Dutta Soumajit, Vahdat Mohammad Tohidi, Rezaei Mojtaba, Agrawal Kumar Varoon
École Polytechnique Fédérale de Lausanne (EPFL), Rue de l'Industrie 17, Sion, 1951, Switzerland.
Sci Rep. 2019 Mar 26;9(1):5202. doi: 10.1038/s41598-019-41645-9.
A robust synthesis methodology for crystallizing nanoporous single-layer graphene hosting a high density of size-selective nanopores is urgently needed to realize the true potential of two-dimensional membranes for gas separation. Currently, there are no controllable etching techniques for single-layer graphene that are self-limiting, and that can generate size-selective nanopores at a high pore-density. In this work, we simulate a unique chemical vapor deposition based crystallization of graphene on Cu(111), in the presence of an etchant, to generate a high density (>10 cm) of sub-nanometer-sized, elongated nanopores in graphene. An equilibrium between the growth rate and the etching rate is obtained, and beyond a critical time, the total number of the carbon atoms and the edge carbon atoms do not change. Using an optimal first-order etching chemistry, a log-mean pore-size of 5.0 ± 1.7 (number of missing carbon atoms), and a pore-density of 3 × 10 cm was achieved. A high throughput calculation route for estimating gas selectivity from ensembles of thousands of nanopores was developed. The optimized result yielded H/CO, H/N and H/CH selectivities larger than 200, attributing to elongated pores generated by the competitive etching and growth. The approach of competitive etching during the crystal growth is quite generic and can be applied to a number of two-dimensional materials.
迫切需要一种强大的合成方法来结晶具有高密度尺寸选择性纳米孔的纳米多孔单层石墨烯，以实现二维膜在气体分离方面的真正潜力。目前，尚无用于单层石墨烯的可控自限性蚀刻技术，且该技术无法在高孔密度下产生尺寸选择性纳米孔。在这项工作中，我们模拟了在蚀刻剂存在下，基于化学气相沉积在Cu(111)上独特的石墨烯结晶过程，以在石墨烯中生成高密度（>10 cm）的亚纳米尺寸的细长纳米孔。获得了生长速率和蚀刻速率之间的平衡，超过临界时间后，碳原子总数和边缘碳原子数不变。使用最佳的一级蚀刻化学方法，实现了对数平均孔径为5.0 ± 1.7（缺失碳原子数），孔密度为3×10 cm。开发了一种高通量计算途径，用于从数千个纳米孔的集合中估计气体选择性。优化结果产生的H/CO、H/N和H/CH选择性大于200，这归因于竞争性蚀刻和生长产生的细长孔。晶体生长过程中的竞争性蚀刻方法非常通用，可应用于多种二维材料。
