氟化铋薄膜的电化学原位合成及光催化活性

doi:10.7503/cjcu20180001

摘要/Abstract

摘要：

采用常温电化学原位法合成了BiF₃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(RhB)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, BiF₃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Bi₆_p和F₂_p轨道电子贡献. 随着电解质浓度的增加, BiF₃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, BiF₃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. BiF₃薄膜在模拟太阳光照射5 h后对RhB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BiF₃薄膜的机制.

关键词: 氟化铋, 电化学法, 薄膜, 光催化, 原位生长

Abstract:

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 BiF₃ thin films were evaluated by the degradation of Rhodamine B(RhB) under simulated sunlight irradiation. The results show that the BiF₃ thin films exhibit the nanosheet structure with high purity, excellent photocatalytic activity and stability. The conduction band minimum and the valence band maximum of BiF₃ thin films are mainly contributed by Bi₆_p and F₂_p orbital electrons, respectively. It was also found that, with the increase of electrolyte concentration, the structural morphologies of BiF₃ thin films changed, resulting in that the photocatalytic activity of BiF₃ thin films first enhances and then decreases. When the electrolyte concentration is 1.5%, the BiF₃ 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 RhB reaches 99.2% after 5 h simulated solar light irradiation, and still remains above 81% after being used 4 times. The possible formation mechanism of BiF₃ thin films on Bi plate via novel in-situ electrochemical method was proposed.

Key words: BiF₃, Electrochemical method, Thin film, Photocatalysis, In-situ synthesis

中图分类号:

O646

TrendMD:

赵祖, 李瑞, 张小超, 张长明, 刘建新, 王雅文, 王韵芳, 樊彩梅. 氟化铋薄膜的电化学原位合成及光催化活性. 高等学校化学学报, 2018, 39(8): 1775.

ZHAO Zu, LI Rui, ZHANG Xiaochao, ZHANG Changming, LIU Jianxin, WANG Yawen, WANG Yunfang, FAN Caimei. Electrochemical In-situ Synthesis and Photocatalytic Properties of BiF₃ Thin Films^†. Chem. J. Chinese Universities, 2018, 39(8): 1775.

图/表 8

Fig.1 XRD patterns of as-prepared samplesa. 1.0%-BiF3; b. 1.5%-BiF3; c. 2.0%-BiF3.

Fig.2 SEM images of 1.0%-BiF3(A), 1.5%-BiF3(B), 2.0%-BiF3 thin films(C)

Fig.3 TEM(A) and HRTEM(B) images of 1.5%-BiF3 thin film

Fig.4 UV-Vis DRS of BiF3 thin films with different NH4F contentsa. 1.0%-BiF3; b. 1.5%-BiF3; c. 2.0%-BiF3.

Fig.5 Photocatalytic activities of 1.0%-BiF3, 1.5%-BiF3, 2.0%-BiF3 thin films and BiF3 powder(A) and results of photocatalytic recycling experiment of 1.5%-BiF3 thin film(B) under simulated solar light irradiationa. No catalyst; b. 1.0%-BiF3; c. 1.5%-BiF3; d. 2.0%-BiF3; e. BiF3.

Fig.6 Band structure of BiF3 crystalInset is the crystal cell model.

Fig.7 Electronic structure of BiF3 crystal

Scheme 1 Possible formation mechanism of BiF3 thin films

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