Electrochemical formation and characterization of Ag2O

Abstract

The process of Ag2O formation has been investigated in 0.1M, 0.3 M, 1.0Mand 2.0 M NaOH solutions on polycrystalline Ag electrodes by cyclic voltammetry potentiostatic pulse and SEM techniques. The SEM micrographs of the chemically polished Ag surface and the surface after oxide formation revealed considerable roughening of the Ag surface after Ag2O formation and reduction. The roughening was more pronounced at higher NaOH concentrations, indicating that only the first cycle or pulse applied on a freshly polished Ag electrode should be considered in mechanistic studies of Ag2O formation. In the given range of NaOH concentrations, it was shown that the process is not controlled simply by the diffusion of the reacting species.Anucleation phenomenon was clearly detected in all the examined solutions. The SEM micrographs confirm that the two anodic peaks, present on the voltammograms of Ag2O formation correspond to two types of oxide film, i.e., non-homogeneously and homogeneously distributed ones. Potentiostatic formation of the oxide at potentials corresponding to the first and second anodic peak yielded simple cubic Ag2O but of very different grain size.

Electrochemical Behavior of Sintered CuAg4 at. pct Alloy

“…Becerra et al [41] have reported that the secondary silver (I) oxide layer can be formed on the primary silver(I) oxide layer by the instantaneous nucleation and 3D growth mechanism under diffusion control. SEM micrographs confirm that the two anodic peaks present on the voltammograms of Ag 2 O formation correspond to two types of oxide film, i.e., nonhomogeneously and homogeneously distributed types [28,29] So, the peaks A 4 and A 5 on our voltammograms are to be connected to formation of these two types of silver(I) oxide, whereas Reaction [7] can be attributed to the peak A 6 .…”

“…To recognize these reactions, the voltammogram obtained on sintered alloy is compared with the voltammograms obtained on pure copper and silver ( Figure 5). The current peak A 1 is attributed to the adsorption of OH − and formation of the first oxide monolayer based on literal [10][11][12][13][14][15][16][26][27][28][29][30][31][32][33][34][35][36][37][38][39][40] data to which, with different in situ techniques, the presence of absorbed hydroxyl ions on the surface of copper and silver in alkaline electrolytes is proved in the quoted area of potential. It is obvious that the current waves marked as A 2 and A 3 correspond to copper oxides formation.…”

“…Pure silver is also investigated widely from the electrochemical point of view. [27][28][29][30][31][32][33][34][35][36][37][38][39][40] The presence of adsorbed hydroxyl ions on both copper and silver electrode surface in alkaline solutions, even in so-called doublelayer region, was proved by in situ scanning electron microscopy [10,12] and other surface analytical methods. Thus, the adsorption of hydroxyl ions is considered to be the first reaction step that can take place during the anodic polarization of CuAg4 at.…”

Impedance study on the capacitance of silver electrode oxidised in alkaline electrolyte

“…10 mV and a corresponding reduction peak (C) seen at potentials more negative than 100 mV (the exact location depends on the amount of Ag compounds subjected to the reduction [37,69]). Detailed discussion of the processes related to the anodic currents (A) can be found elsewhere [21][22][23][24][25][26][27][28][29][70][71][72][73][74][75]. Various products of Ag oxidation at potentials up to ca.…”

“…Silver oxidation in an alkaline electrolyte starts at ca. 10 mV vs. Hg|HgO; the usually reported oxidation products are Ag 2 O and AgO, depending on the oxidation potential [21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38]. AgO is described as a mixture of Ag(I) and Ag(III) species [11,39,40].…”