【摘要】：作為新型可見光光催化劑,Bi2WO6被認(rèn)為是鉍系化合物中具有最佳光催化活性的半導(dǎo)體材料之一。盡管通過優(yōu)化原料和制備工藝來改變Bi2WO6的尺寸和形貌來進(jìn)一步提高其光催化降解污染物的效果,但光生載流子復(fù)合率高、可見光響應(yīng)范圍窄等缺點,還有待于進(jìn)一步提高。因此,對純的Bi2WO6進(jìn)行摻雜、復(fù)合、貴金屬修飾來改變其組分以進(jìn)一步提高其可見光光催化活性仍是研究的主流方向。本論文從提高純的Bi2WO6光催化降解活性這一迫切需要解決的問題出發(fā),采用半導(dǎo)體復(fù)合形成異質(zhì)結(jié)的方式,通過復(fù)合相的選擇和控制Bi2W06基異質(zhì)結(jié)的形貌來解決其在實際應(yīng)用中存在的問題。相關(guān)研究結(jié)果如下：(1)以Bi(NO3)3·5H2O作為鉍源,Na2WO4·2H2O作為鎢源,分別采用水熱-煅燒法和一步水熱法制備花狀WO3/Bi2WO6 n-n型異質(zhì)結(jié)微球。研究了WO3的修飾量對產(chǎn)物結(jié)構(gòu)、形貌、光催化活性等的影響。通過兩種方法的對比得知,一步法所制備的花狀WO3/Bi2WO6異質(zhì)結(jié)微球的納米片更薄更密、比表面積更大、可提供更多的活性位點,有利于光的吸收和污染物的吸附,并且制備工藝簡單可降低成本,可作為后續(xù)形成三元異質(zhì)結(jié)的基體材料。(2)以一步法所制備的花狀WO3/Bi2WO6 n-n型異質(zhì)結(jié)微球為基體,通過浸漬-煅燒工藝制備一系列不同CuO含量修飾的CuO-WO3-Bi2WO6p-n-n型雙異質(zhì)結(jié)復(fù)合體系。UV-vis結(jié)果表明隨著CuO修飾量的增加,CuO-WO3-Bi2WO6雙異質(zhì)結(jié)將Bi2WO6的光吸收范圍拓展至近紅外區(qū)。光催化結(jié)果表明CuO-WO3-Bi2WO6三元復(fù)合體系的降解效果明顯高于純的Bi2WO6和其他Bi2WO6基二元異質(zhì)結(jié),并且適量的CuO能使WO3/Bi2WO6降解RhB的效果最佳。(3)采用水熱-液相法制備BiOBr-WO3-Bi2WO6層級結(jié)構(gòu)。SEM結(jié)果表明BiOBr的復(fù)合并沒有改變WO3/Bi2WO6異質(zhì)結(jié)的花狀超結(jié)構(gòu),且適量BiOBr均勻的分散在WO3/Bi2WO6花狀結(jié)構(gòu)的表面。在可見光的照射下,BiOBr-WO3-Bi2WO6三元層級結(jié)構(gòu)降解RhB的光催化活性明顯高于Bi2WO6和WO3/Bi2WO6,這主要歸結(jié)于花狀結(jié)構(gòu)大的比表面積,界面的緊密接觸和匹配的能帶位置,這些都有利于光生電子-空穴對的有效分離及光催化效果的提高。(4)以WO3/Bi2WO6為基體,采用沉淀法制備出了一系列花狀A(yù)g3PO4-WO3-Bi2WO6三元體系在很大程度上提高了VO3/Bi2WO6對可見光的吸收能力。光催化實驗表明適量Ag3PO4修飾的WO3/Bi2WO6降解RhB的效果最佳,這是因為適量Ag3PO4納米顆粒均勻的分散在花狀WO3/Bi2WO6微球和納米片上,并且Ag3PO4-WO3-Bi2WO6三元復(fù)合光催化材料中的導(dǎo)帶可形成層級結(jié)構(gòu),電子可從Bi2WO6的導(dǎo)帶轉(zhuǎn)移到Ag3PO4,接著轉(zhuǎn)移到WO3的導(dǎo)帶,進(jìn)而有效促進(jìn)光生載流子的分離�？傊�,本論文研究了一系列新型花狀WO3/Bi2WO6基三元異質(zhì)結(jié)光催化劑,該催化劑有效地提高了WO3/Bi2WO6對可見光的吸收以及量子效率。
[Abstract]:As a new visible photocatalyst, Bi2WO6 is considered to be one of the semiconductor materials with the best photocatalytic activity in bismuth compounds. Although the size and morphology of Bi2WO6 can be further improved by optimizing the raw material and preparation process, the high photogenerated carrier recombination rate and narrow visible light response range need to be further improved. Therefore, doping, recombination and noble metal modification of pure Bi2WO6 to change its components to further improve its visible photocatalytic activity are still the main research direction. In this thesis, to improve the photocatalytic degradation activity of pure Bi2WO6, we adopt the method of semiconductor recombination to form heterojunction, which is an urgent problem to be solved in order to improve the photocatalytic degradation activity of Bi2WO6. The problems existing in the practical application of Bi2W06-based heterojunction are solved by selecting the composite phase and controlling the morphology of the heterojunction. The results are as follows: (1) using Bi (NO3) 3 路5H2O as bismuth source and Na2WO4 路2H2O as tungsten source, flower WO3/Bi2WO6 n-type heterojunction microspheres were prepared by hydrothermal-calcination method and one-step hydrothermal method, respectively. The effects of the modification amount of WO3 on the structure, morphology and photocatalytic activity of the products were studied. Through the comparison of the two methods, it was