Nitrogen and sulfur co-doped NaTi2(PO4)3/hole graphene composite as high-performance electrosorption electrodes for hybrid capacitive deionization

In this study, a nitrogen and sulfur co-doped sodium titanium phosphate/hole graphene (N,S-NTP/rHGO) was synthesized by one-step hydrothermal method using thiourea as N/S source. The microstructure characterization confirms that N and S heteroatoms have been integrated into the graphene skeleton. The electrochemistry and electrosorption properties of the N,S-NTP/rHGO electrodes were investigated for hybrid capacitor deionization (HCDI). The results indicate that the specific capacitance of N,S-NTP/rHGO electrodes can reach 530.46 F g−1 at a scan rate of 0.2 mV s−1, which is 33.8% higher than that of the sample without doping. Moreover, the HCDI cell based on the N,S-NTP/rHGO-2 shows a high desalination capacity of 36.87 mg g−1 and a rapid ion removal rate of 0.66 mg g−1 s−1, which is more than twice as high as the sample without doping (0.3 mg g−1 s−1) at an initial NaCl concentration of 800 mg L−1 and applied voltage of 1.4 V. Further, the N,S-NTP/rHGO electrode exhibits excellent regeneration ability. Therefore, this study suggests that as-prepared N,S-NTP/rHGO composite exhibits a great potential application for high-performance HCDI systems.