Two-Dimensional Hetero-structured TiO2/TiS2 Nanosheets for Capacitive Deionization

Capacitive deionization (CDI) is a low-cost, low-energy desalination technology, which is largely affected by electrode materials. Both TiO2 and TiS2 have good sodium storage capacity, however, TiO2 has poor electrical conductivity, and TiS2 has a strong stacking tendency. In this work, a typical transition metal carbide MXene (Ti3C2Tx) was used as the precursor to prepare hetero-structured TiO2/TiS2 by the hydrothermal method. The rough particles between the layers provided a channel for the rapid transport of sodium ions and relieve the stacking state of nanosheets. The maximum desalination capacity of the TiO2/TiS2 electrode was 36.45 mg g–1 (NaCl), and the capacity retention rate was about 75% after 30 cycles. Based on the electrochemical quartz crystal microbalance, the migration behavior of ions in the desalination process was exhibited in situ. This work shows that TiO2/TiS2, as a heterojunction material obtained from MXene, offers a new idea to solve the problem of poor electrochemical properties of TiO2.