For determining the capacitance of a capacitive deionization (CDI) electrode using cyclic voltammetry, the choice of electrolyte solution is critical. The electrolyte should be compatible with the CDI electrode material and must provide suitable ionic species to facilitate the charging and discharging processes during cyclic voltammetry. Here are some considerations for selecting the best electrolyte solution:

Commonly used electrolytes for CDI electrode capacitance measurement include solutions of sodium chloride (NaCl), potassium chloride (KCl), and solutions containing other alkali metal salts or simple ionic compounds.

Remember that the selection of the electrolyte solution should align with the specific CDI electrode material and the intended applications of the device. It's a good practice to consult relevant literature and previous studies on CDI electrodes with similar materials to gain insights into the most suitable electrolyte solutions for your specific setup. Additionally, always perform preliminary tests and control experiments to ensure the chosen electrolyte meets the requirements and provides accurate capacitance measurements.