離子液體中釩酸鐵基材料的設計及其增強光催化性能研究
發(fā)布時間：2018-09-07 16:17
【摘要】：自上世紀以來,環(huán)境污染和能源短缺問題日漸突出,研發(fā)綠色能源是趨大勢之舉。在現(xiàn)有眾多可再生資源中,太陽能作為綠色環(huán)保、安全無害以及儲量最大的資源,利用前景極為廣闊。光催化技術作為一項可直接將太陽能轉化為化學能的新興技術,可有效利用太陽光進行能源轉化和環(huán)境凈化,是同時實現(xiàn)環(huán)保和節(jié)能的有效途徑。在光催化技術中,光催化材料的設計至關重要。如今,研發(fā)高效實用的新型光催化劑已成為光催化領域的研究熱點,通過構建異質(zhì)結體系以開發(fā)新型高效半導體光催化劑是常用的有效策略。本文旨在以鐵基離子液體為鐵源,探索新型釩酸鐵(FeVO_4)催化劑的合成及其復合光催化材料在環(huán)境凈化方面的應用。文中通過簡單可控的方法制備了FeVO_4、gC_3N_4/FeVO_4和Ag_3VO_4/FeVO_4三種新型光催化材料,采用多種表征手段確定上述光催化材料的微觀結構、形貌及光學性能。同時在可見光輻照條件下考察上述材料降解有機污染物的光催化活性及穩(wěn)定性。最后對光催化材料的結構及其活性之間的關系展開了深入研究,并提出了相應的光催化機理。具體研究內(nèi)容如下:(1)以1-辛基-3-甲基咪唑四氯合鐵([Omim]FeCl4)為鐵源,通過離子液體輔助水熱和煅燒兩步法制得介孔FeVO_4納米棒光催化劑。通過對該材料進行X射線衍射(XRD)、掃描電鏡(SEM)、透射電鏡(TEM)、紫外-可見漫反射光譜(DRS)和比表面積分析(BET)等一系列基礎表征方法確定其表觀結構、形貌及內(nèi)在光電性能。結果表明離子液體中所制備的介孔FeVO_4納米棒光催化材料形貌均一,孔徑(3-7 nm)分布均勻,且具有較大的比表面積(255.83 m2/g)。所制備的催化劑禁帶寬度為2.35 eV,有較寬的紫外可見光譜吸收范圍。同時,在可見光輻照條件下,光催化活性實驗顯示介孔FeVO_4納米棒類芬頓光催化劑不僅可應用于有色染料(羅丹明B)的快速有效降解,還對四環(huán)素無色有機污染物也具有較高的光催化降解性能。此外,通過與常規(guī)的無機鹽為鐵源制備的FeVO_4納米材料對比可知,離子液體中合成的FeVO_4具有更為優(yōu)良的表面性能、光電化學性能和光催化活性。由此可確定離子液體[Omim]FeCl4在材料制備過程中不但可作為反應源,還可作為模板劑對納米棒的形成以及結構性能的調(diào)控起到了重要作用。最后提出了FeVO_4作為一種三效異相光芬頓催化劑降解污染物的可能機理。(2)通過水熱合成法成功制備了g-C_3N_4/FeVO_4光催化劑。采用XPS、FT-IR、SEM、TEM和DRS等基礎表征方法確定材料的表觀結構、形貌及光學性能。表征結果表明,FeVO_4納米棒均勻分布并附著在薄層g-C_3N_4表面,并在兩者接觸界面處形成異質(zhì)結結構;薄層g-C_3N_4的引入拓寬了FeVO_4的光吸收閾值,提高了其光生載流子的遷移傳輸效率;可見光催化降解實驗結果表明,在光催化反應6 h后,20 wt%g-C_3N_4/FeVO_4對RhB降解效率(99.4%)最高,而薄層g-C_3N_4和FeVO_4的RhB降解效率分別為74.5%和14.7%。光催化機理分析表明,g-C_3N_4和FeVO_4之間的能帶位置匹配良好,有利于光生載流子的傳輸和分離,從而導致g-C_3N_4/FeVO_4光催化性能相比于單體有極大提升。(3)通過原位合成法成功制備了Ag_3VO_4/FeVO_4光催化劑。采用XRD、XPS、SEM、TEM、DRS和PL等基礎表征確定材料的表觀結構、形貌及光學性能。表征結果表明,Ag_3VO_4顆粒均勻分布并附著在FeVO_4納米棒表面,并在兩者接觸界面處形成異質(zhì)結結構;Ag_3VO_4的引入拓寬了FeVO_4的光吸收閾值,提高了材料光生載流子的遷移傳輸效率;可見光催化降解實驗結果表明,在光催化反應3 h后,40 wt%Ag_3VO_4/FeVO_4對RhB降解效率(99.7%)最高,而Ag_3VO_4單體的RhB降解效率僅為59.4%。光催化機理分析表明,Ag_3VO_4和FeVO_4的能帶位置匹配良好,有利于光生載流子的傳輸和分離,從而致使Ag_3VO_4/FeVO_4光催化性能相比于單體有極大提升。
[Abstract]:Since the last century, the problem of environmental pollution and energy shortage has become increasingly prominent, and the development of green energy is a trend. Among the many existing renewable resources, solar energy, as a green, safe and harmless resource with the largest reserves, has a very broad prospect of utilization. Nowadays, the research and development of new photocatalysts with high efficiency and practicability has become a hot spot in the field of photocatalysis. Heterojunction system can be constructed to develop new photocatalysts. New efficient semiconductor photocatalysts are commonly used as effective strategies. The purpose of this paper is to explore the synthesis of novel ferric vanadate (FeVO_4) catalysts and the application of their composite photocatalytic materials in environmental purification using iron-based ionic liquids as iron sources. Three novel photocatalytic materials, FeVO_4, gC_3N_4/FeVO_4 and Ag_3VO_4/FeVO_4, have been prepared by simple and controllable methods. The microstructure, morphology and optical properties of the photocatalytic materials were determined by various characterization methods. The photocatalytic activity and stability of the materials for degradation of organic pollutants were investigated under visible light irradiation. The specific research contents are as follows: (1) Mesoporous FeVO_4 nanorod photocatalyst was prepared by ionic liquid assisted