Phase Engineering of TiO2/MXene Heterostructure Nanosheets for Enhanced Photocatalysis

TiO2-based heterostructures have attracted considerable attention in photocatalytic pollutant degradation owing to their enhanced photoresponse and improved charge separation. The phase structure of TiO2 strongly affects its band structure and interfacial charge-transfer behavior, making phase structure control critical for optimizing photocatalytic performance. However, due to the small difference in free energy among TiO2 phase structure and the strong dependence of TiO2 nucleation and growth on the local reaction environment, it remains challenging to precisely control the phase structure of TiO2 in the TiO2-based heterostructure nanomaterials. Herein, we achieved the phase engineering of TiO2/MXene heterostructure nanomaterials through a solvent-regulation strategy. Specifically, by regulating the acetonitrile/water ratio in the hydrothermal solvent, TiO2 with distinct phase structures was in situ grown on hydrothermally treated MXene nanosheets, resulting in two representative TiO2/MXene heterostructure nanosheets: anatase TiO2/MXene and rutile TiO2/MXene. Acetonitrile likely acted as a surface-adsorbing agent during TiO2 formation, stabilizing the anatase phase and promoting the preferential formation of anatase TiO2. Benefiting from the optimized heterostructure, TiO2/MXene heterostructure nanosheets promoted the generation of singlet oxygen (1O2), leading to enhanced photocatalytic degradation.