A stable and highly efficient visible-light photocatalyst of TiO2 and heterogeneous carbon core–shell nanofibers

Abstract

A novel core–shell heterostructure of TiO₂ nanofibers with carbon quantum dots embedded in an amorphous carbon shell has been successfully prepared via a simple electrospinning and impregnation process. Here, carbon quantum dots (CQDs) are designed as sensitizers for the visible-light response and amorphous carbon ensures intimate contact with TiO₂. The photocatalytic performance is evaluated by the degradation of rhodamine-B under visible light irradiation. It is found that the composite nanofibers with an appropriate thickness of carbon shell exhibit a stable and highly efficient photocatalytic activity, and the apparent quantum efficiency can reach as high as 52%, which is about 10 times that of pure TiO₂ nanofibers. Structural analyses show that the enhanced photocatalytic activity is attributed to the synergistic effect of TiO₂, the amorphous carbon thin shell and the CQDs embedded inside. Due to the intimate contact between TiO₂ and the carbon shell, the photogenerated electrons can be easily transferred from the CQDs to TiO₂ resulting in a longer lifetime of the photogenerated electron–hole pairs and a higher photocatalytic activity. In addition, the unique upconversion properties of the CQDs enables the nanofibers to utilize more solar energy and increase the photocatalytic activity. Also, the carbon shell can induce more oxygen vacancies on the surface of the nanofibers, which can further enhance the photocatalytic activity. The results in this work may be beneficial to the future study of exploring new carbon-based heterostructured materials for visible-light-driven photocatalysts.