Principles for Optimal Electrode Design and Operation for Desalination with Electrochemical Ion Pumping.

Abstract

Electrochemical ion pumping (EIP) is an emerging electrochemical separation form that eliminates solution mixing in conventional capacitive deionization and enables pseudocontinuous desalination with unidirectional ion flux. In this work, we systematically investigate electrode design and operational parameters governing the performance of EIP desalination using both experiments and modeling. We first evaluated the effect of carbon and polymer fractions on ionic and electronic transport within the cation-shuttling electrodes, demonstrating that optimal performance requires balancing ion mobility through the polymer phase and the electronic conductivity and ion storage capacity provided by the carbon phase. We then assessed the impact of electrode capacity and conductivity on EIP performance by varying the ratio of activated carbon and carbon black, showing that desalination performance is relatively stable over a wide range of capacity and is only undermined at extremely low capacity. Finally, we analyze the role of cycle time and show that EIP has similar specific energy consumption with very different cycle times as long as electrolysis is prevented. Overall, these results establish guiding principles for rational electrode design and operation to achieve optimal EIP performance.