ZnSe/MoO_3/TiO_2复合膜的制备及其光生阴极保护效应

针对TiO_2半导体不能有效吸收可见光,光电转换效率较低等问题,可通过对TiO_2半导体进行修饰和改性,制备TiO_2复合材料,提高其光电化学性能。因此,本工作以Ti表面制备的TiO_2纳米管膜为基础,分别应用循环伏安电沉积法和脉冲电沉积法在膜表面先后沉积MoO3和ZnSe颗粒,获得具有级联能带结构的ZnSe/MoO3/TiO_2纳米管复合膜,并将其应用于对403不锈钢(403SS)实施光生阴极保护。相较于纯TiO_2纳米管膜,紫外-可见(UV-Vis)吸收光谱和光致发光(PL)谱测试表明,ZnSe/MoO3/TiO_2复合膜的吸收边红移,在可见光区具有良好的光吸收性能,光生载流子复合得到更有效抑制。光电化学测试表明,白光照射下,处于0.5 mol·L~(-1) KOH溶液中的ZnSe/MoO3/TiO_2复合膜的光电流密度达到了同条件下纯TiO_2膜的2倍,可使与之耦连的浸泡于0.5 mol·L-1 NaCl溶液中的403SS电极电位下降470 mV,显示出良好的光生阴极保护效应。复合膜还具有一定的储能特性,在光照后又转为暗态的22.5 h内仍对403SS具有一定阴极保护作用。

Fabrication of a ZnSe/MoO3/TiO2 Composite Film Exhibiting Photocathodic Protection Effect

TiO₂ is a semiconductor material with excellent photoelectrochemical properties that can provide photocathodic protection for metals. However, TiO₂ can only absorb ultraviolet (UV) light at wavelengths of < 380 nm because of its wide band gap. In addition, photo-induced electron-hole pairs in the TiO₂ semiconductor easily recombine, which leads to a low photoelectric conversion efficiency. Another shortcoming is that pure TiO₂ semiconductors cannot sustain photocathodic protection in the dark, which may limit their practical applications to provide photocathodic protection. To address these shortcomings, various modification methods have been established by preparing TiO₂ composite materials to improve their photoelectrochemical properties. In this study, a ZnSe- and MoO₃-modified TiO₂ nanotube composite film with charge storage ability was prepared to enhance its photocathodic protection effect on stainless steel. A TiO₂ nanotube array film was prepared on a Ti foil via anodic oxidation and then MoO₃ and ZnSe particles were deposited onto the film by cyclic voltammetry and pulse electrodeposition, respectively, to afford a ZnSe/MoO₃/TiO₂ nanotube composite film having a cascade band structure. Scanning electron microscopy observations showed that the TiO₂ film consisted of ordered nanotubes with an average inner diameter of approximately 100 nm and wall thickness of approximately 15 nm. This nanotube structure remained intact after MoO₃ and ZnSe particle deposition on the film. Energy dispersive spectroscopy, X-ray diffraction, and X-ray photoelectron spectroscopy analyses indicated that the prepared nanotube composite film was composed of ZnSe, MoO₃, and TiO₂. The UV-Vis absorption and photoluminescence spectra showed that the photoresponse of the composite film was extended to the visible light region and the photo-induced electron-hole pair recombination was reduced. Photoelectrochemical and electrochemical measurements indicated that the photocurrent intensity of the composite film in a 0.5 mol·L⁻¹ KOH solution was two-fold higher than that of the pure TiO₂ film. Under white light illumination, the ZnSe/MoO₃/TiO₂ composite film decreased the potential of the coupled 403 stainless steel (403SS) in a 0.5 mol·L⁻¹ NaCl solution by 470 mV (relative to the corrosion potential), demonstrating an effective photocathodic protection effect. It should be noted that the composite film exhibited a charge storage capability and could continuously provide cathodic protection for 22.5 h after illumination was stopped. In addition, electrochemical impedance spectroscopy results indicated that the composite film significantly decreased the charge transfer resistance of the coupled 403SS, highlighting the photocathodic protection effect on 430SS.