Study On Preparation And Its Photocatalytic Properties Of Bi₁₂O₁₇Cl₂ Based Photocatalyst

In recent years,the water pollution,greenhouse effect and rapid energy consumption have seriously affected the ecological balance of the earth.The advent of photocatalytic technology provides a new direction for the treatment of the above problems.Bi₁₂O₁₇Cl₂ is a kind of photocatalyst with excellent performance,but the photoelectron-hole pairs in Bi₁₂O₁₇Cl₂ is easy to recombine,which reduces the activity of photocatalytic reaction.In order to broaden the application of Bi₁₂O₁₇Cl₂ in environment and energy,three different catalyst systems were constructed,namely Bi₁₂O₁₇Cl₂/Ti O₂ composite material,Cd S/Bi₁₂O₁₇Cl₂ heterojunction and CQDs/Bi₁₂O₁₇Cl₂ photocatalyst,respectively.The specific studies are as follows:（1）Bi₁₂O₁₇Cl₂ was synthesized at room temperature using bismuth trichloride as bismuth source.Bi₁₂O₁₇Cl₂ and commercial titanium dioxide（Ti O₂）were used as raw materials to prepare Bi₁₂O₁₇Cl₂/Ti O₂ composites,and the effect of Bi₁₂O₁₇Cl₂ content on the photocatalytic performance of Bi₁₂O₁₇Cl₂/Ti O₂ materials was investigated.It was found that the catalytic activity of Bi₁₂O₁₇Cl₂/Ti O₂ could be improved by the appropriate content of Bi₁₂O₁₇Cl₂ in the degradation of methyl orange（MO）under ultraviolet and UV-vis light conditions.When the content of Bi₁₂O₁₇Cl₂ is in the range of 1%-7%,3%Bi₁₂O₁₇Cl₂/Ti O₂ showed the highest photocatalytic activity.The research results show that 3%Bi₁₂O₁₇Cl₂/Ti O₂ has a higher charge separation efficiency,which is conducive to the enhancement of photocatalytic activity.（2）Cd S/Bi₁₂O₁₇Cl₂ heterojunction photocatalysts were prepared by a simple thermal annealing process.The results of Raman spectroscopy and transmission electron microscopy confirmed the successful construction of the heterojunction.The construction of the heterojunction enables the carriers to be effectively separated,and the activity of Cd S/Bi₁₂O₁₇Cl₂ in phenol degradation and carbon dioxide reduction under visible light was improved.The research results indicate that when the Cd S content varies from 34%to 60%,50%Cd S/Bi₁₂O₁₇Cl₂ has the largest specific surface area,moderate band gap width and strong light absorption capacity.Therefore,50%Cd S/Bi₁₂O₁₇Cl₂ shows the highest photocatalytic activity and has good stability in photocatalytic experiment.（3）Carbon quantum dots（CQDs）/Bi₁₂O₁₇Cl₂ catalysts were synthesized by precipitation method at room temperature.Raman spectra and transmission electron microscopy indicated that CQDs and Bi₁₂O₁₇Cl₂ formed a tight bond.After carbon quantum dot modification,the specific surface area and the pore volume of Bi₁₂O₁₇Cl₂samples increased,and the charge separation efficiency was improved.The performance of the sample was evaluated by photodecomposition of water to generate oxygen under visible light,and the influence of different CQDs content on the photocatalytic performance was investigated.The results indicate that when the volume of carbon quantum dot solution varies between 1-20 m L,the oxygen production rate of CB2 sample（the volume of carbon quantum dot solution was 5 m L）was the best(677μmol·h^-1·g^-1),which was 1.4 times of pure Bi₁₂O₁₇Cl₂(480μmol·h^-1·g^-1).The research results showed that CB2 sample has relatively positive valence band position,excellent light absorption performance,smaller band gap width and good carrier separation efficiency,which effectively promotes the photocatalytic oxygen production rate.