Department of Chemical Engineering , Monash University , Clayton , Victoria 3800 , Australia.
China-Australia Joint Research Center in Future Dairy Manufacturing, School of Chemical and Environmental Engineering, College of Chemistry, Chemical Engineering and Materials Science , Soochow University , Suzhou , Jiangsu Province 215123 , PR China.
ACS Appl Mater Interfaces. 2019 Feb 27;11(8):8483-8491. doi: 10.1021/acsami.9b00492. Epub 2019 Feb 13.
Graphene oxide (GO) membranes assembled by GO nanosheets exhibit high water flux because of the unique water channels formed by their functionalized layer-by-layer structure. Although water transport in the GO membrane is in principle influenced by the functional groups at the edges of GO nanosheets, this is yet to be fully understood. To fill this knowledge gap, molecular dynamics simulation was employed in this work to gain insights into the influences of three typical edge functional groups of GO nanosheets: carboxyl (COOH), hydroxyl (OH), and hydrogen (H). A well-controlled numerical analysis with complete isolation of the functional groups at the edges was undertaken. The results reveal that the COOH group has a negative impact on water transport because of its relatively large steric geometric structure, which resists water flow. By contrast, the OH group promotes water transport by uniquely "pulling" water molecules across the nanosheet layer because of its relatively stronger interaction with water. The H atom promotes water transport as well, mainly because of its low-resistance steric structure. Moreover, the size of the inter-edge hub has an apparent impact on the influence of these functional groups on water transport. The results suggest that in the design of high water flux GO membranes, it would be strategic to remove COOH edge functional groups while maintaining a mixture of OH and H edge functional groups.
氧化石墨烯（GO）膜由 GO 纳米片组装而成，由于其功能化的层层结构形成了独特的水通道，因此表现出高水通量。尽管 GO 膜中的水传输原则上受 GO 纳米片边缘的官能团影响，但这一点尚未得到充分理解。为了填补这一知识空白，本工作采用分子动力学模拟深入了解 GO 纳米片三种典型边缘官能团（羧基（COOH）、羟基（OH）和氢（H））的影响。通过完全隔离边缘官能团进行了精心控制的数值分析。结果表明，COOH 基团由于其较大的空间几何结构，阻碍了水流，对水传输有负面影响。相比之下，OH 基团由于与水的相互作用较强，通过独特的“拉动”水分子穿过纳米片层来促进水传输。H 原子也促进了水的传输，主要是因为其低阻力的空间结构。此外，边缘中心体的大小对这些官能团对水传输的影响有明显的影响。结果表明，在设计高通量 GO 膜时，去除 COOH 边缘官能团，同时保留 OH 和 H 边缘官能团的混合物将是具有策略意义的。
