The electrochemical behaviour of suspended Prussian Blue nanoparticles in forced convection conditions

Abstract

• Electroreduction of Prussian Blue nanoparticles at RDE is described by Levich equation. • Minor fraction of suspended Prussian Blue nanoparticle is reduced at RDE. • Electrochemical detection of suspended Prussian Blue nanoparticles in flow. The electrochemical studies of suspended nanoparticles became an important method of their characterisation. In reported research, Prussian Blue nanoparticles served as a model redox active nanoobjects for studies in forced convection conditions. Recently, (M. Holdynski et al. Electrochem. Commmun. 86 (2018) 130–134), we have demonstrated that injection of these nanoparticles suspension into electrochemical cell results in a sharp decrease or increase of the current at glassy carbon rotating disc electrode set at potential corresponding to their electroreduction or electrooxidation respectively. Here, on the example of the electroreduction of Prussian Blue nanoparticles, we show that the shape of potential vs time dependence is independent of the electrode rotation rate. Analysis of the current–time dependences based on the Levich equation indicates that only an average 0.12 % of Fe 3+ ions present at the surface of the given nanoparticle undergoes electroreduction in the elementary reaction step. Injection of Prussian Blue nanoparticles into flowing aqueous electrolyte produces a sharp increase of the current recorded at glassy carbon electrode of the electrochemical wall-jet detector, followed by its gradual decrease. Such behaviour is generally observed for redox-active molecules. The ratio of the peak currents corresponding to electrooxidation and electroreduction of Prussian Blue nanoparticles colliding with the electrode differs from the expected from the stoichiometry of reactions.