Local Fine Structural Insight into Mechanism of Electrochemical Passivation of Titanium

详细信息    查看全文

• 作者：Lu Wang ; Hongying Yu ; Ke Wang ; Haisong Xu ; Shaoyang Wang ; Dongbai Sun
• 刊名：ACS Applied Materials & Interfaces
• 出版年：2016
• 出版时间：July 20, 2016
• 年：2016
• 卷：8
• 期：28
• 页码：18608-18619
• 全文大小：722K
• 年卷期：0
• ISSN：1944-8252

文摘

Electrochemically formed passive film on titanium in 1.0 M H₂SO₄ solution and its thickness, composition, chemical state, and local fine structure are examined by Auger electron spectroscopy (AES), X-ray photoelectron spectroscopy (XPS), and X-ray absorption fine structure. AES analysis reveals that the thickness and composition of oxide film are proportional to the reciprocal of current density in potentiodynamic polarization. XPS depth profiles of the chemical states of titanium exhibit the coexistence of various valences cations in the surface. Quantitative X-ray absorption near edge structure analysis of the local electronic structure of the topmost surface (∼5.0 nm) shows that the ratio of [TiO₂]/[Ti₂O₃] is consistent with that of passivation/dissolution of electrochemical activity. Theoretical calculation and analysis of extended X-ray absorption fine structure spectra at Ti K-edge indicate that both the structures of passivation and dissolution are distorted caused by the appearance of two different sites of Ti–O and Ti–Ti. And the bound water in the topmost surface plays a vital role in structural disorder confirmed by XPS. Overall, the increase of average Ti–O coordination causes the electrochemical passivation, and the dissolution is due to the decrease of average Ti–Ti coordination. The structural variations of passivation in coordination number and interatomic distance are in good agreement with the prediction of point defect model.