氢气还原法制备Bi/Bi_(2)WO_(6)及其光催化降解性能

Preparation of Bi/Bi_(2)WO_(6)by H_(2)reduction method and its photocatalytic degradation performance

通过H_(2)还原法制备Bi/Bi_(2)WO_(6)以减少杂质的引入,并探讨最佳H_(2)还原条件、Bi/Bi_(2)WO_(6)为光催化剂的降解机制和稳定性。结果表明,200℃下还原30 min制得的Bi/Bi_(2)WO_(6)具有最好的光催化活性,光照240 min后,降解率可达到69.7%。Bi/Bi_(2)WO_(6)光催化活性提高的原因有:表面等离子共振(SPR)效应提高了对450~800 nm波长光的吸收;BWO与金属Bi接触产生的内置电场促进了光生电子空穴对的分离;氧空位的存在降低了禁带宽度、捕获了电子与吸附的O_(2)反应生成促进盐酸四环素降解的活性基团·O_(2)^(-)。盐酸四环素是被羟基自由基(·OH)、超氧自由基(·O_(2)^(-))和空穴(h+)矿化为无机小分子的,这3个活性物质对盐酸四环素降解的贡献顺序由大到小为·O_(2)^(-)、·OH、h+。Bi/Bi_(2)WO_(6)在光催化反应过程中具有良好的稳定性,只要每次循环实验前都用乙醇洗涤试样10次。在循环3次后,降解率从69.7%下降到63.58%,这是氧空位数量的轻微减少导致的。本文的研究结果为原位还原制备Bi/Bi_(2)WO_(6)以增强对可见光的吸收和促进光生载流子的分离提供了新思路。

Bi/Bi_(2)WO_(6)was prepared by H_(2)reduction method to reduce the introduction of impurities.The optimal H_(2)reduction conditions and the degradation mechanism and stability of Bi/Bi_(2)WO_(6)as a photocatalyst were discussed.The results showed that Bi/Bi_(2)WO_(6),prepared by reduction at 200℃for 30 minutes,had the best photocatalytic properties,and its degradation rate could reach 69.7%after 240 minutes of illumination.The reasons for the enhanced photocatalytic activity of Bi/Bi_(2)WO_(6)included:the surface plasmon resonance(SPR)effect enhanced the absorption of light with wavelengths ranging from 450-800 nm;the built-in electric field generated between BWO and metallic Bi promoted the separation of photogenerated electron-hole pairs;and the presence of oxygen vacancies reduced the bandgap and captured electrons that reacted with adsorbed oxygen to generate active groups·O_(2)^(-),which promoted the degradation of tetracycline hydrochloride(TCH).TCH was mineralized into inorganic small molecules by hydroxyl radicals(·OH),superoxide radicals(·O_(2)^(-)),and holes(h+).The contribution of these three active substances to the degradation of TCH was ranked in the descending order of·O_(2)^(-),·OH,and h+.Bi/Bi_(2)WO_(6)exhibited good stability during photocatalytic reactions,provided the sample was washed with ethanol 10 times before each cycle experiment.After three cycles,the degradation rate decreased from 69.7%to 63.58%,which was caused by a slight decrease in the number of oxygen vacancies.The results provide a new way for the in-situ reduction preparation of Bi/Bi_(2)WO_(6)to enhance the absorption of visible light and promote the separation of photogenerated carriers.