甲烷在理想和缺陷石墨烯上解离吸附自由能的从头算模拟
Free energy landscape of dissociative adsorption of methane on ideal and defected graphene from ab initio simulations
摘要：
我们研究了甲烷在石墨烯表面的解离吸附。自由能分布，其中包括不同步骤的反应的活化能，计算从约束从头分子动力学。在300 K时，反应势垒远低于实验测得的气态甲烷的键离解能，表明石墨烯表面对甲烷的分解起催化作用.另一方面，势垒仍然比镍表面高得多。因此，甲烷解离在镍上以比在石墨烯上更高的速率发生。该反应是从前体气体生长石墨烯的先决条件。因此，第一单层的生长应该是快速和有效的过程，而随后的层以减小的速率和更可控的方式生长。缺陷也可能影响反应能量学。这是显而易见的，从我们的结果，其中简单的缺陷（斯通-威尔士缺陷和氮取代）导致不同的自由能景观在解离和吸附的过程中的步骤。
英文摘要：
We study the dissociative adsorption of methane at the surface of graphene. Free energy profiles, which include activation energies for different steps of the reaction, are computed from constrained ab initio molecular dynamics. At 300 K, the reaction barriers are much lower than experimental bond dissociation energies of gaseous methane, strongly indicating that graphene surface acts as a catalyst of methane decomposition. On the other hand, the barriers are still much higher than on nickel surface. Methane dissociation therefore occurs at a higher rate on nickel than on graphene. This reaction is a prerequisite for graphene growth from precursor gas. Thus, the growth of the first monolayer should be a fast and efficient process while subsequent layers grow at diminished rate and in a more controllable manner. Defects may also influence reaction energetics. This is evident from our results, in which simple defects (Stone-Wales defect and nitrogen substitution) lead to different free energy landscapes at both dissociation and adsorption steps of the process.
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