负偏压下Ag@AgBr/Ni膜电极光电催化降解罗丹明B的性能和机理

用电化学方法制备Ag@AgBr/Ni表面等离子体薄膜电极，以扫描电子显微镜（SEM）、X射线衍射（XRD）和紫外-可见漫反射光谱（UV-Vis DRS）对薄膜的表面形貌、晶相结构、光吸收特性进行了表征，在负偏压和可见光作用下，以罗丹明B为模拟污染物对薄膜的光催化活性和稳定性进行了测定，采用电化学技术和向溶液中加入活性物种捕获剂的方法对薄膜光电催化降解机理进行了探索。结果表明：最佳工艺下制备的Ag@AgBr/Ni膜电极是由表面沉积纳米Ag的纳米晶AgBr颗粒构成的薄膜，具有显著的表面等离子共振效应。薄膜具有优异的光电催化活性和良好的催化稳定性，在最佳负偏压和可见光照射下反应12 min，薄膜光电催化罗丹明B（c=5 mg·L^-1）的降解率是多孔TiO₂（P25）/ITO纳米薄膜的10.2倍。相对于未加偏压的光催化，降解率提高了2.0倍；在保持薄膜光催化活性基本不变的前提下可循环使用5次。电极表面纳米Ag粒子的等离子体共振对于光阴极反应（价带反应）的活化作用是光电催化活性提高的重要原因。提出了负偏压下Ag@AgBr/Ni表面等离子体薄膜光电催化降解罗丹明B的反应机理。

Photoelectrocatalytic Property and Reaction Mechanism of Ag@AgBr/Ni Thin Films at Negative Bias for Rhodamine B

Ag@AgBr/Ni thin films plasmonic photocatalyst were prepared by electrochemical method. The surface morphology, phase structure, optical characteristics of the thin films were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and ultraviolet-visible diffuse reflectance spectroscopy (UV-Vis DRS), respectively. Its photoelectrocatalytic properties and stability at negative bias under visible light were evaluated with rhodamine B (RhB) as a model compound. Using eletrochemical technique and a method of adding active species scavenger to the solution, mechanism of photoelectrocatalytic degradation of the films were explored. The results show that the Ag@AgBr/Ni thin film prepared under optimum condition are composed of AgBr microparticles whose surface has silver nanoparticles with a significant surface plasmon resonance (SPR) effects. The Ag@AgBr/Ni film is photoelectrocatalytically more active than TiO₂/ITO (indium tin oxide) film. At optimum cathodic bias and under visible light irradiation in 12 min, the photoelectrocatalytic degradation rate of Ag@AgBr/Ni film is 10.2 times as much as that of porous TiO₂(Degussa P25)/ITO film. Compared with no cathodic bias, the photoeletrocatalytic degradation rate of the Ag@AgBr/Ni thin film to RhB is increased by 2.0 times and the thin film has obvious photoelectric synergistic effect. The photoelectrocatalytic activity almost kept unchanged after five recycled experiments. The improvement in photoelectrocatalytic activity for Ag@AgBr/Ni thin films could be mainly attributed to the activation of nano Ag particles on the electrode for photocathode reaction (Valence band reaction) with a significant SPR effects. Furthermore, the photoelctrocatalytic reaction mechanism of Ag@AgBr/Ni thin films for RhB at negative bias was proposed.