ИСТИНА

Hydrogen peroxide (H2O2) is recognized as one of the most important analytes nowadays, being a chemical threat agent, food additive and a key metabolite of life pathways, acting as oxidases’ side product at the same time. Prussian Blue (PB) or ferric hexacyanoferrate (FeHCF) is considered to be the most advantageous lowpotential transducer for hydrogen peroxide over all known systems, demonstrating both high sensitivity (ca. 1 A•M/cm2) and selectivity in relation to oxygen reduction of more than three orders of magnitude higher, than for platinum electrodes, which are most widely used. Developed by our scientific group method of selective hydrogen peroxide detection by its electroreduction in the presence of oxygen [1] provoked an extensive work at transition metals’ cyanoferrates Prussian Blue analogues. We confirmed that NiHCF, CoHCF, and CuHCF-mediated hydrogen peroxide reduction is due to the presence of FeHCF (Prussian Blue) defects in their structure. Prussian Blue demonstrates high electrocatalytic activity with the half-wave potential of the H2O2 reduction almost coincided with the Prussian Blue|Prussian White redox potential [2]. Nevertheless, electrocatalytic potential windows for the non-iron hexacyanoferrates in H2O2 reduction are separated from the redox activity window, which are at much more anodic potentials. Whereas hydrogen peroxide reduction with NiHCF, CoHCF, and CuHCF occurs in the potential region similar to Prussian Blue and electrocatalytic activities are in average two orders of magnitude less compared to Prussian Blue, we assign the observed activity to Prussian Blue defects in non-iron cyanoferrates’ lattice, which is sustained with differential pulse voltammetry data. Thus, we can conclude electrocatalysis of H2O2 reduction to be an exceptional property of Prussian Blue. Despite of the highest electrocatalytic activity towards H2O2 reduction attributed to Prussian Blue, other transition metal hexacyanoferrates-analogues are of great interest for analytical application as suitable matrixes for superior electrocatalyst entrapment (for instance, Prussian Blue stabilization with layer-by-layer deposition [3]) and construction of sensors and oxidase-based biosensors with improved characteristics. References. [1] A.A. Karyakin, O.V. Gitelmacher, E.E. Karyakina, Analytical chemistry, 67 (1995) 2419-2423. [2] A.A. Karyakin, E.E. Karyakina, L. Gorton, Electrochemistry Communications, 1 (1999) 78-82. [3] N.A. Sitnikova, A.V. Borisova, M.A. Komkova, A.A. Karyakin, Analytical chemistry, 83 (2011) 2359-2363.