【作者】 方舒玫；

【导师】 廖代伟；

【作者基本信息】 厦门大学 ， 物理化学， 2007， 硕士

【摘要】 能源是为人类提供能量的物质或物质运动,是人类活动的基础及人类社会发展的物质前提。与传统化石能源（如煤、石油）燃烧后造成环境污染相比,氢能是一种清洁能源,氢气可以从水中获得,完全燃烧后的产物是水,不会对环境造成任何污染,是世界上最干净的能源。半导体光催化是目前最理想的光解水制氢途径,而开发高效的光催化材料是半导体光催化的关键。传统TiO₂光催化剂和钙钛矿型光催化剂是目前的研究热点。本文以钙钛矿型光催化剂Sr₃Ti₂O₇和传统光催化剂TiO₂作为研究对象。具体内容如下:（1）使用聚合合成法（Polymerized Complex Method,PCM）制备组分化学计量比可控的多金属氧化物Sr₃Ti₂O₇作为光催化剂,进而负载不同质量比的Cu离子,制成ωCu/Sr₃Ti₂O₇催化剂（ω为质量百分比）,以超纯水和甲醇牺牲剂体系的光催化分解水反应为探针,通过检测氢气生成速率来评价催化剂的光催化性能,并借助光电子能谱（XPS）、X射线衍射（XRD）分析、紫外-可见漫反射光谱（UV-Vis DRS）等手段对催化剂进行了表征。实验结果表明,Cu离子在催化剂中以多价态存在,Cu⁺和吸附氧有利于光生电子的转移。ωCu/Sr₃Ti₂O₇催化剂较之纯Sr₃Ti₂O₇催化剂活性大大提高,采用气相色谱对产氢速率进行检测,发现Cu离子最佳负载量为1.5%时,产氢速率可稳定在550-600μmol·h^-1。H₂预还原后的1.5%Cu/Sr₃Ti₂O₇催化剂产氢速率最高可达1140.8μmol·h^-1,约为已报道的NiO/Sr₃Ti₂O₇催化剂产氢速率164μmol·h^-1的7倍。本实验创新之处是:首次将具有多价态的过渡金属Cu(Cu⁺、Cu²⁺)离子负载在钙钛矿型催化剂上,找到最佳Cu离子负载量,大大提高了光催化剂性能,并运用了多价态Cu离子负载能起到协同分离迁移载流子解释了这一现象,同时给出了反应式,并通过XPS测试Cu⁺和吸附氧的含量证明了反应式的合理性。另外,选用同主族元素Ag离子负载在Sr₃Ti₂O₇上,考察Cu、Ag离子负载后的催化剂活性,发现1.5%Cu/Sr₃Ti₂O₇光催化分解水的最大产氢速率是1.5%Ag/Sr₃Ti₂O₇最大产氢速率的35.5倍。（2）使用溶胶-凝胶法,非离子型表面活性剂EO₂₀PO₇₀EO₂₀（P123）为模板剂、钛酸丁脂为钛源、稀土金属氧化物La₂O₃为促进剂,用温和的方式去除模板剂,即溶剂洗脱模板剂的方式,在低温下合成介孔锐钛矿相TiO₂。在钛酸丁脂量确定的前提下,改变模板剂和促进剂的量,能控制孔结构的有序性,改变催化剂的比表面积大小。XRD,BET,IR和HRTEM等表征表明,La₂O₃的掺杂量对TiO₂锐钛矿相的形成具有明显影响,当La₂O₃掺杂量为0.1%（摩尔分数）时,合成的TiO₂锐钛矿相晶型最好,且为介孔结构,孔径大小均一,比表面积达到367.7 m²·g^-1。本实验创新之处是在制备介孔TiO₂的过程中引入稀土元素La,掺杂La₂O₃后,TiO₂的骨架强度增大,结构稳定性得到提高,同时,适量掺杂能促进锐钛矿相的形成,尤其是溶剂洗脱模板剂的同时,得到明显的锐钛矿晶型。研究La₂O₃对介孔TiO₂的结构、晶型、催化性能的影响。两组实验均确定了改性催化剂最适宜的过渡金属Cu离子或稀土金属氧化物La₂O₃的添加量。更多还原

