Abstract
Cr electrodeposition onto glassy carbon rotating disk electrode (GCRDE) was studied from Cr(III) dissolved in the choline chloride and ethylene glycol eutectic mixture (ethaline) under different GCRDE angular speeds, ω, at 343 K. The ethaline kinematic viscosity, ν= 0.17〖 cm〗^2 s^(-1), was estimated, for the first time, from potentiodynamic plots. Analisys of potentiostatic current density transients, j-t plots, recorded at different ω, was based on the Hyde et al. (J. Electroanal. Chem. 534 (2002) 13) model, jdc-fcon(t), complemented by a previous adsorption step, jad(t), and the residual water reduction, jWR(t), taking place on the growing surfaces of the Cr nuclei. Nucleation frequency and number density of active sites showed small dependence on ω; however, jWR(t) clearly depends on it. SEM, EDS and XPS techniques were used to characterize the Cr electrodeposited. Electrodeposits were formed by quasi-spherical conglomerates (ca. 50 and 200 nm diameter for 0 and 1500 rpm, respectively) of nanoparticles (sized less than 30 nm diameter, in both cases). Moreover, these electrodeposits were formed by chromium and oxygen and its content increases with ω. These nanoparticles exhibit a core-shell structure: Cr(0)@ Cr(OH)3@ Cr2O3 which is consistent with the theoretical mechanism used for the analysis of the j-t plots
Electrodeposition of Nanostructured Chromium Conglomerates from Cr(III) Dissolved in a Deep Eutectic Solvent: Influence of Forced Convection