Photocatalytic hydrogen evolution on graphene quantum dots anchored TiO2 nanotubes-array

• GQDs anchored TiO2 nanotubes array (TiO2-NA) or CdS/TiO2-NA was synthesized.
• GQDs improved the light quantum efficiency of both TiO2-NA and CdS/TiO2-NA.
• Loading GQDs into TiO2-NA or CdS/TiO2-NA enhances their activity for H2O splitting.
• Light-filtering effect of graphene sheets is weakened by breaking them into GQDs.

The inversely structured TiO2 nanotubes-array (TiO2-NA) and CdS-modified TiO2 nanotubes-array (CdS/TiO2-NA) with graphene quantum dots (GQDs) anchored inside were prepared through a facile impregnation method. The catalysts were characterized by multiple techniques of SEM, TEM, XRD, Raman spectroscopy, XPS, TG and diffuse reflectance UV/Vis absorption spectroscopy. The results of TEM, XPS and Raman spectroscopy indicate that the GQDs were really formed and successfully anchored into the TiO2-NA and CdS/TiO2-NA. The activity evaluation results show that the hydrogen evolution rate during photocatalytic water splitting was greatly improved after loading GQDs into TiO2-NA and CdS/TiO2-NA. By breaking graphene into GQDs, the light-filtering effect of graphene was remarkably inhibited as compared with that of conventional large graphene sheets. Moreover, the overall morphology of TiO2 nanotube array could be well maintained after anchoring GQDs inside, which is favorable to mass transfer. The catalyst design strategy proposed in present work can be extended to other photocatalytic systems.

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