(130f) One-Pot Granulation of Graphene Oxide Aerogels with Hierarchical Porous Three-Dimensional Structures

Recently, three-dimensional (3D) graphene/graphene oxide (GO) networks have attracted much attention, thanks to their high specific surface areas, large pore volumes, strong mechanical strengths and fast mass and electron transport. These unique properties make them widely applied in the fields of absorbents, catalysis, sensors, energy storage and conversion, and biological applications. Many methods were developed to make 3D graphene porous structures in chunks with fixed shapes similar to the template or the container. Further treatments such as crushing and grinding are needed in various applications.

We have developed a one-pot granulation method to assemble graphene oxide (GO) pallets into 3D microballs at liquid-liquid interface, driven by the dissolution of a droplet immersed in a surrounding liquid phase. The assembled GO structures were highly crumpled with exotic morphology. And the detailed structure of GO microballs was closely related to the dynamics of the droplet, which could be adjusted by the composition of the surrounding liquid, the temperature and the reduction degree of GO. The shape of GO assemblies can be tailored by the pinning effect of the contact line between the droplet and the substrate. Rich morphology of the assembled GO structures, including capsule, dim sum, mushroom, peasecod, and olive shaped assemblies were obtained. By adding salts into the GO droplet, the hybrid structures varies with the concentration and salts solubility in the surrounding solvent. Soluble salt (LiCl) have little effect of the GO assembled structure as expected. Insoluble salt (NaCl, KCl) crystalizes on the GO pallets at high concentration, but between pallets at low concentration. During the granulation process, the GO pallets with different sizes were automatically separated and forming the layered shell of the GO microball. Based on these results, it is clear that the structure of 3D GO assemblies is determined by the dissolution dynamics of the droplet. Perfect spherical GO assemblies can be obtained in the absence of the substrate effect.

With the perfect spherical shape, these porous 3D assemblies should have better processibility. And we believe that our method is suitable to granulate all kinds of 2D nanomaterials, besides GO nanopallets. Granulation in large scale is still wanted to meet the demands of wide applications of these functional 3D porous structures.