石墨相氮化碳的制备及光催化性能调控
发布时间：2018-07-31 16:29
【摘要】：目前,随着工业化进程的不断深入,人类面临着地球环境急剧恶化和全球能源短缺的巨大挑战,尤其是水中的污染物不计其数,来源广泛,其中大部分为有机物,有毒并且性质非常稳定,从而表现出难以降解的特质。光催化技术近年来应用于环境治理和污水处理,效果显著。传统的半导体二氧化钛(TiO2)对可见光的响应性差,不能广泛地应用于实际生活中。新型的光催化剂石墨相氮化碳(g-C_3N_4)不含金属元素、无毒、带隙结构易调控等优势而受到极大的关注。而传统方法制备的g-C_3N_4由于比表面积小、光催化效率低、光生载流子复合率高等缺点,限制其广泛应用。据此,本论文采用复合半导体、负载贵金属、增大比表面积和掺杂非金属元素等方式来提高石墨相氮化碳光催化剂的可见光催化性能,具体研究内容如下:1.利用原位生成法,制备了Bi_2S_3含量可调的Bi_2S_3/g-C_3N_4复合光催化剂。通过X-射线衍射(XRD)、傅里叶红外光谱(FT-IR)、扫描电子显微镜(SEM)、透射电子显微镜(TEM)、紫外-可见光漫反射光谱(DRS)、光致发光光谱(PL)、时间分辨荧光衰减光谱等分析手段对所制备的光催化剂的物相、形貌、结构和性能进行了表征分析。在可见光照射下,以有机染料(罗丹明B)为降解模型评价了Bi_2S_3/g-C_3N_4复合光催化剂的光催化性能。结果表明,短棒状Bi_2S_3沉积在g-C_3N_4表面,显著增强了g-C_3N_4的可见光催化性能,并且随着窄带隙半导体Bi_2S_3含量的不同,复合光催化剂Bi_2S_3/g-C_3N_4的光催化性能发生变化,其中Bi_2S_3含量为5 wt%时表现出最佳的可见光催化活性。利用捕获剂、NBT转化、对苯二甲酸-荧光光谱技术,确定光催化过程中h+是反应体系中主要的活性物种,?O-2是反应体系中的次要活性物种。此外,对复合光催化剂Bi_2S_3/g-C_3N_4光催化活性增强机理进行了研究,Bi_2S_3的加入显著增强了g-C_3N_4对可见光的吸收,并且与g-C_3N_4之间形成了异质结,促进半导体光生电子与空穴的有效分离,延长载流子寿命,从而显著增强g-C_3N_4的光催化性能。2.通过三步法合成g-C_3N_4/PPy/Ag三元复合光催化剂。首先,将三聚氰胺在高温下煅烧得到石墨相氮化碳光催化剂,然后原位聚合吡咯得到一系列的g-C_3N_4/PPy复合光催化剂,最后将Ag沉积在g-C_3N_4/PPy表面得到g-C_3N_4/PPy/Ag复合光催化剂。在可见光下,降解四环素(TC)评价样品的光催化活性。研究了聚吡咯和Ag的负载量对g-C_3N_4/PPy/Ag的光催化活性的影响。通过对样品的光学性质和电子结构进行分析可得,聚吡咯和银对提高g-C_3N_4/PPy/Ag光催化活性起到了协同作用。因此,相比于g-C_3N_4、g-C_3N_4/PPy、g-C_3N_4/Ag降解四环素,g-C_3N_4/PPy/Ag三元复合光催化剂表现出了较高的光催化活性。此外,对g-C_3N_4/PPy/Ag光催化剂的高效光催化机理进行了分析,聚吡咯与g-C_3N_4能带匹配加快了光生载流子分离,负载的银由于SPR效应作为电子受体也起到了重要作用。3.以球型聚酚醛树脂作为模板剂,将三聚氰胺通过液相混合搅拌的方式包覆在模板上,分别在氮气和氧气中进行两次煅烧将聚合物模板除去,最终制备出具有多孔结构的g-C_3N_4(CN)。通过一系列表征测试手段对所制备的产物进行结构、形貌和光学性能分析,结果表明,所制备的g-C_3N_4呈现多孔结构,对可见光地吸收显著增强,光生载流子复合率显著降低。在可见光照射下,以RhB为降解对象,评价合成样品的光催化性能。结果表明经过O2煅烧后得到的多孔g-C_3N_4比直接在N2气氛下煅烧得到的样品光催化性能优越,并且当模板剂投入量为0.021 g时,得到的多孔氮化碳(CN-0.021)光催化性能最佳,分别是纯g-C_3N_4和C/CN-0.021的7.8和2.2倍。此外,对多孔g-C_3N_4光催化性能提高的原因进行了分析,其具有较大的比表面积(150.5 m2/g)和内部的孔道结构,是其光催化性能提高的主要因素。4.在多孔氮化碳的合成基础上,以磷酸氢二铵((NH4)2HPO4)为磷源,同步实现磷掺杂多孔氮化碳光催化材料。固定三聚氰胺和模板剂聚酚醛树脂球的量,改变加入的(NH4)2HPO4的量,制备了一系列磷掺杂多孔氮化碳(PCN)光催化材料。采用RhB为降解模型,评价所制备样品的光催化活性。用氮气吸附脱附等温线测得PCN-0.3的比表面积(131.2 m2/g)小于CN-0.021(150.5 m2/g),但其光催化活性没有降低反而升高。并且探讨了磷元素的最佳掺杂量,当(NH4)2HPO4的投入量为0.3 g时,制备的磷掺杂多孔氮化碳(PCN-0.3)催化效果最好,分别是纯g-C_3N_4、磷掺杂氮化碳(P-C_3N_4)和多孔氮化碳(CN-0.021)的13.4、2.9和1.7倍。通过对纯g-C_3N_4、P-C_3N_4、CN-0.021和PCN-0.3光催化剂的光学性质进行对比,对磷掺杂多孔氮化碳光催化活性提高的原因进行了分析,主要归结于大比表面积提供更多的反应位点和磷掺杂减小禁带宽度共同作用的结果。
[Abstract]:At present, with the continuous deepening of the process of industrialization, human beings are faced with the great challenge of the rapid deterioration of the earth's environment and the global energy shortage, especially the numerous pollutants in the water. Most of them are organic, toxic and very stable, thus showing the characteristics that are difficult to degrade. Photocatalytic technology has been applied in recent years. The effect of the environmental treatment and sewage treatment is remarkable. The traditional semiconductor titanium dioxide (TiO2) has poor response to visible light and can not be widely used in real life. The new type of photocatalyst graphite phase carbon nitride (g-C_3N_4) has been paid great attention to the advantages of non-toxic, non-toxic and easy to regulate the band gap structure. As a result of small specific surface area, low photocatalytic efficiency and