Deconstructing proton transport through atomically thin monolayer CVD graphene membranes

Chaturvedi, Pavan; Moehring, Nicole K.; Peng, Cheng; Vlassiouk, Ivan; Boutilier, Michael S. H.; Kidambi, Piran R.

doi:10.1039/d2ta01737g

Cited by 22 publications

(34 citation statements)

References 77 publications

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“…Scanning electron microscopy (SEM) image (Figure B) of the as-synthesized CVD graphene on Cu foil shows wrinkles (originating from the differences in thermal expansions of graphene and copper), indicating a continuous layer. , Raman spectroscopy (Figure C) with the characteristic graphene peaks (2D ∼2700 cm –1 , G ∼1600 cm –1 ) and the absence of a D peak (∼1350 cm –1 ) confirms the high quality of the synthesized monolayer ( I 2D / I G >1) graphene film . The SEM image of graphene on PCTE support (Figure D) shows a majority of PCTE pores with ∼200 nm diameter covered with graphene (darker contrast in SEM), indicating successful transfer, along with some uncovered regions (brighter regions in SEM) due to tears in the graphene from the manual pressing step of the transfer.…”

Section: Resultsmentioning

confidence: 72%

Nanoporous Atomically Thin Graphene Filters for Nanoscale Aerosols

Peng

Harkaway

Naclerio

et al. 2022

ACS Appl. Mater. Interfaces

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Filtering nanoparticulate aerosols from air streams is important for a wide range of personal protection equipment (PPE), including masks used for medical research, healthcare, law enforcement, first responders, and military applications. Conventional PPEs capable of filtering nanoparticles <300 nm are typically bulky and sacrifice breathability to maximize protection from exposure to harmful nanoparticulate aerosols including viruses ∼20–300 nm from air streams. Here, we show that nanopores introduced into centimeter-scale monolayer graphene supported on polycarbonate track-etched supports via a facile oxygen plasma etch can allow for filtration of aerosolized SiO2 nanoparticles of ∼5–20 nm from air steams while maintaining air permeance of ∼2.28–7.1 × 10–5 mol m–2 s–1 Pa–1. Furthermore, a systematic increase in oxygen plasma etch time allows for a tunable size-selective filtration of aerosolized nanoparticles. We demonstrate a new route to realize ultra-compact, lightweight, and conformal form-factor filters capable of blocking sub-20 nm aerosolized nanoparticles with particular relevance for biological/viral threat mitigation.

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Section: Resultsmentioning

confidence: 72%

Nanoporous Atomically Thin Graphene Filters for Nanoscale Aerosols

Peng

Harkaway

Naclerio

et al. 2022

ACS Appl. Mater. Interfaces

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“…To analyze the proton transportation behavior in different nanochannels, an extra proton was put into the systems forming a hydronium ion with a random water molecule. Since 0.1 M HCl is most commonly used in proton conductivity measurement experiments, , one extra proton in our simulation box, with the corresponding pH even lower than 1, is comparable to the experimental proton transport environment. To identify the hydronium ion from water molecules, we scanned the trajectory files and if one oxygen molecule was found with three bonds attached, then it would be judged as the stable hydronium ion at that frame, while for the transition state hydronium ion, the oxygen from two neighboring water molecules both formed a hydrogen bond with the proton, the closer one was thought to be the hydronium ion; 20 sets of 100 ps simulations of every studied case were analyzed to guarantee the statistical significance of the results.…”

Section: Resultsmentioning

confidence: 88%

Aqueous Proton Transportation in Graphene-Based Nanochannels

et al. 2022

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Graphene oxide (GO) has been unveiled to exhibit high proton conductivity in a humidified or aqueous environment, making it a promising candidate to construct proton conduction nanochannels. In this work, we systematically investigate how the confinement effect and surface chemistry influence the proton transportation behavior in graphene-based nanochannels via extensive ReaxFF MD simulations. Graphene (GE), graphane (GA), and hydroxygraphane (HG) sheets were employed to mimic the graphitic and functionalized region of GO and construct nanochannels with different interlayer distances. We find that confined water molecules are stratified and their orientation is influenced by the surface chemistry, thus impacting the distribution of protons. Surface chemistry makes the compression of the hydrogen-bond network induced by the confinement effect more variable. The hydrogen-bond network between GE slabs is crushed by extreme confinement and ultrafast proton transportation behavior mainly achieved via vehicle mechanism. Meanwhile, the hydrogen-bond network and solvation structure can be kept more complete with the existence of functional groups. The hydrogen bonds formed with surface functional groups impede the transportation of water molecules but allow more Grotthuss hopping of protons to different extents. Our work clarified the proton transportation mechanism in graphene-based nanochannels with different interlayer distances and surface chemistry and can guide the future design of proton conduction devices such as proton exchange membranes.

