Organic solvents tuned polymer derived-sulfonated microporous carbon structures enable resource regeneration and recovery in flow electrode capacitive deionization

The demand for freshwater and energy in today's society is growing rapidly. Although current desalination technologies such as reverse osmosis and electrodialysis are widely used, their high energy consumption remains a major challenge. Recently emerged desalination technology called Flow-electrode Capacitive Deionization (FCDI), offers advantages such as low energy consumption, low pollution, electrode regeneration, and continuous operation. FCDI primarily utilizes activated carbon (AC) as the material for flow electrode, with less research focused on other carbon materials and modifications. Herein, three different solvents induced polyacrylonitrile (PAN) derived microporous carbon structures were tested as flow-electrodes. The carbon structures were sulfonated under different temperatures to explore their impact on desalination. Additionally, by connecting an external capacitor in different operating modes, the charging efficiency and energy recovery during the desalination process were evaluated. The PAN-C@ACE_S150 as flow-electrode exhibited lower ion transfer resistance and higher desalination efficiency. Under short-circuited closed cycle (SCC) operation mode, the average desalination rate within 30 min reached to 0.8 mmol/m2s, approximately 2.5 times higher than that of commercial activated carbon (0.295 mmol/m2s). In Isolated Closed-cycle (ICC) mode, a charging efficiency of 75.73 % was achieved, successfully charging the capacitor from 0 V to 1.02 V and 0 V to 0.6 V with and without system power supply, respectively. These results demonstrated that the PAN-C@ACE_S150 can enhance the desalination capability of the system, achieving the regeneration of fresh water and energy. This opens up new research directions for future advancements in desalination and energy recovery. [Display omitted] •PAN Polymer derived-sulfonated microporous carbon structures were applied as flow-electrodes in FCDI.•Grafting –SO3H− groups on carbon enhanced the ion attraction and desalination efficiency.•PAN-C@ACE_S150 as flow-electrode outperformed the commercial Activated Carbon (AC).•The present study triggers the future advancements in desalination and energy recovery.