high carrier recombination rate, g-C_3N_4 restricts its wide application. Accordingly, this paper uses composite semiconductors, loaded precious metals, increases specific surface area and doping non-metallic elements to improve the visible photocatalytic performance of graphite phase carbon nitride photocatalyst. As follows: 1. the Bi_2S_3/g-C_3N_4 composite photocatalyst with adjustable Bi_2S_3 content was prepared by in situ formation. Through X- ray diffraction (XRD), Fourier infrared spectroscopy (FT-IR), scanning electron microscope (SEM), transmission electron microscope (TEM), UV visible diffuse reflectance spectroscopy (DRS), photoluminescence (PL), and time resolved fluorescence decay spectra, etc. Analysis was made on the phase, morphology, structure and properties of the prepared photocatalyst. Under visible light, the photocatalytic performance of Bi_2S_3/g-C_3N_4 composite photocatalyst was evaluated with organic dye (Luo Danming B) as degradation model. The results showed that the short rod like Bi_2S_3 was deposited on the surface of g-C_3N_4, and the g-C_3N_4 was significantly enhanced. The photocatalytic performance of the photocatalyst is visible, and with the difference of the Bi_2S_3 content of the narrow band gap semiconductor, the photocatalytic performance of the composite photocatalyst Bi_2S_3/g-C_3N_4 changes. The best visible photocatalytic activity is shown when the Bi_2S_3 content is 5 wt%. Using the capture agent, the NBT conversion, the phenylene two formic acid fluorescence spectroscopy, and the determination of the h+ in the photocatalytic process The main active species in the reaction system, O-2 is a secondary active species in the reaction system. In addition, the mechanism of the enhanced photocatalytic activity of the composite photocatalyst was studied. The addition of Bi_2S_3 significantly enhanced the absorption of visible light by g-C_3N_4, and formed a heterojunction with g-C_3N_4 to promote semiconductor light generation. The effective separation of the sub and hole, prolonging the lifetime of the carrier, and significantly enhancing the photocatalytic performance of g-C_3N_4.2. by three step method to synthesize the g-C_3N_4/PPy/Ag three element composite photocatalyst. First, the calcined melamine was calcined at high temperature to get the graphite phase carbon nitride photocatalyst, and then a series of g-C_3N_4/PPy composite light was obtained by in situ polymerization of pyrrole. At last, Ag was deposited on the surface of g-C_3N_4/PPy to obtain the g-C_3N_4/PPy/Ag composite photocatalyst. The photocatalytic activity of the sample was evaluated by degradation of tetracycline (TC) under visible light. The effect of the load of polypyrrole and Ag on the photocatalytic activity of g-C_3N_4/PPy/Ag was investigated. The optical properties and electronic structures of the samples were obtained by analyzing the photocatalytic activity of the samples. Polypyrrole and silver have synergistic effect on improving the photocatalytic activity of g-C_3N_4/PPy/Ag. Therefore, compared with g-C_3N_4, g-C_3N_4/PPy, g-C_3N_4/Ag degradation of tetracycline, g-C_3N_4/PPy/Ag three element