铁酸铋基复合光催化剂的制备及其光催化性能研究

发布时间：2018-08-10 21:04

【摘要】：光催化技术具有能耗低、成本低、无二次污染等优点,使其得到了研究者的广泛关注。然而现有的大部分光催化剂只能吸收紫外区域的高频光子能量,而对可见光区域以内的低频光子能量不能有效利用,并且在光催化反应过程中光生载流子容易二次复合。因此,扩宽光催化剂的可见光响应范围、抑制光生载流子的复合,对提高材料的光催化性能具有实际意义。BiFeO_3是一种钙钛矿型、窄带隙半导体材料,由于其具有良好的可见光催化活性,得到了人们的广泛研究。本文以PEG-20000为分散剂,采用一步水热法制备了纯相BiFeO_3半导体材料。以BiFeO_3为主催化剂,合成了复合光催化剂—Ag/AgCl/BiFeO_3和Ag/RGO/BiFeO_3,研究了两种复合光催化剂对模拟废水的降解效果,并建立了其对罗丹明B的光催化动力学模型。主要研究内容及结论如下:(1)以PEG-20000为分散剂,在温度160℃,水热反应10h,制备了BiFeO_3光催化剂,采用XRD、SEM、EDS、UV-Vis DRS等手段对其相态、结构、形貌、光吸收特性等进行了表征分析。结果表明,在碱性条件下制备BiFeO_3结晶度较好,其微观形貌尺寸大约35μm,微观尺寸均匀,光吸收能力较强。(2)以BiFeO_3、RGO和AgNO_3为原料,采用水热制备了Ag/RGO/BiFeO_3光催化剂;以BiFeO_3、AgCl为原料,在光照条件下合成了Ag/AgCl/BiFeO_3光催化剂。结果表明,在光照条件下,Ag/AgCl/BiFeO_3的光生载流子有两种迁移方式,当加入较少的AgCl时,AgCl显示的是直接带隙,光催化反应基本在BiFeO_3表面进行;当加入较多,AgCl时形成间接带隙,光催化反应在AgCl和BiFeO_3表面进行,反应活性位点相对于前者增多。分析发现,在后一种物质的光催化过程中,光电转化效率明显提高,光生电子-空穴对复合机率减少,载流子利用效率提高。(3)研究了Ag/RGO/BiFeO_3和Ag/AgCl/BiFeO_3光催化剂光催化降解染料废水和含酚废水的性能,结果表明Ag/RGO/BiFeO_3和Ag/AgCl/BiFeO_3对染料废水和含酚废水具有良好的光催化活性。活性自由基实验表明,羟基自由基、超氧自由基、光生空穴对光催化反应过程都有贡献,其中羟基自由基是主要活性物种。(4)建立了基于兰格缪尔的Ag/RGO/BiFeO_3、Ag/AgCl/BiFeO_3表面吸附有机污染物的模型方程式,分别为1/Q_e=10.2429/c_e+0.42384和1/Q_e=10.5017/c_e+0.33483。建立了基于Langmuir-Hinshewood的Ag/RGO/BiFeO_3、Ag/AgCl/BiFeO_3光催化降解有机污染物的动力学方程1/r0=32.5c_0+8.08和1/r_0=27.59/c_0+1.048。
[Abstract]:Photocatalytic technology has many advantages, such as low energy consumption, low cost and no secondary pollution. However, most photocatalysts can only absorb the high-frequency photon energy in the ultraviolet region, but the low-frequency photon energy in the visible region can not be used effectively, and photogenerated carriers are easy to recombine in the photocatalytic reaction. Therefore, broadening the range of visible light response of photocatalyst and restraining photogenerated carrier compounding is of practical significance to improve the photocatalytic performance of the materials. BiFeO3 is a perovskite-type, narrow-band gap semiconductor material. Because of its good visible light catalytic activity, it has been widely studied. In this paper, pure phase BiFeO_3 semiconductor materials were prepared by one step hydrothermal method with PEG-20000 as dispersant. Using BiFeO_3 as the main catalyst, the composite photocatalysts-Ag- / AgCl- / BiFeO3 and Ag- / RGO- BiFeO3 were synthesized. The degradation effect of two kinds of composite photocatalysts on simulated wastewater was studied, and the photocatalytic kinetic model of Rhodamine B was established. The main contents and conclusions are as follows: (1) BiFeO_3 photocatalyst was prepared at 160 鈩，

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