Well-dispersed Prussian blue analogues connected with carbon nanotubes for efficient capacitive deionization process

Abstract

Prussian blue analogs (PBAs) could be used as Faradic electrodes materials in capacitive deionization (CDI) to desalinate seawater or brackish water, because it had the unique open framework that not only enables Na+ with large ion radius to be reversibly embedded/exited during charging/discharging, but also had a large channel structure to the transmission of Na+. However, due to the disadvantages of easy agglomeration, poor conductivity and easy structural collapse, the further applications of PBAs had been seriously limited. To break these limitations, the 3D composite material NaFeHCF@CNT was successfully synthesized by simple coprecipitation method through dotting NaFeHCF nanoparticles on the staggered carbon nanotube network. As expected, the NaFeHCF particles were uniformly embedded in the CNT networks without any agglomeration resulting in higher specific surface area and utilization. Due to the doping of carbon nanotubes, NaFeHCF@CNT enhanced charge transfer and ion diffusion, resulting in low charge transfer resistance and good wettability, thus benefiting CDI performance. In the desalination performance test, the NaFeHCF@CNT electrode could achieve a high desalination capacity of 82.97 mg g−1 and a low energy consumption of 2.78 kg NaCl kWh−1 in 3000 mg L−1 NaCl, and the desalination capacity could still reach 89.82% of the initial value after 50 cycles. Consequently, the NaFeHCF@CNT achieves high desalination performance in CDI systems.