Methane Hydrates Formed in a Porous Graphene Aerogel for Energy Storage

Abstract

The use of porous media as a fixed bed for promoting methane hydrate formation has been endowed with great potential in hydrate-based energy storage. In this work, a graphene aerogel (GA) with a one-piece structure and ultralight weight was prepared and adopted for the first time as a fixed bed for methane hydrate formation. In particular, the effects of the filling ratio and hydrophobic–hydrophilic properties of GA on the promotion efficiency were comprehensively investigated. In the range of 84–95%, a lower filling ratio resulted in higher promotion efficiency, which at 84% increased the methane storage capacity and apparent storage capacity from 114.4 ± 7.6 and 52.4 ± 6.7 V/V to 146.3 ± 6.5 and 91.1 ± 13.0 V/V, respectively. Cryo-scanning electron microscopy (Cryo-SEM) demonstrated that the hydrates formed in the inner pores of GA but also revealed the existence of empty pores, indicating that part of the reaction solution migrated out of the GA. Fortunately, by regulating the hydrophilic–hydrophobic properties of GA, the migration of the reaction solution during hydrate growth could be controlled, and the methane storage capacity could be optimized. More importantly, GA produced excellent advantages in terms of gravimetric storage capacity over traditional media and, therefore, produced great potential in serving as an ultralight fixed bed for the industrial application of hydrate-based energy storage.