Chronoamperometric response of ion-exchange membrane systems

The electrical response of an ion-exchange membrane system to a square shaped electric potential, has been investigated from both experimental and theoretical viewpoints. The chronoamperometric response of a cation-exchange membrane in contact with a NaCl solution was experimentally obtained for different values of the amplitude of the perturbing electric potential. From the theoretical viewpoint, the system under study is considered to be constituted by a cation-exchange membrane and two diffusion boundary layers on both sides of the membrane. The ionic transport processes are prescribed by the Nernst-Planck flux equations, the electrical neutrality condition, and the Donnan equilibrium relations at the membrane/solution interfaces. The theoretical results are numerically obtained by using the network simulation method. Some of our results confirm that the chonoamperometric techniques can be used to measure the thickness of the diffusion boundary layers. Others provide new insights in relation with the time evolution of the short circuit electric current supplied by the salinity gradient due to the concentration polarization in ion-exchange membrane systems, showing the role played by the concentration polarization in the field of the renewable energies.