ABSTRACT
The effect of the applied potential on the crystallography, morphology, optical, and electrical properties of copper-cobalt oxide (Cu2CoO3) co-electrodeposited on ITO (Indium Tin Oxide) substrate has been studied. The electrochemical behavior of Cu2CoO3 using cyclic voltammetry showed that the co-electrodeposition of Cu2CoO3 occurred at a negative potential of - 0.70 V versus SCE, following a quasi-reversible reaction controlled by the diffusion process. Chronoamperometry (CA) revealed that the nucleation and growth mechanism of Cu2CoO3 follows the instantaneous three-dimensional process according to Scharifker and Hill model. X-ray diffraction (XRD) analysis indicated that the resulting layers at different applied potentials exhibited an orthorhombic structure with a preferred orientation of the crystallites (011) plan. The morphology of the surface changes with potential applied. Furthermore, the optical properties of the copper and cobalt oxide films were investigated using UV-visible spectroscopy; showing that the band gap energy for all the materials increases when the applied potential decreases. The Cu2CoO3 layers obtained are p-type semiconductors. The acceptor density (NA) increases with decreasing applied potential.
ABSTRACT
We have elaborated polyaniline films on ITO substrate (indium tin oxide), by electrochemical process in different electrolytes (HCl, H2SO4, HNO3, and H3BO3), which allowed us to study the effect of the counter ion on electrochemical energy storage performances of polyaniline as electrode material in supercapacitors. The study of the different obtained films performances was carried out by cyclic voltammetry and galvanostatic charge-discharge method and is interpreted by the SEM technique. We found that there is a clear dependence on the specific capacitance of the counter ion. Justified by its porous structure, the PANI/ITO electrode doped with SO42- has the highest specific capacitance, 57.3 mF/cm2 at a current density of 0.2 mA/cm2 and 64.8 mF/cm2 at 5 mV/s. The deep analysis by Dunn's method allowed us to conclude that the faradic process dominates the energy storage in the case of PANI/ITO electrode elaborated in boric acid (99%). On the contrary, the capacitive character is the most contributory in the case of electrodes elaborated in H2SO4, HCl, and HNO3. The study at different potentials (0.80, 0.85, 0.90, 0.95, and 1.0 V/SCE) from 0.2 M monomer aniline showed that the deposition at 0.95 V/SCE leads to higher specific capacitance (24.3 mF/cm2 at scan rate 5 mV/s and 23.6 mF/cm2 at 0.2 mA/cm2) with a coulombic efficiency of 94%. By varying the concentration of the monomer while keeping a potential fixed at 0.95 V/SCE, we also found that the specific capacitance increases with monomeric concentration.
ABSTRACT
In order to develop materials able to guarantee optimal characteristics in terms of environmental compatibility, abundance, and photoactivity, zinc telluride (ZnTe) has become a great candidate for optoelectronic and photovoltaic device applications. In this work, on the basis of electrochemical techniques including cyclic voltammetry and chronoamperometry, it was found that the electrodeposition of zinc telluride (ZnTe) on indium tin oxide substrate (ITO) is a quasi-reversible reaction controlled by the diffusion process. The nucleation and growth mechanism follows the instantaneous three-dimensional process according to Scharifker and Hill model. The crystallographic structure and film morphology were studied by XRD and SEM analyses, respectively. ZnTe films have a cubic crystal structure, and they are characterized by good homogeneity. The optical measurements of the deposited films were performed, and a direct energy gap of 2.39 eV was determined by UV-visible spectroscopy.
