Hafnium oxide - graphene electrodes for highly efficient aqueouselectrolyte supercapacitors

Hafnium Oxide (HO) has emerged as a novel material which has significantly revolutionized semi-conductor industry while role of this high-k metal oxide has not been investigated in-depth when it comes to the discovery of electroactive species for energy storage applications. In this context, herein we have reported the excellent electrochemical energy storage of stoichiometrically synthesized (HO)x - (GNPs)1-x nanocomposites (where x = 1, 0.75, 0.50, 0.25, 0) in different weight ratios. The presented research work aims to provide an insight into the charge storage mechanism in HO based energy storage devices by linking structural aspects with physical factors that are instrumental in impacting specific capacitance. Agile experimental techniques have been applied for structural authentication followed by a series of electrochemical experiments that have been conducted to provide in depth account of various physical parameters and their impact in achieving a superior charge storage of 925 F g-1 at a scan rate of 5 mV s-1 in 1 M H2SO4. Moreover, an energy density of 30.67 Wh - kg-1 and a power density of 235 W - kg-1 has been achieved, with a capacity retention of 80 % over 1000 cycles.