简易合成新颖的可见光纳米晶光催化剂及其性能研究
发布时间：2018-08-16 17:14
【摘要】：可调控的合成出具备各种不同形貌的无机半导体纳米材料,研发并探索纳米材料的功能化研究并将其尽快地应用于实际生产一直是材料科学工作者们广泛关注的课题。而将无机半导体材料广泛应用于光催化领域被认为将是一种最终且行之有效的解决方案尤其是面对当前不断增长的能源危机和日益加剧的环境污染问题。在光催化剂的作用下,光解水技术既能把来源丰富的太阳能转化为清洁的氢气有效的储存和再利用,同时光催化降解技术能以一种绿色环保和常温可行的化学流程充分地完成环境中有机污染物的有效降解。鉴于太阳光能量中可见光占43%,而现今广泛研究的宽带隙光催化半导体仅对紫外区的光辐射响应。因此最近,无论是通过改善已有的宽带隙半导体材料的电子价带结构还是不断探索和挖掘新颖的可见光响应的光催化剂最终目的都是为了高效地利用太阳光辐射中可见区域的光子。基于以上因素的考虑,本论文就新颖纳米材料体系的选择、不同制备方法的探索及对比、光催化性能的改善和提出并阐述合理的生成机理等方面进行了详细的系统化研究。在本文中,我们着重介绍了几种在可见光照射下具有高催化活性的纳米光催化剂的设计、合成及性能表征。取得的研究结果如下： 1.特定的合成出具有可调控电子结构的非化学计量比的半导体纳米晶,由于该类型材料在科学和技术上的重要性已经吸引了广泛的关注。在本章内容中,我们发展了一种新颖而简便的方法即通过在温和条件下Sn4+离子和金属锡的歧化反应制备出稳定并有高比表面积的Sn2+自掺杂的SnO2-x纳米晶。我们针对非化学计量比的二氧化锡材料中sn2+的掺杂浓度对纳米颗粒的尺寸,电子价带结构和催化降解甲基橙(MO)活性等的影响进行了一系列实验的考察。实验结果表明,相比于满足化学计量比的SnO2材料我们所制备的深黄色Sn2+自掺杂的SnO2-x样品展示了非常高的可见光催化性能,前者由于其固有的宽带隙只能吸收紫外区域的光辐射。据我们所知,这是目前报道的第一个相关的实验例证,证明自掺杂的还原态金属氧化物纳米晶能作为一种有效的光催化剂在可见光照射(λ≥400nm)下能在15分钟内完成对水中污染物的降解。Sn2+自掺杂的SnO2-x材料优异的光降解活性归因于掺杂的Sn2+进入晶格结构会伴随产生相应的氧空位缺陷,这会导致半导体材料带隙的减小同时增强其在可见光区域吸收光子的能力。值得注意的是,SnO2-x材料产生高浓度且有效分离的光诱导电子-空穴对,这个可通过光电流的显著增强得到确认。此外,在可见光照射下产生的高含量强氧化能力的·OH自由基,SnO2-x样品产生该活性基团的浓度(是Sn02的25倍),是非常有利于改善光催化性能。我们的合成方法可以扩展用来设计更多其他类型的非化学计量比的半导体纳米结构,兼具可调控的能带结构和高度有效的可见光光催化活性,对于将来在有效增强太阳光子利用率的光电催化应用方面有着重要的参考价值。 2.我们发展了一种低温下简单易行的溶液胶体合成法制备出纤锌矿衍生结构的AgGaS2纳米颗粒,首次采用了简单的一步法在合适的配体溶剂中热分解金属盐前体得到具有特定晶相的纳米材料,所获得材料在光催化性能方面展示出非常优越的性能。实验结果显示第一次成功制备出纤锌矿衍生结构的正交晶相AGS胶体纳米晶。这种简便的采用非注射法的合成策略是在热的高沸点溶剂中分解二乙基二硫代氨基甲酸盐前体。我们得到的结论是,使用长链烷基硫醇(DDT和HDT)和脂肪链伯胺(OM和HDA)为配位溶剂会导致正交晶型AGS的生成。斜方晶系AGS的带隙大约为2.7eV,能量吸收范围完全位于可见光区域。在可见光的照射下,正交AGS纳米晶作为光催化剂能有效地降解罗丹明B染料分子。 3.正交相的Cu2ZnGeS4(简写为CZGS)是一种亚稳态纤锌矿衍生结构,目前只能得到大的块状产物,也需要通过传统的固相反应法加热到极高的反应温度(≥790℃)条件下获得。我们发展了一种简易可行的基于溶液法的合成策略,能够在较低的反应温度条件下,获得纳米尺寸的纯正交相CZGS。参考现有已发表的文献,溶液胶体法合成出单一正交相的CZGS,特别是纳米尺寸级别还从未被报道过。我们的实验证明使用配位溶剂和金属盐前体的最优组合对于在溶液中特定专一地合成出这种亚稳态相纳米晶,发挥着至关重要的作用。在分析和讨论表征结果的基础上,我们也提出了一种合理的反应生成机理。基于CZGS均是由对环境友好无毒害的金属元素组成,它也被看作是一种有前途的替代材料能够取代虽然现今在技术上有使用价值却含有毒元素如镉和铅的半导体材料。正交相的CZGS在可见光区展现出强烈的光吸收能力,同时也能作为光催化剂在可见光照射下降解染料分子。 4.通过无模板法直接制备出核-壳结构或者蛋黄-蛋壳结构的纳米功能材料,对于科研者工作而言仍然是一个巨大挑战。在本章工作中,我们发展了一种新颖的合成路径,其中包括简单的化学配位法生成前驱体络合物和热处理得到的无限配位聚合物颗粒从而获得组分可调的蛋黄-蛋壳结构的二氧化铈。所制备的尺寸均匀的yolk-shell结构二氧化铈空心球展现大的比表面积,非常有希望作为支撑材料负载超小的金纳米颗粒(约4nm),形成金/二氧化铈纳米复合材料在催化硝基苯酚加氢实验中表现出卓越的催化活性和高的稳定性。我们也提出了一种合理的yolk-shell结构二氧化铈的形成机理。
[Abstract]:Controllable synthesis of inorganic semiconductor nanomaterials with various morphologies, research and development of functional nanomaterials and their application in practical production as soon as possible have always been a subject of great concern to material scientists. Under the action of photocatalyst, the photocatalytic water technology can not only transform the solar energy with abundant sources into clean hydrogen, but also effectively store and reuse it. At the same time, the photocatalytic degradation technology can be a kind of green environmental protection and environmental