磷酸鉍基光催化材料的制備與性能研究
發(fā)布時間：2018-08-15 18:14
【摘要】：磷酸鉍是一種n型寬^/隙半導體材料,電子結(jié)構(gòu)獨特,^/隙寬在3.85 eV左右,對太陽光的響應在紫外線范圍內(nèi),其催化反應性能穩(wěn)定。對磷酸鉍的研究雖然已取得了一些成果,但還有很多不完善的地方。基于此,本文對磷酸鉍及其異質(zhì)結(jié)構(gòu)的制備和性能進行了深入探討,并進行了計算機模擬研究。(1)采用直接沉淀法、水熱法和二元溶劑熱法合成了不同形貌的磷酸鉍,通過沉淀轉(zhuǎn)化法制備了納米氧化銅,通過葡萄糖還原法制備了微米級氧化亞銅。采用室溫固相反應和水熱法合成了BiPO4/CuO和BiPO4/Cu2O異質(zhì)結(jié)構(gòu)材料,通過對比各樣品降解甲基橙的速率分析了各樣品催化活性的高低。(2)通過X射線衍射(XRD)確定了樣品的晶體結(jié)構(gòu),對樣品粒徑和結(jié)晶度進行了粗略估計,通過晶面指數(shù)、衍射角和相關(guān)計算公式判斷材料的吸收波長。在透射電鏡下觀察樣品形貌,通過樣品分散性、形貌、顆粒尺寸的比較及電子能譜EDS分析其催化性能變化的原因,得出六方相磷酸鉍的催化活性低于單斜相磷酸鉍,甘油含量的增加會對顆粒表面有包覆作用,阻止晶粒的結(jié)晶成長,有利于減小顆粒尺寸;納米粒子的小尺寸效應和表面效應會增大材料的禁帶寬度,但同時增大了表面反應活性中心的范圍,提高了催化過程的穩(wěn)定性。BiPO4/CuO異質(zhì)結(jié)的形成有利于催化性能的提高,但一價銅離子摻雜替換磷酸鉍晶格中的原子會使催化活性降低。(3)采用MS中CASTEP軟件包對材料的能帶以及電子態(tài)密度進行計算。利用第一性原理對磷酸鉍晶體模型進行了計算,坐標參數(shù)來源于Findit軟件,計算得到的磷酸鉍禁帶寬度為3.814 eV,與文獻結(jié)果一致;對氧化銅和氧化亞銅標準晶體結(jié)構(gòu)進行了計算,模型取自于Materials Studio的標準庫。采用廣義梯度近似對晶體結(jié)構(gòu)進行幾何優(yōu)化后,采用局域密度近似對優(yōu)化后的結(jié)構(gòu)進行能帶結(jié)構(gòu)、態(tài)密度等能量計算,都分別得到了與文獻中一致的結(jié)果。在MS中模擬金屬銅離子摻雜磷酸鉍,對異質(zhì)結(jié)中發(fā)生摻雜的情況進行能量計算,結(jié)果表明銅離子進入磷酸鉍晶體結(jié)構(gòu)中后,會降低磷酸鉍的禁帶寬度。
[Abstract]:Bismuth phosphate is a kind of n-type wide ^ / gap semiconductor material with unique electronic structure, ^ / gap width of about 3.85 EV. The response of bismuth phosphate to solar light is in the range of ultraviolet light, and its catalytic reaction performance is stable. Although some achievements have been made on bismuth phosphate, there are still many imperfections. In this paper, the preparation and properties of bismuth phosphate and its heterostructure are discussed, and the computer simulation is carried out. (1) bismuth phosphate with different morphologies has been synthesized by direct precipitation, hydrothermal and binary solvothermal methods. Nanocrystalline copper oxide was prepared by precipitation conversion method and micron copper oxide was prepared by glucose reduction method. BiPO4/CuO and BiPO4/Cu2O heterostructure materials were synthesized by solid state reaction at room temperature and hydrothermal method. The catalytic activity of each sample was analyzed by comparing the degradation rate of methyl orange. (2) the crystal structure of the samples was determined by X-ray diffraction (XRD). The particle size and crystallinity of the sample were roughly estimated, and the absorption wavelength of the material was determined by the crystal plane index, diffraction angle and correlation formula. The morphology of the samples was observed under transmission electron microscope. The results showed that the catalytic activity of hexagonal bismuth phosphate was lower than that of monoclinic bismuth phosphate. The increase of glycerol content will cover the grain surface, prevent the crystal growth, and decrease the particle size, and the small size effect and surface effect of nano-particles will increase the band gap of the material. But at the same time, the range of the active center of the surface reaction was increased, and the stability of the catalytic process was improved. The formation of BiPO _ 4 / CuO heterojunction was beneficial to the improvement of the catalytic performance. However, substitution of atoms in bismuth phosphate lattice by doping of monovalent copper ions will decrease the catalytic activity. (3) the energy bands and the electronic density of states of the materials are calculated by CASTEP software package in MS. The crystal model of bismuth phosphate is calculated by first principle. The coordinate parameters are derived from Findit software. The calculated bandgap of bismuth phosphate is 3.814 EV, which is in agreement with the results in literature, and the crystal structures of copper oxide and copper oxide are calculated. The model is taken from the standard library of Materials Studio. After geometric optimization of crystal structure by generalized gradient approximation, the energy of the optimized structure is calculated by using local density approximation. The results are in agreement with those obtained in the literature. The energy calculation of the doping of bismuth phosphate in heterojunction by simulated metal copper ion doping in MS shows that the band gap of bismuth phosphate decreases when copper ions enter the crystal structure of bismuth phosphate.
