随着工业的快速发展，大量的污染物被排放至自然环境中，造成的负面影响严重危害人类社会的可持续发展。光催化技术具有高效、成本低廉、绿色环保等优点，在降解污染物方面具有独特的优势。光催化技术面临的的核心问题是设计开发高性能的光催化材料。TiO₂、ZnO等传统光催化剂在使用过程中存在对可见光利用率较低和光生电子-空穴对易复合等问题，因此人们已经逐渐开始研究新型可见光响应光催化材料，并采用一些手段对单组分光催化材料进行改性，进一步提升光催化活性，如形貌调控、离子掺杂、构建异质结等，但是通过这些方法对单组分光催化材料的活性提升比较有限。因此，本文以新型可见光响应光催化剂BiOBr和Ag₃PO₄为研究对象，引入氧化石墨烯（GO）和还原氧化石墨烯（rGO），合成复合光催化材料，同时对BiOBr和rGO进行离子掺杂，通过复合碳材料和单组分改性方法的协同效应，有效地降低了光生电子和空穴的复合率，从而改善光催化剂的性能。本研究主要包含以下三个工作内容：

（1）Gd-BiOBr/rGO复合材料的制备及其光催化性能研究

采用溶剂热法成功合成了Gd-BiOBr/rGO复合材料。Gd³⁺掺杂的BiOBr微球分布在褶皱透明的还原氧化石墨烯（rGO）薄片上，rGO的二维平面提供了更多的生长位点，使BiOBr微球的尺寸减小，比表面积增大，进而可以提供更多的吸附位点和光催化活性中心。光催化实验表明，Gd-BiOBr/rGO-30的光催化活性最高，120 min内对罗丹明B的去除率高达96.4%，降解速率是纯BiOBr的2.8倍。光催化性能增强的原因一方面是Gd³⁺掺杂后形成了电子捕获中心，抑制光生载流子重组，另一方面是rGO的引入缩小了带隙能，拓宽光催化剂在可见光区的光响应范围，同时rGO具有优异的电子迁移率，有效的促进光生电子-空穴对的分离和传输。

（2）BiOBr/N-rGO复合材料的制备及其光催化性能研究

采用溶剂热法成功制备了BiOBr/N-rGO复合材料。BiOBr是呈锯齿状边缘的纳米片，均匀的分布在氮掺杂还原氧化石墨烯（N-rGO）上。与原始BiOBr相比，优化后的复合材料具有优异的光催化性能，光照120 min下，BiOBr/N-rGO-50对罗丹明B的降解率高达95.7%，光降解速率是纯BiOBr的9倍。N-rGO可以作为电荷受体和BiOBr的载体，提升光催化活性。BiOBr复合N-rGO后，光生电子在产生后及时被传输到N-rGO上，促进光生电子-空穴对的分离，同时N-rGO提供了更多的成核位点，减少了BiOBr纳米颗粒的团聚，增大了材料的比表面积，有利于染料的吸附和提供更多的光催化反应活性位点。

（3）Ag₃PO₄/GO复合材料的制备及其光催化性能研究

采用室温沉淀法成功制备了一系列的Ag₃PO₄/GO复合材料。Ag₃PO₄纳米颗粒均匀分布在氧化石墨烯（GO）表面，尺寸在200 nm左右，比未负载GO的纯Ag₃PO₄颗粒粒径更小。这是因为Ag⁺与GO薄片之间的静电相互作用，可以控制Ag₃PO₄颗粒的成核和生长。光催化实验表明，Ag₃PO₄/GO在光照35 min内对亚甲基蓝的去除率可以达到98.2%，降解速率是纯Ag₃PO₄的11倍，且在多次使用后仍保有较高的光催化活性。GO的优异导电性可加速电荷的迁移，进而延长光生载流子的寿命，同时GO的包裹保护Ag₃PO₄阻止其发生光腐蚀。

