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Hydrogen-sieving single-layer graphene membranes obtained by crystallographic and morphological optimization of catalytic copper foil
Journal of Membrane Science ( IF 9.5 ) Pub Date : 2020-10-01 , DOI: 10.1016/j.memsci.2020.118406
Mojtaba Rezaei , Shaoxian Li , Shiqi Huang , Kumar Varoon Agrawal

Abstract Gas separation membranes based on single-layer-graphene are highly attractive because the size of graphene nanopores can be tuned to separate gases by the size-sieving mechanism. A prerequisite for this, the synthesis of high-quality polycrystalline single-layer graphene film by chemical vapor deposition (CVD), is extremely crucial. The quality of graphene in the context of membranes is reflected by the size and the density of the intrinsic vacancy defects, and is affected by the catalytic metal substrate and the CVD environment. Generally, expensive high-purity Cu foil is used to obtain gas-sieving performance from single-layer graphene. For the eventual scale-up of graphene membranes, it is highly attractive to use low-cost Cu foils, however, as we show here, these Cu foils are rough and graphene membranes derived from these foils do not yield gas-sieving performance. Herein, we conduct a systematic high-temperature annealing study on two separate, commercial, low-cost Cu foils leading to their transformation to Cu(111). The annealing process smoothened the Cu surface, decreasing the root mean square (RMS) surface roughness from over 200 nm to close to 100 nm. The RMS roughness on the individual Cu step, measured using the scanning tunneling microscopy (STM), was only 0.23 nm. The smooth, oriented Cu grains yielded single-layer graphene with a significantly lower defect density with ID/IG ratio decreasing from 0.18 ± 0.02 to 0.04 ± 0.01. Finally, single-layer graphene films, synthesized on the annealed low-purity Cu foil, yielded H2-selective membranes with H2 permeance reaching 1000 gas permeation units (GPU) in combination with attractive H2/CH4 and H2/C3H8 selectivities of 13 and 26, respectively.

中文翻译:

通过催化铜箔的晶体学和形态优化获得氢筛分单层石墨烯膜

摘要 基于单层石墨烯的气体分离膜极具吸引力,因为石墨烯纳米孔的尺寸可以通过尺寸筛分机制进行调节以分离气体。为此,通过化学气相沉积 (CVD) 合成高质量的多晶单层石墨烯薄膜至关重要。膜中石墨烯的质量由内在空位缺陷的大小和密度反映,并受催化金属基材和 CVD 环境的影响。通常,昂贵的高纯度铜箔用于从单层石墨烯中获得气体筛分性能。对于石墨烯膜的最终放大,使用低成本的铜箔非常有吸引力,然而,正如我们在这里展示的,这些铜箔是粗糙的,由这些箔衍生的石墨烯膜不产生气体筛分性能。在这里,我们对两个独立的、商业的、低成本的铜箔进行了系统的高温退火研究,导致它们转变为 Cu(111)。退火过程使铜表面平滑,将均方根 (RMS) 表面粗糙度从超过 200 nm 降低到接近 100 nm。使用扫描隧道显微镜 (STM) 测量的单个 Cu 步骤的 RMS 粗糙度仅为 0.23 nm。光滑、定向的 Cu 晶粒产生单层石墨烯,其缺陷密度显着降低,ID/IG 比从 0.18 ± 0.02 降低到 0.04 ± 0.01。最后,在退火的低纯度铜箔上合成单层石墨烯薄膜,
更新日期:2020-10-01
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