GO optimization strategies for improved capacity retention in transition metal oxides based ternary nanocomposites for high-performance supercapacitors

Abstract

This work presents the optimization of GO in transition metal oxide based ternary nanocomposites (NiO/ZnO@(GO)x)for electrode materials in supercapacitor applications. The nanocomposites were synthesized using a straightforward sol-gel auto combustion route followed by sonication. It was observed from XRD analysis that crystallite sizes of NiO/ZnO@(GO)x nanocomposites vary between 49 and 24 nm. According to morphological study, the TEM images depict a hybrid nanoarchitecture with NiO/ZnO nanoparticles dispersed on graphene sheets. The maximum specific capacitance of 1833.9Fg−1 was obtained for NZG3 (NiO/ZnO with 6% GO).Furthermore, largest capacity retention of 98.7% was achieved for NZG3 after 6000 continuous cycles. NZ demonstrated 96% capacitance retention, for NZG1 it was 97.2% and capacity retention for NZG3, it was 98.7%. Therefore,optimized concentration of GO in NiO/ZnOnancomposite to achieve maximum specific capacitance and cyclic stability was found to be forNZG3 nanocomposite. The Rs values attained were found to be 6.7 Ω, 5.8 Ω, 5.4 Ω, 4.4 Ω and 4.9 Ω for NZ, NZG1, NZG2, NZG3 and NZG4 respectively whereas Rctvalues for NZ and NZG electrodes i.e. NZG1, NZG2, NZG3 and NZG4 10.0 Ω, 9.4 Ω,8.5 Ω,7.8 Ω and 8.1 Ω respectively, demonstrating that GO plays an important role in enhancing conductivity.