protection. In view of the fact that 43% of the solar energy is visible, and the widely studied broad-band gap photocatalytic semiconductors are only responsive to ultraviolet light radiation, recently, either by improving the electronic valence band structure of existing broad-band semiconductor materials has been achieved. The ultimate goal of the photocatalyst is to exploit and excavate novel visible light response for efficient utilization of photons in the visible region of solar radiation.Considering the above factors, this paper focuses on the selection of novel nano-materials, the exploration and comparison of different preparation methods, the improvement of photocatalytic performance and the proposition and combination. In this paper, we focus on the design, synthesis and characterization of several nano-photocatalysts with high catalytic activity under visible light irradiation.
1. Specific synthesis of non-stoichiometric semiconductor nanocrystals with controllable electronic structures has attracted considerable attention due to the scientific and technological importance of this type of materials. In this chapter, we developed a novel and simple method by disproportionating Sn4+ ions and tin metals under mild conditions. A series of experiments were carried out to investigate the effects of Sn2+ doping concentration on the size, valence band structure and catalytic activity of methyl orange (MO) degradation in nonstoichiometric tin dioxide materials. The dark yellow Sn2+ self-doped SnO2-x samples prepared by us to satisfy the stoichiometric ratio of SnO2 exhibit very high visible-light photocatalytic properties. The former can only absorb ultraviolet radiation due to its inherent wide band gap. As an effective photocatalyst, nanocrystalline metal oxides can degrade pollutants in water in 15 minutes under visible light irradiation (lambda < 400 nm). The excellent photocatalytic activity of Sn2+ self-doped SnO2-x materials is attributed to the oxygen vacancy defect associated with the doping of Sn2+ into the lattice structure. It is noteworthy that SnO2-x materials produce highly concentrated and effectively separated light-induced electron-hole pairs, which can be confirmed by a significant enhancement of photocurrent. In addition, the high content of strong oxidizing OH radicals produced under visible light irradiation. The concentration of the active group produced by SnO2-x sample (25 times that of Sn02) is very helpful to improve the photocatalytic performance. Our synthesis method can be extended to design more types of non-stoichiometric semiconductor nanostructures with both adjustable band structure and highly effective visible light photocatalytic activity for the future. It has important reference value to effectively enhance the photoelectric utilization of solar photons utilization.
