Proton and Li-Ion Permeation through Graphene with Eight-Atom-Ring Defects
Eoin Griffin, Lucas Mogg, Guang-Ping Hao, Gopinadhan Kalon, Cihan Bacaksiz, Guillermo Lopez-Polin, T. Y. Zhou, Victor Guarochico, Junhao Cai, Christof Neumann, … 展开作者
Eoin Griffin, Lucas Mogg, Guang-Ping Hao, Gopinadhan Kalon, Cihan Bacaksiz, Guillermo Lopez-Polin, T. Y. Zhou, Victor Guarochico, Junhao Cai, Christof Neumann, Andreas Winter, Michael Mohn, Jong Hak Lee, Junhao Lin, Ute Kaiser, Irina V. Grigorieva, Kazu Suenaga, Barbaros Ozyilmaz, Hui-Min Cheng, Wencai Ren, Andrey Turchanin, Francois M. Peeters, Andre K. Geim, Marcelo Lozada-Hidalgo
Defect-free graphene is impermeable to gases and liquids but highly permeable to thermal protons. Atomic-scale defects such as vacancies, grain boundaries and Stone-Wales defects are predicted to enhance graphene's proton permeability and may even allow small ions through, whereas larger species such as gas molecules should remain blocked. These expectations have so far remained untested in experiment. Here we show that atomically thin carbon films with a high density of atomic-scale defects continue blocking all molecular transport, but their proton permeability becomes ~1,000 times higher than that of defect-free graphene. Lithium ions can also permeate through such disordered graphene. The enhanced proton and ion permeability is attributed to a high density of 8-carbon-atom rings. The latter pose approximately twice lower energy barriers for incoming protons compared to the 6-atom rings of graphene and a relatively low barrier of ~0.6 eV for Li ions. Our findings suggest that disordered graphene could be of interest as membranes and protective barriers in various Li-ion and hydrogen technologies.
Water transport through graphene-derived membranes has gained much interest recently due to its promising potential in filtration and separation applications. In this work, we explore water permeation in graphene oxide membranes using atomistic simulations, by considering flow through interlayer gallery, expanded pores such as wrinkles of interedge spaces, and pores within the sheet. We find that although flow enhancement can be established by nanoconfinement, fast water transport through pristine graphene channels is prohibited by a prominent side-pinning effect from capillaries formed betwee…
Permeation through nanometer pores is important in the design of materials for filtration and separation techniques and because of unusual fundamental behavior arising at the molecular scale. We found that submicron-thick membranes made from graphene oxide can be completely impermeable to liquids, vapors and gases, including helium, but allow unimpeded permeation of water (H2O permeates through the membranes at least 10^10 times faster than He). We attribute these seemingly incompatible observations to a low-friction flow of a monolayer of water through two dimensional capillaries formed by cl…
The layers of graphene oxide (GO) are found to be good for permeation of water but not for helium (Science 2012 335 (6067): 442-444) suggesting that the GO layers are dynamic in the formation of permeation route depending on the environment they are in (i.e, water or helium). To probe the microscopic origin of this observation we calculate the potential of mean force (PMF) of GO sheets (oxidized and reduced parts), with inter-planar distance as reaction coordinate in helium and water. Our PMF calculation shows that equilibrium interlayer distance between oxidized part of GO sheets in helium is…
Developing 'smart' membranes that allow precise and reversible control of molecular permeation using external stimuli would be of intense interest for many areas of science: from physics and chemistry to life-sciences. In particular, electrical control of water permeation through membranes is a long-sought objective and is of crucial importance for healthcare and related areas. Currently, such adjustable membranes are limited to the modulation of wetting of the membranes and controlled ion transport, but not the controlled mass flow of water. Despite intensive theoretical work yielding conflic…
Graphene-based membranes have been investigated as promising candidates for water filtration and gas separation applications. Experimental evidences have shown that graphene oxide can be impermeable to liquids, vapors and gases, while allowing a fast permeation of water molecules. This phenomenon has been attributed to the formation of a network of nano capillaries that allow nearly frictionless water flow while blocking other molecules by steric hindrance effects. It is supposed that water molecules are transported through the percolated two-dimensional channels formed between graphene-based …
Graphene oxide (GO) membranes continue to attract intense interest due to their unique molecular sieving properties combined with fast permeation rates. However, the membranes' use has been limited mostly to aqueous solutions because GO membranes appear to be impermeable to organic solvents, a phenomenon not fully understood yet. Here, we report efficient and fast filtration of organic solutions through GO laminates containing smooth two-dimensional (2D) capillaries made from flakes with large sizes of ~ 10-20 micron. Without sacrificing their sieving characteristics, such membranes can be mad…
