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Control of graphene aerogel self-assembly in strongly acidic solution via solution polarity tuning

机译：通过溶液极性调节控制强酸性溶液中石墨烯气凝胶的自组装

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In view of their advantages (plasticity, low density, adjustable pore size, high porosity of >99.9%), three-dimensional graphene aerogels (GAs) are widely used for energy storage and adsorption separation, which has inspired the development and optimization of the corresponding synthetic techniques. In particular, self-assembly in the liquid phase features the benefits of tunability and sustainability and is viewed as a promising strategy of GA synthesis. During hydrothermal GA preparation, hydrophilic graphene oxide (GO) gradually turns lipophilic upon reduction, and the resulting phase transition separation and polarity change induce self-assembly into an aerogel. However, the effect of solution polarity on the structure or state of dispersed GO nanosheets, which affects the final property-determining process of automatic assembly, is still unclear. Herein, we prepared a series of GAs by hydrothermal reduction of unwashed GO with vitamin C in liquid-phase systems of different polarity and investigated the effects of polarity on the self-assembly process and aerogel properties using a range of instrumental techniques. The results showed that GO reduction is slowed down in weakly polar systems and further demonstrated that the shape of partially reduced graphene oxide (rGO) flakes depends on solution polarity. Flaky, layered, and stacked rGO particles obtained in strongly polar media self-assembled into anisotropic gully aerogels that were brittle and almost completely inelastic. Conversely, in weakly polar media, the prepared rGO sheets were twisted, which increased the number of contact points and modes between sheets and resulted in self-assembly into uniform-pore-structure honeycomb aerogels that showed good elasticity and could be repeatedly compressed.
机译：鉴于其优势（可塑性，低密度，可调节孔径，高孔隙率> 99.9％），三维石墨烯气凝胶（GAs）被广泛用于能量存储和吸附分离，这激发了碳纳米管气雾剂的开发和优化。相应的合成技术。特别是，液相中的自组装具有可调节性和可持续性的优势，被视为GA合成的有前途的策略。在水热GA制备过程中，亲水性氧化石墨烯（GO）还原后逐渐变成亲脂性，并且相变分离和极性变化引起自组装成气凝胶。然而，溶液极性对分散的GO纳米片的结构或状态的影响（影响自动组装的最终特性确定过程）的影响仍不清楚。本文中，我们通过在不同极性的液相系统中对维生素C进行未洗GO的水热还原，制备了一系列GA，并使用多种仪器技术研究了极性对自组装过程和气凝胶性质的影响。结果表明，GO的还原在弱极性体系中减慢了速度，并进一步证明了部分还原的氧化石墨烯（rGO）薄片的形状取决于溶液的极性。在强极性介质中获得的片状，分层和堆叠的rGO粒子会自组装成各向异性的沟状气凝胶，这些气凝胶易碎，几乎完全无弹性。相反，在弱极性介质中，制备的rGO片材会扭曲，从而增加了片材之间的接触点和模式，并导致自组装成具有良好弹性并可以反复压缩的均匀孔结构蜂窝状气凝胶。

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