Reduced graphene oxide/oyster shell powers/iron oxide composite electrode for high performance supercapacitors

Abstract Recently, the awareness of energy crisis and environmental protection have remarkably increased. In this regard, supercapacitors have attracted significant attention due to their high-power performance and long cycle life. Herein, we propose the design and fabrication of a supercapacitor which possesses a hierarchical structure constructed by reduced graphene oxide (rGO) and oyster shell powder (OSP). The presence of OSP can prevent re-stacking of rGO during hydrothermal, as a result, build the basis of hierarchical structure for Fe2O3 deposition. Depending on the amount of OSP, the Fe2O3 nanoparticles with different morphologies of small particle, rod, needle, and large particle can be obtained via the hydrothermal process. Because of the synergistic effects contributed by rGO, OSPs, and Fe2O3, the as-synthesized rGO/Oyster/Fe2O3 composite electrode exhibits an excellent specific capacitances of 473.9 F g−1 and 214.1 F g−1 at the scanning rates of 5 and 100 mV s−1, respectively. Furthermore, an aqueous asymmetric supercapacitor, having the structure of rGO/Oyster/Fe2O3/Na2SO3//AC-MnO2/Na2SO4, shows a high operating voltage of 2.2 V, and performs a high energy density of 31.2 W h kg−1 at a power density of 2200 W kg−1.