Improving capacitive deionization performance through tailored iodine-loaded ZIF-8 composites

The increasing demand for clean water necessitates the development of advanced desalination technologies. Capacitive deionization (CDI) utilizing porous carbon electrodes presents a sustainable approach to the need for abundant fresh water. However, traditional carbon-based materials suffer from low efficiency and high manufacturing costs. This study dealt with this problem by modifying the I2@ZIF-8 material to improve CDI performance. By adding redox iodine, we were able to increase electrical conductivity while keeping the ZIF material's high porosity. The I2@ZIF-8 (2:1) demonstrates remarkable desalination capabilities, exhibiting 53.12 mg/g salt adsorption capacity (SAC) in a 1500 ppm NaCl solution. Notably, the electrodes remain stable and demonstrate excellent regeneration properties over 40 charge-discharge cycles, utilizing a potential range of −0.2 to 1.0 V with a current density of 25 mA/g. On the other hand, the I2@ZIF-8 (2:1) material effectively removes various other metals from the aqueous solution, with desalination efficiency following the order Ca2+ > Mg2+ > K+ > Na+, attributed to the combined influence of ionic charge and hydrated radius. Thus, our study presents an effective strategy for designing non-pyrolyzed materials having a hierarchical structure, resulting in enhanced SAC with low energy consumption in CDI applications.