Efficient high-rate brackish water desalination via solid-electrolyte-assisted flow-electrode capacitive deionization

Flow-electrode capacitive deionization (FCDI) holds promise for energy-efficient brackish water desalination. Despite the considerable research effects on flow-electrode and flow-channel structure optimization, the key kinetic indicator, the average salt removal rate (ASRR), has seen limited improvement due to the intrinsically low conductivity of brackish water. We hereby report a new solid-electrolyte-assisted FCDI device (SE-FCDI), which tackles the conductivity issue by its enhanced ion transport and reduced concentration polarization. At applied voltage of 1.0 V, SE-FCDI shows a record-high ASRR of 4.8μmol cm⁻² min⁻¹ for 1 g/L saline water, which is over four times higher than conventional FCDI. Coupled with its higher current efficiency of 96 %, low energy consumption of 0.25 kWh/m³ is achieved for potable water production. The solid electrolyte strategy provides new insights into the design and optimization of FCDI for efficient high-rate brackish water desalination, which can be combined with other innovations in FCDI to further boost the overall performances of brackish water desalination.