Membranes that selectively filter for both anions and cations are central to technological applications from clean energy generation to desalination devices. 2D materials have immense potential as these ion-selective membranes due to their thinness, mechanical strength, and tunable surface chemistry; however, currently, only cation-selective membranes have been reported. Here we demonstrate the controllable cation and anion selectivity of both monolayer graphene and hexagonal boron nitride. In particular, we measure the ionic current through membranes grown by chemical vapor deposition containing well-known defects inherent to scalably produced and wet-transferred 2D materials. We observe a striking change from cation selectivity with monovalent ions to anion selectivity by controlling the concentration of multivalent ions and inducing charge inversion on the 2D membrane. Furthermore, we find good agreement between our experimental data and theoretical predictions from the Goldman-Hodgkin-Katz equation and use this model to extract selectivity ratios. These tunable selective membranes conduct up to 500 anions for each cation and thus show potential for osmotic power generation.

中文翻译：

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通过单层石墨烯和六方氮化硼的可调节阴离子选择性传输。

选择性过滤阴离子和阳离子的膜对于从清洁能源生产到脱盐设备的技术应用至关重要。由于这些离子选择膜的薄度，机械强度和可调节的表面化学性质，二维材料具有巨大的潜力。然而，目前仅报道了阳离子选择性膜。在这里，我们证明了单层石墨烯和六方氮化硼的可控阳离子和阴离子选择性。特别是，我们测量通过化学气相沉积法生长的膜的离子电流，该膜包含可缩放生产和湿转移的2D材料固有的众所周知的缺陷。我们通过控制多价离子的浓度并诱导二维膜上的电荷反转，观察到从单价离子的阳离子选择性到阴离子选择性的惊人变化。此外，我们在实验数据和高盛-霍奇金-卡兹方程的理论预测之间找到了很好的一致性，并使用该模型提取了选择性比。这些可调节的选择性膜对每个阳离子最多传导500个阴离子，因此显示出潜在的渗透动力产生能力。