受热自转变制备异质结型卤氧化铋光催化剂及其光催化性能增强机理

Nowadays, the design and fabrication of the photocatalytic materials with large spectrum responsible range, high activity, high photocatalytic stability,and environmental amity are crucial to enlarge the application of photocatalytic technology in environmental purification. Bismuth oxyhalide compounds-BiOX (X=Cl,Br,I) have poor thermo-stability which easy causes the crystal transformation or the release of halogen. This research proposal suggested that by employing their property of poor thermo-stability to prepare the hetero-structure bismuth oxyhalide photocatalysts through its self-transformation under different heating conditions. The formation of hetero-structure in photocatalyst could greatly enhance the efficiency of quanta and photocatalytic stability in photocatalytic reaction. To prepare the new bismuth oxyhalide photocatalysts,the relationship between the heating conditions and phase transformation will firstly be investigated and analysed. The structure property of the band gap energy and electron of these prepared new bismuth oxyhalide photocatalysts prepared by phase transformation will be characterized and investigated by some advanced technology, such as X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), high resolution- transmission electron microscopy (HRSTEM), Raman spectroscopy, thermogravimetric analysis (TGA), energy-dispersive X-ray (EDX) spectroscopy, photo-luminescence spectroscopy (PL), electrochemistry, Brunauer-Emmett-Teller (BET) surface areas, and etc. Through the exact control of the calcineation conditions, such as temperature, time, and atmosphere to prepare the catalyst with hetero-structure which has different content and structure. The formation mechanism of the hetero-structure in photocalysts will be investigated and clarified. The influences of the hetero-structure on the photocatalytic degradation rate and photocatalytic degradation route of model pollutant, photocatalytic stability and photo-corrosion of the photocatalyst will be characterized and investigated in detail. The reason and mechanism of the enhancing role of the hetero-structure to photocatalytic activity and photocatalytic stability will be illuminated. This research project has the positive role in design and fabrication of the photocatalytic materials with large spectrum responsible range, high activity, and high photocatalytic stability. Therefore, this research project will enrich and develope the method of fabrication of new photocatalytical materials and the new theory of photocatalysis.

研制宽光谱响应、高活性、高光稳定性和环境友好的光催化材料对于扩大光催化技术在环境净化的运用极为关键。本项目提出利用BiOX(X=Cl、Br、I) 热稳定性差，受热易引起晶格转变或卤元素释放的特点，自转变制备异质结型卤氧化铋光催化材料，通过异质相结大幅度提高其光催化反应的量子效率和稳定性。首先考察BiOX在不同焙烧条件下的相转变规律，制备各新型卤氧化铋光催化材料，研究其能带结构和电子结构；然后通过相转变区间受热温度、时间和气氛的精确调控，形成不同含量、不同结构的异质相结，研究异质相结的形成机制及其对不同波长光源下模型污染物光催化降解反应速率、反应途径、光催化剂稳定性和光腐蚀行为的影响规律。深入理解并阐明形成异质相结对卤氧化铋光催化活性、稳定性增强的原因、内在机理。本研究将为宽光谱、高活性、高稳定性的新型半导体光催化材料的大规模制备和应用提供理论根据和技术支持，具有重要理论价值和实际意义。

通过BiOX (X=Cl、Br、I)受热引起晶格转变或释放卤元素，自转变制备异质结型卤氧化铋光催化材料, 主要研究内容如下：.（1）研究了BiOX(Cl、Br、I) 在不同气氛（空气、氮气和真空）下随焙烧温度、陪烧时间的相变规律。BiOI的相转变规律基本为：BiOI在360℃时开始失去碘逐渐变成Bi5O7I， Bi5O7I在850℃可完全转变为α- Bi2O3。BiOBr在空气气氛下的相转变规律基本为：在575℃时开始失去Br逐渐变成Bi24O31Br10，Bi24O31Br10在970℃,可完全转变为α- Bi2O3。BiOCl的晶格氯原子只有在690℃的高温才可能脱离，此时样品已经发生严重烧结，基本无催化活性。.（2）发现以BiOI为原料在360℃~500℃控制不同的煅烧时间能获得高活性BiOI/Bi5O7I复合光催化剂，在650℃~700℃控制不同的煅烧时间可以制备异质结的Bi5O7I/Bi2O3。而以BiOBr为原料，在575℃~670℃可以获得高活性BiOBr/Bi24O31Br10复合光催化剂，在710℃~750℃可以制备异质结的Bi24O31Br10/Bi2O3。.（3）研究了不同形貌的BiOClxBr1-x、BiOBrxI1-x和BiOClxI1-x相转变规律研。研究发现在卤氧化铋复合半导体中，其稳定性不如纯的卤氧化铋，且在受热条件下，原子量比较大的卤素容易脱出，可以在卤素脱除生成微球等不同形貌的异质结光催化剂。.（4）研究发现，在NH3气氛下BiOBr和BiOI容易被还原，成金属Bi, 而BiOCl中的晶格氧可以被N取代，生成具有可见光活性的N-BiOCl光催化剂。. 以上相转变策略制备的异质相结铋氧卤光催化剂由于异质相结的生成具有更高的催化活性，在光催化降解染料﹑苯酚﹑邻苯二甲酸酯等表现较好的光催化活性。本项目丰富和完善了相变异质相结的概念，并在在其它半导体受热自转变制备异质相光催化剂获得重要应用。.该项目直接研究内容发表论文9篇，其中SCI 5篇，EI 4篇，发表相关SCI论文28篇，论文水平较高，如在Advanced Materials等发表影响因子大于18的论文1篇，影响因子大于7的3篇。论文获全球高被引ESI热点论文1篇。申报发明专利1项，获批发明专利2项。培养6名毕业硕士研究生。项目成果获江西省自然科学一等奖一项。