磷酸鉍基復合材料的制備及性能研究
發(fā)布時間：2018-10-30 11:01
【摘要】：近幾年來,生態(tài)環(huán)境污染越來越嚴重,而傳統(tǒng)的治理方法因其處理成本較高、周期長、效率低等缺點不能滿足要求。半導體光催化劑因其在環(huán)境治理方面的優(yōu)勢引發(fā)了越來越多的關(guān)注。作為一種含氧酸鹽催化劑,BiPO4展現(xiàn)出良好的光催化性能,然而其光響應范圍位于紫外光區(qū),光生電子-空穴對分離效率較低,故需要對BiPO4進行改性來提高它的催化性能,擴展光響應范圍。本文中采用一步水熱法合成的BiPO4納米棒為基體,通過非金屬元素摻雜、貴金屬修飾、半導體復合等方法對BiPO4進行改性,結(jié)合一些測試手段,對材料的晶型、微觀形貌、吸光性能進行表征,對材料的光電轉(zhuǎn)化性能和體系中的光生電子-空穴對的分離效率和載流子的遷移速率進行測試分析,以甲基橙(MO)為模擬污染物,對材料的光催化性能進行測試。(1)以NaN3為N源,通過一步水熱法合成了不同摻雜比的N摻雜BiPO4 (N-BiPO4)。利用第一性原理,對于樣品的價帶和導帶的能帶位置和電子態(tài)密度進行模擬計算。實驗結(jié)果發(fā)現(xiàn),BiPO4和N-BiPO4的晶型結(jié)構(gòu)相同,N3-取代了BiPO4中的02-之后,材料的光吸收邊際發(fā)生了微弱的紅移,樣品的形貌也發(fā)生了變化。在紫外光的照射下,與純的BiPO4相比,N/Bi摩爾比為0.2的樣品的催化效率提升了50%,原因歸結(jié)為N3-的引入限制了光生電子和光生空穴的再復合,然而,過量的摻雜反而會降低樣品的光催化活性。(2)在有機溶液C2H5OH中通過原位生長的方法合成了核殼結(jié)構(gòu)Ag3PO4/N-BiPO4光催化劑,通過在模擬太陽光照射下降解MO的效率來評價樣品的光催化效率,Ag3PO4/N-BiPO4在光照40min后降解了95%的污染物。體系中光催化活性的提高歸因于N摻雜之后,引入的N-O雜質(zhì)能級促進了電子-空穴對的分離效率。同時,Ag3PO4和N-BiPO4間經(jīng)過原位反應之后生成的化學鍵,加速了電子-空穴對的分離速率。(3)以硫脲為前驅(qū)體制備出了g-C3N4,在不同的反應溫度下通過三步反應法制備出了Z型g-C3N4/Au/BiPO4分層體系。通過降解MO,評價材料的光電性能和光催化性能。與g-C3N4、BiPO4和g-C3N4/BiPO4相比,樣品g-C3N4/Au/BiPO4表現(xiàn)出了良好的光電化學性能和光催化性能。交流阻抗譜和光電流測試結(jié)果都證明了,g-C3N4/Au/BiPO4中的光電子分離速率和遷移速率較高。樣品g-C3N4/Au/BiPO4性能的提升歸因于體系中構(gòu)造的Z型結(jié)構(gòu),在Z型體系中,經(jīng)光照之后所產(chǎn)生的載流子的分離速率加快,阻止了光照后產(chǎn)生的電子和空穴的又一次結(jié)合。值得指出的是,Au顆粒不僅作為一種固態(tài)電介質(zhì),而且在光照下吸收光子發(fā)生等離子共振效應。(4)以Bi(NO3)3·5H2O為原料,采用水熱法制備出P-N型Bi2O3/BiPO4異質(zhì)結(jié),再將g-C3N4包覆在其表面,形成g-C3N4/Bi203/BiP04材料體系,研究了樣品BiPO4、g-C3N4/BiPO4、Bi2O3/BiPO4和g-C3N4/Bi2O3/BiPO4的光學性能、形貌和光電化學性能。在模擬太陽光照射160min后樣品g-C3N4/Bi2O3/BiPO4的降解效率達到90%,遠高于其他樣品。交流阻抗譜和光電流測試結(jié)果都證明了,g-C3N4/Bi2O3/BiPO4中的光電子分離速率和遷移速率較高�？偟膩碚f,g-C3N4的加入,引領(lǐng)P型Bi2O3上剩余的電子與g-C3N4價帶位置的光生空穴進行復合,留下氧化和還原能力更強的光生載流子促進活性基團的產(chǎn)生。
[Abstract]:In recent years, the ecological environment pollution is becoming more and more serious, and the traditional treatment method can not meet the requirements because of its high processing cost, long cycle and low efficiency. Semiconductor photocatalyst has attracted more and more attention because of its advantages in environmental governance. As a salt catalyst, BiPO4 exhibits good photocatalytic performance. However, the light response range is located in the ultraviolet region, and the light-generating electron-hole has lower separation efficiency. Therefore, BiPO4 needs to be modified to improve its catalytic performance and extend the light response range. BiPO4 nano-rod synthesized by one-step hydrothermal method is used as the substrate, and BiPO4 is modified by non-metal element doping, noble metal modification, semiconductor recombination and the like, and the crystal type, the micro-morphology and the light absorption performance of the material are characterized by combining with some testing methods. The photoelectric conversion performance of materials and the separation efficiency of the photogenic electron-hole pairs in the system and the migration rate of carriers were tested and analyzed, and the photocatalytic properties of the materials were tested with methyl orange (MO) as the simulated pollutant. (1) N-doped BiPO4 (N-BiPO4) with different doping ratios was synthesized by one-step hydrothermal method with NaN3 as N source. With the first principle, the energy band position and electron density of the valence band and conduction band of the sample are simulated. The experimental results show that the crystal structure of BiPO4 and N-BiPO4 is the same, N3-substituted for 02-in BiPO4, the light absorption margin of the material has changed slightly, and the morphology of the sample also changes. Under the irradiation of ultraviolet light, the catalytic efficiency of N/ Bi molar ratio of 0. 