Deep Eutectic Solvent-Mediated Nucleation Engineering of Bi ₂ WO ₆ Photocatalysts for Enhanced Visible Light Degradation of Organic Pollutants

Morphological and electronic features of the photocatalysts are established together during the nucleation phase and are central to their activities. Solvent-based approaches can be effective in comodulating these properties, owing to their direct influence on the nucleation dynamics of the photocatalysts. Building on this realization, the present study demonstrates how a simple change in the reaction medium of a model photocatalyst, Bi2WO6, can remarkably transform both its morphological and electronic features. The nucleation dynamics of Bi2WO6 was analyzed using four solvent systems, i.e., water, ethylene glycol (EG), urea/choline chloride-based deep eutectic solvents (DES) (U:Ch), and urea/fructose-based natural deep eutectic solvents (NADES) (U:F). The extensive hydrogen-bond frameworks of Bi2WO6/U:Ch and Bi2WO6/U:F showed a remarkable influence on the morphology and electronic properties, likely via effects on nucleation and growth control. The effect of altered morphological and electronic features was validated using photocatalytic experiments against model pollutants, malachite green (MG) and tetracycline hydrochloride (TC), wherein Bi2WO6/U:Ch and Bi2WO6/U:F systems with enhanced morphological and electronic attributes exhibited a maximum degradation performance. The obtained results were rigorously validated using scavenging analysis, and a detailed mechanistic outlook was presented using precise electronic structure investigation. With these outcomes, this study shows that hydrogen-rich solvent systems such as DESs and NADESs are not merely a green replacement of the conventional solvents but can be effectively utilized as strategic tools to precisely engineer key structural features of the photocatalysts.