2. We have developed a simple solution colloid synthesis method to prepare wurtzite-derived AgGaS2 nanoparticles at low temperature. For the first time, a simple one-step method was used to thermal decompose metal salt precursors in suitable ligand solvents to obtain nanomaterials with specific crystalline phases. The obtained materials exhibit very good photocatalytic properties. The experimental results show that the orthorhombic crystalline AGS colloidal nanocrystals with wurtzite-derived structure have been successfully prepared for the first time. This simple non-injection synthesis strategy is to decompose diethyldithiocarbamate precursors in hot, high boiling solvents. Our conclusion is that long-chain alkylthiols (DDT and HDT) are used. The orthorhombic AGS with a band gap of about 2.7 eV and an energy absorption range completely located in the visible region can be effectively degraded by using the orthorhombic AGS nanocrystals as photocatalysts under visible light irradiation.
3. Orthogonal phase Cu2ZnGeS4 (CZGS) is a metastable wurtzite derivative structure. At present, only bulk products can be obtained. It also needs to be heated to very high reaction temperature (> 790) by traditional solid-state reaction method. We have developed a simple and feasible synthesis strategy based on solution method, which can be used in the lower reaction temperature. Pure orthogonal phase CZGS with nano-size was obtained at temperature. Referring to the published literature, CZGS with single orthogonal phase was synthesized by solution colloid method, especially at nano-scale. Our experiments show that the optimal combination of coordination solvents and metal salt precursors can be specifically synthesized in solution. The metastable phase nanocrystals play an important role. On the basis of the analysis and discussion of the characterization results, a reasonable reaction formation mechanism has been proposed. CZGS is composed of environmentally friendly and non-toxic metal elements. It is also considered as a promising alternative material that can replace the present technology. Technically useful but toxic elements such as cadmium and lead are found in semiconductors. Orthogonal CZGS exhibit strong light absorption in the visible region and can also be used as photocatalysts to degrade dye molecules under visible light irradiation.
4. Preparation of core-shell or yolk-eggshell nano-functional materials by template-free method is still a great challenge for researchers. In this chapter, we have developed a novel synthesis route, which includes the formation of precursor complexes by simple chemical coordination method and the infinity obtained by heat treatment. The prepared hollow spheres of yolk-shell structure exhibit large specific surface area and are very promising as support materials to support the formation of gold/cerium dioxide nanocomposites in the catalytic nitro group. The phenol hydrogenation experiment showed excellent catalytic activity and high stability. We also proposed a reasonable mechanism for the formation of yolk-shell cerium dioxide.
【学位授予单位】：中国科学技术大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：O643.36;TB383.1
[Abstract]:Controllable synthesis of inorganic semiconductor nanomaterials with various morphologies, research and development of functional nanomaterials and their application in practical production as soon as possible have always been a subject of great concern to material scientists. Under the action of photocatalyst, the photocatalytic water technology can not only transform the solar energy with abundant sources into clean hydrogen, but also effectively store and reuse it. At the same time, the photocatalytic degradation technology can be a kind of green environmental protection and environmental protection. In view of the fact that 43% of the solar energy is visible, and the widely studied broad-band gap photocatalytic semiconductors are only responsive to ultraviolet light radiation, recently, either by improving the electronic valence band structure of existing broad-band semiconductor materials has been achieved. The ultimate goal of the photocatalyst is to exploit and excavate novel visible light response for efficient utilization of photons in the visible region of solar radiation.Considering the above factors, this paper focuses on the selection of novel nano-materials, the exploration and comparison of different preparation methods, the improvement of photocatalytic performance and the proposition and combination. In this paper, we focus on the design, synthesis and characterization of several nano-photocatalysts with high catalytic activity under visible light irradiation.
