Abstract
The processes of film formation and reduction of bismuth in pure methanol are phenomenologically studied by means of cyclic, ac voltammetric and electrochemical impedance spectroscopic methods. Film formation takes place under low electrode potentials within the potential range from -0.1 to about 0.2 V vs. Ag|AgCl resulting in the development of Bi(CH3O)ads layer. The scan rate effect on the anodic current profile is interpreted in terms of a gradual variation of uncompensated resistance, accompanying the processes of film formation and reduction. Phase sensitive ac voltammetry measurements suggest leaky insulating character of a thin anodic film in agreement with the results of electrochemical impedance experiments.
Highlights
Electrochemical studies have confirmed that in pure methanol solutions methoxy anions, resulting from the solvent self-dissociation, interact with various electrode materials viz. Cu, Ni, Zn, Fe Ti, Si and the valve metal Al
The characteristic features of voltammetry curves are the following: At potentials positive to -0.40 V vs. Ag|AgCl, the anodic current increases leading to a single anodic current peak, which depending on the scan rate is located within the potential range (-0.25±0.07) V vs. Ag|AgCl
It can be reasonably assumed that E ≈ 0.20 V vs. Ag|AgCl is the positive limit of anodic film formation in the neutral methanol solution of 0.1 M LiClO4
Summary
Electrochemical studies have confirmed that in pure methanol solutions methoxy anions, resulting from the solvent self-dissociation, interact with various electrode materials viz. Cu, Ni, Zn, Fe Ti, Si and the valve metal Al. It is surprising that up to now, there is nothing reported in the literature about the electrochemical study of another valve metal Bi in pure methanol solutions. Bi2O3 is anodically formed on Bi surface by diffusion and field assisted migration of Bi3+ ions through the film under the influence of the so-called high field mechanism [4], resulting in both thickening and spreading of oxide islets.
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