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首页> 外文期刊>Proceedings of the National Academy of Sciences of the United States of America >Insights into proton-coupled electron transfer mechanisms of electrocatalytic H_2 oxidation and production
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Insights into proton-coupled electron transfer mechanisms of electrocatalytic H_2 oxidation and production

机译：对电催化H_2氧化与生成的质子耦合电子传递机理的见解

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摘要

The design of molecular electrocatalysts for H_2 oxidation and production is important for the development of alternative renewable energy sources that are abundant inexpensive, and environmentally benign. Recently, nickel-based molecular electrocatalysts with pendant amines that act as proton relays for the nickel center were shown to effectively catalyze H_2 oxidation and production. We developed a quantum mechanical approach for studying proton-coupled electron transfer processes in these types of molecular electrocatalysts. This theoretical approach is applied to a nickel-based catalyst in which phosphorous atoms are directly bonded to the nickel center, and nitrogen atoms of the ligand rings act as proton relays. The catalytic step of interest involves electron transfer between the nickel complex and the electrode as well as intramolecular proton transfer between the nickel and nitrogen atoms. This process can occur sequentially, with either the electron or proton transferring first, or conceitedly, with the electron and proton transferring simultaneously without a stable intermediate. The electrochemical rate constants are calculated as functions of over-potential for the concerted electron-proton transfer reaction and the two electron transfer reactions in the sequential mechanisms. Our calculations illustrate that the concerted electron-proton transfer standard rate constant will increase as the equilibrium distance between the nickel and nitrogen atoms decreases and as the pendant amines become more flexible to facilitate the contraction of this distance with a lower energy penalty. This approach identifies the favored mechanisms under various experimental conditions and provides insight into the impact of substituents on the nitrogen and phosphorous atoms.
机译：用于H_2氧化和生产的分子电催化剂的设计对于开发价格低廉且对环境有益的替代可再生能源至关重要。近来，具有悬垂胺的镍基分子电催化剂被用作镍中心的质子中继剂，已被证明可有效催化H_2的氧化和生成。我们开发了一种量子力学方法来研究这些类型的分子电催化剂中质子偶联的电子转移过程。这种理论方法适用于镍基催化剂，其中磷原子直接键合到镍中心，并且配体环的氮原子充当质子中继。感兴趣的催化步骤涉及镍配合物与电极之间的电子转移以及镍与氮原子之间的分子内质子转移。该过程可以依次发生，电子或质子先转移，或者自发地电子和质子同时转移而没有稳定的中间体。电化学速率常数被计算为协同机制中电子-质子转移反应和两个电子转移反应的超电势函数。我们的计算表明，随着镍原子和氮原子之间的平衡距离减小，并且随着侧链胺变得更加柔韧性，以促进该距离的收缩且能量损失更低，协调一致的电子-质子传递标准速率常数将增加。该方法确定了各种实验条件下的有利机理，并提供了对取代基对氮和磷原子的影响的了解。

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