论文标题：Stabilizing mechanism of single-atom catalysts on a defective carbon surface

期刊：npj Computational Materials

作者：Lianping Wu, Shuling Hu et.al

发表时间：2020/03/19

数字识别码： 10.1038/s41524-020-0292-y

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负载型单原子催化剂因其超高的金属原子利用率和新奇的催化特性，在加氢、一氧化碳氧化、甲烷氧化、氧还原等反应中均表现出优异的活性和选择性。但单原子容易发生团聚而使其催化活性降低，因此获得稳定的单原子催化剂成为当前催化领域的重大挑战。尽管负载型单原子的制备和实现方面近期取得了长足的进展，但是单原子的形成机理以及影响单原子形成因素等问题的探究尚不足。

为此，马里兰大学李腾教授与西安交通大学申胜平教授合作，利用分子动力学方法模拟了碳材料表面的纳米金颗粒在高温下向单原子演化的过程。这项研究考虑了碳表面的空位浓度对单原子形成的影响，并由此首次揭示了高温下Au-NP在缺陷碳表面转变成稳定的Au-SAs阵列现象的原子尺度机制，而且进一步考察了单原子在高温下的热稳定性和催化性能。

该研究发现，碳材料表面的空位使碳原子的悬挂键与金原子形成共价键，而增加碳材料表面的空位能够促进单原子的完全分散。这种原子尺度的转换机制具有Au-SA从Au-NP分解的低能垒和高Au-C结合能，从而稳定所得的Au-SA特征。进一步研究还发现，金单原子催化甲烷氧化的效率可以高达金纳米颗粒催化效率的4倍。该转化机制为了解在缺陷碳纳米纤维上稳定形成Au-SA的实验现象提供了重要启示。

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摘要：Single-atom (SA) catalysts represent the ultimate limit of atom use efficiency for catalysis. Promising experimental progress in synthesizing SA catalysts aside, the atomic-scale transformation mechanism from metal nanoparticles (NPs) to metal SAs and the stabilization mechanism of SA catalysts at high temperature remain elusive. Through systematic molecular dynamics simulations, for the first time, we reveal the atomic-scale mechanisms associated with the transformation of a metal NP into an array of stable SAs on a defective carbon surface at a high temperature, using Au as a model material. Simulations reveal the pivotal role of defects in the carbon surface in trapping and stabilizing the Au-SAs at high temperatures, which well explain previous experimental observations. Furthermore, reactive simulations demonstrate that the thermally stable Au-SAs exhibit much better catalyst activity than Au-NPs for the methane oxidation at high temperatures, in which the substantially reduced energy barriers for oxidation reaction steps are the key. Findings in this study offer mechanistic and quantitative guidance for material selection and optimal synthesis conditions to stabilize metal SA catalysts at high temperatures.

（来源：科学网）