通过化学蚀刻提高Bi_2WO_6/Bi_2MoO_6光催化活性的机理探析

Photocatalytic Activity Enhancement for Bi_2WO_6/Bi_2MoO_6 by Chemical Etching Treatment

Bi_2WO_6/Bi_2MoO_6复合半导体已经能够利用无模板一步水热法得到,并通过简单的化学蚀刻方法处理实现其催化性能的提升,使用氢氧化钠作为蚀刻剂.光催化测试表明碱蚀刻催化剂的降解率提升了约60%,捕获剂实验为催化机理的分析提供了有力的证据,电子顺子共振(EPR)直接证明蚀刻使得样品中形成大量的氧空位;阻抗测试表明该样品具有更高的电子转移活性.结合上述结论对蚀刻催化剂性能提升的机理做出了以下分析:复合催化剂中Bi_2WO_6和Bi_2MoO_6相互匹配的能带结构使得光生电子的转移和传输极为顺利,碱蚀刻使催化剂微观结构改变,并在Bi_2WO_6和Bi_2MoO_6表面制造大量氧穴位,光催化过程中氧空位有效捕获水分子中的氧原子;后续电子参与的两步还原反应将溶液中的溶解氧转化成·OH.上述分析结果为光催化反应中催化剂催化性能的提高做出实质贡献.

The nanocomposite semiconductor Bi2WO6/Bi2MoO6 has been prepared by one-step hydrothermal method without formwork successfully, improvement photocatalytic activity for them by simple chemical etching method, using sodium hydroxide as etching agents. Photocatalytic test has indicated that degradation rate of catalysts used etching treatment has risen by about 60%, the trapping agent text has provided strong evidence for analysis of catalytic mechanism, electron paramagnetic resonance(EPR) has directly showed that etch treatment results in a large number of oxygen vacancies in the catalyst, the impedance curves has exhibited that the catalyst has higher electron transfer activity in the photocatalytic process. Based on the above conclusions, the mechanism possible of photocatalytic performance improvement of etched catalyst is discussed as follows: the matching energy band structure of Bi2WO6 and Bi2MoO6 in the composite catalyst makes the transfer and transport of photogenerated electrons extremely smooth, the change of microstructure of photocatalyst by etching is beneficial to the utilization of light energy, further more the etching treatment has made a great quantity oxygen vacancies on the surface of Bi2WO6 and Bi2MoO6, oxygen vacancies effectively capture oxygen atoms of water molecules;and then, dissolved oxygen is transformed in solution to hydroxyl radical in a two-step reduction reaction involving electrons. Above analysis results make substantial contributions to the improvement of photocatalytic performance of photocatalyst in photocatalytic reaction.