2.4. Charge/Discharge Test

There were two active electrolytic solutions, 1.0 M Ce(NO₃)₃·6H₂O) and 1.0 M I₂, employed as positive and negative electrolytes. Both 2.0 M H₂SO₄ and 2.0 M CH₃SO₃H were used as the supporting electrolytes, respectively. The 1.0 M I₂/ascorbic acid/2.0 M H₂SO₄ solutions were obtained through dissolving the KIO₃ and KI in acidic reaction, as expressed in Equation (1), then adding 0.25 M ascorbic acid. All chemicals used were of analytical reagent grade.

The charge/discharge tests were carried out using 1.0 M Ce(NO₃)₃·6H₂O/2.0 M CH₃SO₃H as the positive electrolyte, 1.0 M I₂/ascorbic acid/2.0 M H₂SO₄ as the negative electrolyte, C–TiO₂–PdO as both positive and negative electrodes, and Nafion 117–SiO₂–SO₃H as the separation membrane at a current density of 20 mA/cm² and using 20 mL of electrolyte solutions. A charge/discharge test was conducted using a WBCS3000 battery cycler system (Top Trans, Korea) and CT2001C 10 V/2A (Wuhan Land Co., Wuhan, China) apparatus.