Element strategy of oxygen evolution electrocatalysis based on in situ spectroelectrochemistry
Element strategy of oxygen evolution electrocatalysis based on in situ spectroelectrochemistry
复制标题
DOI：
10.1039/c7cc02204b
复制
发表时间：
2017-07-07
影响因子：
4.9
通讯作者：
Nakamura, Ryuhei
中科院分区：
文献类型：
--
作者：
Ooka, Hideshi;Takashima, Toshihiro;Nakamura, Ryuhei
析氧电催化由于其在生物学、化学和技术上的重要意义而受到广泛关注。然而，目前还不清楚如何利用丰富的3d元素来驱动水的四电子氧化，就像在自然界中一样有效。在这篇专题文章中，我们将根据我们正在进行的Mn，Fe和Ir析氧催化剂的光谱电化学研究，提出一种关于电荷积累过程优化的设计策略。反应中间体的光谱鉴定表明，MnO 2和Fe 2 O3的活性取决于Mn 3+和Fe 4+的产生，而在IrOx的情况下，活性与Ir的价态变化无关。通过价态变化的电荷积累效率与金属中心的自旋构型密切相关，因为电荷反折，被发现可以抑制高自旋3d金属中的电荷积累，需要e（g）轨道中的电子。除了通过产生不稳定的中间体直接增加过电位之外，电荷极化通过耗散系统的总氧化能量来抑制电荷积累。由于反应速率和电化学驱动力之间的耦合增强，有利的电荷积累过程也可能有利于电极动力学。这项研究中提出的模型可能有助于解释为什么低自旋4d/5d稀有金属通常比丰富的高自旋3d材料更活跃，并提供了新的见解如何通过优化键形成和电荷积累的能量来合成活性3d金属催化剂。
Oxygen evolution electrocatalysis has received extensive attention due to its significance in biology, chemistry, and technology. However, it is still unclear how the abundant 3d-elements can be used to drive the four-electron oxidation of water as efficiently as in Nature. In this Feature Article, we will propose a design strategy concerning the optimization of the charge accumulation process based on our ongoing spectroelectrochemical study on Mn, Fe, and Ir oxygen evolution catalysts. Spectroscopic identification of the reaction intermediates showed that the activity of MnO2 and Fe2O3 was dictated by the generation of Mn3+ and Fe4+, whereas in the case of IrOx, the activity did not correlate with the valence change of Ir. The efficiency of charge accumulation through valence change is closely linked with the spin configuration of the metal center, because charge disproportionation, which was found to inhibit charge accumulation in the high-spin 3d metals, requires an electron in the e(g) orbital. In addition to directly increasing the overpotential through the generation of an unstable intermediate, charge disproportionation inhibits charge accumulation by dissipating the total oxidative energy of the system. A favorable charge accumulation process may also be beneficial for electrode kinetics due to the enhanced coupling between reaction rates and electrochemical driving force. The model proposed in this study may help explain why low-spin 4d/5d rare metals are often more active than the abundant high-spin 3d materials for multi-electron transfer reactions in general, and provides new insight into how active 3d-metal catalysts can be synthesized by optimizing the energetics of both bond formation and charge accumulation.