Decoding the Interplay between Topology and Surface Charge in Graphene Oxide Membranes During Humidity Induced Swelling.
Decoding the Interplay between Topology and Surface Charge in Graphene Oxide Membranes During Humidity Induced Swelling.
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DOI：
10.1021/acsnano.3c08260
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发表时间：
2023-11-14
期刊：
影响因子：
17.1
通讯作者：
Carbone, Paola
中科院分区：
文献类型：
--
作者：
bin Shaharudin, Mohd Rafie;Williams, Christopher D.;Achari, Amritroop;Nair, Rahul R.;Carbone, Paola
已知氧化石墨烯（GO）膜具有复杂的形态，其取决于石墨烯薄片的氧化程度和膜制备技术。在这项研究中，使用大正则蒙特卡罗模拟，我们研究了暴露于不同相对湿度（RH）值的GO膜的溶胀机制，并显示了这与石墨烯表面化学密切相关。我们表明，GO膜的结构发生变化，而膜从环境中吸附水，并且氧化石墨烯薄片随着膜加载水和膨胀而带电。模拟和实验吸附数据之间的详细比较表明，薄片表面电荷驱动的水吸附机制在低RH时，膜的拓扑结构仍然是无序的，内部孔隙小，不对称。当膜暴露于更高的RH（80%）时，薄片获得更多的表面电荷，因为更多的氧化物基团去质子化，并且孔的尺寸增大，但保持其无序的几何形状。只有在非常高的相对湿度（98%）下，膜才会发生结构变化。在这种湿度水平下，膜中的孔变成狭缝状，但薄片表面电荷保持恒定。我们的研究结果揭示了一个非常复杂的膨胀机制，并表明，一个单一的分子模型不能完全捕捉不断变化的化学和形态的膜，因为它膨胀。我们的计算过程提供了第一个原子解析的洞察到GO膜结构的实验样品。
Graphene oxide (GO) membranes are known to have a complex morphology that depends on the degree of oxidation of the graphene flake and the membrane preparation technique. In this study, using Grand Canonical Monte Carlo simulations, we investigate the mechanism of swelling of GO membranes exposed to different relative humidity (RH) values and show how this is intimately related to the graphene surface chemistry. We show that the structure of the GO membrane changes while the membrane adsorbs water from the environment and that graphene oxide flakes become charged as the membrane is loaded with water and swells. A detailed comparison between simulation and experimental adsorption data reveals that the flake surface charge drives the water adsorption mechanism at low RH when the membrane topology is still disordered and the internal pores are small and asymmetric. As the membrane is exposed to higher RH (80%), the flake acquires more surface charge as more oxide groups deprotonate, and the pores grow in size, yet maintain their disordered geometry. Only for very high relative humidity (98%) does the membrane undergo structural changes. At this level of humidity, the pores in the membrane become slit-like but the flake surface charge remains constant. Our results unveil a very complex mechanism of swelling and show that a single molecular model cannot fully capture the ever-changing chemistry and morphology of the membrane as it swells. Our computational procedure provides the first atomically resolved insight into the GO membrane structure of experimental samples.
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