Study of Indium electrodeposition and nucleation mechanism in acidic solution using EQCM

Abstract

The electrochemical behavior and electrodeposition mechanism of indium in acidic aqueous solution were studied using cyclic voltammetry (CV), chronoamperometry by electrochemical quartz crystal microbalance (EQCM). The cyclic voltammetry of indium on Pt electrode was more complex than that on glassy carbon (GC) electrode. Only one reduction peak and an oxidation peak could be seen in the CV curve of GC, which were attributed to the electrodeposition and dissolution of indium, respectively. In contrast, an extra reduction and several oxidation peaks were observed in the CV curve on Pt electrode. EQCM results illuminated the difference of CV curves between the two electrodes. The hydrogen reduction takes place simultaneously during indium electrodeposition on the Pt electrode, while on the GC electrode, the hydrogen evolution is suppressed. Passivation of indium during the stripping of deposit on Pt electrode is confirmed. The participation of low-valent indium ions is also confirmed in the dissolution process by the analysis of EQCM results. The analysis of current transients and SEM images indicates that the indium electrodeposition on GC and Pt follows progressive nucleation and three-dimensional growth controlled by diffusion, and the diffusion coefficient of In3+ on Pt and GC was calculated as (1.31±0.15)×10−5 cm2 s−1 and (1.2±0.1)×10−5 cm2 s−1, respectively. By separating the electrodeposion current from total current using EQCM, the current characteristics of nucleation and growth of indium which was covered by the hydrogen evolution can be reproduced. The current due to indium electrodeposition on Pt substrate was calculated from the mass change signal recorded by EQCM, which fitted well with the nonlinear fitting result.