Reconfiguring the interface charge of Co@Carbon polyhedron for enhanced capacitive deionization

In this work, the Co-metal organic framework (ZIF-67) is employed as the template to prepare 3D mesoporous Co@carbon polyhedron (Co@CP) for capacitive deionization (CDI) anodes with improved salt removal capacity. The as-prepared Co@CP exhibits a novel dodecahedron structure with abundant nanopores and embeds with Co nanoparticles which are uniformly distributing on the carbon skeleton. Such structure not only enhances the conductivity and structural durability of the whole electrode, but also provides a convenient transport channel for ions/electrons and thereby promoting the desalination kinetics. Remarkably, the reversible electrochemical conversion between the Co-0 to some extent improves the storage of Na+, accompanied by the desalination/regeneration. Regarding the preparation, as the temperature increased from 600 to 800 degrees C, the dominant particle size rises from 5 to 7 nm to 12-18 nm. The density functional theory calculation features that the conductivity and charge transport ability of Co@CP can be reinforced by optimizing the Co-C interface. Accordingly, the charge density difference simulation demonstrates that the Co doping and the existence of defects benefits to generate great potential active sites, leading to the enhanced adsorption of Na+. As a result, the optimized Co@CP possesses the large pore volume, high degree of graphitization and large specific surface area (515.6 m(2)/g). Towards the desalination, the highest desalination capacity reaches to 47.8 mg/gin 1000 mu S/cm NaCl at 1.2 V with adsorption rate of 3.28 mg/g/min.

Automated summary

In this study, the Co-metal organic framework (ZIF-67) was used as a template to prepare 3D mesoporous Co@carbon polyhedron (Co@CP) for capacitive deionization (CDI) anodes, resulting in improved salt removal capacity. The optimized Co@CP exhibited large pore volume, high degree of graphitization, and large specific surface area, with the highest desalination capacity reaching 47.8 mg/g.