Advances in electrochemical treatment for state-of-the-art abatement of gaseous air pollutants: A review

Effective abatement of air pollutants in their gaseous state is essential for achieving a cleaner environment. A promising and environment-friendly technology for this purpose involves the use of electrons as clean energy or solvents. The field of electrochemical abatement of air pollutants using electrons has made significant progress in recent years, particularly in terms of solid-gas electrochemical reactions within suitable cell assemblies. Herein, we provide a comprehensive overview of the absorption of gaseous volatile organic compounds (VOCs) into liquids involved in electrochemical abatement at the solid-liquid or liquid-gas interfaces. Techniques such as electroscrubbing, which use electrically charged ions for the treatment of flue gases, odor gases, and VOCs with wet scrubbers, are explored. Advances in the abatement of gaseous pollutants include the development of tri-phase interfaces using gas diffusion electrodes (GDE) in electrochemical cell assemblies, which have subsequently progressed to membrane electrode assemblies (MEA) in all-solid-cell configurations. A recent innovation involves a half-cell approach that eliminates the need for liquid electrolytes and minimizes humidity supply to the gaseous pollutant stream. This review highlights the importance of mediators or catalysts at the liquid-gas and solid-gas interfaces in improving the effectiveness of air pollutant abatement. Furthermore, a potential application of a gel membrane design for a liquid-electrolyte-free one-half-cell configuration is suggested, which could facilitate the abatement of gaseous pollutants at solid-gas electrochemical interfaces.