Understanding electrochemical and structural properties of copper hexacyanoferrate: Application in hydrogen peroxide analysis

Abstract

Copper hexacyanoferrate (CuHCF) exhibits great electrocatalytic activity towards H2O2 reduction, making it a suitable electrode material for H2O2 sensors and H2O2-based energy storage devices. In this work, the crystal structures, electronic structures, and electrochemical properties of CuHCF were investigated in detail by both experiments and simulation. Several different samples of CuHCF were synthesized and tested. The effects of Fe oxidation states and the Cu-to-Fe ratios on the electroactivities of CuHCF were evaluated. In-depth voltammetric and X-ray absorption near edge structure (XANES) studies revealed the underlying redox chemistry which contribute to the voltammetric responses of CuHCF. High electroactivity of CuHCF, high cycling stability, and high electrocatalytic activity towards H2O2 reduction were observed for the porous K0.09Cu[Fe(CN)6]0.6 •2.56 H2O particles synthesized at room temperature from chemical co-precipitation of CuSO4 and K3Fe(CN)6 at a 2:1 molar ratio. DFT calculation revealed favorable adsorption of H2O2 on Fe sites. The presence of Cu lowered the local charge on Fe, assisting the adsorption of electron-donating H2O2 molecule on the neighboring Fe atom. The excellent analytical performance of CuHCF towards H2O2 detection was further demonstrated, giving the linear range of 0.0 – 10.0 mM, the sensitivity of 10.6 µA mM‒1, and the limit of detection (3sB/m) of 0.033 mM.