High-Performance Three-Dimensional Mesoporous Graphene Electrode for Supercapacitors using Lyophilization and Plasma Reduction.

In this study, a three-dimensional (3D) mesoporous plasma-reduced graphene oxide web (mPrGO web) was fabricated via lyophilization of graphene oxide (GO) solution and subsequent plasma reduction. The lyophilized graphene oxide web (GO web) was successfully reduced by a short plasma treatment (<2 s) using a commercially available plasma apparatus. The degree of reduction of the mPrGO web was determined by the applied plasma power (W) of the apparatus; the optimum power level for effective reduction was identified. The as-synthesized mPrGO web showed a high degree of reduction and robust graphitic characteristics, with a unique crack-like mesoporous structure created on corrugated graphene sheets. In addition to the above characteristics, the mPrGO web possessed a 3D web-like architecture that provided enhanced surface area along with ion-transportable channels derived from lyophilization. Owing to the synergistic effect of lyophilization and plasma reduction, the mPrGO web exhibited high electrical conductivity (87 S cm-1) and increased surface area (642 m2 g-1). Accordingly, the mPrGO web showed outstanding specific capacitance of 253.8 F g-1 at 0.2 A g-1 along with the excellent rate capability (76% capacitance retention at 5 A g-1). Furthermore, the assembled all-solid-state symmetric supercapacitor also exhibited remarkable electrochemical performances, demonstrating the potential applicability of the mPrGO web as an effective supercapacitor electrode material.