High-Resolution Ion-Flux Imaging of Proton Transport through Graphene|Nafion Membranes.
High-Resolution Ion-Flux Imaging of Proton Transport through Graphene|Nafion Membranes.
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通过石墨烯|Nafion 膜进行质子传输的高分辨率离子通量成像。
DOI：
10.1021/acsnano.1c05872
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发表时间：
2022-04-26
期刊：
影响因子：
17.1
通讯作者：
Unwin, Patrick R.
中科院分区：
文献类型：
--
作者：
Bentley, Cameron L.;Kang, Minkyung;Bukola, Saheed;Creager, Stephen E.;Unwin, Patrick R.
2014年，据报道，质子可以在环境条件下在由名义上原始的单层石墨烯和六方氮化硼（h-BN）膜（膜）分开的水相之间穿行。单原子厚度晶体的质子导电性，以及通过平面传导，挑战了石墨烯对原子、离子和分子不渗透的观念。最近的证据指出了一种缺陷促进的传输机制，类似于通过基于石墨烯和氢氮化硼的传统离子选择膜的传输。本文采用扫描电化学电池显微镜（SECCM）的“电化学离子（质子）泵电池”模式对化学气相沉积（CVD）石墨烯b| Nafion膜进行局部离子通量成像。在一个典型的实验中，我们以没有可见宏观缺陷（如裂缝、孔洞等）的区域为目标，评估了石墨烯表面数百到数千个不同的位点，发现大多数CVD石墨烯|Nafion膜对质子传输是不渗透的，质子传输通常发生在约0.003 mm2膜面积上的约20-60个局部位点上（共约5000个测量值）。当局部质子输运发生时，它可能是一个高度动态的过程，在外加电场的作用下，在秒时间尺度上有额外的传输位点“打开”和少数位点“关闭”。应用离子通过圆柱形纳米孔的简单等效电路模型，估计局部传输位点具有（亚）纳米尺度的尺寸（半径），这意味着罕见的原子缺陷是导致质子电导的原因。总的来说，这项工作加强了SECCM作为微观复杂（电）材料结构-性能映射的首要工具，本文介绍的局部离子通量映射配置广泛适用于功能膜表征及其他领域，例如诊断保护表面涂层的失效机制。
In 2014, it was reported that protons can traverse between aqueous phases separated by nominally pristine monolayer graphene and hexagonal boron nitride (h-BN) films (membranes) under ambient conditions. This intrinsic proton conductivity of the one-atom-thick crystals, with proposed through-plane conduction, challenged the notion that graphene is impermeable to atoms, ions, and molecules. More recent evidence points to a defect-facilitated transport mechanism, analogous to transport through conventional ion-selective membranes based on graphene and h-BN. Herein, local ion-flux imaging is performed on chemical vapor deposition (CVD) graphene|Nafion membranes using an “electrochemical ion (proton) pump cell” mode of scanning electrochemical cell microscopy (SECCM). Targeting regions that are free from visible macroscopic defects (e.g., cracks, holes, etc.) and assessing hundreds to thousands of different sites across the graphene surfaces in a typical experiment, we find that most of the CVD graphene|Nafion membrane is impermeable to proton transport, with transmission typically occurring at ≈20–60 localized sites across a ≈0.003 mm2 area of the membrane (>5000 measurements total). When localized proton transport occurs, it can be a highly dynamic process, with additional transmission sites “opening” and a small number of sites “closing” under an applied electric field on the seconds time scale. Applying a simple equivalent circuit model of ion transport through a cylindrical nanopore, the local transmission sites are estimated to possess dimensions (radii) on the (sub)nanometer scale, implying that rare atomic defects are responsible for proton conductance. Overall, this work reinforces SECCM as a premier tool for the structure–property mapping of microscopically complex (electro)materials, with the local ion-flux mapping configuration introduced herein being widely applicable for functional membrane characterization and beyond, for example in diagnosing the failure mechanisms of protective surface coatings.
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影响因子：
16.6
作者：
Achtyl, Jennifer L.;Unocic, Raymond R.;Xu, Lijun;Cai, Yu;Raju, Muralikrishna;Zhang, Weiwei;Sacci, Robert L.;Vlassiouk, Ivan V.;Fulvio, Pasquale F.;Ganesh, Panchapakesan;Wesolowski, David J.;Dai, Sheng;van Duin, Adri C. T.;Neurock, Matthew;Geiger, Franz M.
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影响因子：
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影响因子：
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影响因子：
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通讯作者：
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