Mechanistic Insights and Performance Advancements in Flow Capacitive Deionisation for Sustainable Energy Conversion

ABSTRACT

Flow capacitive deionisation is an advanced electrochemical technology for water purification and energy‐related applications. It represents a viable alternative to conventional desalination methods due to its low operating voltage, continuous electrode regeneration, and stable performance under moderate‐to‐high salinity conditions. The use of circulating carbon‐based flow electrodes prevents electrode saturation and enables sustained ion removal during continuous operation. Recent advances in electrode materials, including activated carbon, mesoporous carbon, carbon nanotubes, and conductive additives, have resulted in notable improvements in charge efficiency, salt removal capacity, and energy consumption. Progress in membrane development, current collector configuration, and flow‐channel design has further reduced internal resistance and enhanced ion transport efficiency. Various operational strategies, including isolated closed cycle, short‐circuited closed cycle, and single cycle modes, have been investigated to optimise electrode regeneration and energy recovery. Integration of flow capacitive deionisation with salinity‐gradient energy systems, particularly reverse electrodialysis, offers prospects for energy‐neutral or energy‐positive desalination. Furthermore, the technology demonstrates strong potential for the selective recovery of valuable and hazardous ions, including lithium, fluoride, ammonium, and heavy metals. This review systematically evaluates material innovations, transport mechanisms, cell architecture, performance metrics, and emerging applications, highlighting flow capacitive deionisation as a scalable and energy‐efficient platform for desalination, resource recovery, and hybrid energy systems.