【Abstract】 Energy sources are materials or movements providing energy for human.They are the foundation for human activity and development of human society.Compared with traditional fossil fuels,such as coal and oil,bring destruction on the environment; Hydrogen is an alternative energy source with high efficiency and pollution free. Hydrogen can be produced from clean and renewable energy sources,and thus its life cycle is clean and renewable.The photocatalytic water-splitting into hydrogen using semiconductor is a potentially clean and renewable method which is of both theoretical and practical significance.Searching for highly reactive and functional photocatalyst is the key.TiO₂ as a traditional photocatalyst and another photocatalyst with perovskite-layered structure have drawn more and more attention.The paper reports synthesis and modification of Sr₃Ti₂O₇ and TiO₂ semiconductor.The detailed contents are as follows:（1） Sr₃Ti₂O₇ photocatalyst with perovskite-layered structure was synthesized by polymerized complex method（PCM）.Cu ion as an effective dopant was loaded onto Sr₃Ti₂O₇ catalyst,ωCu/Sr₃Ti₂O₇ catalyst was applied in the mixture of water and methanol,methanol was used as a sacrificial agent under ultra-violet irradiation,and the catalyst was characterized by XPS,XRD,and UV-Vis DRS.The results showed that Cu ion existed in several kinds of valence and the photocatalytic activity of Cu/ Sr₃Ti₂O₇ was superior to that of pure Sr₃Ti₂O₇.Cu⁺ and adsorption oxygen can accelerate the interfacial electron transfer.When the amount of Cu ion was 1.5%（w）, the best catalytic effect was obtained and the stable average hydrogen evolution rate was about 550-600μmol·h^-1.TheωCu/Sr₃Ti₂O₇ after reduction attained the highest hydrogen evolution rate that was close to 1140.8μmol·h^-1.The value was seven times of NiO/Sr₃Ti₂O₇ reported before.The paper reported that synthesis method of Sr₃Ti₂O₇ with perovskite-layered structure loaded with transition metal ion（Cu,Ag ion） with several valences.The optimal loading of Cu ion could enhance the photocatalytic activity greatly and that was explained by the mechanism that of loading Cu ion like such several valences can help semiconductor transferring charge and reaction.The content of Cu⁺ and adsorption oxygen in photocatalyst tested by XPS characterization could testify the explanation.In addition,loading of the same main group Ag ion has been investigated. At the optimal loading of Cu ion,hydrogen production rate was enhanced as much as 35.5 times higher than loading of Ag ion.（2） Mesoporous TiO₂ nanocrystals with anatase phase and high specific surface area was synthesized by sol-gel process using nonionic surfactant EO₂₀PO₇₀EO₂₀ as a structure-directing agent,C₁₆H₃₆Ti as Ti precursor,La₂O₃ as catalyst support and ethanol as an extraction agent.Then removed template in moderate condition that was washing by reagent.The results indicated that the amount of doped La₂O₃ greatly effected on the formation of TiO₂ with anatase phase,and the optimal content of doped La₂O₃ was 0.1%（mole fraction）.The characterizations of XRD,BET,IR and HRTEM showed that an ordered mesostructure of TiO₂ with narrow pore size distribution and large surface area(～367.7 m²·g^-1) was obtained under the synthesis conditions.In the paper,Mesoporous TiO₂ doped with rare earth was synthesized.The intensity of TiO₂ inorganic framework and the stability of the mesoporous structure were stronger than non-La₂O₃ doped.When the template was washed by boiling ethanol,anatase phase was formed.It indicated that doping La₂O₃ could accelerate the formation of anatase phase.Study on rare earth how to affect structure,crystal and photocatalytic activity.Both of two experiments have indicated the optimal loading of Cu or doping of La₂O₃ clearly.更多还原