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“…Graphene on Cu is cut to ∼2.25 cm 2 pieces and N211-K + is placed on top. A thin layer of Nafion solution (1100 MW, 1 wt %) is applied to a PTFE-coated fiberglass mat (15 mil thickness) and placed on the N211-K + . An additional fiberglass mat is placed on the bottom, below the graphene on Cu and the whole stack is hot pressed at 145 °C for 3 min at ∼1000 psi.…”

Section: Experimental Methodsmentioning

confidence: 99%

“…A thin layer of Nafion solution (1100 MW, 1 wt %) is applied to a PTFE-coated fiberglass mat (15 mil thickness) and placed on the N211-K + . 90 An additional fiberglass mat is placed on the bottom, below the graphene on Cu and the whole stack is hot pressed at 145 °C for 3 min at ∼1000 psi. The bottom fiberglass mat is removed and the remaining Cu|Graphene|N211-K + |fiberglass stack is pre-etched in APS solution (0.2 M) for 15 min and rinsed in DI water to remove the bottom layer of graphene from the Cu.…”

Section: Experimental Methodsmentioning

confidence: 99%

Kinetic Control of Angstrom-Scale Porosity in 2D Lattices for Direct Scalable Synthesis of Atomically Thin Proton Exchange Membranes

et al. 2022

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Angstrom-scale pores introduced into atomically thin 2D materials offer transformative advances for proton exchange membranes in several energy applications. Here, we show that facile kinetic control of scalable chemical vapor deposition (CVD) can allow for direct formation of angstrom-scale proton-selective pores in monolayer graphene with significant hindrance to even small, hydrated ions (K+ diameter ∼6.6 Å) and gas molecules (H2 kinetic diameter ∼2.9 Å). We demonstrate centimeter-scale Nafion|Graphene|Nafion membranes with proton conductance ∼3.3–3.8 S cm–2 (graphene ∼12.7–24.6 S cm–2) and H+/K+ selectivity ∼6.2–44.2 with liquid electrolytes. The same membranes show proton conductance ∼4.6–4.8 S cm–2 (graphene ∼39.9–57.5 S cm–2) and extremely low H2 crossover ∼1.7 × 10–1 – 2.2 × 10–1 mA cm–2 (∼0.4 V, ∼25 °C) with H2 gas feed. We rationalize our findings via a resistance-based transport model and introduce a stacking approach that leverages combinatorial effects of interdefect distance and interlayer transport to allow for Nafion|Graphene|Graphene|Nafion membranes with H+/K+ selectivity ∼86.1 (at 1 M) and record low H2 crossover current density ∼2.5 × 10–2 mA cm–2, up to ∼90% lower than state-of-the-art ionomer Nafion membranes ∼2.7 × 10–1 mA cm–2 under identical conditions, while still maintaining proton conductance ∼4.2 S cm–2 (graphene stack ∼20.8 S cm–2) comparable to that for Nafion of ∼5.2 S cm–2. Our experimental insights enable functional atomically thin high flux proton exchange membranes with minimal crossover.

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Deconstructing proton transport through atomically thin monolayer CVD graphene membranes

Abstract: Selective proton (H+) permeation through the atomically thin lattice of graphene and other 2D materials offers new opportunities for energy conversion/storage and novel separations. Practical applications necessitate scalable synthesis via...

Cited by 22 publications

References 77 publications

Nanoporous Atomically Thin Graphene Filters for Nanoscale Aerosols

Nanoporous Atomically Thin Graphene Filters for Nanoscale Aerosols

Aqueous Proton Transportation in Graphene-Based Nanochannels

Kinetic Control of Angstrom-Scale Porosity in 2D Lattices for Direct Scalable Synthesis of Atomically Thin Proton Exchange Membranes

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