【作者】 黄徽；

【导师】 杨平；

【作者基本信息】 苏州大学 ， 物理化学， 2014， 博士

【摘要】 在全球能源短缺、环境污染问题日益严峻的大背景下，利用高效、洁净、低能耗、无二次污染的光催化技术成为研究的热点。目前，科学家们正在努力探索高效可见光型催化材料的开发。其中，有序介孔金属氧化物材料以其高的比表面积、规则有序的孔道结构、孔径大小可调及内表面可修饰等特点而备受青睐。随着有序介孔金属氧化物催化功能化、孔道尺寸调变、原位谱学表征和分子设计等关键问题的解决，许多具有不同形貌特征、介孔结构、骨架成分的有序介孔材料被成功合成并广泛应用于催化、传感、能源等领域，促进了光催化技术的创新。本文选取极具潜力的金属氧化物光催化剂为研究对象，探讨了有序介孔金属氧化物的制备方法及其介孔结构的形成机理。系统研究了可见光条件下有序介孔金属氧化物的光催化性能及其潜在的应用价值，为开发高性能可见光型催化剂，拓展其在太阳能转换及环境领域的应用提供新思路和基础理论参考，主要研究内容如下：(1)以介孔二氧化硅(KIT-6)为硬模板，磷钨酸为前驱物，用硬模板法制备WO3-SiO2复合材料，再利用氢氟酸（HF）除去二氧化硅，制得介孔三氧化钨（m-WO3）光催化剂。在可见光条件下，以IO-3作为电子受体，铂修饰的介孔三氧化钨光催化分解水产氧量达276.1mol·g-1，是纳米三氧化钨（c-WO3）的3.5倍。因此，有序介孔WO3的规则孔道结构利于光生载流子在其表面的传输与分离，降低光生电子-空穴对的复合几率，提高了可见光催化性能。(2)以有序介孔WO3(m-WO3)和还原石墨烯氧化物(RGO)为原料采用紫外光协助照射法合成了m-WO3-RGO复合型光催化剂。复合材料中的m-WO3与RGO的有效结合促进了载流子的分离和产氧量的提高。在可见光照射下，m-WO3-RGO-6光催化剂的产氧量可达437.3μmol·g-1，为m-WO3的5.1倍。光催化活性的增强可以归咎于作为固态电子受体的RGO，促进了光生电子-空穴对的传输和分离，有效抑制了电子-空穴对在复合材料中的复合。这种新型介孔金属氧化物/石墨烯复合材料表现出稳定、优异的光催化活性，为开发可见光型光催化剂提供了新的思路。(3)采用软模板法，以尿素为氮源，通过简单的固态反应法合成了氮掺杂有序介孔五氧化二铌光催化剂。介孔五氧化二铌的有序孔道结构利于N元素有效掺入其晶格内部。氮掺杂后介孔五氧化二铌光催化剂的吸收带边由3.1eV降至2.61eV，对应的光响应范围由400nm拓展至475nm。以0.5wt%Pt作为助催化剂，可见光下照射5h后，1.53%氮掺杂介孔五氧化二铌的催化产氢量为介孔五氧化二铌的3.4倍。在光催化反应中，有序介孔结构可以提供更多的活性位，加速体系内的电子-空穴对在其表面的转移和分离，大大提高了可见光催化活性。(4)以硝酸铈为铈源，介孔二氧化硅(KIT-6)为模板，采用硬模板法制备了介孔二氧化铈(m-CeO2)。通过浸渍法合成了铋掺杂介孔二氧化铈(m-CeO2/Bi)光催化剂。m-CeO2/Bi光催化剂具有完整的晶型和规则的孔道结构，有利于光生电子和空穴的分离，同时Bi的掺入降低了催化剂的带隙能，有效提高了可见光催化性能。在可见光(λ＞420nm)条件下，以对氯苯酚(4-CP)为目标污染物，考察了m-CeO2/Bi光催化剂的催化性能。2%Bi掺杂的m-CeO2/Bi光催化剂性能最佳，光照4h可将4-CP降解91%以上，催化剂经5次循环使用后，其光催化活性基本保持不变。更多还原