hydrothermal method and calcination using 1-octyl-3-methylimidazolium ferric tetrachloride ([Omim] FeCl_4) as iron source. The results show that the mesoporous FeVO_4 nanorods prepared in ionic liquids have uniform morphology, uniform pore size (3-7 nm) distribution and large specific surface area (255.83 m2/g). The band gap of the catalyst is 2.35 eV and the absorption range of UV-Vis spectrum is wider. At the same time, the photocatalytic activity experiment shows that the mesoporous FeVO_4 nanorod-like Fenton photocatalyst can be used not only for the fast and effective degradation of colored dye (Rhodamine B), but also for the colorless organic pollutants of tetracycline. In addition, compared with the conventional inorganic salts as iron source, the synthesized FeVO_4 nano-materials have better surface properties, photoelectrochemical properties and photocatalytic activity. As a template, FeVO_4 plays an important role in the formation of nanorods and the regulation of their structure and properties. Finally, the possible mechanism of FeVO_4 as a three-way heterogeneous photocatalyst for the degradation of pollutants is proposed. (2) The g-C_3N_4/FeVO_4 photocatalyst was successfully prepared by hydrothermal synthesis. The basic characterization methods such as XPS, FT-IR, SEM, TEM and DRS were used to confirm the results. The characterization results show that the FeVO_4 nanorods are uniformly distributed and adhere to the thin layer of g-C_3N_4 and form a heterojunction structure at the contact interface between the two materials; the introduction of thin layer of g-C_3N_4 broadens the optical absorption threshold of FeVO_4 and improves the transport efficiency of the photogenerated carriers; and the visible-light catalysis decreases. The results showed that 20 wt% g-C_3N_4/FeVO_4 had the highest degradation efficiency (99.4%) for RhB after 6 h of photocatalytic reaction, while the degradation efficiency of thin layer g-C_3N_4 and FeVO_4 was 74.5% and 14.7% respectively. The photocatalytic mechanism analysis showed that the energy band position between g-C_3N_4 and FeVO_4 matched well, which was beneficial to the transmission and separation of photogenerated carriers, and thus conducting. (3) Ag_3VO_4/FeVO_4 photocatalyst was successfully prepared by in-situ synthesis. The material was characterized by XRD, XPS, SEM, TEM, DRS and PL to determine the apparent structure, morphology and optical properties. The characterization results showed that Ag_3VO_4 particles were uniformly distributed and adhered to FeVO_4 nanorods. The introduction of Ag_3VO_4 broadened the optical absorption threshold of FeVO_4 and improved the transport efficiency of photogenerated carriers. The results of visible-light photocatalytic degradation showed that 40 wt% Ag_3VO_4/FeVO_4 had the highest degradation efficiency (99.7%) for RhB after 3 h of photocatalytic reaction, while Ag_3VO_4 had the highest degradation efficiency (99.7%) for RhB. The photocatalytic degradation efficiency of Ag_3VO_4 and FeVO_4 was only 59.4%. The analysis of photocatalytic mechanism showed that the band positions of Ag_3VO_4 and FeVO_4 matched well, which was beneficial to the transmission and separation of photogenerated carriers, and the photocatalytic performance of Ag_3VO_4/FeVO_4 was greatly improved compared with that of monomer.
