Modeling a CuCl(aq)/HCl(aq) Electrolyzer using Thermodynamics and Electrochemical Kinetics

Research efforts on the CuCl(aq)/HCl(aq) electrolyzer would greatly benefit from the ability to quantify the dissipative processes that undesirably increase the cell's applied potential, E_cell, which decreases its efficiency. To date, little is known about what impact further improvements to active surface area, extent of CuCl(aq) conversion and ohmic resistance would exactly have on the electrolyzer performance. To better understand how this electrolyzer can be improved, a model was developed to quantify and separate the effects of electrochemical kinetics, membrane transport and open circuit potential, E_OCP, on E_cell for a given current density. By employing data obtained from previous studies with electrochemical cells into the developed model, it was possible to calculate E_cell values that agreed with data collected from a lab scale electrolyzer using just one adjustable parameter, the Nernst diffusion layer at limiting current. The model was then used to identify the predicted E_cell contributions as a function of CuCl(aq) conversion, active electrode area and ohmic resistance. It was found that the extent of CuCl(aq) conversion can dramatically impact the electrolyzer electrode kinetics and E_OCP. More importantly, as CuCl(aq) conversion increased, the E_cell values needed consistently increased to keep the same current density. Overall, E_cell could be most readily reduced by improving R_ohm, whereas improvements to electrode kinetics have limited impacts.