composite photocatalyst has higher photocatalytic activity. In addition, the high effective photocatalytic mechanism of g-C_3N_4/PPy/Ag photocatalyst was analyzed. The matching of pyrrole and g-C_3N_4 energy band accelerates the separation of light generated carriers. The loaded silver has played an important role in the SPR effect as the electron acceptor..3. is coated on the template by mixing the liquid phase with the polyphenol formaldehyde resin. The two times calcined in nitrogen and oxygen, the polymer mold is carried out respectively. The porous structure of g-C_3N_4 (CN) was finally prepared. The structure, morphology and optical properties of the prepared products were analyzed by a series of characterization tests. The results showed that the prepared g-C_3N_4 showed a porous structure, significantly enhanced the visible light and ground absorption, and reduced the recombination rate of the optical carrier significantly. Under visible light, The photocatalytic performance of the synthetic samples was evaluated with RhB as the degradation object. The results showed that the porous g-C_3N_4 obtained after O2 calcined was superior to the calcined samples directly under the N2 atmosphere, and when the input amount of the template was 0.021 g, the photocatalytic performance of the porous carbon (CN-0.021) was the best, which was pure g-C_3N_4 and C/, respectively. 7.8 and 2.2 times of CN-0.021. In addition, the reasons for the enhancement of the photocatalytic performance of porous g-C_3N_4 have been analyzed. It has a larger specific surface area (150.5 m2/g) and internal pore structure, which is the main factor to improve the photocatalytic performance of.4.. On the basis of the synthesis of porous carbon nitride, the phospho diammonium phosphate ((NH4) 2HPO4) is used as the phosphorus source to synchronize the phosphorus. A series of phosphorus doped porous carbon nitride (PCN) photocatalytic materials were prepared by fixing the amount of melamine and template polyphenolic resin balls fixed with melamine and template and changing the amount of (NH4) 2HPO4. The photocatalytic activity of the prepared samples was evaluated by using RhB as degradation model. PCN-0.3 was measured with nitrogen adsorption desorption isotherm. The specific surface area (131.2 m2/g) is less than CN-0.021 (150.5 m2/g), but its photocatalytic activity is not reduced, but the optimum doping amount of phosphorus is discussed. When the input of (NH4) 2HPO4 is 0.3 g, the preparation of phosphorus doped porous carbon nitride (PCN-0.3) is the best catalyst, which is pure g-C_3N_4, phosphorus doped carbon nitride (P-C_3N_4) and porous nitrogen, respectively. By comparing the optical properties of pure g-C_3N_4, P-C_3N_4, CN-0.021 and PCN-0.3 photocatalysts, the reasons for the enhancement of photocatalytic activity of phosphorus doped porous carbon nitride were analyzed by comparing the optical properties of the pure g-C_3N_4, P-C_3N_4, CN-0.021 and PCN-0.3 photocatalysts. The main attributable to the larger surface area provided more reaction sites and the combination of phosphorus doping to reduce the band gap width. The result.
