Systematic assessment of adsorption-coupled electron transfer toward voltammetric discrimination between concerted and non-concerted mechanisms
Systematic assessment of adsorption-coupled electron transfer toward voltammetric discrimination between concerted and non-concerted mechanisms
复制标题
吸附耦合电子转移对协同机制和非协同机制伏安区分的系统评估
DOI：
10.1016/j.electacta.2022.140912
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发表时间：
2022
影响因子：
6.6
通讯作者：
Amemiya, Shigeru
中科院分区：
文献类型：
--
作者：
Janda, Donald C.;Barma, Kiran;Kurapati, Niraja;Klymenko, Oleksiy V.;Oleinick, Alexander;Svir, Irina;Amatore, Christian;Amemiya, Shigeru
在许多重要的电极反应中，氧化还原活性分子的电子转移和特定吸附是耦合的。在这里，我们报告了一个理论框架，用于区分吸附耦合电子转移(ACET)反应的协同和非协同机制。在协同机理中，溶液中的氧化剂同时被还原并被吸附，以在电极表面沉积还原剂。或者，电子转移和吸附步骤在非协调机制中分别被调节。我们的模型包含了两种机制的共同吸附步骤，以确保氧化还原对一致的吸附性质。为了简单起见，我们假设了一个对电流响应没有贡献的弱吸附步骤。我们预测，不仅需要一个动力学控制的吸附步骤，而且还需要一个化学上可逆的电子转移步骤来确定反应机理。在循环伏安法(CV)中，需要较高的扫描速度来控制吸附步骤的动力学。在氧化剂或还原剂的可逆吸附过程中，预计每个机制都有独特的CV形状或其中的特征变化。我们模拟了氧化剂和还原剂在银电极上的可逆吸附。这个化学不可逆的ACET反应的实验CV控制着吸附步骤，但与定量验证我们的模型的任何一个机理都是一致的。尚未显示出对协调机制和非协调机制的伏安区分，但如果同时满足这两项要求，就有可能做到这一点。
The electron transfer and specific adsorption of a redox-active molecule are coupled in many important electrode reactions. Herein, we report a theoretical framework for the voltammetric discrimination of the concerted and non-concerted mechanisms of adsorption-coupled electron-transfer (ACET) reactions. In the concerted mechanism, an oxidant in the solution is simultaneously reduced and adsorbed to deposit a reductant on the electrode surface. Alternatively, electron-transfer and adsorption steps are mediated separately in the non-concerted mechanism. Our model involves the common adsorption step for both mechanisms to ensure consistent adsorption properties of the redox couple. For simplicity, we assumed a weak adsorption step that does not contribute to the current response. We predicted that not only a kinetically controlled adsorption step but also a chemically reversible electron-transfer step is required for the voltammetric identification of the reaction mechanism. High scan rates were required during cyclic voltammetry (CV) for the kinetic control of the adsorption step. Unique CV shapes, or characteristic changes therein, were expected for each mechanism during the reversible adsorption of oxidants or reductants. We modelled the reversible adsorption of both the oxidant and reductant for the reduction of benzyl chloride at a Ag electrode. The experimental CV of this chemically irreversible ACET reaction kinetically controlled the adsorption step but was consistent with either mechanism to quantitatively validate our model. A voltammetric discrimination of the concerted and non-concerted mechanisms has not been demonstrated, but it will be possible if both requirements are satisfied.