Upcycling air pollutants to fuels and chemicals via electrochemical reduction technology

Abstract

The intensification of fossil fuel usage results in significant air pollution levels. Efforts have been put into developing efficient technologies capable of converting air pollution into valuable products, including fuels and valuable chemicals (e.g., CO₂ to hydrocarbon and syngas and NO_x to ammonia). Among the strategic efforts to mitigate the excessive concentration of CO₂ and NO_x pollutants in the atmosphere, the electrochemical reduction technology of CO₂ (CO₂RR) and NO_x (NO_xRR) emerges as one of the most promising approaches. It is even more attractive if CO₂RR and NO_xRR are paired with renewables to store intermittent electricity in the form of chemical feedstocks. This review provides an overview of the electrochemical reduction process to convert CO₂ to C₁ and/or C₂₊ chemicals and NO_x to ammonia (NH₃) with a focus on electrocatalysts, electrolytes, electrolyzer, and catalytic reactor designs toward highly selective electrochemical conversion of the desired products. While the attempts in these aspects are enormous, economic consideration and environmental feasibility for actual implementation are not comprehensively provided. We discuss CO₂RR and NO_xRR from the life cycle and techno-economic analyses to perceive the feasibility of the current achievements. The remaining challenges associated with the industrial implementation of electrochemical CO₂ and NO_x reduction are additionally provided.

Keywords: Air pollutions; Electrocatalysis; Life cycle assessment; Sustainability; Techno-economic analysis; Waste-to-chemicals.