Membrane Transport in a CuCl(aq)/HCl(aq) Electrolytic Cell

Recent developments in membrane and electrocatalyst characterization techniques for materials used in the CuCl(aq)/HCl(aq) electrolytic cell have significantly increased the amount of experimental data available in literature. Rotating disc electrode (RDE) and membrane conductivity cells capable of operating in highly concentrated HCl(aq) were developed to characterize the material performance of key MEA materials for this electrolytic cell. Specifically, exchange current density and transfer coefficient values for platinum and carbon as the electrocatalyst material for the anode reaction of this electrolytic cell were quantified in highly concentrated HCl(aq)¹. Additionally, conductivity and permeability parameters of hot-pressed Nafion 117 were characterized for applications in highly concentrated HCl(aq) and CuCl(aq) solutions². Though these fundamental properties are now available, there remained a need for a simple model to connect these properties appropriately to overall cell performance. While equilibrium thermodynamics of this electrolytic cell was carefully studied³, the cell electrode kinetics and transport in the membrane have not been modeled yet. Principles of non-equilibrium thermodynamics have the potential to incorporate membrane transport properties and electrochemical kinetic data together into a simple but useful model of this electrolytic cell. The use of linear phenomenological equations with phenomenological coefficients can be used to model the effects of permeability and conductivity on the ohmic resistance of the electrolytic cell. In addition to linear non-equilibrium processes, non-linear nonequilibrium thermodynamic expressions of the electrochemical reactions can be used to model the effects of electrocatalyst properties on the overall cell performance. As a result, suitable electrocatalysts and membrane materials were identified and their effects on the electrolytic cell performance were quantified in the form of a non-equilibrium thermodynamic model.

References:

1. D. M. Hall, E. G. LaRow, R. S. Schatz, J. R. Beck, and S. N. Lvov, J. Electrochem. Soc., 162, F108–F114 (2015).

2. R. Schatz, S. Kim, S. Khurana, M. Fedkin, and S. N. Lvov, ECS Trans., 50, 153–164 (2013).

3. D. M. Hall, N.N. Akinfiev, E. G. LaRow, R. S. Schatz, and S. N. Lvov,  Electrochim. Acta, 143, 70-82 (2014).