High-performance capacitive deionization using 3D porous Ti3C2Tx with improved conductivity

Abstract Ti3C2Tx MXene has shown a great application potential in the field of capacitive deionization (CDI) due to its good in-sheet conductivity, good hydrophilicity, and large intercalation capacitance. However, the two-dimensional (2D) stacking structure easily results in poor conductivity perpendicular to the sheets. Herein, the three-dimensional (3D) porous Ti3C2Tx (3D-Na+-Ti3C2Tx) has been fabricated via NaOH-induced crumpling of the Ti3C2Tx nanosheets. The interlaced Ti3C2Tx layers form a 3D network structure and significantly enhance the conductivity. The specific surface area and average pore diameter of 3D-Na+-Ti3C2Tx is 49.15 m2 g−1 and 13.9 nm, which is higher than that of 2D-Na+-Ti3C2Tx of 4.72 m2 g−1 and 7.6 nm. Without conductive additives, the 3D-Na+-Ti3C2Tx electrode shows a lower resistance of 4.6 × 102 Ω/□ compared with 2D-Na+-Ti3C2Tx electrode of 6.37 × 107 Ω/□. In addition, the 3D-Na+-Ti3C2Tx electrode also shows a higher electrosorption capacity of 16.2 mg g−1 at 1.2 V in 100 mg L-1 NaCl solution even without conductive additives, which is higer than that of 2D-Na+-Ti3C2Tx electrode with conductive additives of 11.4 mg g−1.