Volume 60, Nº 11 (2024): Special issue “Electrochemistry-2023”, part 2

Copper oxides in combination with other materials, for example, zinc oxide, are considered promising materials for photocatalytic processes of oxidation of organic impurities or photoelectrochemical water splitting. One of the methods for one-stage production of oxide structures of complex composition is the anodic oxidation of alloys. Evaluation of the photocatalytic or photoelectrochemical activity of the obtained materials is possible using photoelectrochemical parameters – the value of photocurrent or photopotential generated under illumination. The purpose of the work is to determine the effectiveness of using Cu(I) oxides, anodically formed in an alkaline solution on alloys of the Cu-Zn system with a zinc concentration of 34 to 50 at. %, in the process of photoelectrochemical decomposition of water. The elemental composition of the alloys was determined using energy-dispersive microanalysis. With increasing concentration of zinc in the studied concentration range, the phase composition changes from á- to β-phase, which is confirmed by the results of X-ray diffractometry. The change in the composition and structure of the alloy is reflected in the photoelectrochemical parameters of the anodic oxide films formed on it. The most promising material for photoelectrocatalytic transformations is an oxide film anodically formed in 0.1 M KOH on an alloy with a zinc concentration of 50 at. % and a β-phase structure. At a relatively low concentration of defects, the highest values of photocurrent are recorded in it at a high enough value of quantum efficiency.

Using the method of electrochemical measurements on electrodes with mechanically renewable surface, we studied the behavior of graphite electrode in aqueous solutions of surface inactive electrolytes. The potential region in which this electrode can be considered as ideally polarizable was found. Capacitance curves measured in this potential range have some characteristic properties. Namely, the values of double layer capacitance on graphite electrode at potentials corresponding to positive surface charges (σ > 0) are ca. 1.5–2 times lower than those values at typical mercury-like metals. At the same time, we can observe that these double layer capacitances draw together (up to practical confluence) at potentials corresponding to negative surface charges (σ < 0). Analysis of experimental data have shown that peculiarities of capacitance curves on graphite electrode are resulted from the semi-conductive properties of material of this electrode. We have proposed and substantiated new approach to the model description of experimental data that allowed us to quantitatively estimate the values of such important semi-conductive parameters as a flat-band potential and a concentration of charges in the conduction zone of the graphite material under consideration. Taking into account the active use of graphite and other carbon materials in science and practice, we believe that results of this investigation will promote to more deep understanding the mechanism of electrochemical processes realizing on like materials in different systems.

The development of vanadium flow batteries requires the development of new materials to improve their performance. To date, research on electrode materials for these storage devices is focused on increasing specific power and energy efficiency. As is known, energy efficiency can be increased by reducing the polarization of the electrodes due to losses in the transport of charge carrier ions between half-elements, and this can be achieved if an electrochemically active layer is located directly near the surface of the membrane. In this paper, we propose the use of two-layer composite electrodes for this purpose, where the active layer will be located directly at the electrode/membrane boundary. When using CH210 soot with PVDF binder as an active layer at a coating density of 20 mg/cm², the energy efficiency remains at 79.6% at a current density of 150 mA/cm², however, an increase in the thickness of the applied layer leads to a decrease in the discharge capacity to 1% of the initial capacity obtained on uncoated electrodes at a density of The current is 25 mA/cm². Thus, the creation of an active layer on the surface of a commercially available GFD4.6 EA material by airbrush spraying is a fairly simple way to increase the efficiency of the charge-discharge cycle of a vanadium flow battery cell.