Back Seoin, Lim Juhyung, Kim Na-Young, Kim Yong-Hyun, Jung Yousung
Graduate School of EEWS , Korea Advanced Institute of Science and Technology (KAIST) , 291 Daehakro , Daejeon 34141 , Korea . Email:
Graduate School of Nanoscience and Technology , Korea Advanced Institute of Science and Technology (KAIST) , 291 Daehakro , Daejeon 34141 , Korea.
Chem Sci. 2017 Feb 1;8(2):1090-1096. doi: 10.1039/c6sc03911a. Epub 2016 Sep 19.
A single-atom catalyst (SAC) has an electronic structure that is very different from its bulk counterparts, and has shown an unexpectedly high specific activity with a significant reduction in noble metal usage for CO oxidation, fuel cell and hydrogen evolution applications, although physical origins of such performance enhancements are still poorly understood. Herein, by means of density functional theory (DFT) calculations, we for the first time investigate the great potential of single atom catalysts for CO electroreduction applications. In particular, we study a single transition metal atom anchored on defective graphene with single or double vacancies, denoted M@sv-Gr or M@dv-Gr, where M = Ag, Au, Co, Cu, Fe, Ir, Ni, Os, Pd, Pt, Rh or Ru, as a CO reduction catalyst. Many SACs are indeed shown to be highly selective for the CO reduction reaction over a competitive H evolution reaction due to favorable adsorption of carboxyl (*COOH) or formate (*OCHO) over hydrogen (*H) on the catalysts. On the basis of free energy profiles, we identified several promising candidate materials for different products; Ni@dv-Gr (limiting potential = -0.41 V) and Pt@dv-Gr (-0.27 V) for CHOH production, and Os@dv-Gr (-0.52 V) and Ru@dv-Gr (-0.52 V) for CH production. In particular, the Pt@dv-Gr catalyst shows remarkable reduction in the limiting potential for CHOH production compared to any existing catalysts, synthesized or predicted. To understand the origin of the activity enhancement of SACs, we find that the lack of an atomic ensemble for adsorbate binding and the unique electronic structure of the single atom catalysts as well as orbital interaction play an important role, contributing to binding energies of SACs that deviate considerably from the conventional scaling relation of bulk transition metals.
单原子催化剂（SAC）具有与其块状对应物截然不同的电子结构，并且在CO氧化、燃料电池和析氢应用中表现出出乎意料的高比活性，同时贵金属用量显著减少，尽管这种性能增强的物理起源仍知之甚少。在此，通过密度泛函理论（DFT）计算，我们首次研究了单原子催化剂在CO电还原应用中的巨大潜力。特别地，我们研究了锚定在具有单空位或双空位的缺陷石墨烯上的单个过渡金属原子，记为M@sv-Gr或M@dv-Gr，其中M = Ag、Au、Co、Cu、Fe、Ir、Ni、Os、Pd、Pt、Rh或Ru，作为CO还原催化剂。由于催化剂上羧基（*COOH）或甲酸根（*OCHO）比氢（*H）具有更有利的吸附，许多单原子催化剂在竞争性析氢反应中对CO还原反应确实具有高度选择性。基于自由能分布，我们确定了几种针对不同产物的有前景的候选材料；用于生成CHOH的Ni@dv-Gr（极限电位 = -0.41 V）和Pt@dv-Gr（-0.27 V），以及用于生成CH的Os@dv-Gr（-0.52 V）和Ru@dv-Gr（-0.52 V）。特别地，与任何已合成或预测的现有催化剂相比，Pt@dv-Gr催化剂在生成CHOH的极限电位方面有显著降低。为了理解单原子催化剂活性增强的起源，我们发现缺乏用于吸附质结合的原子集合、单原子催化剂独特的电子结构以及轨道相互作用起着重要作用，这导致单原子催化剂的结合能与块状过渡金属的传统比例关系有很大偏差。
