Sharif Digital Repository

Electrocatalytic activity of electrodeposited nanocrystalline CoNiFe alloy in hydrogen evolution reaction (HER) was studied in 1 M NaOH solution. The steady-state polarization measurement and electrochemical impedance spectroscopy were used to determine the Tafel slope, the exchange current density and the activation energy. The simulation of the data obtained from these two methods, using a nonlinear fitting procedure, allowed us to determine the surface coverage and the rate constants associated with the mentioned reaction. The ac-impedance spectra measured at various overpotentials in the HER region exhibited three semicircles in the complex plane plots. The high-frequency semicircle was... 

Hydrogen evolution and electrosorption on/in TiHg alloy have been investigated in acidic solution using cyclic voltammetry, open circuit potential transient, steady-state polarization, chronopotentiometry and electrochemical impedance measurements. Comparison has been made with pure Ti. Cyclic voltammetry and open circuit potential measurements show that hydrogen absorption into the electrode material occurs during proton discharge. The steady-state polarization curves in the course of positive and negative potential scans illustrate that the formation of absorbed hydrogen slightly improves the electrocatalytic properties of the electrode. The hydrogen diffusion coefficient into the bulk of... 

The processes of adsorption and absorption of H atoms on silver electrode in alkaline media has been studied using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The potential range in the CV studies has been between -0.1 and -1.6 V /Ag-AgCl. In the first cycle, two cathodic and three anodic peaks have been observed. The H atom electrosorption current peak at ca. -0.6 V/Ag-AgCl, which appears at second cycle, is assigned to hydrogen absorption states. Nyquist plots consist of two overlapping semi-circles of variable diameters depending on the extent of the cathodic dc-potential offset. Hydrogen absorption occurs simultaneously with the hydrogen evolution reaction... 

The electrochemical adsorption and diffusion (dissolution) of hydrogen into mercury have been studied by the methods of cyclic voltammetry and impedance spectroscopy. In the potential range of -0.15 to -1.5 V (vs: Ag/AgCl) two peaks at -0.4 and -0.8 V have been observed and are associated with the adsorption and absorption of hydrogen. Impedance studies exhibit two overlapping semi-circles terminating in a straight line in the low potential region. The size of the semi-circles increases as the potential is raised and is attributed to the increased resistive effect of the dissolved hydrogen. The value of the real component upon increasing the measurement potential to -0.9 V is followed by a...