类石墨相碳化氮基复合纳米光催化体系构筑及分解水产氢性能研究

发布时间：2018-05-06 15:19

本文选题：类石墨碳化氮 + 一步法　；参考：《江苏大学》2017年硕士论文

【摘要】：随着科学技术的进步和发展,给人类社会带来越来越多的便利,但是同时也带来一些负面影响。尤其是在最近今年,随着工业发展,全球化能源危机和环境污染问题严重影响我们的生活和身体健康。其中最严峻的就是石油、煤炭等化石燃料的过度消耗致使能源危机加重,另一方面则是化石燃料使用过程中会产生二次污染加剧环境污染问题。因此寻找一种高效、环保的新能源可以从根本上解决目前的全球性问题。自1972年日本科学家发现TiO2在紫外光下可以分解水产氢后,利用光催化技术进行光分解水产氢被认为是解决上述问题最佳手段。但是,传统光催化剂由于一些自身的缺陷导致无法满足科学家的要求,因此寻找一种新型光催化剂是目前将光催化技术进行实际应用的关键。近几年,一种类石墨相g-C_3N_4光催化剂引起各国科学家的关注,由于其具有较窄禁带宽度(2.7 eV)、合适的价导带位置可以在可见光下进行分解水产氢;另一方面g-C_3N_4的合成方法简单、合成原料较广可以进行大规模生产令其成为光催化领域研究的热点。然而,纯相的g-C_3N_4的自身电荷与空穴的分离率较低严重抑制其光催化性能。本文根据g-C_3N_4的自身缺点,通过一步法合成Ag量子点/g-C_3N_4复合催化剂、原位生长法合成CuS/g-C_3N_4复合光催化剂提高g-C_3N_4的电子与空穴的分离率进而增强光催化性能;将g-C_3N_4制备成量子点与SnNb_2O_6提高太阳光利用率,进而提高产氢性能,并对g-C_3N_4进行进一步的研究。本文的重点研究有一下几点:(1)利用一步法合成Ag QDs/g-C_3N_4复合光催化剂,简化光催化剂的制备过程。通过一系列表征发现,Ag量子点的等离子共振作用可以有效提高催化剂对于可见光的吸收强度,有利于对于太阳光的利用率;另一方面,Ag量子点可以作为助催化剂提高光催化剂的电子与空穴的分离率。我们通过分解水产氢实验发现复合光催化剂的产氢性能得到极大提高。(2)利用原位生长法合成新型光催化剂CuS/g-C_3N_4,在可见光下,通过界面电子转移,g-C_3N_4价带上的被激发的电子可以直接转移到CuS纳米粒子,部分CuS被还原为Cu2S,CuS/Cu2S纳米簇可以有效捕获激发电子,防止电子与空穴的复合,提高光催化活性,Cus/g-C_3N_4在产氢实验中表现出高效产氢性能和的良好的稳定性。(3)通过水热法合成CNQDs/SnNb_2O_6光催化剂,CNQDs既可以作为助催化剂捕获被激发的电子并在助催化剂表面参与产氢过程,另一方面,CNQDs具有上转换效应,可以将长波长的光转换为短波长的光被纯SnNb_2O_6多利用,激发更多的电子参与光催化反应,进而提高光催化性能。
[Abstract]:With the progress and development of science and technology, it brings more and more convenience to human society, but also brings some negative effects. Especially this year, with the development of industry, global energy crisis and environmental pollution have seriously affected our lives and health. The most severe is the excessive consumption of fossil fuels such as oil and coal, which makes the energy crisis worse. On the other hand, the secondary pollution in the use of fossil fuels will aggravate the environmental pollution problem. Therefore, looking for an efficient and environmentally-friendly new energy can fundamentally solve the current global problems. Since Japanese scientists discovered in 1972 that TiO2 can decompose aquatic hydrogen under ultraviolet light, photocatalytic technology is considered to be the best way to solve the above problems. However, the traditional photocatalyst can not meet the requirements of scientists due to its own defects, so finding a new photocatalyst is the key to the practical application of photocatalytic technology. In recent years, a kind of graphite phase g-C_3N_4 photocatalyst has attracted the attention of scientists all over the world. Due to its narrow band gap of 2.7 EV, the suitable valence band position can be used to decompose aquatic hydrogen under visible light. On the other hand, the synthetic method of g-C_3N_4 is simple. The wide range of synthetic raw materials can be used in mass production, so it has become a hot spot in the field of photocatalysis. However, the photocatalytic activity of pure phase g-C_3N_4 is seriously inhibited by the low separation rate of its own charge and hole. According to the shortcomings of g-C_3N_4, Ag quantum dots / g-C _ 3N _ 4 composite catalysts were synthesized by one-step method, and CuS/g-C_3N_4 composite photocatalysts were synthesized by in-situ growth method to improve the separation rate of electrons and holes of g-C_3N_4 and thus enhance its photocatalytic performance. Quantum dots (QDs) prepared by g-C_3N_4 and SnNb_2O_6 were used to improve the utilization of solar light and hydrogen production. The further study of g-C_3N_4 was carried out. This paper focuses on the following points: 1) Synthesis of Ag QDs/g-C_3N_4 composite photocatalyst by one-step method to simplify the preparation process of photocatalyst. Through a series of characterization, it is found that the plasmon resonance of Ag quantum dots can effectively increase the absorption intensity of visible light of the catalyst, and is beneficial to the utilization of solar light. On the other hand, Ag quantum dots can be used as cocatalyst to improve the separation efficiency of electron and hole in photocatalyst. We found that the hydrogen production performance of the composite photocatalyst has been greatly improved by the experiment of decomposing aquatic hydrogen. (2) A new photocatalyst, CuS / g-C _ 3N _ 4, was synthesized by in-situ growth method. Through the interfacial electron transfer, the excited electrons in the valence band of Mr _ 3N _ 4 can be transferred directly to the CuS nanoparticles, and some of the CuS can be reduced to Cu _ 2S / Cu _ S / Cu _ 2S nanoclusters, which can effectively capture the excited electrons and prevent the recombination of electrons and holes. In the hydrogen production experiment, Cus / g-C _ 3N _ 4 showed high hydrogen production performance and good stability. The photocatalyst can be used as a co-catalyst to capture the excited electrons and participate in the hydrogen production process on the surface of the co-catalyst. On the other hand, CNQDs have upconversion effect, which can convert long wavelength light to short wavelength light and be used by pure SnNb_2O_6 to stimulate more electrons to participate in photocatalytic reaction, thus improving photocatalytic performance.
【学位授予单位】：江苏大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：O643.36;TQ116.2

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