Jiang Hongliang, He Qun, Zhang Youkui, Song Li
National Synchrotron Radiation Laboratory, CAS Centre for Excellence in Nanoscience , University of Science and Technology of China , Hefei 230029 , P. R. China.
State Key Laboratory of Environment-friendly Energy Materials, School of National Defense Science & Technology , Southwest University of Science and Technology , Mianyang , Sichuan 621010 , China.
Acc Chem Res. 2018 Nov 20;51(11):2968-2977. doi: 10.1021/acs.accounts.8b00449. Epub 2018 Oct 30.
Recent years have witnessed significant development of electrocatalysis for clean energy and related potential technologies. The precise identification toward active sites of catalysts and the monitoring of product information are highly desirable to understand how the materials catalyze a specific electrocatalytic reaction. For a long period, the identification of active sites and the cognition of corresponding catalytic mechanisms are generally based on various ex situ characterization methods which actually could not capture dynamic structure and intermediate information during electrocatalytic processes. With recent developments of in situ and operando characterization techniques, it has been extensively observed that most of the catalysts would undergo structural self-reconstruction as a result of electro-derived oxidation or reduction process of the catalysts at a given potential, often accompanied by the increase or decrease of catalytic activity as well as the change of catalytic selectivity. In fact, such structural self-change in the catalytic process does make it difficult to identify the true catalytically active sites efficiently, thus hindering the understanding of the real catalytic mechanism. Therefore, we believe that understanding the self-reconstruction by the combination of reliable characterization techniques and theoretical calculations holds the key to rational design of advanced catalysts. In this Account, we provide in-depth insights into recent progress regarding structural self-reconstruction of electrocatalysts in several typical electrochemical reactions with the emphasis on fundamental knowledge, structure-property relationships, structural evolution process, and modulation of self-reconstruction. To deliver a clear understanding, it has to be pointed out in advance that these catalysts with drastic structural and activity self-change in electrocatalytic processes are suggested to be called precatalysts under nonreaction conditions. The restructured active components in realistic reaction conditions are true catalysts. The structural self-reconstruction process bridges the precatalysts with true catalysts. To understand the self-reconstruction behavior, the following three critical aspects will be carefully disclosed and discussed in depth. First, fundamental origin of structural self-reconstruction of electrocatalysts is introduced. It is noteworthy that the atomic-level correlations between the self-reconstruction behavior and intrinsic structure of precatalysts are emphasized due to the fact that even if some precatalysts are congeneric, they often exhibit a diverse self-reconstruction phenomenon and catalytic performance. Second, the self-reconstruction process should be monitored by advanced characterization techniques, which is central to precisely unveil the self-reconstruction behavior. In situ or operando characterizations have been considered as judicious methods to track the self-reconstruction, capture dynamic structure and analyze real-time reaction products. Finally, based on the dynamic structure and product information together with comprehensive theory calculations, the enhancement or degradation mechanism of catalytic activities can be unambiguously clarified. With thoughtful studies toward the complete self-reconstruction process of electrocatalysts, some feasible methods to tune the self-reconstruction and improve the performance can be rationally proposed. Based on this progress, we hope to provide new insight into electrocatalysis, particularly the self-reconstruction and true active sites of electrocatalysts, and then to offer guidelines for rational design of advanced electrocatalysts.
近年来，用于清洁能源及相关潜在技术的电催化取得了显著进展。精确识别催化剂的活性位点并监测产物信息对于理解材料如何催化特定的电催化反应非常有必要。长期以来，活性位点的识别和相应催化机制的认知通常基于各种非原位表征方法，而这些方法实际上无法捕捉电催化过程中的动态结构和中间体信息。随着原位和 operando 表征技术的发展，人们广泛观察到，在给定电位下，大多数催化剂会由于电衍生的氧化或还原过程而发生结构自重构，通常伴随着催化活性的增加或降低以及催化选择性的变化。事实上，催化过程中的这种结构自我变化确实使得难以有效地识别真正的催化活性位点，从而阻碍了对真实催化机制的理解。因此，我们认为，通过可靠的表征技术和理论计算相结合来理解自重构是合理设计先进催化剂的关键。在本综述中，我们深入探讨了电催化剂在几种典型电化学反应中的结构自重构方面的最新进展，重点关注基础知识、结构 - 性能关系、结构演变过程以及自重构的调控。为了清晰理解，必须预先指出，在非反应条件下，这些在电催化过程中具有剧烈结构和活性自我变化的催化剂被建议称为前催化剂。在实际反应条件下重构的活性组分才是真正的催化剂。结构自重构过程将前催化剂与真正的催化剂联系起来。为了理解自重构行为，将仔细揭示并深入讨论以下三个关键方面。首先，介绍电催化剂结构自重构的基本起源。值得注意的是，强调了自重构行为与前催化剂固有结构之间的原子级关联，因为即使一些前催化剂是同类的，它们也常常表现出多样的自重构现象和催化性能。其次，应通过先进的表征技术监测自重构过程，这对于精确揭示自重构行为至关重要。原位或 operando 表征被认为是追踪自重构、捕捉动态结构和分析实时反应产物的明智方法。最后，基于动态结构和产物信息以及全面的理论计算，可以明确阐明催化活性的增强或降低机制。通过对电催化剂完整自重构过程的深入研究，可以合理地提出一些调节自重构和提高性能的可行方法。基于这一进展，我们希望为电催化，特别是电催化剂的自重构和真正活性位点提供新的见解，进而为先进电催化剂的合理设计提供指导。