【学位授予单位】：江南大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：O643.36;O644.1
本文编号：2156151
[Abstract]:At present, with the continuous deepening of the process of industrialization, human beings are faced with the great challenge of the rapid deterioration of the earth's environment and the global energy shortage, especially the numerous pollutants in the water. Most of them are organic, toxic and very stable, thus showing the characteristics that are difficult to degrade. Photocatalytic technology has been applied in recent years. The effect of the environmental treatment and sewage treatment is remarkable. The traditional semiconductor titanium dioxide (TiO2) has poor response to visible light and can not be widely used in real life. The new type of photocatalyst graphite phase carbon nitride (g-C_3N_4) has been paid great attention to the advantages of non-toxic, non-toxic and easy to regulate the band gap structure. As a result of small specific surface area, low photocatalytic efficiency and high carrier recombination rate, g-C_3N_4 restricts its wide application. Accordingly, this paper uses composite semiconductors, loaded precious metals, increases specific surface area and doping non-metallic elements to improve the visible photocatalytic performance of graphite phase carbon nitride photocatalyst. As follows: 1. the Bi_2S_3/g-C_3N_4 composite photocatalyst with adjustable Bi_2S_3 content was prepared by in situ formation. Through X- ray diffraction (XRD), Fourier infrared spectroscopy (FT-IR), scanning electron microscope (SEM), transmission electron microscope (TEM), UV visible diffuse reflectance spectroscopy (DRS), photoluminescence (PL), and time resolved fluorescence decay spectra, etc. Analysis was made on the phase, morphology, structure and properties of the prepared photocatalyst. Under visible light, the photocatalytic performance of Bi_2S_3/g-C_3N_4 composite photocatalyst was evaluated with organic dye (Luo Danming B) as degradation model. The results showed that the short rod like Bi_2S_3 was deposited on the surface of g-C_3N_4, and the g-C_3N_4 was significantly enhanced. The photocatalytic performance of the photocatalyst is visible, and with the difference of the Bi_2S_3 content of the narrow band gap semiconductor, the photocatalytic performance of the composite photocatalyst Bi_2S_3/g-C_3N_4 changes. The best visible photocatalytic activity is shown when the Bi_2S_3 content is 5 wt%. Using the capture agent, the NBT conversion, the phenylene two formic acid fluorescence spectroscopy, and the determination of the h+ in the photocatalytic process The main active species in the reaction system, O-2 is a secondary active species in the reaction system. In addition, the mechanism of the enhanced photocatalytic activity of the composite photocatalyst was studied. The addition of Bi_2S_3 significantly enhanced the absorption of visible light by g-C_3N_4, and formed a heterojunction with g-C_3N_4 to promote semiconductor light generation. The effective separation of the sub and hole, prolonging the lifetime of the carrier, and significantly enhancing the photocatalytic performance of g-C_3N_4.2. by three step method to synthesize the g-C_3N_4/PPy/Ag three element composite photocatalyst. First, the calcined melamine was calcined at high temperature to get the graphite phase carbon nitride photocatalyst, and then a series of g-C_3N_4/PPy composite light was obtained by in situ polymerization of pyrrole. At last, Ag was deposited on the surface of g-C_3N_4/PPy to obtain the g-C_3N_4/PPy/Ag composite photocatalyst. The photocatalytic activity of the sample was evaluated by degradation of tetracycline (TC) under visible light. The effect of the load of