纳米二氧化钛的改性及其光催化分解水制氢性能研究

发布时间：2018-03-23 09:41

本文选题：光催化　切入点：改性　出处：《华南理工大学》2015年硕士论文　论文类型：学位论文

【摘要】：随着人们对清洁能源和可再生能源的重视,光催化分解水制取氢气已经引起了国内外学者的广泛兴趣。Ti O2具有强氧化还原能力、高稳定性、低价格和容易获取等特点,是备受瞩目的半导体光催化材料之一。纳米Ti O2作为半导体光催化材料已被广泛应用到光解水产氢、光降解污染物、大气净化、杀菌消毒等方面。但是由于光生载流子电荷的高复合率和本身较小比表面积,Ti O2单独使用时催化性能并不理想。改性Ti O2以提高其光催化制氢活性,一直是富有挑战并极具理论和实践意义的课题。研究人员通过在Ti O2表面添加不同助催化剂,形成新的催化剂捕获光生载流子缺陷,以延长光生载流子寿命,提高光催化性能。此外,不同形貌纳米Ti O2,如纳米棒、纳米线、纳米管等,被证实在形成更大比表面积同时确保光生电子的快速传递,因而获得更好制氢活性。本文利用溶剂热法合成了Ni S/Ti O2和Ni S/Ti O2纳米管(TNTs)催化剂,考察了催化剂的制氢活性,探讨了影响光催化效率的因素,并对其光催化机理等做了初步探讨。主要工作内容和结论如下:1.以P25、硝酸镍和硫脲为原料,通过溶剂热法制备纳米Ni S/Ti O2光催化剂,采用XRD、TEM、UV-vis、PL等对催化剂的晶型、形貌、光响应特性等性能进行了测试和表征,考察了Ni S添加量对催化剂制氢活性的影响,探讨了Ni S/Ti O2光催化机理。结果表明:Ni S添加量为5 wt%,催化剂用量为0.5 g/L,牺牲试剂为甲醇时,Ni S/Ti O2催化剂的产氢活性最佳,达3090μmol·h-1·g-1,约是纯Ti O2产氢活性的96倍。光催化产氢活性提高的原因归属于Ni S与Ti O2形成的协同效应:1)Ni2+/Ni还原电势(-0.23 e V)略低于Ti O2导带位置(-0.26 e V),有利于Ti O2上光生电子转移到Ni S纳米簇上;2)部分Ni2+被还原成Ni单质,金属Ni与Ti O2形成肖特基势垒,一定程度上加速电子的转移并抑制光生载流子的复合。2、以P25为原料,在10 M Na OH的强碱环境下,采用水热法成功制备出二氧化钛纳米管(TNTs),并通过溶剂热法制备Ni S/TNTs光催化剂,采用XRD、TEM、UV-vis、BET、PL等对催化剂的晶型、形貌、光响应特性等性能进行了测试,并探究Ni S添加量对光催化活性的影响,探讨了Ni S/TNTs光催化反应机理。结果表明:碱性水热法制备的TNTs具有一维中空结构,管径范围为10-15 nm,比表面积达到313.79 m2·g-1,约为P25比表面积的6倍;Ni S添加量为8 wt%,催化剂用量为0.5 g/L,牺牲试剂为甲醇时,Ni S/TNTs催化剂的产氢活性最佳,达7486μmol·h-1·g-1。Ni S/TNTs高催化活性的原因在于TNTs的独特结构,大的比表面积使Ni S纳米簇高度分散,以形成更多还原活性位;一维电子传输结构使载流子电荷定向输,减少光生电子迁移距离,实现快速转移,减少了光生电子-空穴对的复合率。
[Abstract]:With the attention paid to clean energy and renewable energy, photocatalytic decomposition of water to produce hydrogen has attracted wide interest of scholars at home and abroad. TIO 2 has the characteristics of strong redox ability, high stability, low price and easy to obtain. Nanocrystalline TIO _ 2 as semiconductor photocatalytic material has been widely used in photodegradation of aquatic hydrogen, photodegradation of pollutants, atmospheric purification. However, due to the high recombination rate of photogenerated carrier charge and the low specific surface area of TIO _ 2 alone, the catalytic performance of TIO _ 2 is not ideal. Modification of TIO _ 2 can improve its photocatalytic activity for hydrogen production. It has always been a challenging subject with great theoretical and practical significance. By adding different co-catalysts to the surface of TIO _ 2, researchers have formed a new catalyst to capture photogenerated carrier defects in order to prolong the lifetime of photogenerated carriers. In addition, different morphologies of nanocrystalline TIO _ 2, such as nanorods, nanowires, nanotubes, etc., have been shown to generate larger specific surface areas while ensuring the rapid transfer of photogenerated electrons. In this paper, Ni S/Ti O 2 and Ni S/Ti O 2 nanotube TNTs catalysts were synthesized by solvothermal method. The hydrogen production activity of the catalysts was investigated, and the factors affecting the photocatalytic efficiency were discussed. The main work contents and conclusions are as follows: 1. Using P25, Nickel nitrate and thiourea as raw materials, nanometer Ni S/Ti O 2 photocatalyst was prepared by solvothermal method. The properties of the catalyst were tested and characterized, and the effect of the amount of Ni S on the activity of the catalyst for hydrogen production was investigated. The photocatalytic mechanism of Ni S/Ti O 2 was discussed. The results showed that Ni / Ni S/Ti O 2 catalyst had the best hydrogen production activity when the amount of Ni / Ni S was 5 wt. the amount of catalyst was 0.5 g / L, and the sacrificial reagent was methanol. The increase of photocatalytic hydrogen production activity is attributed to the synergistic effect of Ni / S and TIO _ 2 formed by Ni / 1 / Ni _ 2 / Ni _ 2 / Ni reduction potential = -0.23e / V), which is slightly lower than that of TIO _ 2 conductance band ~ (-0.26) e V ~ (-1), which is beneficial to the uplight of TIO _ 2. Electron transfer to Ni S nanoclusters) partial Ni2 is reduced to Ni elements. Metal Ni and TIO _ 2 form Schottky barrier, accelerate electron transfer to some extent and inhibit photogenerated carrier compound. Using P25 as raw material, under the strong alkali environment of 10m NaOH, the metal Ni and TIO _ 2 form Schottky barrier, and accelerate the electron transfer to some extent. Titanium dioxide nanotubes were successfully prepared by hydrothermal method, and Ni S/TNTs photocatalysts were prepared by solvothermal method. The effect of Ni S addition on photocatalytic activity was investigated and the mechanism of Ni S/TNTs photocatalytic reaction was discussed. The results showed that the TNTs prepared by alkaline hydrothermal method had one-dimensional hollow structure. The diameter range of tube is 10-15 nm, the specific surface area is 313.79 m ~ 2 g ~ (-1), about 6 times the specific surface area of P25, the addition amount of Ni S is 8 wt, the amount of catalyst is 0.5 g / L, and the sacrificial reagent is methanol, the activity of Ni S/TNTs catalyst is the best. The reason for the high catalytic activity of 7486 渭 mol h-1 g-1.Ni S/TNTs lies in the unique structure of TNTs, the large specific surface area makes the Ni S nanoclusters highly dispersed to form more reductive active sites, and the one-dimensional electron transport structure leads to the directional transport of charge of carriers and reduces the distance of photoelectron migration. Fast transfer is realized, and the recombination rate of photogenerated electron-hole pair is reduced.
【学位授予单位】：华南理工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：O643.36;TQ116.2

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