Iron triad-mate hexacyanoferrates as Prussian Blue stabilizers: Toward the advanced hydrogen peroxide transducer

Iron triad-mate hexacyanoferrates (Ni- and Co-hexacyanoferrates) are investigated as stabilizers for Prussian Blue (Fe-hexacyanoferrate) known to be the most advantageous hydrogen peroxide transducer. Both diffusion coefficients of potassium ions and the electron transfer rate constants for transition metal hexacyanoferrates as well as for their composites were determined. Being isostructural to Prussian Blue (PB) on the one hand, and much less suffering from drying–washing cycles compared to polymeric materials on the other hand, triad-mate hexacyanoferrates (HCFs) provide synthesis of the electrocatalyst with the dramatically improved operational stability. Composite films synthesized via layer-by-layer deposition of the catalytic and the stabilizing layers, demonstrate stable response under continuous flow of 1 mM hydrogen peroxide during one (PB/CoHCF) and two even hours (PB/NiHCF). Despite the lower sensitivity of PB/NiHCF-based sensor compared to the PB-based one, the decreased noise allows to maintain linear calibration range from 5 × 10−8 M to 5 × 10−4 M of H2O2.