Intercalation of mesoporous carbon spheres between reduced graphene oxide sheets for preparing high-rate supercapacitor electrodes

A method for preparing three-dimensional (3D) carbon-based architectures consisting of mesoporous carbon spheres intercalated between graphene sheets is demonstrated in this paper. Colloidally dispersed negatively charged graphene oxide (GO) sheets strongly interacted with positively charged mesoporous silica spheres (MSS) to form a MSS-GO composite. The MSS were then used as template for replicating mesoporous carbon spheres (MCS) via a chemical vapor deposition process, during which the GO sheets were reduced to reduced graphene oxide (RGO). Removal of the silica spheres left behind a 3D hierarchical porous carbon architecture with slightly crumpled graphene sheets intercalated with MCS. The 3D carbon structure contained a low amount of oxygen (3.2% of atomic ratio of O/C) than a RGO sample (10.1%), which was prepared by using the chemical reduction method with hydrazine as the reducing agent. Thermal annealing of the 3D carbon structure in ammonia atmosphere further reduced the O/C atomic ratio to 1.6%. The capacitive performance of the samples as supercapacitor electrodes was investigated using the cyclic voltammetry, galvanostatic charge-discharge, and electrochemical impedance spectroscopy techniques. The 3D carbon structure showed a substantially lower equivalent series resistance and a higher power capability than the RGO electrode. In addition, the 3D carbon electrode exhibited an excellent electrochemical cyclability with 94% capacitance retention after 1000 cycles of galvanostatic charge-discharge. The method demonstrated in this work opens up a new route to the preparation of 3D graphene-based architectures for supercapacitor applications.