Investigation of zinc electronucleation and growth mechanisms onto platinum electrode from a deep eutectic solvent for gas sensing applications

This paper shows a study of Zn electrodeposition on platinum electrode from a deep eutectic solvent (DES) based on choline chloride and its applications to manufacture gas sensors. Mechanisms and kinetics of the Zn electrodeposition onto platinum electrode from DES were studied using cyclic voltammetry (CV) and chronoamperometry (CA). The results have shown that Zn electrodeposition is governed by instantaneous nucleation mechanism. The CA behavior can be described by a model comprising three-dimensional nucleation and diffusion-controlled growth of Zn nuclei. From model fitting, kinetic parameters (such as nucleation frequency, A, and number density of active sites, N0) of Zn electrodeposition onto platinum (disk) electrode were determined. Also, diffusion coefficient, D, was calculated from both CV and CA techniques. From this information, Zn nanoparticles were electrodeposited in Pt microelectrodes and subsequently stabilized (oxidizing) by annealing treatment (to form ZnO film) to evaluate their performance as gas sensors. SEM and EDX techniques were used to verify the presence and the zinc nucleation type onto platinum electrode. It has also demonstrated that the developed sensor is suitable for application in H2S gas detection at low concentration levels, which could expand the potential of DES in gas sensor applications.