Hybrid Reduced Graphene Oxide/Manganese Diselenide Cubes: A New Electrode Material for Supercapacitors

The integration of 2 D graphene nanosheets and layered transition-metal dichalcogenides has been recognized as one of the most extensive strategies for the synthesis of promising electrode materials for energy-storage devices. In this study, cubic manganese diselenide (MnSe2) and hybrid reduced graphene oxide/MnSe2 (G-MnSe2) materials were synthesized by a facile hydrothermal method. Metallic selenium impurities are considered to be a major unwanted byproduct in this method. An effective means to remove such bulk chalcogenides is a key challenge. For the synthesis of the G-MnSe2 hybrid material, we used a strategy in which the graphene oxide was mixed with manganese and selenium precursors. Surprisingly, the final G-MnSe2 product contained a negligible amount of selenium impurity. The MnSe2 and G-MnSe2 hybrid materials were characterized in detail. For the first time, the electrochemical energy-storage behavior of MnSe2-based materials was assessed for supercapacitor applications. The specific capacitance of the MnSe2 electrode was approximately 57.8 mF cm−2, whereas the hybrid G-MnSe2 electrode showed a much higher specific capacitance of 93.3 mF cm−2 at a scan rate of 1 mV s−1. A symmetric cell made from the G-MnSe2 hybrid material showed excellent long-term stability for 4500 cycles and approximately 106 % retention of its initial capacitance, which is impressive compared with the cycle life of the MnSe2-based symmetric cell (80 % capacitance retention at the 4500th cycle).