Combined Experimental and Theoretical Insights into Energy Storage Applications of a VO2(D)-Graphene Hybrid

Abstract

In this work, a rare VO2(D) phase plate-like structures and integrated with graphene [reduced graphene oxide (rGO)/VO2(D)] has been developed by facile hydrothermal route, explored their activity towards supercapacitor application and validated by the extensive ab initio simulations using density functional theory (DFT) study. After successful synthesis, the samples have been characterized by various techniques to know their crystal phase, surface morphology, and elemental composition. The energy storage performance of these electrode materials was studied by both symmetric and asymmetric supercapacitor devices. In a symmetric supercapacitor device, the hybrid material shows a high specific capacitance of 737 F g(-1) at a scan rate of 1 mV s(-1) and 244 F g(-1) at a current density 1 A g(-1) with an excellent cycle life of over 5000 cycles without any capacitance loss. Further, an asymmetric coin-cell supercapacitor device has been fabricated by using rGO as a negative electrode and the rGO/VO2(D) hybrid as a positive electrode. The energy storage performance was measured at a wide potential of 2 V, and the powering of a light-emitting diode has been demonstrated. The DFT simulations predict that the significant synergistic effect on enhanced capacitance can be attributed to orbital interactions and enhancement of electronic states near the Fermi level because of additional C 2p states from graphene.