Coal pitch-based nanosheets enhance the electronic and ionic transport of flow electrode capacitive deionization

High-salinity wastewater treatment has always been a challenging issue. In this study, coal tar pitch was used as the carbon source and melamine as the nitrogen source to prepare coal tar pitch-based nanosheets (CPN-9) using a salt-template method. The desalination performance of CPN-9 was evaluated using flow-electrode capacitive deionization technology. The results showed that CPN-9 has a high specific surface area (466.34 m 2 /g), a rich pore structure (micro-/ meso -pore volume was 0.28), excellent rheological properties, and hydrophilicity (contact angle of 20.44°), thereby accelerating ion transport. Electrochemical results indicated that CPN-9 exhibits a significant double-layer ion storage mechanism, with a specific capacitance of 176.66 F/g at a current density of 0.5 A/g. CPN-9 has a very low charge transfer resistance. The synergistic effect of aromatic carbon and nitrogen doping (the content of pyrrole and pyridine nitrogen was 36.40% and 35.83%, respectively) in coal tar pitch accelerates electron transfer in CPN-9. The good ion diffusion performance and low impedance of CPN-9 accelerate the ion exchange rate, resulting in outstanding desalination performance. At 1.2 V and 3% mass loading, with a CPN-9 to conductive carbon black ratio of 4:1, the average desalination rate, charge efficiency, and energy consumption reached 0.039 mg/(cm 2 ·min), 48.47%, and 0.012 kWh/mol, respectively. In summary, this study optimized the structure of CPN-9 from the perspective of electronic and ionic transport, enhancing its desalination performance and providing theoretical support for the deionization of high-salinity wastewater.