【學位授予單位】：江蘇大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：O643.36;X505
本文編號：2228768
[Abstract]:Since the last century, the problem of environmental pollution and energy shortage has become increasingly prominent, and the development of green energy is a trend. Among the many existing renewable resources, solar energy, as a green, safe and harmless resource with the largest reserves, has a very broad prospect of utilization. Nowadays, the research and development of new photocatalysts with high efficiency and practicability has become a hot spot in the field of photocatalysis. Heterojunction system can be constructed to develop new photocatalysts. New efficient semiconductor photocatalysts are commonly used as effective strategies. The purpose of this paper is to explore the synthesis of novel ferric vanadate (FeVO_4) catalysts and the application of their composite photocatalytic materials in environmental purification using iron-based ionic liquids as iron sources. Three novel photocatalytic materials, FeVO_4, gC_3N_4/FeVO_4 and Ag_3VO_4/FeVO_4, have been prepared by simple and controllable methods. The microstructure, morphology and optical properties of the photocatalytic materials were determined by various characterization methods. The photocatalytic activity and stability of the materials for degradation of organic pollutants were investigated under visible light irradiation. The specific research contents are as follows: (1) Mesoporous FeVO_4 nanorod photocatalyst was prepared by ionic liquid assisted hydrothermal method and calcination using 1-octyl-3-methylimidazolium ferric tetrachloride ([Omim] FeCl_4) as iron source. The results show that the mesoporous FeVO_4 nanorods prepared in ionic liquids have uniform morphology, uniform pore size (3-7 nm) distribution and large specific surface area (255.83 m2/g). The band gap of the catalyst is 2.35 eV and the absorption range of UV-Vis spectrum is wider. At the same time, the photocatalytic activity experiment shows that the mesoporous FeVO_4 nanorod-like Fenton photocatalyst can be used not only for the fast and effective degradation of colored dye (Rhodamine B), but also for the colorless organic pollutants of tetracycline. In addition, compared with the conventional inorganic salts as iron source, the synthesized FeVO_4 nano-materials have better surface properties, photoelectrochemical properties and photocatalytic activity. As a template, FeVO_4 plays an important role in the formation of nanorods and the regulation of their structure and properties. Finally, the possible mechanism of FeVO_4 as a three-way heterogeneous photocatalyst for the degradation of pollutants is proposed. (2) The g-C_3N_4/FeVO_4 photocatalyst was successfully prepared by hydrothermal synthesis. The basic characterization methods such as XPS, FT-IR, SEM, TEM and DRS were used to confirm the results. The characterization results show that the FeVO_4 nanorods are uniformly distributed and adhere to the thin layer of g-C_3N_4 and form a heterojunction structure at the contact interface between the two materials; the introduction of thin layer of g-C_3N_4 broadens the optical absorption threshold of FeVO_4 and improves the transport efficiency of the photogenerated carriers; and the visible-light catalysis decreases. The results showed that 20 wt% g-C_3N_4/FeVO_4 had the highest degradation efficiency (99.4%) for RhB after 6 h of photocatalytic reaction, while the degradation efficiency of thin layer g-C_3N_4 and FeVO_4 was 74.5% and 14.7% respectively. The photocatalytic mechanism analysis showed that the energy band position between g-C_3N_4 and FeVO_4 matched well, which was beneficial to the transmission and separation of photogenerated carriers, and thus conducting. (3) Ag_3VO_4/FeVO_4 photocatalyst was successfully prepared by in-situ synthesis. The material was characterized by XRD, XPS, SEM, TEM, DRS and PL to determine the apparent structure, morphology and optical properties. The characterization results showed that Ag_3VO_4 particles were uniformly distributed and adhered to FeVO_4 nanorods. The introduction of Ag_3VO_4 broadened the optical absorption threshold of FeVO_4 and improved the transport efficiency of photogenerated carriers. The results of visible-light photocatalytic degradation showed that 40 wt% Ag_3VO_4/FeVO_4 had the highest degradation efficiency (99.7%) for RhB after 3 h of photocatalytic reaction, while Ag_3VO_4 had the highest degradation efficiency (99.7%) for RhB. The photocatalytic degradation efficiency of Ag_3VO_4 and FeVO_4 was only 59.4%. The analysis of photocatalytic mechanism showed that the band positions of Ag_3VO_4 and FeVO_4 matched well, which was beneficial to the transmission and separation of photogenerated carriers, and the photocatalytic performance of Ag_3VO_4/FeVO_4 was greatly improved compared with that of monomer.
【學位授予單位】：江蘇大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：O643.36;X505
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