Electrochemical Study of the Diffusion and Nucleation of Gallium(III) in [Bmim][TfO] Ionic Liquid

The electrochemical behaviors of Ga³⁺ ions in 1-butyl-3-methylimidazolium trifluoromethanesulfonate ([BMIM][TfO]) ionic liquid are investigated by electrochemical methods and SEM. The cyclic voltammetry study reveals that both the temperature and the material of the electrodes have a significant influence on the electrochemical kinetics. The three methods involved rotating disk electrode have been used to obtain the diffusion coefficient (around 5.57 × 10^-8 cm²/s) of Ga³⁺ ions in [BMIM][TfO] ionic liquid at 70 °C. Meanwhile, the diffusion coefficients at 40, 50, 60 °C and the activation energy are obtained by two of the three methods. By analyzing the current transients and the SEM images of the Ga particles formed during the transients, it is found that the nucleation of Ga on both the glass carbon electrode (GCE) and the Mo electrode in [BMIM][TfO] ionic liquid is a 3-D instantaneous process at 70 °C, while a 3-D progressive process on GCE at 25 °C. The compact and smooth Ga layer is electrodeposited on Mo film sputtered on ITO glass at -1.5 V (vs Pt) and 20 °C from the [BMIM][TfO] ionic liquid. Increasing the overpotential of the electrodeposition makes the Ga layer more porous. When the temperature is higher than the melting point of gallium metal, it has no significant influence on the morphology of the Ga deposits.