Design of graphene-coated hollow mesoporous carbon spheres as high performance electrodes for capacitive deionization

Graphene-coated hollow mesoporous carbon spheres (GHMCSs) are rationally designed and originally used as efficient electrode materials for capacitive deionization. The GHMCSs are fabricated by a simple template-directed method using phenolic polymer coated polystyrene spheres as templates. The resulting graphene-based composites have a hierarchically porous nanostructure with hollow mesoporous carbon spheres uniformly embedded in the graphene sheets. The hierarchically porous structure of GHMCS electrodes can guarantee fast transport of salt ions, and the improved specific surface area of GHMCSs provides more adsorption sites for the formation of an electrical double layer. In addition, the graphene sheets in the GHMCSs as the interconnected conductive networks lead to fast charge transfer. The unique GHMCS structure exhibits enhanced electrochemical performance with high specific capacitance, low inner resistance and long cycling lifetime. Besides, a remarkable capacitive deionization behavior of GHMCSs with low energy consumption is obtained in a NaCl solution. The proposed carbon composite architectures are expected to lay the foundation for the design and fabrication of high-performance electrodes in the field of energy and electrochemistry.