Copper hexacyanoferrate-graphene nanocomposite: synthesis, characterisation and application for the electrocatalytic oxidation and determination of thiosulfate

摘要

Copper hexacyanoferrate-graphene nanocomposite was synthesised by a facile precipitation route. The morphology and structure of the nanocomposite were evaluated by scanning electron microscopy, X-ray diffraction and infrared spectroscopy. A nanocomposite-modified carbon paste electrode was fabricated and its redox behaviour was characterised by means of different electrochemical techniques. The diffusion of the counter cation into the nanocomposite and the charge transfer kinetics across the electrode/electrolyte interface were studied by chronocoulometry and cyclic voltammetry. In the Nyquist diagrams, different time constants related to different physical and electrochemical processes appeared. In these diagrams, percolation of electron in the copper hexacyanoferrate nanoparticles appeared at very high frequencies, and exhibited the feature of a diffusion process with a transmissive boundary condition at the interface of nanocomposite/graphite particles. At medium frequencies, the redox reaction of copper hexacyanoferrate was performed. At very low frequencies, the diffusion of counter cation into the copper hexacyanoferrate nanoparticles dominated. The diffusion coefficients of electron and the counter cation and also the charge transfer rate constant within the nanocomposite were obtained using impedance spectroscopy. The modified electrode showed an efficient electrocatalytic activity toward the electrooxidation of thiosulfate.