Tunable Nanofluidic Transport Through Graphene Nanopores—Mechanism Illumination and Application Exploration

Confined (sub)nano fluidic transport exhibits numerous intriguing phenomena which are different from bulk media, as a result of the dominant rules of surface when the dimension approaches molecular level. Owing to the one-atomic-thickness nature and stable physical and chemical properties, graphene is considered a suitable platform to investigate the transport mechanisms and potential applications in a wide variety from biologically aquaporin, DNA sequencing to gas purification, energy conversion, organic solvent nanofiltration, etc. On one hand, revealing the mechanisms of nanofluidic transport is fundamentally significant for understanding of basic physical and chemical phenomena, such as etching dynamics, electrostatic force between graphene and molecules, friction on graphene surface, electron transfer between graphene and substrates, etc. On the other hand, utilizing these mechanisms to tailor the transport process in (sub)nano confinement could guide and promote the design and control the molecule transport under such nano scale for nano fluid devices and specific applications.<br/>Our group follows a thread that runs through basic research and practical applications.<br/>Focusing on the etching dynamics of graphene nanopores, we found out the dominant factors affecting pore size distribution and pore density. Based on this, a method was developed to introduce nanopores with narrow size distribution and high density (exceeds 10¹² cm^-2), exhibiting broad compatibility for different realistic separation processes from sub-nanometer in gas separation, gas–liquid separation and ionic sieving to a few nanometers in dialysis. Moreover, to clarify the transport behavior of ions through graphene nanopores in the above applications, we disclosed the roles of different kinds of defects to tailor ionic transport via defect structure design by either bottom-up method (controllable intrinsic defects introduction during CVD graphene growth step) or top-down method (biomimetic N-doping by post plasma treatment). As a paradigm, proton transport could be tailored with a range of 2 orders of magnitude by grain boundary design during graphene growth process. The enhanced proton transport by biomimetic N doping graphene outperformed the state-of-the-art commercial Nafion membranes in both areal proton conductivity (2−3 orders of magnitude) and selectivity of proton to methanol (1−2 orders of magnitude), which proved great potential in related fields such as proton exchange membranes. Our work highlights the coherence from fundamental to practice. And we provide typical examples starting from basic principles to technologies development, and finally bridging the gap between theory and reality to utilize them in specific applications of nanofluidics.