Atomically Thin Nanoporous Graphene Membranes for Fluid Separation
Abstract
Membrane separation applications such as water desalination and carbon capture require high permeance and selectivity. For such processes, nanoporous graphene membranes promise 100-fold higher permeance at comparable selectivity to conventional polymer membranes, but remain under development. This thesis reports fluid permeance through both simulated and experimental graphene nanopores. Molecular dynamics simulations were performed to investigate liquid advection-diffusion through graphene nanopores and how the transport rates differ from continuum predictions. Furthermore, a technique for measuring the gas permeance of nanoscopic areas of graphene was developed. Here, a single layer of graphene seals a ~10 nm diameter hole in a multi-layer graphene nanoballoon over a pressurized cavity and atomic force microscopy is used to track its deflection over time. The results demonstrate helium/air selectivity through defects in five-layer graphene. We anticipate that this measurement technique can be adapted to determine the permeance of other atomically thin materials as well.