Abstract We demonstrate how hydrogen influences graphene nucleation on two archetypal catalysts, Cu(111) and Ni(111), using first-principles methods. The graphene nucleation mechanism is shown to be the result of the balance between the nature and strength of the carbon – metal interaction, and the influence of the hydrogen chemical potential on adsorbed carbon fragments. While the former drives the formation of ring structures in carbon fragments, the latter promotes the growth of saturated carbon chain structures during the nucleation process. Importantly, our results reveal how the presence of hydrogen dramatically influences the nature of the sp → sp2 transition, a key step in the nucleation of both graphene and carbon nanotubes. Increasing the presence of hydrogen during nucleation stabilises smaller ring structures earlier in the nucleation process, in fragments as small as carbon pentagons, which are known to be a key intermediate structure in carbon nanostructure nucleation. Conversely, lower hydrogen chemical potentials lead to the formation of carbon ring structures only in much larger fragments. These results present a new potential route by which hydrogen leads to greater control over CVD-synthesised carbon nanotubes and graphene, i.e. by driving the formation of smaller, more stable ring structures earlier in the growth process.

中文翻译：

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氢对过渡金属的影响-催化石墨烯成核

摘要 我们使用第一性原理方法展示了氢如何影响两种原型催化剂 Cu(111) 和 Ni(111) 上的石墨烯成核。石墨烯成核机制被证明是碳 - 金属相互作用的性质和强度之间平衡的结果，以及氢化学势对吸附的碳碎片的影响。前者推动碳碎片中环结构的形成，而后者在成核过程中促进饱和碳链结构的生长。重要的是，我们的结果揭示了氢的存在如何显着影响 sp → sp2 转变的性质，这是石墨烯和碳纳米管成核的关键步骤。在成核过程中增加氢的存在可以在成核过程的早期稳定较小的环结构，小到碳五边形的碎片，这是碳纳米结构成核的关键中间结构。相反，较低的氢化学势导致仅在更大的片段中形成碳环结构。这些结果提出了一种新的潜在途径，通过该途径，氢可以更好地控制 CVD 合成的碳纳米管和石墨烯，即通过在生长过程的早期推动形成更小、更稳定的环结构。较低的氢化学势导致仅在更大的片段中形成碳环结构。这些结果提出了一种新的潜在途径，通过该途径，氢可以更好地控制 CVD 合成的碳纳米管和石墨烯，即通过在生长过程的早期推动形成更小、更稳定的环结构。较低的氢化学势导致仅在更大的片段中形成碳环结构。这些结果提出了一种新的潜在途径，通过该途径，氢可以更好地控制 CVD 合成的碳纳米管和石墨烯，即通过在生长过程的早期推动形成更小、更稳定的环结构。