关键词: CeO₂薄膜, 电沉积, 光助, 波长, 溶解氧

Abstract:

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.

Key words: CeO₂ thin film, electrodeposition, photo-assisted, wavelength, dissolving oxygen