Abstract In the present work we have studied the pH dependence of the voltammetric response of polyaniline (Pani) in three different electrolytic media: HCl, H2SO4 and HClO4 at constant ionic strength. The electrochemical stability of Pani as a function of the pH is different for the three electrolytes. As the pH increases, the stability limit decreases in the order HCl > HClO4 > H2SO4. The voltammetric data were analyzed based on a theoretical expression for the redox potential as a function of the oxidation degree of the polymer. This analysis allows obtaining the acid dissociation constant for the three electrolytes, and an interaction parameter that reflects the change in the interaction energy between the redox centres of the polymer as the pH is increased. Particularly interesting is the HCl system, in which the pH can be increased up to about 5.0 without loss of the electrochemical activity. A further proof that the current vs. potential response may be represented by a reversible confined redox couple with interactions comes from the pH dependence of the peak current for the three electrolytes. As expected, the acid dissociation constants of the reduced and oxidized polymer do not depend much on the nature of the anions studied here.

中文翻译：

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聚苯胺在盐酸、硫酸和高氯酸溶液中的氧化还原交换特性

摘要 在目前的工作中，我们研究了聚苯胺 (Pani) 在三种不同电解介质中的伏安响应的 pH 依赖性：HCl、H2SO4 和 HClO4 在恒定离子强度下。对于三种电解质，Pani 的电化学稳定性作为 pH 值的函数是不同的。随着 pH 值的增加，稳定性极限以 HCl > HClO4 > H2SO4 的顺序降低。基于作为聚合物氧化度函数的氧化还原电位的理论表达式分析伏安数据。该分析允许获得三种电解质的酸解离常数，以及反映聚合物氧化还原中心之间相互作用能随着 pH 值增加而变化的相互作用参数。特别有趣的是 HCl 系统，其中pH值可以增加到约5.0而不损失电化学活性。电流与电位响应可以由具有相互作用的可逆受限氧化还原对表示的进一步证明来自三种电解质峰值电流的 pH 依赖性。正如预期的那样，还原和氧化聚合物的酸解离常数不太取决于此处研究的阴离子的性质。