【學位授予單位】：石家莊鐵道大學
【學位級別】：碩士
【學位授予年份】：2015
【分類號】：TQ135.32;O643.36
[Abstract]:Bismuth phosphate is a kind of n-type wide ^ / gap semiconductor material with unique electronic structure, ^ / gap width of about 3.85 EV. The response of bismuth phosphate to solar light is in the range of ultraviolet light, and its catalytic reaction performance is stable. Although some achievements have been made on bismuth phosphate, there are still many imperfections. In this paper, the preparation and properties of bismuth phosphate and its heterostructure are discussed, and the computer simulation is carried out. (1) bismuth phosphate with different morphologies has been synthesized by direct precipitation, hydrothermal and binary solvothermal methods. Nanocrystalline copper oxide was prepared by precipitation conversion method and micron copper oxide was prepared by glucose reduction method. BiPO4/CuO and BiPO4/Cu2O heterostructure materials were synthesized by solid state reaction at room temperature and hydrothermal method. The catalytic activity of each sample was analyzed by comparing the degradation rate of methyl orange. (2) the crystal structure of the samples was determined by X-ray diffraction (XRD). The particle size and crystallinity of the sample were roughly estimated, and the absorption wavelength of the material was determined by the crystal plane index, diffraction angle and correlation formula. The morphology of the samples was observed under transmission electron microscope. The results showed that the catalytic activity of hexagonal bismuth phosphate was lower than that of monoclinic bismuth phosphate. The increase of glycerol content will cover the grain surface, prevent the crystal growth, and decrease the particle size, and the small size effect and surface effect of nano-particles will increase the band gap of the material. But at the same time, the range of the active center of the surface reaction was increased, and the stability of the catalytic process was improved. The formation of BiPO _ 4 / CuO heterojunction was beneficial to the improvement of the catalytic performance. However, substitution of atoms in bismuth phosphate lattice by doping of monovalent copper ions will decrease the catalytic activity. (3) the energy bands and the electronic density of states of the materials are calculated by CASTEP software package in MS. The crystal model of bismuth phosphate is calculated by first principle. The coordinate parameters are derived from Findit software. The calculated bandgap of bismuth phosphate is 3.814 EV, which is in agreement with the results in literature, and the crystal structures of copper oxide and copper oxide are calculated. The model is taken from the standard library of Materials Studio. After geometric optimization of crystal structure by generalized gradient approximation, the energy of the optimized structure is calculated by using local density approximation. The results are in agreement with those obtained in the literature. The energy calculation of the doping of bismuth phosphate in heterojunction by simulated metal copper ion doping in MS shows that the band gap of bismuth phosphate decreases when copper ions enter the crystal structure of bismuth phosphate.
【學位授予單位】：石家莊鐵道大學
【學位級別】：碩士
【學位授予年份】：2015
【分類號】：TQ135.32;O643.36
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