Synergistic effect of nitrogen, sulfur-codoping on porous carbon nanosheets as highly efficient electrodes for capacitive deionization

Dual heteroatom-codoped carbon materials have attracted great interest in electrochemical researches due to a synergistic effect. However, evaluation and analyses of promotional effect of codoped carbons materials as electrodes on capacitive deionization have not been extensively studied. Here we prepare N, S- codoped porous carbon nanosheets (N, S-CN-x, x indicates carbonization temperature) by one-pot molten salt strategy as efficient electrodes for electrosorptive desalination. The N, S-CN sample carbonized at 600 °C (N, S-CN-600) possesses a high specific area, unique meso-/microporous interconnected structure, fine wettability, and double functional groups on the surface. Meanwhile Raman spectra revealed N, S-CN materials have a higher degree of structure defects than undoped and solely N or N-doped carbon samples. Additionally, systematic investigation demonstrates that N, S-codoping has distinct promotional effect on electrochemical properties (higher specific capacitance and lower internal impedance) and capacitive deionization performance compared with undoping, solely N or S doping. What's more, N, S-CN-600 displays great cycling stability and an outstanding deionization capacity of 55.79 mg g^-1 at 1.4 V in a 330 mg L^-1 NaCl solution. Hence, the N, S-codoped carbon nanosheets should be promising electrode materials for capacitive deionization. Our work could pave a way for the application of multiple heteroatom codoped carbon materials in capacitive deionization.