Three-dimensional micro/mesoporous carbon composites with carbon nanotube networks for capacitive deionization

The three-dimensional micro/mesoporous carbon composites with carbon nanotube networks for capacitive deionization (CDI) were synthesized through an organic–inorganic self-assemble route with the subsequent activation by KOH. The crucial factors for the textural properties of composites were investigated. It was demonstrated that the new micropores emerge on the mesoporous framework of composites with suitable activation conditions, and some generated micropores also interconnect with others, which gives rise to the broaden pore size in the inner carbon channels and finally forms the efficient three-dimensional micro/mesoporous structure. In the meantime, the activation creates abundant defects on carbon nanotube networks, which also increase the surface area and ion diffusion channels. The electrochemical test shows that the activated composites exhibit the improved electrosorption capacitance. Through the inner resistance and energy density analyses, the activated composite electrode shows a slightly higher resistance but almost an approximate energy density as compared with the pristine one. Meanwhile, the activated composites are revealed to be more effective to adsorb ions in an aqueous solution under a lower CDI voltage, making it possible for the energy saving during CDI procedures. The results mentioned above prove that the activated composites are candidate electrode materials for CDI application, for its high surface area, suitable pore size/volume and special interconnected micro/mesoporous structure, superior electrochemical and CDI performances.