Carbon quantum dots-decorated ZnO heterostructure nanoflowers grown on nanofiber membranes as high-efficiency photocatalysts

Nano semiconductor photocatalysts have attracted more and more attention and developed rapidly because of their high degradation efficiency, low energy consumption and non-toxic and harmless in sewage treatment. In this work, a simple three-step preparation method combining electrospinning, heat treatment and hydrothermal synthesis was applied to obtain carbon quantum dots (CQDs)-decorated ZnO heterostructure nanoflowers grown on nanofiber membranes (NFMs), which were composed of CQDs-decorated ZnO nanorods. The morphology, structure, chemical composition and properties of nanocomposites were characterized by using scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction spectroscopy, X-ray photoelectron spectroscopy, UV–Vis-NIR spectrometer and fluorescence spectrometer, determining the formation of CQDs-decorated ZnO heterostructure nanoflowers and the optimum experimental parameters. Moreover, the photocatalytic degradation mechanism was further revealed by the Mott-Schottky test and active radical capture experiment. The results demonstrated that when the addition amount of CQD solution was 300 μL, the produced NFMs with CQDs-decorated ZnO had the best light absorption performance, leading to its best degradation effect on methylene blue (degradation efficiency over 88 %, 4 h) under natural sunlight irradiation.