Pseudo-continuous and scalable electrochemical ion pumping with circuit-switching-induced ion shuttling

Abstract

Despite the potential of electrosorption to address many challenges in sustainability at the water–energy–food nexus, the performance of conventional electrosorption is hindered by the technical limitations associated with the need to switch solutions in the flow channels between the charging and discharging half-cycles. Here we show that electrochemical ion pumping (EIP), powered by the mechanism of ion shuttling induced by circuit switching, offers a highly scalable approach to overcome the limitations of solution switching and achieve pseudo-continuous ion separation with unidirectional ion flux. We demonstrate the feasibility of EIP with symmetric and asymmetric configurations and report a systematic investigation of symmetric EIP with both a single electrode and multiple electrodes. We unveil interesting system behaviours of multi-electrode EIP that are critical to scaling up EIP for practical applications. We also show salient performance enhancement of EIP compared with conventional electrosorption using various types of configurations for brackish water desalination. In addition to its exceptional scalability and performance, the ability of EIP to operate with ultrashort half-cycles with minimum capacitance has a strong potential to shift the paradigm of system and electrode design in a broad range of electrochemical separation applications. Unlike solution switching in conventional electrosorption, electrochemical ion pumping achieves ion separation via circuit switching, enabling pseudo-continuous desalination with a unidirectional ion flux and a very high frequency of charging and discharging.