磷酸盐材料的结构调控及光催化性能研究

发布时间：2018-08-05 12:29

【摘要】：磷酸盐是一类非常常见的无机材料,其中,PO43-拥有较大的负电荷和偶极矩,表现出很强的诱导效应。在光催化过程中,PO43-的诱导效应增强了对光生空穴的吸引,可以显著提高光生载流子的分离效率,从而提高光催化效率。因此,设计开发新型磷酸盐光催化剂或基于结构调控提高磷酸盐光催化剂的光催化性能具有重要研究价值。本论文主要研究了Ag_3PO_4、Cd_5H_2(PO_4)_4·4H2O、Cd_5(PO_4)_2P_2O_7、Cd_5(PO4)3OH几种磷酸盐材料的结构调控和光催化性能。具体研究内容如下:(1)室温下采用简单沉淀法制备了Ag_3PO_4/SiO_2复合光催化剂。SiO_2微球的载体效应提高了复合材料中Ag_3PO_4纳米颗粒的分散度,改变了Ag_3PO_4的表面结构,同时大大降低了Ag_3PO_4的含量。Ag_3PO_4/SiO_2复合光催化剂表现出了优异的可见光光催化性能。Ag_3PO_4负载量为20%时复合光催化剂表现出最高的降解性能,约为纯Ag_3PO_4的2倍。活性提高的主要原因是复合材料的光生载流子分离效率提高及参与反应的活性物种h+和·O_2-浓度增加。本文提出了一种通过廉价载体修饰策略提高光催化性能同时降低光催化剂成本的方法。(2)采用磷酸盐固化的方法将溶液中的无机金属离子Cd~(2+)沉淀,得到了具有分级结构的Cd_5H_2(PO_4)_4·4H2O花状微球。详细探究了镉盐与磷酸盐种类以及溶液pH值对产物形貌和晶相结构的影响。将Cd_5H_2(PO_4)_4·4H2O花状微球进一步煅烧处理,得到Cd_5(PO_4)_2P_2O_7分级微球。由于Cd_5(PO_4)_2P_2O_7微球独特的分级结构和强的氧化还原能力,Cd_5(PO_4)_2P_2O_7花状微球在紫外光照射下对RhB染料表现出优异的光催化降解性能和活性稳定性,其活性优于报道的Ca(PO4)6(OH)2和Ti2O(PO4)2(H2O)2光催化材料,与BiPO4相当。(3)在无模板剂或表面活性剂的情况下,通过简单水热法合成出了具有棒束、花生状和花状分级结构形貌的羟基磷酸镉(Cd_5(PO4)3OH,Cd-Hap)。探究了初始反应溶液的pH值、反应温度及反应时间对Cd-Hap结构和形貌的影响,提出了分级结构的形成机理。进一步以Cd-Hap为载体,制备了Ag_3PO_4/Cd-Hap和CdS QDs@Cd-Hap两种复合光催化材料。Ag_3PO_4/Cd-Hap在可见光照射下对MO表现出了优异的可见光催化活性,当Ag_3PO_4负载量为15%时光催化活性最高。CdS QDs@Cd-Hap表现出了可观的可见光分解水产氢性能,当S/P摩尔比为7.5时,复合光催化剂催化产氢效率为1100μmol·h-1·g-1,是纯CdS纳米颗粒的5.5倍。
[Abstract]:Phosphate is a very common kind of inorganic materials, in which PO43- has a large negative charge and dipole moment, showing a strong inductive effect. In the process of photocatalysis, the inductive effect of PO43- enhances the attraction of photogenerated holes, which can improve the separation efficiency of photogenerated carriers and thus improve the photocatalytic efficiency. Therefore, it is of great value to design and develop new phosphate photocatalysts or to improve the photocatalytic performance of phosphate photocatalysts based on structural regulation. In this paper, the structural regulation and photocatalytic properties of several kinds of phosphate materials, such as PO_4 (PO_4), 4H _ 2O _ 2 (PO_4) _ 2P _ S _ 2O _ 7, CD _ 5 (PO4) 3OH, have been studied in this paper. The main contents are as follows: (1) the support effect of Ag_3PO_4/SiO_2 composite photocatalyst 路SiO2 microspheres prepared by simple precipitation method at room temperature improves the dispersion of Ag_3PO_4 nanoparticles and changes the surface structure of Ag_3PO_4. At the same time, the content of Ag_3PO_4 was greatly reduced. The composite photocatalyst showed excellent visible photocatalytic performance. The composite photocatalyst exhibited the highest degradation performance when the loading amount of AgStup _ 3PO _ 4 was 20, which was about twice as high as that of pure Ag_3PO_4. The main reasons for the increase of activity are the increase of photogenerated carrier separation efficiency and the increase of h and O _ 2- concentration of active species participating in the reaction. In this paper, a method of improving photocatalytic performance and reducing the cost of photocatalyst by means of cheap carrier modification strategy is proposed. (2) the inorganic metal ion Cd2 in solution is precipitated by phosphate curing method. Cd_5H_2 (PO_4) 4 4H2O floral microspheres with hierarchical structure were obtained. The effects of cadmium salt and phosphate species and pH value of solution on the morphology and crystal structure of the product were investigated in detail. The Cd_5H_2 (PO_4) 4 4H2O flower-like microspheres were further calcined and the Cd_5 (PO_4) 2P _ 2O _ 7 microspheres were obtained. Due to the unique grading structure and strong redox capacity of the Cd_5 (PO_4) 2P2O7 microspheres, CDSIL _ 5 (PO_4) _ 2P _ 2O _ 7 microspheres exhibit excellent photocatalytic degradation and active stability to RhB dyes under UV irradiation, and their activity is superior to the reported Ca (PO4) _ 6( OH) _ 2 and Ti2O (PO4) _ 2 (H _ 2O) _ 2 photocatalytic materials, (3) in the absence of template or surfactant, Cd_5 (PO4) 3OHCd-Hap (Cd_5 (PO4) 3OHCd-Hap) was synthesized by a simple hydrothermal method with the morphology of rod bundle, peanut shape and flower shape. The effects of pH value of initial reaction solution, reaction temperature and reaction time on the structure and morphology of Cd-Hap were investigated. Furthermore, two kinds of composite photocatalytic materials, Ag_3PO_4/Cd-Hap and CdS QDs@Cd-Hap, were prepared by using Cd-Hap as the carrier. The Cd-Hap showed excellent visible light catalytic activity to MO under visible light irradiation. The photocatalytic activity of CDs QDs@Cd-Hap was the highest when the amount of Ag_3PO_4 loading was 15. When the molar ratio of S / P was 7.5, the hydrogen production efficiency of the composite photocatalyst was 1100 渭 mol h-1 g-1, which was 5.5 times of that of pure CdS nanoparticles.
【学位授予单位】：曲阜师范大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：O643.36;O644.1

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