Creating Nitrogen-Doped Hollow Multiyolk@Shell Carbon as High Performance Electrodes for Flow-Through Deionization Capacitors

A novel electrode material for flow-through deionization capacitors consisting of the hollow multiyolk@shell carbon (HMYSC) with effective nitrogen doping has been rationally designed and originally prepared by a template-directed coating method. The HMYSC can be divided into several hollow carbon spheres cores and the nitrogen-doped shell. The as-obtained HMYSC shows many favorable features for flow-through deionization capacitors, such as large specific surface area (910 m<sup>2</sup> g<sup>–1</sup>), hierarchical pores, high conductivity and good wettability. With the multiple synergistic effects of the above features, the as-prepared HMYSC electrode has higher specific capacitance, lower inner resistance and good stability. In the deionization test, the HMYSC electrode exhibits a high salt adsorption capacity of 16.1 mg g<sup>–1</sup> under the applied voltages of 1.4 V in a 500 mg L<sup>–1</sup> NaCl solution. Furthermore, it has been demonstrated that the HMYSC electrodes presented faster salt adsorption rate under the applied voltages of 0.8–1.4 V and in the NaCl solution with the concentration of 100–500 mg L<sup>–1</sup>. The HMYSC electrodes also exhibits an excellent regeneration performance in the repeated adsorption–desorption experiments. The HMYSC developed in this work is promising to be an effective electrode material for the flow-through deionization capacitors and other electrochemistry applications.