Li Xiaodong, Wang Shumin, Li Li, Zu Xiaolong, Sun Yongfu, Xie Yi
Hefei National Laboratory for Physical Sciences at Microscale, University of Science and Technology of China, Hefei 230026, P.R. China.
Institute of Energy, Hefei Comprehensive National Science Center, Hefei, Anhui 230031, China.
Acc Chem Res. 2020 Dec 15;53(12):2964-2974. doi: 10.1021/acs.accounts.0c00626. Epub 2020 Nov 25.
ConspectusExcessive use of fossil fuels has not only led to energy shortage but also caused serious environmental pollution problems due to the massive emissions of industrial waste gas. As the main component of industrial waste gas, CO molecules can also be utilized as an important raw material for renewable fuels. Thus, the effective capture and conversion of CO has been considered one of the best potential strategies to mitigate the energy crisis and lower the greenhouse effect simultaneously.In this case, CO electroreduction to high-value-added chemicals provides an available approach to accomplish this important goal. Nonetheless, the CO molecule is extremely stable with a high dissociation energy. With regard to the traditional electrocatalytic systems, there are three main factors that hinder their practical applications: (i) sluggish carrier transport dynamics; (ii) high energy barrier for CO activation; (iii) poor product selectivity. Therefore, solving these three crucial problems is the key to the development of efficient electrocatalytic CO reduction systems.Considering that the CO molecule is a typical Lewis acid with a high first ionization energy and electronic affinity, electron-rich catalysts could help to activate the CO molecule and improve the conversion efficiency. In view of this, atomically thin two-dimensional electrocatalysts, benefiting from their significantly increased density of states near the Fermi level, have great potential to effectively accelerate the dynamics of electron transport. Moreover, their high fraction of surface active sites and enhanced local charge density could remarkably reduce the energy barrier for CO activation. Furthermore, their modulated electronic structure could alter the catalytic reaction pathway and improve the product selectivity. Meanwhile, the concise two-dimensional configuration facilitates characterization as well as the establishment and simulation of theoretical models, which helps to reveal the mechanism of electrocatalytic CO reduction, thereby speeding up the development of CO conversion technology.In this Account, we summarize recent progress in tailoring the electronic structure of atomically thin two-dimensional electrocatalysts by different methods. Meanwhile, we highlight the structure-property relationship between the electronic structure regulation and the catalytic activity/product selectivity of atomically thin two-dimensional electrocatalysts, and discuss the underlying fundamental mechanism with the aid of characterization techniques. Finally, we discuss the major challenges and opportunities for the future development of CO electroreduction. It is expected that this Account will help researchers to better understand CO electroreduction and guide better design of high-performance electrocatalytic systems.
概述
过度使用化石燃料不仅导致能源短缺，还因工业废气的大量排放引发了严重的环境污染问题。作为工业废气的主要成分，CO分子也可被用作可再生燃料的重要原料。因此，CO的有效捕获和转化被认为是同时缓解能源危机和降低温室效应的最佳潜在策略之一。
在这种情况下，将CO电还原为高附加值化学品提供了一种实现这一重要目标的可行方法。然而，CO分子极其稳定，具有较高的离解能。对于传统的电催化系统，有三个主要因素阻碍其实际应用：（i）缓慢的载流子传输动力学；（ii）CO活化的高能量壁垒；（iii）较差的产物选择性。因此，解决这三个关键问题是高效电催化CO还原系统发展的关键。
考虑到CO分子是一种具有高第一电离能和电子亲和性的典型路易斯酸，富电子催化剂有助于活化CO分子并提高转化效率。鉴于此，原子级薄的二维电催化剂受益于其在费米能级附近显著增加的态密度，具有有效加速电子传输动力学的巨大潜力。此外，它们高比例的表面活性位点和增强的局部电荷密度可显著降低CO活化的能量壁垒。此外，它们调制的电子结构可改变催化反应途径并提高产物选择性。同时，简洁的二维结构便于表征以及理论模型的建立和模拟，这有助于揭示电催化CO还原的机理，从而加速CO转化技术的发展。
在本综述中，我们总结了通过不同方法调整原子级薄的二维电催化剂电子结构的最新进展。同时，我们强调了电子结构调控与原子级薄的二维电催化剂催化活性/产物选择性之间的结构-性能关系，并借助表征技术讨论了潜在的基本机理。最后，我们讨论了CO电还原未来发展的主要挑战和机遇。预计本综述将帮助研究人员更好地理解CO电还原，并指导高性能电催化系统的更好设计。
