Carbon nanofiber@ZIF-8 derived carbon nanosheet composites with a core–shell structure boosting capacitive deionization performance

Abstract

This work demonstrated the development of a hierarchical porous carbon–carbon composite used as an electrode material for capacitive deionization. The novel core–shell composite consisting of carbon nanofibers and N-rich porous carbon nanosheets (CNF_ZIF) was obtained by in situ growth of zeolitic imidazolate framework-8 (ZIF-8) nanosheets on electrospun nanofibers. By tailoring the composition and porosity of CNF_ZIF, ion transport and adsorption in the composite were tuned to achieve a large desalination capacity and a high desalination rate. Thanks to the synergistic effect of its N-rich carbon surface, high hydrophilicity, large specific surface area and unique hierarchical porous structure, the engineered CNF_ZIF sample exhibited an excellent capacitive deionization performance with a maximum desalination capacity of up to 50.88 mg g⁻¹ for NaCl solution and a high capacity retention rate of 97% after 30 cycles. Remarkably, CNF_ZIF also demonstrated high desalination capacities of 27.19 mg g⁻¹, 25.35 mg g⁻¹ and 20.46 mg g⁻¹ for CaCl₂, MgCl₂, and KCl solutions, respectively. This work provided a new route for the design of advanced electrode materials, and therefore represents a major step forward in the development of electrodes for capacitive deionization applications.