Effect of pH on the anodic Behavior of tungsten
Effect of pH on the anodic Behavior of tungsten
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DOI：
10.1149/1.1471544
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发表时间：
2002-06-01
影响因子：
3.9
通讯作者：
Osseo-Asare, K
中科院分区：
文献类型：
--
作者：
Anik, M;Osseo-Asare, K
采用动电位极化、恒电位极化和旋转圆盘电极技术，研究了钨（W）在宽pH范围（0.5-13.5）的H_3PO_4/KOH缓冲溶液中的阳极行为。表面氧化物在钨的阳极氧化和溶解过程中起着重要的作用。五个不同的pH制度和相应的反应机理进行了鉴定。低于pH 1（区域A）H+辅助溶解是主要的溶解途径。随着pH值的增加，H+的作用减弱，在pH 2.6（区域B），这被确定为表面氧化钨的零电荷点（pzc），溶解主要是H2O辅助的。在pzc以上观察到溶解是OH-辅助的。OH-的反应级数在pH 4.5和6.5之间（区域C）。反应级数在pH 8（区域D）变为零。该观察结果归因于水合氧化物相的pH非依赖性溶解。在pH 10以上，阳极电流的OH-依赖性开始，并且在pH 12.5左右（区域E），OH-的反应级数变为1。(C)2002年电化学学会。
Potentiodynamic and potentiostatic polarization, and the rotating disk electrode technique, were used to study the anodic behavior of tungsten (W) in a broad pH range (0.5-13.5) in H3PO4/KOH buffered solution. Surface oxides were found to play a prominent role in the anodic oxidation and dissolution of tungsten. Five distinct pH regimes and the corresponding reaction mechanisms were identified. Below pH 1 (region A) H+-assisted dissolution was the main dissolution pathway. As the pH increased, the role of H+ diminished and at pH 2.6 (region B), which was identified as the point of zero charge (pzc) of the surface tungsten oxide, dissolution was mainly H2O-assisted. The dissolution was observed to be OH--assisted above the pzc. The reaction order for OH- was one between pH 4.5 and 6.5 (region C). The reaction order became zero at pH 8 (region D). This observation was attributed to the pH-independent dissolution of the hydrated oxide phase. Above pH 10, OH- dependence of the anodic current commenced and at around pH 12.5 (region E) the reaction order for OH- became one. (C) 2002 The Electrochemical Society.