Polypyrrole-Coated Three-Dimensional Graphenized Surface for Superior Supercapacitor Performance

A highly electrochemically active graphene/polypyrrole electrode is developed using a facile two-step method comprising top-down and bottom-up electrochemical processing of a graphite electrode, resulting in polypyrrole deposition into a three-dimensional surface graphene host matrix. The active surface graphene/polypyrrole layer is directly connected to the core graphite current collector with no need for external binders. The graphene/polypyrrole electrode is optimized by controlling the polypyrrole deposition via tuning the electrodeposition voltage and duration. The highly functional electrodes are tested as supercapacitors showing excellent performance with an areal capacitance of > 1400 mF/cm2 and a high rate capability of ~ 141 mF/cm2 at 20 mA/cm2. A symmetric cell based on the optimal electrode achieved ~ 213 mF/cm2 at 0.25 mA/cm2 with a high stability of ~ 90% after 2500 cycles. The high areal capacitance, rate capability, and stability are attributed to the unique electrode design that allows excellent graphene/polypyrrole connectivity over the entire surface with no isolated polypyrrole deposits. Our highly electrochemically active electrode has outstanding potential for further investigations in the energy storage field and electrochemical sensing.