g-C3N4/TiO2 composite microspheres: in situ growth and high visible light catalytic activity

The morphology, structure and composition of a photocatalyst are the key factors affecting its photocatalytic activity. Herein, g-C3N4 nanosheets were successfully grown in situ on the surface of TiO2 microspheres, and then a three-dimensional (3D) flower-like g-C3N4/TiO2 composite microsphere photocatalyst (FCTM) was formed with the self-assembly of TiO2 nanosheets. The effects of g-C3N4 nanosheets on the growth process, physical adsorption and photocatalytic activity of FCTM samples were studied. Compared with pure TiO2, the 3D flower-like g-C3N4/TiO2 composite microsphere photocatalyst had a larger specific surface area, and the specific surface area of FCTM-20 was 239.75 m2 g−1. Additionally, the addition of g-C3N4 nanosheets also changed the surface charge of TiO2 microspheres, resulting in the improvement of the physical adsorption capacity of FCTM-20. The degradation rates with FCTM-20 of MO and MB solutions were 51.7% and 92.5% after visible light irradiation for 5 h, which were 41.6% and 111.2% higher than those with pure TiO2 microspheres, respectively. During the photocatalytic process, FCTM-20 exhibited the best adsorption and degradation of MB solution. This is because the chromophoric groups of MO and MB lead to different energy requirements for FCTM-20 in the degradation process. Furthermore, the self-assembled 3D flower-like morphology of FCTM-20 provided more active sites for the degradation of MO and MB, and the heterojunction structure formed between TiO2 and g-C3N4 was more conducive to the transmission of photogenerated carriers.