Move contrast X-ray imaging of electrochemical reaction process in electrolytic cell

Abstract

The <i>in-situ</i> dynamic observation of ion migration and redox reactions during electrochemical reactions is critical for the understanding of the charging and discharging performance, ion migration characteristics, causes and preventives of defects in cells and electrolytic cells. For the convenience of parameter tuning, an electrolytic cell is adopted to investigate the electrochemical reaction. The processes of ion migration and redox reaction are investigated based on move contrast X-ray imaging. The experimental results demonstrate that the contrast-to-noise ratio of move contrast X-ray imaging is one order higher than that of the conventional temporal subtraction imaging. The initial status of the electrochemical reaction is successfully revealed by move contrast X-ray imaging. The images show that at the very beginning of the reaction, the signals of move contrast distribute almost evenly in the electrolytic cell, which implicates that the ion migration is initiated as soon as the cell is switched on and redox reaction occurs simultaneously all over the cell, other than the fact that ions are driven by electric field, approach to the cathode and then are reduced through electron gain. The signals of move contrast imaging are obviously stronger at positions inside the shadow of the electrodes than elsewhere. This means that the redox processes react densely at the electrodes. When the electrical voltage is adjusted to a critical value and the conventional methods are hard to observe ion migration or atom accumulation, the move contrast X-ray imaging can still disclose evidently the trace of ion migration or movement of atom clusters. Therefore, the move contrast X-ray imaging can improve significantly the sensitivity of observation to the trace of ions or atoms in the electrolyte and has great potentials in in-situ investigating the characteristics of electrochemical reactions.