Three-electrode cell calorimeter for electrical double layer capacitors.

A calorimeter was built to measure the heat from a porous capacitive working electrode connected in a three-electrode configuration. This makes it possible to detect differences between cathodic and anodic heat production. The electrochemical cell contains a large electrolyte solution reservoir, ensuring a constant concentration of the salt solution probed by the reference electrode via a Luggin tube.

Electric Potential of Ions in Electrode Micropores Deduced from Calorimetry.

The internal energy of capacitive porous carbon electrodes was determined experimentally as a function of applied potential in aqueous salt solutions. Both the electrical work and produced heat were measured. The potential dependence of the internal energy is explained in terms of two contributions, namely the field energy of a dielectric layer of water molecules at the surface and the potential energy of ions in the pores.