1. Specific synthesis of non-stoichiometric semiconductor nanocrystals with controllable electronic structures has attracted considerable attention due to the scientific and technological importance of this type of materials. In this chapter, we developed a novel and simple method by disproportionating Sn4+ ions and tin metals under mild conditions. A series of experiments were carried out to investigate the effects of Sn2+ doping concentration on the size, valence band structure and catalytic activity of methyl orange (MO) degradation in nonstoichiometric tin dioxide materials. The dark yellow Sn2+ self-doped SnO2-x samples prepared by us to satisfy the stoichiometric ratio of SnO2 exhibit very high visible-light photocatalytic properties. The former can only absorb ultraviolet radiation due to its inherent wide band gap. As an effective photocatalyst, nanocrystalline metal oxides can degrade pollutants in water in 15 minutes under visible light irradiation (lambda < 400 nm). The excellent photocatalytic activity of Sn2+ self-doped SnO2-x materials is attributed to the oxygen vacancy defect associated with the doping of Sn2+ into the lattice structure. It is noteworthy that SnO2-x materials produce highly concentrated and effectively separated light-induced electron-hole pairs, which can be confirmed by a significant enhancement of photocurrent. In addition, the high content of strong oxidizing OH radicals produced under visible light irradiation. The concentration of the active group produced by SnO2-x sample (25 times that of Sn02) is very helpful to improve the photocatalytic performance. Our synthesis method can be extended to design more types of non-stoichiometric semiconductor nanostructures with both adjustable band structure and highly effective visible light photocatalytic activity for the future. It has important reference value to effectively enhance the photoelectric utilization of solar photons utilization.
2. We have developed a simple solution colloid synthesis method to prepare wurtzite-derived AgGaS2 nanoparticles at low temperature. For the first time, a simple one-step method was used to thermal decompose metal salt precursors in suitable ligand solvents to obtain nanomaterials with specific crystalline phases. The obtained materials exhibit very good photocatalytic properties. The experimental results show that the orthorhombic crystalline AGS colloidal nanocrystals with wurtzite-derived structure have been successfully prepared for the first time. This simple non-injection synthesis strategy is to decompose diethyldithiocarbamate precursors in hot, high boiling solvents. Our conclusion is that long-chain alkylthiols (DDT and HDT) are used. The orthorhombic AGS with a band gap of about 2.7 eV and an energy absorption range completely located in the visible region can be effectively degraded by using the orthorhombic AGS nanocrystals as photocatalysts under visible light irradiation.
3. Orthogonal phase Cu2ZnGeS4 (CZGS) is a metastable wurtzite derivative structure. At present, only bulk products can be obtained. It also needs to be heated to very high reaction temperature (> 790) by traditional solid-state reaction method. We have developed a simple and feasible synthesis strategy based on solution method, which can be used in the lower reaction temperature. Pure orthogonal phase CZGS with nano-size was obtained at temperature. Referring to the published literature, CZGS with single orthogonal phase was synthesized by solution colloid method, especially at nano-scale. Our experiments show that the optimal combination of coordination solvents and metal salt precursors can be specifically synthesized in solution. The metastable phase nanocrystals play an important role. On the basis of the analysis and discussion of the characterization results, a reasonable reaction formation mechanism has been proposed. CZGS is composed of environmentally friendly and non-toxic metal elements. It is also considered as a promising alternative material that can replace the present technology. Technically useful but toxic elements such as cadmium and lead are found in semiconductors. Orthogonal CZGS exhibit strong light absorption in the visible region and can also be used as photocatalysts to degrade dye molecules under visible light irradiation.
4. Preparation of core-shell or yolk-eggshell nano-functional materials by template-free method is still a great challenge for researchers. In this chapter, we have developed a novel synthesis route, which includes the formation of precursor complexes by simple chemical coordination method and the infinity obtained by heat treatment. The prepared hollow spheres of yolk-shell structure exhibit large specific surface area and are very promising as support materials to support the formation of gold/cerium dioxide nanocomposites in the catalytic nitro group. The phenol hydrogenation experiment showed excellent catalytic activity and high stability. We also proposed a reasonable mechanism for the formation of yolk-shell cerium dioxide.
【学位授予单位】：中国科学技术大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：O643.36;TB383.1
【共引文献】
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2 付安安;张庆武;高剑;王莉;何向明;;锂离子电池负极材料Li_4Ti_5O_(12)的研究进展[J];电源技术;2013年12期
3 郁美霞;郑小平;韩昕s，
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