Ti 3 C 2 -MXene Partially Derived Hierarchical 1D/2D TiO 2 /Ti 3 C 2 Heterostructure Electrode for High-Performance Capacitive Deionization.

Constructing faradaic electrode with superior desalination performance is important for expanding the applications of capacitive deionization (CDI). Herein, a simple one-step alkalized treatment for in situ synthesis of 1D TiO 2 nanowires on the surface of 2D Ti 3 C 2 nanosheets, forming a Ti 3 C 2 -MXene partially derived hierarchical 1D/2D TiO 2 /Ti 3 C 2 heterostructure as the cathode electrode is reported. Cross-linked TiO 2 nanowires on the surface help avoid layer stacking while acting as the protective layer against contact of internal Ti 3 C 2 with dissolved oxygen in water. The inner Ti 3 C 2 MXene nanosheets cross over the TiO 2 nanowires can provide abundant active adsorption sites and short ion/electron diffusion pathways. . Density functional theory calculations demonstrated that Ti 3 C 2 can consecutively inject electrons into TiO 2 , indicating the high electrochemical activity of the TiO 2 /Ti 3 C 2 . Benefiting from the 1D/2D hierarchical structure and synergistic effect of TiO 2 and Ti 3 C 2 , TiO 2 /Ti 3 C 2 heterostructure presents a favorable hybrid CDI performance, with a superior desalination capacity (75.62 mg g -1 ), fast salt adsorption rate (1.3 mg g -1 min -1 ), and satisfactory cycling stability, which is better than that of most published MXene-based electrodes. This study provides a feasible partial derivative strategy for construction of a hierarchical 1D/2D heterostructure to overcome the restrictions of 2D MXene nanosheets in CDI.