【摘要】：可調(diào)控的合成出具備各種不同形貌的無機(jī)半導(dǎo)體納米材料,研發(fā)并探索納米材料的功能化研究并將其盡快地應(yīng)用于實(shí)際生產(chǎn)一直是材料科學(xué)工作者們廣泛關(guān)注的課題。而將無機(jī)半導(dǎo)體材料廣泛應(yīng)用于光催化領(lǐng)域被認(rèn)為將是一種最終且行之有效的解決方案尤其是面對(duì)當(dāng)前不斷增長的能源危機(jī)和日益加劇的環(huán)境污染問題。在光催化劑的作用下,光解水技術(shù)既能把來源豐富的太陽能轉(zhuǎn)化為清潔的氫氣有效的儲(chǔ)存和再利用,同時(shí)光催化降解技術(shù)能以一種綠色環(huán)保和常溫可行的化學(xué)流程充分地完成環(huán)境中有機(jī)污染物的有效降解。鑒于太陽光能量中可見光占43%,而現(xiàn)今廣泛研究的寬帶隙光催化半導(dǎo)體僅對(duì)紫外區(qū)的光輻射響應(yīng)。因此最近,無論是通過改善已有的寬帶隙半導(dǎo)體材料的電子價(jià)帶結(jié)構(gòu)還是不斷探索和挖掘新穎的可見光響應(yīng)的光催化劑最終目的都是為了高效地利用太陽光輻射中可見區(qū)域的光子。基于以上因素的考慮,本論文就新穎納米材料體系的選擇、不同制備方法的探索及對(duì)比、光催化性能的改善和提出并闡述合理的生成機(jī)理等方面進(jìn)行了詳細(xì)的系統(tǒng)化研究。在本文中,我們著重介紹了幾種在可見光照射下具有高催化活性的納米光催化劑的設(shè)計(jì)、合成及性能表征。取得的研究結(jié)果如下： 1.特定的合成出具有可調(diào)控電子結(jié)構(gòu)的非化學(xué)計(jì)量比的半導(dǎo)體納米晶,由于該類型材料在科學(xué)和技術(shù)上的重要性已經(jīng)吸引了廣泛的關(guān)注。在本章內(nèi)容中,我們發(fā)展了一種新穎而簡便的方法即通過在溫和條件下Sn4+離子和金屬錫的歧化反應(yīng)制備出穩(wěn)定并有高比表面積的Sn2+自摻雜的SnO2-x納米晶。我們針對(duì)非化學(xué)計(jì)量比的二氧化錫材料中sn2+的摻雜濃度對(duì)納米顆粒的尺寸,電子價(jià)帶結(jié)構(gòu)和催化降解甲基橙(MO)活性等的影響進(jìn)行了一系列實(shí)驗(yàn)的考察。實(shí)驗(yàn)結(jié)果表明,相比于滿足化學(xué)計(jì)量比的SnO2材料我們所制備的深黃色Sn2+自摻雜的SnO2-x樣品展示了非常高的可見光催化性能,前者由于其固有的寬帶隙只能吸收紫外區(qū)域的光輻射。據(jù)我們所知,這是目前報(bào)道的第一個(gè)相關(guān)的實(shí)驗(yàn)例證,證明自摻雜的還原態(tài)金屬氧化物納米晶能作為一種有效的光催化劑在可見光照射(λ≥400nm)下能在15分鐘內(nèi)完成對(duì)水中污染物的降解。Sn2+自摻雜的SnO2-x材料優(yōu)異的光降解活性歸因于摻雜的Sn2+進(jìn)入晶格結(jié)構(gòu)會(huì)伴隨產(chǎn)生相應(yīng)的氧空位缺陷,這會(huì)導(dǎo)致半導(dǎo)體材料帶隙的減小同時(shí)增強(qiáng)其在可見光區(qū)域吸收光子的能力。值得注意的是,SnO2-x材料產(chǎn)生高濃度且有效分離的光誘導(dǎo)電子-空穴對(duì),這個(gè)可通過光電流的顯著增強(qiáng)得到確認(rèn)。此外,在可見光照射下產(chǎn)生的高含量強(qiáng)氧化能力的·OH自由基,SnO2-x樣品產(chǎn)生該活性基團(tuán)的濃度(是Sn02的25倍),是非常有利于改善光催化性能。我們的合成方法可以擴(kuò)展用來設(shè)計(jì)更多其他類型的非化學(xué)計(jì)量比的半導(dǎo)體納米結(jié)構(gòu),兼具可調(diào)控的能帶結(jié)構(gòu)和高度有效的可見光光催化活性,對(duì)于將來在有效增強(qiáng)太陽光子利用率的光電催化應(yīng)用方面有著重要的參考價(jià)值。 