Efficient Sodium-Ion Intercalation into the Freestanding Prussian Blue/Graphene Aerogel Anode in a Hybrid Capacitive Deionization System

In this study, we introduced an efficient hybrid capacitive deionization (HCDI) system for removal of NaCl from brackish water, in which Prussian blue nanocubes embedded in a highly conductive reduced graphene oxide aerogel have been used as a binderfree intercalation anode to remove Na+ ions. The combination of redox-active nanocubes and the three-dimensional porous graphene network yielded a high salt removal capacity of 130 mg g-1 at the current density of 100 mA g-1. Moreover, energy recovery and energy consumption upon different desorption voltages of the HCDI system were investigated and the result showed a notably low energy consumption of 0.23 Wh g-1 and a high energy recovery of 39%. Furthermore, the real-time intercalation process was verified by in situ X-ray powder diffraction measurements, which confirmed the intercalation and deintercalation processes during charging and discharging, respectively. Eventually, a perfect stability of the desalination unit was confirmed through the steady performance of 100 cycles. The improved efficiency as well as ease of fabrication opens a shiny horizon for our HCDI system toward commercialization of such technology for brackish water desalination.