pH-dependent anodic reaction behavior of tungsten in acidic phosphate solutions
pH-dependent anodic reaction behavior of tungsten in acidic phosphate solutions
复制标题
DOI：
10.1016/j.electacta.2009.02.014
复制
发表时间：
2009-06-01
影响因子：
6.6
通讯作者：
Anik, Mustafa
中科院分区：
文献类型：
--
作者：
Anik, Mustafa
利用动电位和恒电位极化实验以及电化学阻抗谱技术研究了钨（W）在酸性磷酸盐溶液中的pH依赖性阳极行为。在非常低的pH值（pH < 2.6）下，钨的溶解是W辅助的，并且当pzc（pH 2.6）接近时，H(2)O辅助的溶解成为主要的溶解途径。然而，当 pH 值高于 2.6 时，钨的溶解是由 CH 辅助的。在腐蚀电位下，观察到钨氧化物阻挡层的厚度和介电性能几乎与 pH 无关。穿过氧化膜的氧空位传输在非常酸性的溶液（pH 4.5）下引起电容响应，由于塔菲尔区域负表面电荷的加速作用，电容响应转变为电感响应。随着伪平台区和电势独立区域中钨溶解速率的降低，钨阻抗谱中的感应响应转移到非常低的频率范围。根据表面电荷方法拟合钨阻抗数据表明，随着接近 pzc，对缺陷迁移的阻力增加，并且由于金属氧化物表面上非保护性松散结合水合层的形成速度加快，薄膜电容在 pH 3.5 以上下降。 (C) 2009 Elsevier Ltd. 保留所有权利。
Potentiodynamic and potentiostatic polarization experiments, and the electrochemical impedance spectroscopy technique were used to study the pH dependent anodic behavior of tungsten (W) in acidic phosphate solution. At very low pH values (pH < 2.6) the dissolution of tungsten was W-assisted and as the pzc (pH 2.6) was approached H(2)O-assisted dissolution became main dissolution pathway. Above pH 2.6, however, tungsten dissolution was CH-assisted. The thickness and dielectric properties of the W-oxide barrier layer were observed almost pH independent at corrosion potential. The oxygen vacancy transport across the oxide film caused a capacitive response at very acidic solutions (pH 4.5) the capacitive response turned into the inductive one due to the accelerating effect of negative surface charge in Tafel region. The inductive response in the tungsten impedance spectra shifted to a very low frequency range as the tungsten dissolution rate decreased in the pseudo-plateau and potential independent regions. Fitting of the tungsten impedance data according to the surface charge approach showed that the resistance to the defect migration increased as the pzc was approached and the film capacitance decreased above pH 3.5 due to the accelerated formation rate of the non-protective loosely bound hydrated layer on the metal oxide surface. (C) 2009 Elsevier Ltd. All rights reserved.