2.我們發(fā)展了一種低溫下簡單易行的溶液膠體合成法制備出纖鋅礦衍生結(jié)構(gòu)的AgGaS2納米顆粒,首次采用了簡單的一步法在合適的配體溶劑中熱分解金屬鹽前體得到具有特定晶相的納米材料,所獲得材料在光催化性能方面展示出非常優(yōu)越的性能。實(shí)驗(yàn)結(jié)果顯示第一次成功制備出纖鋅礦衍生結(jié)構(gòu)的正交晶相AGS膠體納米晶。這種簡便的采用非注射法的合成策略是在熱的高沸點(diǎn)溶劑中分解二乙基二硫代氨基甲酸鹽前體。我們得到的結(jié)論是,使用長鏈烷基硫醇(DDT和HDT)和脂肪鏈伯胺(OM和HDA)為配位溶劑會(huì)導(dǎo)致正交晶型AGS的生成。斜方晶系A(chǔ)GS的帶隙大約為2.7eV,能量吸收范圍完全位于可見光區(qū)域。在可見光的照射下,正交AGS納米晶作為光催化劑能有效地降解羅丹明B染料分子。 3.正交相的Cu2ZnGeS4(簡寫為CZGS)是一種亞穩(wěn)態(tài)纖鋅礦衍生結(jié)構(gòu),目前只能得到大的塊狀產(chǎn)物,也需要通過傳統(tǒng)的固相反應(yīng)法加熱到極高的反應(yīng)溫度(≥790℃)條件下獲得。我們發(fā)展了一種簡易可行的基于溶液法的合成策略,能夠在較低的反應(yīng)溫度條件下,獲得納米尺寸的純正交相CZGS。參考現(xiàn)有已發(fā)表的文獻(xiàn),溶液膠體法合成出單一正交相的CZGS,特別是納米尺寸級(jí)別還從未被報(bào)道過。我們的實(shí)驗(yàn)證明使用配位溶劑和金屬鹽前體的最優(yōu)組合對(duì)于在溶液中特定專一地合成出這種亞穩(wěn)態(tài)相納米晶,發(fā)揮著至關(guān)重要的作用。在分析和討論表征結(jié)果的基礎(chǔ)上,我們也提出了一種合理的反應(yīng)生成機(jī)理�；贑ZGS均是由對(duì)環(huán)境友好無毒害的金屬元素組成,它也被看作是一種有前途的替代材料能夠取代雖然現(xiàn)今在技術(shù)上有使用價(jià)值卻含有毒元素如鎘和鉛的半導(dǎo)體材料。正交相的CZGS在可見光區(qū)展現(xiàn)出強(qiáng)烈的光吸收能力,同時(shí)也能作為光催化劑在可見光照射下降解染料分子。 4.通過無模板法直接制備出核-殼結(jié)構(gòu)或者蛋黃-蛋殼結(jié)構(gòu)的納米功能材料,對(duì)于科研者工作而言仍然是一個(gè)巨大挑戰(zhàn)。在本章工作中,我們發(fā)展了一種新穎的合成路徑,其中包括簡單的化學(xué)配位法生成前驅(qū)體絡(luò)合物和熱處理得到的無限配位聚合物顆粒從而獲得組分可調(diào)的蛋黃-蛋殼結(jié)構(gòu)的二氧化鈰。所制備的尺寸均勻的yolk-shell結(jié)構(gòu)二氧化鈰空心球展現(xiàn)大的比表面積,非常有希望作為支撐材料負(fù)載超小的金納米顆粒(約4nm),形成金/二氧化鈰納米復(fù)合材料在催化硝基苯酚加氫實(shí)驗(yàn)中表現(xiàn)出卓越的催化活性和高的穩(wěn)定性。我們也提出了一種合理的yolk-shell結(jié)構(gòu)二氧化鈰的形成機(jī)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.
【學(xué)位授予單位】：中國科學(xué)技術(shù)大學(xué)
【學(xué)位級(jí)別】：博士
【學(xué)位授予年份】：2015
【分類號(hào)】：O643.36;TB383.1

【共引文獻(xiàn)】

相關(guān)期刊論文 前10條

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2 付安安;張慶武;高劍;王莉;何向明;;鋰離子電池負(fù)極材料Li_4Ti_5O_(12)的研究進(jìn)展[J];電源技術(shù);2013年12期

3 郁美霞;鄭小平;韓昕s，

本文編號(hào)：2186648