Adsorption and absorption of hydrogen species on silver electrode in alkaline solution

Abstract

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.<i> </i>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 and competes with it. The H atoms are converted to H₂ rather than being sorbed into the polycrystalline Ag when the potential is more negative. These H atoms in the bulk of Ag electrode can be removed only by heating the electrode on flame.