Mechanistic Insights about Electrochemical Proton-Coupled Electron Transfer Derived from a Vibrational Probe
Mechanistic Insights about Electrochemical Proton-Coupled Electron Transfer Derived from a Vibrational Probe
复制标题
关于振动探针产生的电化学质子耦合电子转移的机理见解
DOI：
10.1021/jacs.1c01977
复制
发表时间：
2021
影响因子：
15
通讯作者：
Dawlaty, Jahan M.
中科院分区：
文献类型：
--
作者：
Sarkar, Sohini;Maitra, Anwesha;Lake, William R.;Warburton, Robert E.;Hammes-Schiffer, Sharon;Dawlaty, Jahan M.
质子耦合电子转移（PCET）是广泛的电化学过程中的一个基本步骤，包括那些感兴趣的能量转换和存储。尽管它的重要性，这样的反应的几个机制的细节仍然不清楚。在这里，我们结合了质子供体（叔铵）与振动斯塔克位移探针（苯甲腈），跟踪从反应物进入双电层（EDL）的过程，与质子捐赠到电极的PCET反应，和产品的形成。在电化学偏压下，我们用恒振动光谱和周期密度泛函理论对反应物和产物峰及其Stark位移进行了归属。我们已经确定了三个主要阶段的PCET反应的进展作为一个功能的应用潜力。首先，我们已经确定了潜在的必要的反应物的去溶剂化和他们进入的极化环境的EDL。第二，我们已经观察到在稳态电化学电流开始之前产物峰的出现，表明形成了不翻转的产物的固定群体。最后，起始电位更负，电极吸引额外的反应物，取代静止产物并实现稳态电流。这项工作表明，整合的振动斯塔克位移探针与质子供体提供了关键的洞察界面静电和非均相化学反应之间的相互作用。这样的洞察力不能单独从电化学测量中获得。
Proton-coupled electron transfer (PCET) is a fundamental step in a wide range of electrochemical processes, including those of interest in energy conversion and storage. Despite its importance, several mechanistic details of such reactions remain unclear. Here, we have combined a proton donor (tertiary ammonium) with a vibrational Stark-shift probe (benzonitrile), to track the process from the entry of the reactants into the electrical double layer (EDL), to the PCET reaction associated with proton donation to the electrode, and the formation of products. We have usedoperandovibrational spectroscopy and periodic density functional theory under electrochemical bias to assign the reactant and product peaks and their Stark shifts. We have identified three main stages for the progress of the PCET reaction as a function of applied potential. First, we have determined the potential necessary for desolvation of the reactants and their entry into the polarizing environment of the EDL. Second, we have observed the appearance of product peaks prior to the onset of steady state electrochemical current, indicating formation of a stationary population of products that does not turn over. Finally, more negative of the onset potential, the electrode attracts additional reactants, displacing the stationary products and enabling steady state current. This work shows that the integration of a vibrational Stark-shift probe with a proton donor provides critical insight into the interplay between interfacial electrostatics and heterogeneous chemical reactions. Such insights cannot be obtained from electrochemical measurements alone.