found that the nanospheres of flower-like WO3/Bi2WO6 heterojunction microspheres prepared by one-step method were thinner and denser, and the specific surface area was larger, which could provide more active sites and facilitate the absorption of light and the adsorption of pollutants. Moreover, the simple preparation process can reduce the cost and can be used as the matrix material for the subsequent formation of ternary heterojunction. (2) the flower-like WO3/Bi2WO6 n-n heterojunction microspheres prepared by one-step method are used as the matrix. A series of CuO-WO3-Bi2WO6p-n- n-type double heterojunction composite systems modified with different CuO content were prepared by impregnation-calcination process. The results of UV-vis showed that with the increase of CuO content, the amount of CuO was increased. CuO-WO3-Bi2WO6 double heterojunction extends the optical absorption range of Bi2WO6 to near infrared region. The photocatalytic results showed that the degradation efficiency of CuO-WO3-Bi2WO6 ternary composite system was significantly higher than that of pure Bi2WO6 and other Bi2WO6-based binary heterojunctions. Moreover, appropriate amount of CuO could make WO3/Bi2WO6 degrade RhB best. (3) BiOBr-WO3-Bi2WO6 hierarchical structure was prepared by hydrothermal-liquid phase method. SEM results showed that the composite of BiOBr did not change the flower-like superstructure of WO3/Bi2WO6 heterojunction. And appropriate amount of BiOBr dispersed evenly on the surface of WO3/Bi2WO6 flower-like structure. Under visible light irradiation, the photocatalytic activity of BiOBr-WO3-Bi2WO6 ternary hierarchy degradation of RhB is obviously higher than that of Bi2WO6 and WO3/Bi2WO6, which is mainly attributed to the large specific surface area of flower-like structure, the close contact of the interface and the matching position of energy band. All of these are beneficial to the effective separation of photogenerated electron-hole pairs and the improvement of photocatalytic efficiency. (4) WO3/Bi2WO6 as the matrix. A series of flowered Ag3PO4-WO3-Bi2WO6 ternary systems were prepared by precipitation method to improve the absorption ability of VO3/Bi2WO6 to visible light to a great extent. Photocatalytic experiments showed that the appropriate amount of Ag3PO4 modified WO3/Bi2WO6 had the best effect on the degradation of RhB, which was due to the uniform dispersion of appropriate amount of Ag3PO4 nanoparticles on flower-like WO3/Bi2WO6 microspheres and nanoparticles. In addition, the conduction band in Ag3PO4-WO3-Bi2WO6 ternary composite photocatalyst can form a hierarchical structure, and electrons can transfer from Bi2WO6 band to Ag3PO4, band and then to WO3 band, thus effectively promote the separation of photogenerated carriers. In conclusion, a series of novel floral WO3/Bi2WO6-based ternary heterojunction photocatalysts have been studied in this paper, which can effectively improve the absorption of visible light and the quantum efficiency of WO3/Bi2WO6.
【學(xué)位授予單位】：陜西科技大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2016
【分類號】：O643.36;O644.1

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