2 was increased by 50% as compared with pure BiPO4, because the introduction of N3-was restricted to recombination of light-generating electrons and light-generating holes, however, excessive doping would decrease the photocatalytic activity of samples. (2) The Ag3PO4/ N-BiPO4 photocatalyst of nuclear shell structure was synthesized by in situ growth method in the organic solution C2H5OH, and the photocatalytic efficiency of the sample was evaluated by simulating the efficiency of the degradation solution MO. Ag3PO4/ N-BiPO4 degraded 95% of the pollutants after illumination for 40min. The enhancement of photocatalytic activity in the system is due to N doping, and the introduced N-O impurity level promotes the separation efficiency of electron-hole pairs. Meanwhile, the chemical bonds generated after the in situ reaction between Ag3PO4 and N-BiPO4 accelerated the separation rate of electron-hole pairs. (3) The g-C3N4/ Au/ BiPO4 layered system was prepared by three-step reaction at different reaction temperatures. The photoelectric properties and photocatalytic properties of the materials were evaluated by degradation of MO. Compared with the g-C3N4, BiPO4 and g-C3N4/ BiPO4, the sample g-C3N4/ Au/ BiPO4 exhibited good photoelectrochemical performance and photocatalytic performance. The results of AC impedance spectroscopy and photocurrent measurements show that the photoelectron separation rate and migration rate in g-C3N4/ Au/ BiPO4 are high. The performance of the sample g-C3N4/ Au/ BiPO4 is attributed to the Z-type structure constructed in the system. In the Z-type system, the separation rate of carriers generated after illumination is accelerated, and the electrons and holes generated after illumination are prevented from being combined again. It is worth noting that Au particles not only act as a solid dielectric but also absorb photons under illumination to generate a plasma plume effect. (4) Bi (NO3) 3 路 5H2O was used as raw material, P-N Bi2O3/ BiPO4 heterojunction was prepared by hydrothermal method, and g-C3N4 was coated on its surface to form g-C3N4/ Bi203/ BiP04 material system. The optical properties, morphology and photoelectrochemical properties of BiPO4, g-C3N4/ BiPO4, Bi2O3/ BiPO4 and g-C3N4/ Bi2O3/ BiPO4 were studied. The degradation efficiency of g-C3N4/ Bi2O3/ BiPO4 was up to 90% after irradiation with simulated sunlight for 160min, much higher than that of other samples. The results of AC impedance spectroscopy and photocurrent tests show that the photoelectron separation rate and migration rate in g-C3N4/ Bi2O3/ BiPO4 are high. In general, the addition of the g-C3N4 leads to recombination of the remaining electrons on the P-type Bi2O3 with the light-generating holes in the valence band position of the g-C3N4, leaving more light-generating carriers with higher oxidation and reduction ability to promote the generation of the active groups.
