Graphene and graphene oxide membranes for gas separation applications

Graphene and its derivatives possess outstanding properties as membrane materials for gas separation. A number of graphene-based membrane types have been extensively studied. Most experimental studies have focused on porous graphene, multilayer graphene or graphene oxide (GO), and polymer membranes embedded with graphene or GO nanosheets. Porous graphene membranes are created on porous supports by top-down methods, for example, focused ion or electron beam irradiation, ultraviolet-induced oxidative etching, and oxygen plasma etching. Multilayer graphene membranes are prepared using direct transfer or stacking of graphene or GO sheets, and gas separation in these materials occurs mainly through their two-dimensional nanochannels. Finally, graphene or GO nanosheets are incorporated into polymer matrices to form mixed matrix membranes. These membranes exhibit unique gas separation properties for various gas pairs, overcoming the typical tradeoffs between permeability and selectivity of polymeric membranes. However, graphene-based membranes are still at an early stage, and much more study should be undertaken to understand their fundamental transport mechanisms and to make graphene membranes viable materials for practical gas separation applications.