Facet-dependent photocatalytic and photoelectric properties of CQDs/TiO2 composites under visible irradiation

The construction of photocatalytic heterostructures and the study of carrier kinetics are significant for developing novel functional materials and understanding catalytic mechanisms. Here, we synthesized the heterostructural composites of carbon quantum dots (CQDs) and TiO 2 nanoparticles with (101) or (001) as the main exposed facets by hydrothermal method, named CQDs/TiO 2 (101) and CQDs/TiO 2 (001). The facet-dependent sensitization and photocatalysis properties of these composites have been investigated using steady-state and time-resolved spectroscopy. The results indicate that the electron transfer process between CQDs and TiO 2 is associated with the exposed facet of TiO 2 . The electron transfer rate from CQDs to TiO 2 (101) is two orders of magnitude larger than that to TiO 2 (001). The CQDs/TiO 2 (101) composite also demonstrates three times higher photoelectric conversion than CQDs/TiO 2 (001). The facet-dependent catalytic performances of CQDs/TiO 2 composites have been evaluated by the degradation of Rhodamine B (RhB) under visible light irradiation. The rate constant of CQDs/TiO 2 (101) for the degradation of intermediates (Rh-110) shows 1.82 times higher than that of CQDs/TiO 2 (001). These findings indicate the effective loading of CQDs on TiO 2 (101) nanoparticles can be expected to efficiently improve the photoelectric and photocatalytic properties of TiO 2 -based heterostructure under visible irradiation, and are significant for deep understanding the facet-dependent photocatalytic mechanism and property. • CQDs/TiO 2 (101) and CQDs/TiO 2 (001) heterostructure photocatalysts were constructed. • The electron transfer rate from CQDs to TiO 2 (101) is larger than that of TiO 2 (001). • The catalytic rate constant of CQDs/TiO 2 (101) is higher than that of CQDs/TiO 2 (001). • The CQDs/TiO 2 (101) shows three times higher photocurrent than CQDs/TiO 2 (001).