【學位授予單位】：陜西科技大學
【學位級別】：碩士
【學位授予年份】：2016
【分類號】：O643.36;O644.1
本文編號：2299820
[Abstract]:In recent years, the ecological environment pollution is becoming more and more serious, and the traditional treatment method can not meet the requirements because of its high processing cost, long cycle and low efficiency. Semiconductor photocatalyst has attracted more and more attention because of its advantages in environmental governance. As a salt catalyst, BiPO4 exhibits good photocatalytic performance. However, the light response range is located in the ultraviolet region, and the light-generating electron-hole has lower separation efficiency. Therefore, BiPO4 needs to be modified to improve its catalytic performance and extend the light response range. BiPO4 nano-rod synthesized by one-step hydrothermal method is used as the substrate, and BiPO4 is modified by non-metal element doping, noble metal modification, semiconductor recombination and the like, and the crystal type, the micro-morphology and the light absorption performance of the material are characterized by combining with some testing methods. The photoelectric conversion performance of materials and the separation efficiency of the photogenic electron-hole pairs in the system and the migration rate of carriers were tested and analyzed, and the photocatalytic properties of the materials were tested with methyl orange (MO) as the simulated pollutant. (1) N-doped BiPO4 (N-BiPO4) with different doping ratios was synthesized by one-step hydrothermal method with NaN3 as N source. With the first principle, the energy band position and electron density of the valence band and conduction band of the sample are simulated. The experimental results show that the crystal structure of BiPO4 and N-BiPO4 is the same, N3-substituted for 02-in BiPO4, the light absorption margin of the material has changed slightly, and the morphology of the sample also changes. Under the irradiation of ultraviolet light, the catalytic efficiency of N/ Bi molar ratio of 0. 2 was increased by 50% as compared with pure BiPO4, because the introduction of N3-was restricted to recombination of light-generating electrons and light-generating holes, however, excessive doping would decrease the photocatalytic activity of samples. (2) The Ag3PO4/ N-BiPO4 photocatalyst of nuclear shell structure was synthesized by in situ growth method in the organic solution C2H5OH, and the photocatalytic efficiency of the sample was evaluated by simulating the efficiency of the degradation solution MO. Ag3PO4/ N-BiPO4 degraded 95% of the pollutants after illumination for 40min. The enhancement of photocatalytic activity in the system is due to N doping, and the introduced N-O impurity level promotes the separation efficiency of electron-hole pairs. Meanwhile, the chemical bonds generated after the in situ reaction between Ag3PO4 and N-BiPO4 accelerated the separation rate of electron-hole pairs. (3) The g-C3N4/ Au/ BiPO4 layered system was prepared by three-step reaction at different reaction temperatures. The photoelectric properties and photocatalytic properties of the materials were evaluated by degradation of MO. Compared with the g-C3N4, BiPO4 and g-C3N4/ BiPO4, the sample g-C3N4/ Au/ BiPO4 exhibited good photoelectrochemical performance and photocatalytic performance. The results of AC impedance spectroscopy and photocurrent measurements show that the photoelectron separation rate and migration rate in g-C3N4/ Au/ BiPO4 are high. The performance of the sample g-C3N4/ Au/ BiPO4 is attributed to the Z-type structure constructed in the system. In the Z-type system, the separation rate of carriers generated after illumination is accelerated, and the electrons and holes generated after illumination are prevented from being combined again. It is worth noting that Au particles not only act as a solid dielectric but also absorb photons under illumination to generate a plasma plume effect. (4) Bi (NO3) 3 路 5H2O was used as raw material, P-N Bi2O3/ BiPO4 heterojunction was prepared by hydrothermal method, and g-C3N4 was coated on its surface to form g-C3N4/ Bi203/ BiP04 material system. The optical properties, morphology and photoelectrochemical properties of BiPO4, g-C3N4/ BiPO4, Bi2O3/ BiPO4 and g-C3N4/ Bi2O3/ BiPO4 were studied. The degradation efficiency of g-C3N4/ Bi2O3/ BiPO4 was up to 90% after irradiation with simulated sunlight for 160min, much higher than that of other samples. The results of AC impedance spectroscopy and photocurrent tests show that the photoelectron separation rate and migration rate in g-C3N4/ Bi2O3/ BiPO4 are high. In general, the addition of the g-C3N4 leads to recombination of the remaining electrons on the P-type Bi2O3 with the light-generating holes in the valence band position of the g-C3N4, leaving more light-generating carriers with higher oxidation and reduction ability to promote the generation of the active groups.
【學位授予單位】：陜西科技大學
【學位級別】：碩士
【學位授予年份】：2016
【分類號】：O643.36;O644.1
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