Synthesis of novel p-n heterojunction m-Bi_2O_4/BiOCl nanocomposite with excellent photocatalytic activity through ion-etching method

离子刻蚀法制备具有高效催化性能的m-Bi_2O_4/BiOCl p-n异质结催化剂（英文）

A novel p‐n heterostructure photocatalyst m‐Bi2O4/BiOCl was successfully synthetized through a facile ion‐etching method.Via adjusting the added volume of HCl solution,a series of different ratios of composite photocatalysts were obtained.The as‐prepared samples of physical,chemical and optical characteristics were examined by X‐ray diffraction,scanning electron microscope,transmission electron microscope,energy dispersive X‐ray spectroscopy,selected‐area electron diffraction,Fourier transform infrared absorption,Raman microscope,N2 adsorption‐desorption,X‐ray photoelectron spectroscopy and UV‐vis spectrum technologies.The photocatalysts showed high degradation rate and complete mineralization ability for methyl orange and tetracycline solution under visible light.The reaction rate constant of m‐Bi2O4/BiOCl for methyl orange was 52.28 times higher than that of BiOCl.The characterization presented a good stability of materials.Furthermore,the photocurrent response test certified that the heterostructure effectively accelerated the separation and migration of photo‐generated carries.The scavenger experiments evidenced that hole(h+)and superoxide radical(?O2?)were the primary active radicals.A possible photocatalytic mechanism was proposed.This work provided an alternative photocatalyst applied to water environmental remediation.

光催化技术作为一种绿色的环境修复方法而备受关注,它直接利用太阳光作为能源,可有效地降解有机污染物.铋系化合物具有化学稳定性强、抑制光腐蚀、无毒和来源广泛等优点,被认为是一种环境友好的光催化剂,广泛用于降解染料、苯酚和其他有机污染物.BiOCl具有独特的内部结构,可形成内电场促进电子和空穴的移动,抑制其复合.但是BiOCl本身带隙能过大,只能被紫外光激发,对光的利用率较低,限制了其在环境治理中的应用.近两年来发现,m-Bi_2O_4带隙能小,可吸收大波长的可见光,催化性能好.为充分发挥m-Bi_2O_4的优异性质,改善BiOCl的性能,本文将BiOCl与m-Bi_2O_4复合制得新型催化剂,降低催化剂的带隙能,增强对光的吸收,提高量子效率,促进光生载流子的分离,抑制电子-空穴复合,从而提高催化剂性能,加速降解反应进程.本文通过离子刻蚀法制备具有p-n异质结的m-Bi_2O_4/BiOCl复合催化剂,通过调节HCl的加入量制得不同比例的催化剂,并考察了其在可见光下催化降解MO(甲基橙)的性能.结果表明,m-Bi_2O_4/BiOCl复合催化剂在可见光下表现出优异的光催化降解MO和四环素的性能,反应10内min可降解95%的MO,反应150 min内四环素的降解率为85.5%;该复合催化剂对MO和四环素的光降解效率分别是纯BiOCl的52.3和4.9倍.活性自由基捕获实验表明,空穴在光催化降解过程中起最主要的作用,其次是超氧自由基,羟基自由基对降解反应也起到一定的作用.采用XRD,SEM,EDS,TEM,SAED,FT-IR,Raman,XPS,BET,UV-vis和光电流等表征方法分析了催化剂的结构、形貌、化学组成、元素价态、孔结构、带隙能、光学性质和载流子复合效率.结果表明,与BiOCl的斜四方体相比,m-Bi_2O_4/BiOCl复合催化剂呈现纳米片状结构,氯离子进入晶格的内部,颜色也由BiOCl原来的深褐色变为黄色.m-Bi_2O_4/BiOCl为介孔结构,比表面积为112.90 m^2/g,其吸收波长红移,由紫外光扩展至可见光区域,带隙能也由3.2降低为1.87 eV,能带弯曲形成p-n异质结,提高了电子-空穴的转移效率,抑制其复合;m-Bi_2O_4/BiOCl的光电流密度高于m-Bi_2O_4和BiOCl,电子-空穴的分离效率更高,因而其催化性能更优越.