In situ synthesis of ultrasmall NaTi2(PO4)3 nanocube decorated carbon nanofiber network enables ultrafast and superstable rocking-chair capacitive deionization

Abstract

Faradic-based capacitive deionization (CDI), as an important derivative of conventional CDI, has received wide attention in the desalination community. Yet, oriented from its intrinsic ion storage mechanism, faradic-based CDI has been plagued by several serious issues (e.g., imbalanced ion storage capacity, low desalination rate, and poor cycling stability), which greatly constrained its further development. Herein, we put forward an innovative strategy by using carbon nanofiber-reinforced NaTi2(PO4)3 (eCNF/NTP) as the core material (for Na+-capturing) and further coupling it with rational rocking-chair capacitive deionization (RCDI) cell architecture. Of note, owing to the unique 3D network structure of eCNF/NTP that not only provides sufficient redox-activate sites but also offers a rigid network structure to prevent the potential aggregation during cycling, as well as the rational RCDI symmetric cell architecture to avoid the imbalanced cation and anion storage capacity, the RCDI system equipping with eCNF/NTP electrode displays an excellent desalination performance (desalination capacity: 168.2 mg g−1; desalination rate: 0.46 mg g−1 s−1) with outstanding cycling stability (only 6 % desalination capacity degradation after 80 cycles). This work is interesting because it showcases the critical importance of both delicate material design and rationalized cell architecture in addressing the bottleneck issue of CDI, which could shed light on the future development of other high-performance desalination systems.