Nitrogen-doped graphene–TiOxNy nanocomposite electrode for highly efficient capacitive deionization

Abstract

In this work, the first-ever reported nanocomposite electrode of nitrogen-doped graphene–titanium oxynitride (NG–TiO_xN_y) for capacitive deionization (CDI) was synthesized via hydrothermal reaction and a high-temperature nitridation process. The physiochemical characterizations revealed that the nitrogen was doped in the graphene structure mainly in the form of graphitic nitrogen and the TiO_xN_y was successfully formed via TiO₂ nitridation process. The layered NG nanosheets facilitated the diffusion of ions in saline water and formed electrical double layer on the surface of the electrode material, while the presence of TiO_xN_y enhanced the electrochemical performance by increasing surface area and generating surface vacancies via nitridation. The CDI cell employed NG–TiO_xN_y electrode delivered a breakthrough salt adsorption capacity of 26.1 mg g⁻¹ in 500 mg L⁻¹ saline water, and retained over 90% of its initial salt removal efficacy after 12 regeneration cycles. Such high CDI performance exhibits the promising application of NG–TiO_xN_y as a novel CDI electrode candidate.