Carbon quantum dots/TiO2 nanosheets with dominant (001) facets for enhanced photocatalytic hydrogen evolution

Carbon quantum dots/TiO₂ nanosheets with a majority of (001) facet (CQDs/TiO₂-001) samples are successfully prepared via a facile method. Compared to TiO₂-001 and CQDs/P25, the synthesized CQDs/TiO₂-001 presents a remarkably higher photocatalytic activity for H₂ evolution with a considerable stability. XRD, XPS, HRTEM, FESEM, FTIR, Photoluminescence (PL) spectroscopy, Fluorescence spectroscopy and UV–visible reflectance spectroscopy are adopted to investigate the morphology, structure and properties of synthesized CQDs/TiO₂-001. The mechanism of the improved photocatalytic activity over CQDs/TiO₂-001 is also investigated. The results show that the improved photocatalytic activity over CQDs/TiO₂-001 can be attributed to the synergistic effects of TiO₂-001 and CQDs: the highly exposed (001) facets of TiO₂-001 promote the transportation of photogenerated electrons and the loading of CQDs restrains the recombination of electrons-holes on (001) facets. Meanwhile, the visible-light absorption is extended because the CQDs serve as a photosensitizer and sensitize TiO₂-001 through the newly formed TiOC bond between the CQDs and TiO₂-001.