溶解氧及波长对光助阳极沉积CeO2薄膜的影响

本文主要研究在含有0.05 mol·L^-1硝酸铈、0.1 mol·L^-1乙酸铵和70%（体积比）乙醇的镀液中通过阳极电沉积法在316 L不锈钢电极表面上制备CeO₂薄膜,并讨论了三种单色光波长以及镀液中溶解氧对阳极沉积CeO₂的影响. 采用计时安培曲线、椭圆偏振光谱、扫描电子显微镜、掠角X射线衍射和拉曼光谱方法研究了薄膜的电镀行为、表面形貌及其结构. 结果表明,本研究中的有效光照射波长为365 nm和254 nm,415 nm的波长不足以将电子从导带激发到价带. 随着入射光波长从254 nm增加到415 nm,薄膜的厚度与结晶度均逐渐减小,波长的变化对CeO₂薄膜表面形貌的影响很小. 少量的氧气对光助阳极沉积CeO₂薄膜有积极作用,但会生成较多的铈的氧化物颗粒吸附在电极表面. 在光电化学系统中,O₂常用作电子捕获剂. 随着溶解氧含量的增加,O₂将捕获对沉积有积极作用的光生电子,进而抑制阳极沉积的反应速率.

Synergistic Effect of Dissolving O2 and Wavelength on the Photo-Assisted Anodic Deposition of CeO2 Thin Films

Cerium dioxide (CeO₂) thin films have been applied as new material in many technical fields such as solid oxide fuel cells, catalysts, UV absorbents, pharmacology, and coatings for corrosion protection of many metals and alloys. Electrodeposition is widely considered to be one of the best preparation methods for CeO₂ film. In this work, the CeO₂ films were prepared by photo-assisted anodic deposition in the bath solutions containing 0.05 mol·L^-1 cerium (III) nitrate, 0.1 mol·L^-1 ammonia acetate and 70% (V/V) ethanol onto 316L stainless steel (SS) surface. The synergistic effects of three monochromatic light wavelengths (i.e., 254 nm, 365 nm and 415 nm) and the dissolving O₂ have been discussed. The influences of dissolving O₂ and light wavelength on the electroplating behavior, morphology and structure of the CeO₂ films were studied by chronoamperometry, ellipsometry, scanning electron microscopy, X-ray diffraction, and Raman spectroscopy. Results showed that photo-irradiation was helpful to the anodic growth of CeO₂ films. With the increase of wavelength from 254 nm to 415 nm, both the crystallinity and film thickness were decreased. Surface morphologies of the CeO₂ films on the anode were slightly affected by the wavelength. The effective light wavelengths in this study were 365 nm and 254 nm and the photon energy of 415 nm was not enough to excite electrons from the conduction band to the valence band. A small amount of oxygen had a positive effect on the photo-assisted anode electrodeposition of the CeO₂ thin film, but it would generate more CeO₂ adsorbed on the surface. In the photo electrochemical system, ethanol is usually used as a hole scavenger and O₂ is usually used as an electron scavenger. Due to the presence of ethanol in the bath, as the dissolved oxygen content increasing, O₂ would capture the photo-generated electrons which are able to produce positive effect on the deposition, leading to the slower deposition reaction.