Proton-Electron Transport and Transfer in Electrocatalytic Films. Application to a Cobalt-Based O2-Evolution Catalyst
Proton-Electron Transport and Transfer in Electrocatalytic Films. Application to a Cobalt-Based O2-Evolution Catalyst
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DOI：
10.1021/ja403656w
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发表时间：
2013-07-17
影响因子：
15
通讯作者：
Saveant, Jean-Michel
中科院分区：
文献类型：
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作者：
Bediako, D. Kwabena;Costentin, Cyrille;Saveant, Jean-Michel
与现代能源挑战相关的太阳能驱动的小分子电化学转化，例如水分解和二氧化碳还原，需要催化剂的帮助，催化剂最好沉积在导电或半导电表面上。了解机制和确定控制这些系统的功能的因素是合理的催化剂优化和提高性能所必需的。提出了一种方法，在旋转盘电极伏安法的框架中，分析预期的电流响应的情况下，半一般的反应方案，涉及质子耦合的催化反应与质子耦合的电子跳跃通过膜作为速率控制因素的情况下，没有限制基板扩散。预测关注的电流密度与超电势（塔菲尔）图和它们的依赖于缓冲液浓度（包括没有缓冲液），膜厚度和转速。塔菲尔图可以具有各种斜率（例如，F/RTln 10，F/2 RTln 10，0），甚至可以共存于一个单一的情节过电位范围内。我们发现，存在一个最佳的膜厚度，超过该膜平台的活动。通过钴基氧化物催化剂的膜对水氧化的应用提供了对所提出的方法的适用性的成功测试，这也提供了对这些钴基膜催化水氧化的机制的进一步了解。的动力学和热力学特性，已来自分析的确切性质进行了讨论，以及它们在催化剂基准的使用。
Solar-driven electrochemical transformations of small molecules, such as water splitting and CO2 reduction, pertinent to modem energy challenges, require the assistance of catalysts preferably deposited on conducting or semi-conducting surfaces. Understanding mechanisms and identifying the factors that control the functioning of such systems are required for rational catalyst optimization and improved performance. A methodology is proposed, in the framework of rotating disk electrode voltammetry, to analyze the current responses expected in the case of a semigeneral reaction scheme involving a proton-coupled catalytic reaction associated with proton-coupled electron hopping through the film as rate controlling factors in the case where there is no limitation by substrate diffusion. The predictions concern the current density vs overpotential (Tafel) plots and their dependence on buffer concentration (including absence of buffer), film thickness and rotation rate. The Tafel plots may have a variety of slopes (e.g., F/RTln 10, F/2RTln 10, 0) that may even coexist within the overpotential range of a single plot. We show that an optimal film thickness exists beyond which the activity of the film plateaus. Application to water oxidation by films of a cobalt-based oxidic catalyst provides a successful test of the applicability of the proposed methodology, which also provides further insight into the mechanism by which these cobalt-based films catalyze the oxidation of water. The exact nature of the kinetic and thermodynamic characteristics that have been derived from the analysis is discussed as well as their use in catalyst benchmarking.