Very recently, Kim et al.  and Pan et al.  reported on reduced graphene oxide-ZnO nanocomposites for supercapacitor
electrodes by microwave-assisted method, which exhibited a specific capacitance of 109 F g−1 at a scan rate of 2 mV s−1 and 146 F g−1 at selleck chemical a scan rate of 2 mV s−1, respectively. But only approximately 30 F g−1 at a scan rate of 100 mV s−1. A sandwiched nanoarchitecture of reduced graphene oxide/ZnO/deducted graphene oxide is fabricated by Huang et al.  using chemical vapor deposition method, which exhibited a specific capacitance of 51.6 F g−1 at a scan rate of 10 mV s−1. Additionally, graphene-ZnO nanocomposites synthesized by other method such as ultrasonic spray pyrolysis method and their electrochemical performance were reported [33, 34]. However, these materials were limited by a low specific capacitance and poor stability at higher scan rate or high current densities. An effective regulation of graphene-ZnO
hybrid for high performance of supercapacitors is still challenging. On the other hand, the investigation ABT-888 manufacturer of solid-state supercapacitors based on graphene-ZnO hybrid is very limited. In this report, a simple and facile synthesis route is developed to prepare graphene-ZnO hybrid as an electrode material for supercapacitors using one-step hydrothermal technique. Initially, graphene oxide (GO) was synthesized using the well-known modified Hummer’s method. ZnO nanorods are inserted between the graphene nanosheets layer-by-layer rather than simply decorated on the surface Clomifene of graphene during GO hydrothermal reduction process. This strategy provides a novel method for the preparation of highly active materials (ZnO nanorods)
directly grown on Gr surface that avoids the restacking of Gr sheets, which show high specific capacitance even at higher scan rate and excellent long-term cycle stability applied in a all solid-state supercapacitor device. Such high electrochemical properties provide important prospects for graphene-ZnO hybrid to be widely used as electrode material in supercapacitor. Methods Materials Graphite powder was purchased from Sigma Aldrich (St. Louis, MO, USA). All other reagents were commercially available and analytic grade and were used directly without any purification. Double-distilled water was used throughout the experiments. Synthesis of graphene oxide Graphite oxide was prepared from natural graphite powder through a modified Hummers method . One gram of graphite powder, 1.1 g sodium nitrate, and 46 ml sulfuric acid were mixed and stirred for 10 min. Then, 3.0 g potassium permanganate was added slowly and temperature maintained below 20°C. DI water was added slowly and the temperature was raised to 90°C. The solution turned bright yellow when 3.0 ml of hydrogen peroxide (30%) was added. The mixture was filtered while warm and washed with warm DI water. Then GO was subjected to dialysis to completely remove metal ions and acids.