High retention supercapacitors using carbon nanomaterials/iron oxide/nickel-iron layered double hydroxides as electrodes

People's awareness regarding the environmental protection and energy crisis has greatly boost rapid development of advanced energy storage devices. In this regard, supercapacitors with long operation life and superior properties have considered as one of the powerful candidates for energy storage. Herein, electrodes with a 3D structure are fabricated by first mixing oyster shell powder with graphene oxide (GO) and iron sulfate solution and subsequently subjected to the hydrothermal reaction, in which GO is reduced to form reduced GO (rGO) and afterwards to fabricate rGO-FeOOH. Using dried rGO-FeOOH as the framework in the following chemical vapor deposition process, carbon nanotubes (CNTs) are successfully grew on the rGO surface. Then, NiFe layered double hydroxide (NiFeLDH) is deposited by electrochemical deposition to prepare the rGO-FeO-CNT-NiFeLDH electrodes. The rGO-FeO-CNT-700-NiFeLDH electrode performs an excellent capacitance of 411.9 F g(-1) at a scan rate of 5 mV s(-1). The rGO-FeO-CNT-700-NiFeLDH-60//AC-NiO asymmetric supercapacitor performs an energy density of 41.4 W h kg(-1) with a power density of 5600 W kg(-1). The capacitance increases up to 144.89% of its initial capacitance after operation for 3200 cycles and remains 102.2% capacitance retention after 5000 cycles demonstrating that the electrode with excellent property is applicable for energy storage devices.