With the rapid development of industry, a large number of pollutants are released into the natural environment, causing negative impacts that seriously endanger the sustainable development of human society. Photocatalytic technology is highly efficient, cost effective and environmentally friendly, and has unique advantages in degrading pollutants. Traditional photocatalysts such as TiO₂ and ZnO suffer from low utilisation of visible light and easy compounding of photogenerated electron-hole pairs. Therefore, new visible light responsive photocatalytic materials have been gradually investigated, and some means have been used to modify the single component photocatalytic materials to further enhance the photocatalytic activity, such as morphology modulation, ion doping and construction of heterojunctions, etc. However, the activity enhancement of single component photocatalytic materials by these methods is relatively limited. Thus, in this paper, the new visible light responsive photocatalysts BiOBr and Ag₃PO₄ were investigated by introducing graphene oxide (GO) and reduced graphene oxide (rGO) to synthesise composite photocatalytic materials, while ion doping was applied to BiOBr and rGO. Through the synergistic effect of the composite carbon materials and single-component modification methods, the composite rate of photogenerated electrons and holes was effectively reduced, leading to improve the performance of the photocatalyst. This study consists of three main lines of work as follows:

(1) Preparation of Gd-BiOBr/rGO composites and study of their photocatalytic properties

The Gd-BiOBr/rGO composites were successfully synthesized by a solvothermal method. Gd³⁺-doped BiOBr microspheres were distributed on folded transparent reduced graphene oxide (rGO) sheets, and the two-dimensional planes of rGO provided more growth sites, which reduced the size of BiOBr microspheres and increased the specific surface area, and thus could provide more adsorption sites and photocatalytic active centres. Photocatalytic experiments showed that Gd-BiOBr/rGO-30 had the highest photocatalytic activity, with a removal rate of 96.4% for rhodamine B within 120 min, and a degradation rate 2.8 times higher than that of pure BiOBr. The enhanced photocatalytic performance is on the one hand due to the formation of electron capture centres after Gd³⁺ doping, which inhibits photogenerated carrier recombination, and on the other hand due to the introduction of rGO which narrows the band gap energy and broadens the photoresponse range of the photocatalyst in the visible region, while rGO has excellent electron mobility and effectively promotes the separation and transport of photogenerated electron-hole pairs.

(2) Preparation of BiOBr/N-rGO composites and study of their photocatalytic properties

BiOBr/N-rGO composites were successfully prepared using a solvothermal method. BiOBr are nanosheets with jagged edges, uniformly distributed on nitrogen-doped reduced graphene oxide (N-rGO). Compared with pristine BiOBr, the optimised composite has excellent photocatalytic performance. Under 120 min of light, BiOBr/N-rGO-50 degraded rhodamine B by up to 95.7% and the photodegradation rate was 9 times higher than that of pure BiOBr. N-rGO can act as a charge acceptor and a carrier for BiOBr to enhance photocatalytic activity. After the compounding of BiOBr with N-rGO, photogenerated electrons are promptly transferred to N-rGO after generation, promoting the separation of photogenerated electron-hole pairs. Meanwhile, N-rGO provides more nucleation sites, reduces the agglomeration of BiOBr nanoparticles and increases the specific surface area of the material, which is conducive to the adsorption of dyes and provides more active sites for photocatalytic reaction.

(3) Preparation of Ag₃PO₄/GO composites and their photocatalytic properties

A series of Ag₃PO₄/GO composites were successfully prepared by a room temperature precipitation method. Ag₃PO₄ nanoparticles were uniformly distributed on the graphene oxide (rGO) surface with a size of around 200 nm, which is smaller than the size of pure Ag₃PO₄ particles without GO loading. This is due to the electrostatic interaction between Ag⁺ and GO flakes, which can control the nucleation and growth of Ag₃PO₄ particles. Photocatalytic experiments have shown that Ag₃PO₄/GO can remove 98.2% of methylene blue within 35 min of light exposure, a degradation rate 11 times higher than that of pure Ag₃PO₄, and retains high photocatalytic activity after repeated use. The excellent electrical conductivity of GO accelerates charge migration and thus extends the lifetime of photogenerated carriers. At the same time, the encapsulation of GO protects Ag₃PO₄ from photocorrosion.