Study of functional properties of some spinel materials as electrodes for Supercapacitor applications

Abstract

Energy storage is one of the most essential topics that scientists have been working on in recent times. Supercapacitors are one of the most important energy storage devices which are used in many applications. CuCo2O4 is a highly promising supercapacitors electrode material that has a theoretical specific capacitance higher than its experimental one. So, researchers work on it to enhance the experimental values. This can be achieved either by preparing the CuCo2O4 in different shapes and crystallite sizes and/or preparing it as a composite with other compounds or as a solid solution with suitable elements. In this work, the CuCo2O4 is prepared as a composite with the transition metal chalcogenides (CuS and MnS) as they have high electrical conductivity and high specific capacitance. (1-x)CuCo2O4/xCuS (x=0, 0.1, 0.25, 0.5, 0.75, 1) and (1- x)CuCo2O4/xMnS (x=0, 0.25, 0.5) nanocomposite samples were synthesized by hydrothermal then thermolysis routes. Crystal structure and microstructure properties were studied by applying Rietveld analysis to the measured XRD patterns: the phase composition and percentages, the lattice parameters, the cation distribution, and the crystallite size were accurately determined for the prepared samples. HRTEM and FESEM measurements were used for investigating the particle size distribution, particles morphology, and lattice defects. SAED patterns were taken to confirm the formation of desired phases. The X-ray photoelectron spectroscopy (XPS) was utilized to investigate the type of ions that existed in the samples and their oxidation states. FTIR measurements were applied for further studying the phases developed and the cation distribution that was obtained from the XRD analysis. The variations in band gap values for all samples were studied from UV-Vis diffuse reflectance spectroscopy. Analysis of photoluminescence (PL) spectra of the samples revealed the variation of the colors emitted and their intensities with the alloying ratio (x). The electrochemical measurements for (1-x)CuCo2O4/xCuS (x=0, 0.1, 0.25, 0.5) and (1-x)CuCo2O4/xMnS (x=0, 0.25, 0.5) were studied.