis.