Photocatalytic Degradation Of Dyes Over SiO₂/G-C₃N₄ And ZrO₂/g-C₃N₄ Photocatalysts

Photocatalysis technology has attracted great interest because it offers a sustainable pathway to drive chemical reactions, such as the degradation of organic pollutants, water splitting and carbon fixation. TiO2 is considered as the one of the best photocatalyst due to its non-toxicity, good stability and excellent photocatalytic activity. However, TiO2 is only responsive to ultraviolet light because of its wide band gap, which occupies no more than 4% of the solar spectrum. In view of the better utilization of solar light, it is appealing to develop visible light-sensitive photocatalysts that are active enough for practical applications. Therefore, great efforts were devoted to develop an efficient visible-light-driven photocatalysts, such as TaON, BiVO4, g-C3N4, In this paper, we prepared two novel g-C3N4 based composite photocatalysts and tested their catalytic activity in photodegradation of RhB solution.A visible-light driven SiO2/g-C3N4 composite was prepared by heating a mixture of SiO2 and melamine. The products were characterized by X-ray diffraction, Brunaue-Emmett-Teller analysis, transmission electron microscopy, and ultraviolet visible diffuse reflectance spectroscopy. Results indicate that the composite contained SiO2 and g-C3N4. The addition of SiO2 had minimal influence on light absorption, but the specific surface area was increased. In addition, the aggregation of g-C3N4 in the SiO2/g-C3N4 composite was weakened. The increased surface area and decreased aggregation of g-C3N4 are considered as the cause of the strong activity of the SiO2/g-CsN4 composite in rhodamine(RhB) photodegradation.The visible-light-driven ZrO2/g-C3N4 hybrid photocatalysts were prepared direct heating of ZrO2 and melamine. Compared to pure g-C3N4 or ZrO2, the synthesized ZrO2/g-C3N4 exhibited much higher photocatalytic activity for RhB degradation under visible light irradiation. In order to reveal the origin of the high photocativity, the ZrO2/g-C3N4 composites were characterized by various techniques including N2 adsorption, thermogravimetric analysis (TG), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), Scanning electron microscopy (SEM), transmission electron (DRS), photoluminescence spectroscopy (PL), and electrochemical methods. The characterization results demonstrated that ZrO2 nanoparticles were well distributed on the surface of g-C3N4. Although the anchoring of ZrO2 on g-C3N4 increased the surface area and light absorption ability, the hetero-junctions formed between the two semiconductors which retarded the recombination of electrons and holes were believed to result in the enhanced photoactivity of the ZrO2/g-C3N4 composite. In addition, it was found that holes and·O2- generated in the photocatalytic process played a key role in RhB degradation over the ZrO2/g-C3N4 hybrids.