Effects of Amino Acids Protonation on Double-Layer Parameters of the Electrode/Chlorates(VII) Interface, as well as Kinetics and Mechanism of Bi(Ⅲ) Ion Electroreduction in the Aspect of the 'Cap-Pair' Effect

摘要

20.1 Introduction Irreversibility of metal ions electroreduction in the solutions of poor complex creative properties makes their determination by simple electrochemical methods difficult or even impossible. Knowledge of the organic substances effect on the rate of electrode reactions is of significant importance in analytics and elaboration of technological characteristics. Organic substances can inhibit, accelerate the electrode process or not affect its course. The inhibition of electroreduction processes by organic substances has been described in many papers [1-4]. It was shown that the adsorption of organic substances on the electrode blocks its surface, changing the surface charge and the potential of the internal Helmholtz plane. This affects the mechanism and kinetics of the electrode reaction, especially in the area of large covering of the electrode surface with adsorbate [5]. The first papers on the catalytic activity of organic substances discussed: - Lowering the detection limit of Cd(Ⅲ), Cu(Ⅱ) and Ni(Ⅲ) ions by hexamine [6] - Increase of the peak currents Pb(Ⅱ), Sn(Ⅱ), T1(I), Bi(Ⅲ) and In(Ⅲ) in the presence of methylene blue and thymol blue [7] - Catalytic effect of toluene ions - p-sulfonate on electroreduction of Cr(Ⅲ) ions and 1,10-phenanthroline and chinaldine acid on electroreduction of Eu(Ⅲ) ions [8, 9] Systematic research of the catalytic activity of organic substances on the selected electrode processes carried out by Sykut et al. [10] led to the formulation in 1978 of the "cap-pair" rule, determining the conditions which must be satisfied by the depolarizer-supporting electrolyte - organic substance system for the electrode processes to be accelerated by organic substances. It was stated that an important role in accelerating the electrode process is played by the ability of the organic substance - undergoing adsorption on the electrode - to create in the by-electrode layer complexes with a depolariser and locate the potential of dep