Potential of deep eutectic solvent in photocatalyst fabrication methods for water pollutant degradation: A review

Deep eutectic solvents (DESs) are the emerging solvent alternatives attributed to their biodegradability, sustainability, and tunability by which their incorporation in material synthesis technology can hasten the research field's progress. In relation, this review analyzes the potential of DES integration into the photocatalytic material fabrication area, particularly for water remediation purposes. It is discovered that DES influences the physicochemical properties and activity of the photocatalysts due to its structure-directing behavior, by regulating phase composition, or as a source of precursor during sol-gel, hydrothermal, solvothermal, ionothermal, and wet-chemical methods. Whereas for the electrosynthesis route, good solvating power, suitable electrochemical window, tunable ionic conductivity and viscosity allow DES to function as a viable electrolytic medium and encounter the shortages of the conventional electrolytes. Despite the challenges, the incorporation of DES in other unexplored techniques such as co-precipitation and microwave-assisted methods may yield unique photocatalyst structures based on its templating mechanism and microwave absorbing capacity respectively. The excellent photodegradation efficiencies of numerous water pollutants by the photocatalyst generated by the DES-assisted methods further validated the DES practicability in photocatalyst synthesis. Finally, the future perspectives and apparent shortcomings of DES are outlined as well for consideration. As the recent research trends are steering towards sustainable and green chemistry, it is believed that the investigation on DESs technology will intensify. Thus, it is wished that the insights attributed from this work can be a part of the upcoming DES knowledge exploration. • DES is a green solvent alternative for photocatalyst fabrication. • DES significantly affects the structural characteristics of photocatalyst during the synthesis process. • DES acts as a viable electrolyte in electrosynthesis due to its superior electrochemical properties. • High photodegradation rates of water contaminants are achieved by photocatalyst generated via DES-assisted methods.