This paper reports on the preparation of graphene oxide (GO) modified with hafnium oxide (HO) nanoparticles composites by a simple mixing and their use as efficient electrode in electrochemical supercapacitors. The technique relies on simple mixing the aqueous solutions of hafnium oxide (HO) nanoparticles and graphene oxide (GO) at different ratios of GO content (20, 30 and 40 wt%). The morphological studies, chemical composition and electrochemical behavior of the resulting HO/GO nanocomposites were investigated by using UV/vis spectrometry, X-Ray Diffraction (XRD), scanning electron microscope (SEM), transmission electron microscopy (TEM) and electrochemical respectively. The electrochemical performance, including the capacitive behavior of the HO/GO nanocomposites were investigated by cyclic voltammetry and galvanostatic charge-discharge curves. The HO/GO nanocomposites (40 wt%) ratio exhibited the best performance with a specific capacitance of 268 Fg -1 at a scan rate 5 mVs -1 in 1 M H2SO4 and it shows excellent long-term cycle stability.

Functionalized metal oxide electrode material plays an important role in the energy application of the supercapacitor. In this work, the comparative study of super-capacitance performance of hafnium oxide (HfO2) and sulfonated hafnium oxide (S-HfO2) nanomaterials is reported. The HfO2 nanoparticles were synthesized by the precipitation method. Subsequently, the prepared HfO2 nanoparticles were functionalized using sulfuric acid (H2SO4). Further, the synthesized nanoparticles were characterized and confirmed by X-Ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, High-resolution transmission electron microscope (HR-TEM), Field-Emission scanning electron microscope (FE-SEM) and Energy Dispersive X-Ray spectroscopy (EDS) techniques. The electrochemical properties and ion transfer characteristics of the supercapacitor were investigated by the cyclic voltammeter (CV) and galvanostatic charge-discharge (GCD) experiments. Moreover, the internal resistances of the material (HfO2 and S-HfO2) were analysed using Electrochemical Impedance Spectroscopy