氟化铋薄膜的电化学原位合成及光催化活性

Electrochemical In-situ Synthesis and Photocatalytic Properties of BiF_3 Thin Films

采用常温电化学原位法合成了Bi F3薄膜,通过X射线衍射(XRD)、扫描电子显微镜(SEM)、透射电子显微镜(TEM)、紫外-可见漫反射光谱(UV-Vis DRS)及密度泛函理论(DFT)对薄膜的晶型、形貌、光学性质和能带结构进行了表征;以罗丹明B(Rh B)为目标降解物,考察了薄膜的光催化活性和稳定性.结果表明,Bi F3薄膜具有纳米片状结构、较高的结晶纯度、良好的光催化活性和稳定性,其导带底和价带顶分别主要由Bi6p和F2p轨道电子贡献.随着电解质浓度的增加,Bi F3薄膜的结构、形貌发生变化,使光催化活性先升高后降低,在电解质NH4F浓度(质量分数)为1.5%时,Bi F3薄膜的纳米薄片之间呈现出明显的交错分布,而此类结构排列有利于反应物的传输和光的反射,从而增大催化剂的反应空间和提高光的利用率,表现出最佳的光催化活性.Bi F3薄膜在模拟太阳光照射5 h后对Rh B降解率为99.1%,且重复使用4次,仍维持在81%以上.本文还提出了电化学Bi板上原位生长Bi F3薄膜的机制.

BiF3 thin films were prepared by simple in-situ electrochemical method at room temperature. The X-ray diffraction（ XRD）,scanning electron microscopy（ SEM）,transmission electron microscopy（ TEM）,UV-Vis diffuse reflection spectroscopy（ UV-Vis DRS） and density functional theory（ DFT） were employed to characterize the crystallinities,structures,morphologies,optical properties and energy band structures of the as-prepared BiF3 thin films. The photocatalytic activity and stability of Bi F3 thin films were evaluated by the degradation of Rhodamine B（ Rh B） under simulated sunlight irradiation. The results show that the Bi F3 thin films exhibit the nanosheet structure with high purity,excellent photocatalytic activity and stability. The conduction band minimum and the valence band maximum of Bi F3 thin films are mainly contributed by Bi6 pand F2 porbital electrons,respectively. It was also found that,with the increase of electrolyte concentration,the structural morphologies of Bi F3 thin films changed,resulting in that the photocatalytic activity of Bi F3 thin films first enhances and then decreases. When the electrolyte concentration is 1. 5%,the Bi F3 nano-film is obviously staggered,which is conducive to the transport of reactants and light reflection,thereby increasing the reaction space of catalyst and the utilization efficiency of light. The photocatalytic degradation efficiency of Rh B reaches99. 2% after 5 h simulated solar light irradiation,and still remains above 81% after being used 4 times. The possible formation mechanism of Bi F3 thin films on Bi plate via novel in-situ electrochemical method was proposed.