【作者】 刘超；

【导师】 徐春明； 李永峰；

【作者基本信息】 中国石油大学(北京) ， 化学工程与技术， 2016， 硕士

【摘要】 太阳能是地球上丰富、清洁的可持续绿色能源,半导体光催化技术在治理环境污染和解决能源危机方面引起了研究者们的广泛关注。二氧化钛是研究最为广泛的一种半导体光催化剂,具有催化性能优良、安全无毒、无副作用、化学性质稳、使用寿命长等优点,但是,TiO₂的禁带宽度大,导致其仅能在紫外光条件下进行光催化反应,限制了TiO₂的实际应用。因此,TiO₂与其他材料复合,开发新型可见光响应催化剂,增强其在可见光范围的吸收并且限制光生电子与空穴的复合,有着十分现实的意义和深远的影响。石墨烯和g-C3N4是被认为最有望应用于光催化领域的新型非金属材料,它们常被应作催化剂载体,起到增加对目标产物的吸附,增强催化剂的可见光吸收,促进光催化反应的速率。本论文旨在设计出具有可见光响应和高光催化活性的新型复合光催化剂,并探讨其光催化反应机理。本论文包括两部分内容:第一部分:采用廉价尿素作为氮源,通过简单的水热合成法制备出具有可见光响应的N-TiO₂/NG复合光催化材料。采用XRD、XPS、SEM、TEM、UV-Vis和BET等手段对复合催化剂进行了表征,结果表明,TiO₂晶型为锐钛矿型,N原子不仅掺杂进入TiO₂ NWs晶格中,也掺杂进入石墨烯骨架中,N-TiO₂/NG复合光催化剂具有可见光响应。在可见光条件下降解MB的光催化实验也表明了其具有较高的光催化活性,在可见光照3 h后降解率可达87.9%,其降解动力学常数为0.0107 min-1,远大于TiO₂ NWs和未进行氮掺杂的TiO₂/G光催化剂。第二部分:首先通过超声剥离法制备出g-C3N4纳米片,再通过光催化还原法制备出TiO₂/g-C3N4/G复合光催化材料。采用XRD、XPS、SEM、TEM、UV-Vis和BET等手段对复合催化剂进行了表征,结果表明,TiO₂晶型为锐钛矿与板钛矿混晶型,通过超声剥离制备出的复合材料比表面积有了明显提高。紫外可见吸收显示复合光催化材料在紫外可见光都有光响应,同时通过光激电流测试得到TiO₂/g-C₃N₄/G具有良好的光电响应,能产生很高的电流响应。在光催化还原硝基苯实验中,在模拟太阳光条件下TiO₂/g-C₃N₄/G显示了较高的光催化还原活性,在可见光照4 h后硝基苯转化率可达98.1%,远大于单一的TiO₂ NWs或g-C₃N₄,并且TiO₂/g-C3N4/G拥有很高的选择性。总之,本论文通过以TiO₂ NWs、石墨烯和g-C₃N₄构建出新型可见光响应光催化剂,增加太阳光的利用效率,提高光催化反应速率,推动光催化技术的实际应用。更多还原

【Abstract】 Solar energy is abandant,clean and renewable energy.Recently,photocatalytic technology has attracted tremendous attention owing to its application on solving environmentental pollution and globle energy crisis.TiO₂ becomes the most extensively researched photocatalyst because of its low cost,nontoxicity and chemical stability.Howerer,its large band gap and high recombination rate of photoinduced electron-hole pairs under radiation seriously restricted the practical application of TiO₂.Therfore,it is of great significance to develop new visible light response photocatalyst by compositing with other semiconductors.Meanwhile,the introduction of other semiconductors can reduce the recombination rate of electron-hole paris.Graphene and g-C₃N₄ materials are considered as novle types of non-metallic materials which can be widely used in the field of photocatalytic technology.They are widely used as substrates for its strong adsorption capacity and enhance the adsorption of visible light,which can increase photocatalytic reaction rate.Herein high efficient visible light driven p hotocatalysts with high photocatalytic activity have been developed.The plausible machanism was proposed for photocatalytic reaction.This paper is devided into two parts:The first part: We demonstrated that N-TiO₂/NG,comprising N-TiO₂ NWs and N-doped graphene nanosheets,can be fabricated with urea through a facile hydrothermal method.The as-prepared materials were characterized by XRD,XPS,SEM,TEM,UV-Vis and so on.The results show that N from the decomposition of urea can enter not only into the lattice of TiO₂ but also into the skeleton of graphene nanosheets.The UV-Vis characterization shows that N-TiO₂/NG has visible light response.The efficiency of MB detradation using N-TiO₂/NG was 89.7% in 3 h under visible light.The kinetic constant of MB degration using N-TiO₂/NG was 0.0107 min-1,which is much high than the kinetic constants of TiO₂ and TiO₂/G.The second part: Firstly Ultrathin g-C₃N₄ nanosheets were obtained via a simply ultrasonic exfoliation method.Then TiO₂/g-C₃N₄/G composite were synthesised by photoreduction method.The as-prepared materials were characterized by XRD,XPS,SEM,TEM,UV-Vis and so on.The XRD result shows that TiO₂ NWs are composed of anatase and brookite.The specific surface area of TiO₂/g-C₃N₄/G composite is high than TiO₂ NWs and g-C₃N₄.The UV-Vis result demonstrated that TiO₂/g-C₃N₄/G composite has both visible light response and ultraviolet light response.Meanwhile,the photo-induced current is the highest of all prepared catalysts.The photoreduction efficiency of NB using TiO₂/g-C₃N₄/G was 98.1% in 4 h under irradiation with a Xe lamp,which is much high than TiO₂ NWs and g-C₃N₄.Meanwhile,TiO₂/g-C₃N₄/G composite has very high selectivity.In conclusion,TiO₂ NWs,graphene and g-C₃N₄ were fabricated as novle photocatalytic materials in this study.By means of doping and cmpositing,visible light driven photocatalysts with high photocatalytic activity have been develped for increasing photocatalytic reaction rates and application of photocatalytic technolog.更多还原