Study On Preparation And Application Of G-C₃N₄/Bi₂MoO₆ And Cu₂O/BiVO₄ Composite Photocatalysts

The photocatalytic technique is considered to be one of the most promising technology to solve the problem of energy short-aged and environmental protection. It has been used in the fields, for example, degradation of organic dyes, photocatalysis of water spliting into hydrogen and oxygen, reduction of CO₂ to organic compounds and synthesis of fine organics. In recent years, more and more studies have tended to the photocatalytic oxidation of cylohexane and simultaneous oxidation of organic dyes and reduction of Cr?VI?. However, most of catalysts are suffuring the disadvantages of low acivity, poor repeatability and difficult in catalyst regeneration. Owing to the excellent characteristic of Bi-based photocatalyst of visible-light response and the construction of heterojunction helps charge carriers sepration, g-C₃N₄/Bi₂MoO₆ and Cu₂O/BiVO₄ composites were prepared under mild condition, they were used for photocatalytic oxidation of cyclohexane and the simultaneous oxidation of organic dyes and reduction of Cr?VI?, respectively. The possible photocatalytic mechanisms were also put forward.g-C₃N₄/Bi₂MoO₆ composite photocatalyst with heterojunction was prepared by hydrothermal method. It showed enhanced photocatalytic activity towards partial oxidation of cyclohexane into cyclohexanone and cyclohexanol under visible light irradiation. The reaction was processed at room temperature and pure O₂ atmosphere. Higher than 99% selectivity for cyclohexanone and cyclohexanol with ca. 1.02% conversion of cyclohexane was achieved after being irradiated for 3 h, and the production of cyclohexanone and cyclohexanol reached 233 ?mol and 183 ?mol per hour per gram of catalyst. The match of band gap energies and the formation of heterojunctions between g-C₃N₄ and Bi₂MoO₆ can not only avoid deeply oxidation of cyclohexane into CO₂ and H₂O, but also enhance the charge carriers' separation which are the main reasons for the high activity.Cu₂O/BiVO₄ composites were synthesized by growing Cu₂O nanoparticles on BiVO₄ under mild condition. The photocatalyst can be used for the degradation of cationic or anionic dyes as well as a mixture of them under visible light irradiation. At the same time, it showed high photocatalytic efficiency in the simultaneous oxidation of organic dyes and reduction of Cr?VI? in neutral media. The photocatalytic activity of the composite can be ascribed to two reasons: the heterojunctions between Cu₂O and BiVO₄, which facilitate the separation of photogenerated electrons and holes; the oxidation and reduction reaction occurs at the same time can inhibit the recombination of photo-induced charge carriers. The as-synthesized Cu₂O/BiVO₄ composite has a good application prospect in the treatment of wastewater that contains organic dyes and Cr?VI? ions.