Kong De-Sheng
Department of Chemistry, Qufu Normal University, Qufu, Shandong 273165, PR China.
Langmuir. 2008 May 20;24(10):5324-31. doi: 10.1021/la703258e. Epub 2008 Apr 29.
The influence of fluoride (and its concentration) on the electrochemical and semiconducting properties of anodic oxide films formed on titanium surfaces was investigated by performing electrochemical measurements (potentiodynamic/pontiostatic polarization, open circuit potential (OCP), and capacitance measurements) for a titanium/oxide film/solution interface system in fluoride-containing 1.0 M HClO(4) solution. On the basis of the Mott-Schottky analysis, and with taking into account both the surface reactions (or, say, the specifically chemical adsorption) of fluoride ions at the oxide film surface and the migration/intercalation of fluoride ions into the oxide film, the changes in the electrochemical behavior of titanium measured in this work (e.g., the blocked anodic oxygen evolution, the increased anodic steady-state current density, the positively shifted flat band potential, and the positively shifted film breakdown potential) were interpreted by the changes in the surface and the bulk physicochemical properties (e.g., the surface charges, surface state density, doping concentration, and the interfacial potential drops) of the anodic films grown on titanium. The fluoride concentrations tested in this work can be divided into three groups according to their effect on the electrochemical behavior of the oxide films: < or =0.001 M, 0.001-0.01 M, and >0.01 M. By tracing the changes of the OCP of the passivated titanium in fluoride-containing solutions, the deleterious/depassive effect of fluoride ions on the titanium oxide films was examined and evaluated with the parameter of the film breakdown time. It was also shown that the films anodically formed on titanium at higher potentials (>2.5 V) exhibited significantly higher stability against the fluoride attack than that either formed at lower potentials (<2.5 V) or formed natively in the air.
通过对含氟的1.0 M高氯酸（HClO₄）溶液中的钛/氧化膜/溶液界面系统进行电化学测量（动电位/恒电位极化、开路电位（OCP）和电容测量），研究了氟化物（及其浓度）对钛表面形成的阳极氧化膜的电化学和半导体性能的影响。基于莫特-肖特基分析，并考虑到氟离子在氧化膜表面的表面反应（或者说，特异性化学吸附）以及氟离子向氧化膜中的迁移/嵌入，本工作中测量的钛的电化学行为变化（例如，阳极析氧受阻、阳极稳态电流密度增加、平带电位正向移动以及膜击穿电位正向移动）可通过在钛上生长的阳极膜的表面和体相物理化学性质变化（例如，表面电荷、表面态密度、掺杂浓度和界面电位降）来解释。根据其对氧化膜电化学行为的影响，本工作中测试的氟化物浓度可分为三组：≤0.001 M、0.001 - 0.01 M和＞0.01 M。通过追踪含氟溶液中钝态钛的开路电位变化，以膜击穿时间为参数，研究并评估了氟离子对钛氧化膜的有害/去钝化作用。还表明，在较高电位（＞2.5 V）下阳极氧化形成的钛膜对氟侵蚀的稳定性明显高于在较低电位（＜2.5 V）下形成的膜或在空气中自然形成的膜。