【Abstract】 How to utilize photocatalytic technique with high efficiency, low energy consumption,clean and no secondary pollution properties become a hot issue in the context of theuniversal crisis of energy shortage and environmental pollution. Recently, scientists aremaking great efforts to probe into the way to explore the highly efficient visible lightphotocatalytic materials. Among them, the ordered mesoporous metal oxides with highspecific surface area, ordered pore structure, adjustable aperture and the modified internalsurface are gaining popularity by the researchers. Many different morphologies,mesoporous structure and skeleton composition of ordered mesoporous structure have beensuccessful prepared and widely used in catalysis, sensing, energy and other fields,combining with the critical issues settlement of ordered mesoporous metal oxides ofcatalytic function, pore size adjustment, in-situ spectroscopic characterization andmolecular design, thereby promoted the development of photocatalytic technology. In thispaper, we discuss the preparation of mesoporous metal oxides and formation mechanism ofmesoporous structure. At the same time, the photocatalytic properties and potentialapplications of the mesoporous metal oxide photocatalysts have been systematicallyinvestigated under visible light irradiation. This study will contribute to the development ofnovel photocatalyst with high performance, and provide a new idea in the field of solarenergy conversion and basic theories of reference, the main research contents are asfollows:(1) Three-dimensionally ordered mesoporous WO3was successfully synthesized by ahydrothermal method using mesoporous silica KIT-6as a hard template andphosphotungstic acid as a precursor. Investigations of optical and photoelectrochemicalproperties showed that the mesoporous WO3was a n-type semiconductor with a band gapof2.6eV and demonstrated prompt, steady, and reproducible photocurrent responsesduring repeated on/off cycles of visible light illumination (λ>420nm). The mesoporous WO3modified by platinum nanoparticles could be used as a stable photocatalyst forphotoinducing O2evolution. Under visible light irradiation, the average O2evolution ratereached to34.5μmol g-1h-1with the presence of an electron acceptor of IO-3. This workdemonstrated a potential application of using mesoporous WO3modified by platinumnanoparticles as a novel photocatalyst in the field of solar energy conversion.(2) We report the synthesis, characterization, and photocatalysis of a novel composite,composed of high-ordered mesoporous WO3(m-WO3) and reduced graphene oxide(RGO). The superior contact between two moieties in the composites facilitates the chargecarrier separation and the evolution of oxygen. Under visible light irradiation, the amountof oxygen evolution from the optimized photocatalyst containing ca.6wt%RGO reachedto437.3μmol·g1, which was5.1times as high as that from m-WO3. The enhancement ofphotocatalytic activity could be ascribed to that RGO acts herein as a solid-state electronmediator, promoting the charge transportation and separation, as well as suppressing theelectron-hole recombination in the composite. This study might provide a prototype forconstructing a novel photocatalytic system by hybridizing graphene with a mesoporoussemiconductor for solar energy conversion.(3) The high-ordered N-doped mesoporous niobium oxide (NMNb) was prepared viaa facile solid state reaction method using urea as a nitrogen source. The inheritedmesoporous structure of NMNb making the N dopants effective incorporated in lattice ofmesoporous niobium oxide (MNb), result in a significant enhanced visible light response,corresponding to a reduced band gap of2.61eV. Subsequently, the optimized hydrogengeneration efficiency over N-doped MNb photocatalyst was14.8times as high as that fromN-P25under5h visible light irradiation with0.5wt%Pt as a cocatalyst. The improvedphotocatalytic activity of NMNb was mainly due to the ordered mesostructure could offermore active sites for the photocatalytic reaction, as well as accelerate the photogeneratedelectron-hole pairs transfer and separation. It is hoped that this study could promoteincreasing interest in designing N doped diverse structure of semiconductor photocatalystsfor solar water splitting.(4) Mesoporous cerium oxides were prepared by a hard templating method usingmesoporous silica dioxide (KIT-6) as the hard template, cerium nitrate as the source ofcerium. The photodegradation activity of m-CeO2/Bi powders was evaluated by using4-chlorophenol (4-CP) as pollutant targets under visible light irradiation (λ＞420nm). The results demonstrate that the m-CeO2/Bi photocatalyst equipped with high crystallinity andcontinuous pore channels, which benefit for the electron-hole pairs separation.Simultaneously, doped Bi could reduce the bandgap of the m-CeO2photocatalyst, therebyeffectively improve the visible light photocatalytic properties. The photodegradation yieldof4-CP was beyond91%under visible light irradiation for four hours. The photocatalystcan be recycled several times without losing its photocatalytic activity.更多还原