Performance of asymmetric supercapacitor using CoCr-layered double hydroxide and reduced graphene-oxide

Cobalt chromium-layered double hydroxides (CoCr-LDHs) were electrodeposited on to carbon paper by potentiostatic method from the respective cobalt and chromium ion sources. The electrodeposited CoCr-LDHs were characterized by x-ray diffraction (XRD), Fourier transferred infrared (FT-IR) spectroscopy, scanning electron microscope (SEM), energy-dispersive x-ray analysis (EDX) and x-ray fluorescence (XRF) elemental mapping. The XRD and IR data confirmed that the deposits were CoCr-LDH with carbonate and nitrate ions in the basal space. The SEM observations confirmed that the CoCr-LDH surface had distinct morphology consisting of aggregate size of about 100 nm. For the first time, the supercapacitor characteristics of the CoCr-LDHs were assessed in three-electrode configuration in 1 M KOH or two-electrode (asymmetric capacitor device with reduced graphene-oxide (RGO)). It turned out that the asymmetric capacitor consisted of the CoCr-LDH and the RGO exhibited higher energy density with excellent power density. The higher energy density and power density of the asymmetric capacitor device is believed to be due to the unique LDH morphology in addition to the Faradaic and non-Faradaic contributions. It was demonstrated that the two asymmetric capacitor devices connected in series could light an LED bulb.