Despite being only one-atom thick, defect-free graphene is considered to be completely impermeable to all gases and liquids. This conclusion is based on theory and supported by experiments that could not detect gas permeation through micrometre-size membranes within a detection limit of 10^5 to 10^6 atoms per second. Here, using small monocrystalline containers tightly sealed with graphene, we show that defect-free graphene is impermeable with an accuracy of eight to nine orders of magnitude higher than in the previous experiments. We could discern permeation of just a few helium atoms per hou…
Graphene oxide membranes show exceptional molecular permeation properties, with a promise for many applications. However, their use in ion sieving and desalination technologies is limited by a permeation cutoff of ~9 Angstrom, which is larger than hydrated ion diameters for common salts. The cutoff is determined by the interlayer spacing d ~13.5 Angstrom, typical for graphene oxide laminates that swell in water. Achieving smaller d for the laminates immersed in water has proved to be a challenge.Here we describe how to control d by physical confinement and achieve accurate and tuneable ion sie…
Graphene-based laminates, with ultralong and tortuous nanocapillaries formed by simply stacking graphene flakes together, have great promises in filtration and separation. However, the information on liquid water trans-membrane permeation is lacking, which is the most fundamental problem and of crucial importance in solution-based mass transport. Here, based on isotope labelling, we investigate the liquid water transportation through graphene-based nanocapillaries under no external hydrostatic pressures. Liquid water can afford an unimpeded permeation through graphene-based nanochannels with a…
Barrier films preventing permeation of gases and moistures are important for many industries ranging from food to medical and from chemical to electronic. From this perspective, graphene has recently attracted particular interest because its defect free monolayers are impermeable to all gases and liquids. However, it has proved challenging to develop large-area defectless graphene films suitable for industrial use. Here we report barrier properties of multilayer graphitic films made by chemical reduction of easily and cheaply produced graphene oxide laminates. They are found to provide a pract…
Density functional theory has been employed to study graphene on the (111), (100) and (110) surfaces of silicon (Si) substrates. There are several interesting findings. First, carbon atoms in graphene form covalent bonds with Si atoms, when placed close enough on Si (111) and (100) surfaces, but not on the (110) surface. The presence of a Si (111) surface shifts the Fermi level of graphene into its conduction band, resulting in an increase of the work function by 0.29 eV and of the electron density by three orders of magnitude. The carrier density of graphene can also be increased by eighty ti…
While graphene is a semi-metal, a recently synthesized hydrogenated graphene called graphane, is an insulator. We have probed the transformation of graphene upon hydrogenation to graphane within the framework of density functional theory. By analyzing the electronic structure for eighteen different hydrogen concentrations, we bring out some novel features of this transition. Our results show that the hydrogenation favors clustered configurations leading to the formation of compact islands. The analysis of the charge density and electron localization function (ELF) indicates that as hydrogen co…
The elemental two-dimensional (2D) materials such as graphene, silicene, germanene, and black phosphorus have attracted considerable attention due to their fascinating physical properties. Structurally they possess the honeycomb or distorted honeycomb lattices, which are composed of six-atom rings. Here we find a new structure of 2D allotropes of group V elements composed of eight-atom rings, which we name as the octagonal tiling (OT) structure. First-principles calculations indicate that these allotropes are dynamically stable and are also thermally stable at temperatures up to 600 K. These a…
Four sp3 carbon allotropes with six, eight, and 16 atoms per primitive cell have been derived using a combination of metadynamics simulations and topological scan. A chiral orthorhombic phase oC16 (C2221) was found to be harder than monoclinic M-carbon and shows excellent stability in the high-pressure range. A second orthorhombic phase of Cmmm symmetry, by \sim 0.028 eV/atom energetically lower than W-carbon, can be formed from graphite at \sim 9 GPa. In general, the mechanical response under pressure was found to depend on the structure topology, which reflects the way rings are formed from …
The adsorption characteristics of alkali, alkaline earth and transition metal adatoms on silicene, a graphene-like monolayer structure of silicon, are analyzed by means of first-principles calculations. In contrast to graphene, interaction between the metal atoms and the silicene surface is quite strong due to its highly reactive buckled hexagonal structure. In addition to structural properties, we also calculate the electronic band dispersion, net magnetic moment, charge transfer, workfunction and dipole moment of the metal adsorbed silicene sheets. Alkali metals, Li, Na and K, adsorb to holl…