polypyrrole and Ag on the photocatalytic activity of g-C_3N_4/PPy/Ag was investigated. The optical properties and electronic structures of the samples were obtained by analyzing the photocatalytic activity of the samples. Polypyrrole and silver have synergistic effect on improving the photocatalytic activity of g-C_3N_4/PPy/Ag. Therefore, compared with g-C_3N_4, g-C_3N_4/PPy, g-C_3N_4/Ag degradation of tetracycline, g-C_3N_4/PPy/Ag three element composite photocatalyst has higher photocatalytic activity. In addition, the high effective photocatalytic mechanism of g-C_3N_4/PPy/Ag photocatalyst was analyzed. The matching of pyrrole and g-C_3N_4 energy band accelerates the separation of light generated carriers. The loaded silver has played an important role in the SPR effect as the electron acceptor..3. is coated on the template by mixing the liquid phase with the polyphenol formaldehyde resin. The two times calcined in nitrogen and oxygen, the polymer mold is carried out respectively. The porous structure of g-C_3N_4 (CN) was finally prepared. The structure, morphology and optical properties of the prepared products were analyzed by a series of characterization tests. The results showed that the prepared g-C_3N_4 showed a porous structure, significantly enhanced the visible light and ground absorption, and reduced the recombination rate of the optical carrier significantly. Under visible light, The photocatalytic performance of the synthetic samples was evaluated with RhB as the degradation object. The results showed that the porous g-C_3N_4 obtained after O2 calcined was superior to the calcined samples directly under the N2 atmosphere, and when the input amount of the template was 0.021 g, the photocatalytic performance of the porous carbon (CN-0.021) was the best, which was pure g-C_3N_4 and C/, respectively. 7.8 and 2.2 times of CN-0.021. In addition, the reasons for the enhancement of the photocatalytic performance of porous g-C_3N_4 have been analyzed. It has a larger specific surface area (150.5 m2/g) and internal pore structure, which is the main factor to improve the photocatalytic performance of.4.. On the basis of the synthesis of porous carbon nitride, the phospho diammonium phosphate ((NH4) 2HPO4) is used as the phosphorus source to synchronize the phosphorus. A series of phosphorus doped porous carbon nitride (PCN) photocatalytic materials were prepared by fixing the amount of melamine and template polyphenolic resin balls fixed with melamine and template and changing the amount of (NH4) 2HPO4. The photocatalytic activity of the prepared samples was evaluated by using RhB as degradation model. PCN-0.3 was measured with nitrogen adsorption desorption isotherm. The specific surface area (131.2 m2/g) is less than CN-0.021 (150.5 m2/g), but its photocatalytic activity is not reduced, but the optimum doping amount of phosphorus is discussed. When the input of (NH4) 2HPO4 is 0.3 g, the preparation of phosphorus doped porous carbon nitride (PCN-0.3) is the best catalyst, which is pure g-C_3N_4, phosphorus doped carbon nitride (P-C_3N_4) and porous nitrogen, respectively. By comparing the optical properties of pure g-C_3N_4, P-C_3N_4, CN-0.021 and PCN-0.3 photocatalysts, the reasons for the enhancement of photocatalytic activity of phosphorus doped porous carbon nitride were analyzed by comparing the optical properties of the pure g-C_3N_4, P-C_3N_4, CN-0.021 and PCN-0.3 photocatalysts. The main attributable to the larger surface area provided more reaction sites and the combination of phosphorus doping to reduce the band gap width. The result.
【学位授予单位】：江南大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：O643.36;O644.1
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