Facile and mild preparation of brookite-rutile heterophase junction TiO2 with high photocatalytic activity based on deep eutectic solvent (DES)

The phase junction of nano-TiO2 plays an important role in enhancing its photocatalytic activity. However, the achievement of the green, mild and controllable synthesis of phase-junction nano-TiO2 still remains a big challenge for the large-scale preparation and application. Deep eutectic solvents (DESs) show many advantages in the green and mild preparation of highly active nanomaterials due to their low cost, high environmental friendliness, easy large-scale preparation, tailored structures and tunable properties. In this study, by sharing two H-bond acceptors with one H-bond donor, we successfully used DES as a solvent, template, inhibitor and crystalline phase control agent simultaneously to controllably synthesize heterophase-junction nano-TiO2 with different phase ratios under green and mild reaction conditions (at 180 °C for 18 h). The H2 production rate of photocatalytic water splitting with this catalyst reached up to 14.51 mmol h−1 g−1, which was 20-fold greater than that of commercial P25 TiO2 and also much higher than those of other TiO2 nanostructures. To the best of our knowledge, this rate is the highest value reported so far for photocatalytic H2 production catalyzed by sole TiO2. This higher activity was mainly attributed to the phase junctions and defects. This study will provide a new way for the green, mild, easily controllable and versatile preparation of phase-junction photocatalysts with high efficiency.