氧化铁、石墨烯复合物的光催化与吸附性能研究

发布时间：2018-10-10 07:07

【摘要】：铁的氧化物由于拥有丰富的原料来源、对环境没有污染、安全性好以及优异的光吸收性能等优点,得到了研究者的重视。其中,α-Fe_2O_3是一种化学性质稳定、禁带宽度较窄,拥有很强的可见光吸收效率的半导体材料;通过控制反应条件来合成α-Fe_2O_3纳米颗粒,并探究形貌与尺寸对其光电性能的影响是目前的研究热点之一。另外,Fe_3O_4磁性纳米颗粒,在处理工业污水中的有毒重金属离子方面的应用也非常广泛。石墨烯(Graphene)是一种二维碳材料,有着优异的光学、热学、电学以及机械性能,是研究非常热门的新型材料。还原氧化石墨烯(RGO)与石墨烯相比,其表面含有许多含氧官能团,这些含氧官能团以及sp2杂化区域都能成为某些半导体颗粒的复合位点,这为制备晶粒尺寸更小、分散性更高的半导体复合物提供了可能。α-Fe_2O_3通过与RGO复合,可以有效增大比表面积、拓宽光谱吸收范围以及降低光生电子空穴对复合率,有利于光催化性能的提高。Fe_3O_4纳米颗粒通过与RGO复合,有利于增大其比表面积,从而增加吸附剂表面的吸附位点,吸附效果因此会得到提高。本论文主要的研究内容有以下几个方面:1、分别制备出了棒状、米粒状、纺锤形以及斜六方体四种不同形貌与尺寸的α-Fe_2O_3颗粒,并探究形貌与尺寸对α-Fe_2O_3颗粒的光电性能以及光催化性能的影响。实验结果表明:纳米尺寸的α-Fe_2O_3颗粒的光催化效果好于微米尺寸的;同为纳米尺寸的几种不同形貌α-Fe_2O_3颗粒的光催化效果也不一样,这主要是因为不同形貌的α-Fe_2O_3其表面暴露晶面不一样,电子传输的路径以及速率都不同,电化学测试显示:纺锤形α-Fe_2O_3的电子传输速率快于米粒状和斜六方体α-Fe_2O_3,这与光催化测试结果相吻合。2、通过水热法制备出了α-Fe_2O_3/RGO复合物,并探究RGO的复合对α-Fe_2O_3颗粒光催化性能的影响。光催化结果显示:当α-Fe_2O_3与RGO复合后,它对甲基橙溶液的光降解率从59%左右提高到接近100%;紫外可见吸收光谱结果显示:复合物对光谱的吸收范围从600 nm拓宽到了900 nm,表明了复合物提高了对可见光部分的吸收;同时,复合物中光生电子空穴对的复合率减小,导电能力提高,有利于更多光生电子传输到表面参与光催化反应。3、分别通过共沉淀法制备Fe_3O_4纳米磁性颗粒以及原位生长法制备Fe_3O_4与RGO的复合物,并用CTAB修饰后作为吸附剂对铬酸钾进行吸附。探究了时间、温度、PH值以及石墨烯复合比例对吸附性能的影响。结果表明:该吸附反应为放热反应,所以在低温下吸附效果更好;吸附反应的速率非常快,在30 min内即可达到吸附饱和;当PH值在3.5附近时,以Fe_3O_4与RGO的2:1复合物作为吸附剂对铬酸钾溶液进行吸附,在常温下,每克的吸附容量可达251 mg。
[Abstract]:Iron oxides have attracted much attention due to their abundant sources of raw materials, no pollution to the environment, good safety and excellent light absorption properties. Among them, 伪 -Fe _ 2O _ 3 is a kind of semiconductor material with stable chemical properties, narrower band gap and high visible light absorption efficiency; 伪 -Fe _ 2O _ 3 nanoparticles are synthesized by controlling the reaction conditions. It is one of the hot research topics to explore the influence of morphology and size on its optoelectronic properties. In addition, Fe3O4 magnetic nanoparticles are widely used in the treatment of toxic heavy metal ions in industrial sewage. Graphene (Graphene) is a two-dimensional carbon material with excellent optical, thermal, electrical and mechanical properties. Compared with graphene, reduced graphene (RGO) has many oxygen-containing functional groups on its surface. These oxygen-containing functional groups and the sp2 hybrid region can be used as composite sites for some semiconductor particles, which makes the grain size smaller. 伪 -Fe _ 2O _ 3 can effectively increase the specific surface area, widen the spectral absorption range and reduce the recombination rate of photogenerated electron holes by compounding with RGO. Fe3O4 nanoparticles can increase the specific surface area by compounding with RGO, thus increasing the adsorption sites on the surface of adsorbent, so the adsorption effect will be improved. The main research contents of this thesis are as follows: 1. Four kinds of 伪 -Fe _ S _ 2O _ 3 particles, such as rod, rice grain, spindle-shaped and oblique hexagonal, have been prepared. The effects of morphology and size on the optoelectronic and photocatalytic properties of 伪 -Fe _ S _ 2O _ 3 particles were investigated. The experimental results show that the photocatalytic effect of nano-sized 伪 -Fe2O3 particles is better than that of micron size, and the photocatalytic effect of 伪 -Fe2O3 particles with the same nanometer size is different. This is mainly due to the fact that the surface of 伪 -Fe _ 2O _ 3 with different morphologies is different in exposed crystal planes, and the path and rate of electron transport are different. Electrochemical tests showed that the electron transport rate of spindle-shaped 伪 -Fe2O3 was faster than that of 伪 -Fe2O3, which coincided with the photocatalytic test results. The 伪 -Fe2O3 / RGO complex was prepared by hydrothermal method, and the effect of RGO composite on the photocatalytic performance of 伪 -Fe2O3 / RGO particles was investigated. The photocatalytic results showed that when 伪 -Fe _ s _ p _ 2O _ 3 was combined with RGO, The photodegradation rate of methyl orange solution was increased from about 59% to nearly 100%. The UV-Vis absorption spectra showed that the absorption range of the complex was widened from 600 nm to 900 nm,. The recombination rate of photogenerated electron hole pair in the composite decreases and the conductivity increases. More photogenerated electrons were transported to the surface to participate in photocatalytic reaction. The magnetic nanoparticles of Fe_3O_4 were prepared by co-precipitation method and the complexes of Fe_3O_4 and RGO were prepared by in-situ growth method. Potassium chromate was adsorbed by CTAB as adsorbent. The effects of time, temperature, PH value and graphene ratio on adsorption properties were investigated. The results show that the adsorption reaction is exothermic, so the adsorption effect is better at low temperature, the rate of adsorption reaction is very fast, and the adsorption saturation can be reached within 30 min. When the PH value is near 3.5, The 2:1 complex of Fe_3O_4 and RGO was used as adsorbent to adsorb potassium chromate solution. At room temperature, the adsorption capacity per gram can reach 251 mg..
【学位授予单位】：中国石油大学(华东)
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TB383.1

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