ИСТИНА

Prussian Blue (PB) is considered to be the most advantageous low-potential transducer for hydrogen peroxide over all known systems. Both the high sensitivity (more than 0.5 A/M·cm2) and selectivity in presence of oxygen are more than three orders of magnitude higher, than for commonly used Pt electrodes [1]. In water solutions PB, as well as other transition metals cyanoferrates, possesses electronic and ionic conductivity. As soon as the counter-ions are involved into electrocatalytic process, transport characteristics are crucial for the electrocatalysis efficiency. To this end, electrochemical impedance spectroscopy, one of the most informative, sensitive and, besides, non-destructive tools for transport characteristics’ investigation was used. That was shown that Prussian Blue (as well as Ni cyanoferrate) impedance spectra can be approximated with analog of Randles equivalent circuit with diffusion impedance with reflective boundary condition. Non-uniformity of the electrocatalyst coverage was considered by using constant phase element instead of the ideal spectra approximation. Non-uniformity of the electrocatalyst coverage was considered by using constant phase element instead of the ideal capacitor. The constant potential (EDC) has been chosen close to the Prussian Blue |Prussian White formal potential found from its cyclic voltammogram in the same solution. Due to the approximation curve fits the experimental data well and the standard errors of experimental parameters are lower than 10 %, the electrochemical impedance spectra can be evaluated quantitatively. The dependence of the charge-transfer resistance from transition metals cyanoferrates amount was studied for the large range of the latter. The RCT resistance corresponds to the electrode | electrocatalyst interface. Anti-Ohm’s law behavior of the RCT vs. electrocatalyst amount can be explained, thus, with the increase of the electrode | electrocatalyst interface border with the growth of electrocatalyst nuclei while electrodeposition process ending up with the continuous film formation. This was confirmed with SEM micrographs demonstrating the increase of the nuclei size over time and the electrode | electrocatalyst interface border enlargement. Such a principle provides an opportunity of the electrocatalyst’s coverage degree and is a rapid and non-destructive tool to control the continuity of films which can be used efficiently for the electrochemical sensors design, including microelectrode arrays construction. Literature: Arkady A. Karyakin, Prussian Blue and Its Analogues: Electrochemistry and Analytical Applications // Electroanalysis, 2001, 13(10), 813-819.