The enhanced synergistic capacitive desalination enabled by Ni@NiO@C hybrid anode

In this work, the nickel-based metal-organic framework (Ni-MOF) has been employed as template to prepare the Ni@NiO@C hybrid anode for efficient capacitive deionization (CDI). The as-prepared Ni@NiO@C inherit the spherical structure of Ni-MOF, which provides multidirectional channels for ion diffusion and charge transport, thereby promoting the desalination kinetics. On the other hand, the robust carbon skeleton assures the structure stability upon the cycling. As a result, the Ni@NiO@C demonstrates the high desalination capacity of 2.18 mmol/g in 1500 μS/cm NaCl solution. The theoretical calculations feature that the NiO layer has a strong adsorption effect on Na+, and the involvement of Ni metal improves the overall conductivity. Thus, the synergistic effect between the inner Ni nanoparticles and the outer NiO layer as well as the stable carbon skeleton greatly enhances the salt removal capacity of the electrode.