Electrochemical investigation of ZnNPs and Zn(OH)₂NPs thin films behaviour grown on graphite rod by a two-step electrochemical conversion process

Herein, a simple electrochemical process was proposed for the electrochemical modification of a graphite rod electrode (GrE) with a zinc hydroxide thin film. Two sequential steps were enough for the modification of the graphite rod using chronoamperometry technique. In the first step, the metallic zinc film was electrochemically deposited on GrE surface at pH 4.5, by reducing Zn²⁺ on GrE at − 1.78 V vs. saturated calomel electrode (SCE) for only 210 s forming GrE@ZnNPs. In the second step, the electrode previously coated with a metallic zinc film was oxidized in buffer solution at pH 7, at 0.1 V vs. SCE for 360 s to form GrE@Zn(OH)₂NPs. X-ray diffraction, optical microscope and interferometric microscope were used to confirm and identify the obtaining of the desired layer (Zn and Zn(OH)₂ nanoparticles (NPs) thin layer). Then, several electrochemical techniques were used before and after the modification in order to study the electrochemical properties of the bare and modified electrodes. These analyses are based on the comparison of open-circuit potentials, polarization resistances of fast electrochemical systems (R_p), potentiodynamic polarizations (Tafel curves) and electrochemical impedances.