Enhanced hybrid capacitive deionization performance by sodium titanium phosphate/reduced porous graphene oxide composites

In this study, sodium titanium phosphate/reduced porous graphene oxide (NTP/rPGO) composites are used as novel electrode materials for hybrid capacitive deionization (HCDI). The composites are synthesized through assembling the NaTi2(PO4)3 precursor with etched graphene oxide under hydrothermal condition. The NTP/rPGO composites demonstrate a porous hierarchical structure, where uniformly dispersed NaTi2(PO4)3 particles are attached on the rPGO sheets, which provide abundant adsorption sites, highly conductive networks, and short diffusion lengths for salt ions. Benefiting from the redox reaction of the NTP and electrical double-layer capacity of the rPGO, the NTP/rPGO composite containing 77 wt % NaTi2(PO4)3 presents a high specific capacity of 396.42 F g–1 and a high electrosorption capacity of 33.25 mg g–1 at the voltage of 1.4 V with the initial salt conductivity of 1600 μS cm–1 (786 mg L–1). Further, it also shows excellent recycling stability and rapid desalination rate of 0.30 mg g–1 s–1 (100 times as fast as the bare graphene electrode). Therefore, the NTP/rPGO composites exhibit a promising prospect for desalination application in the HCDI system.