Surface functional modification of Nb 2 CT x MXene for high performance capacitive deionization

MXene, show a promising electrode material for capacitive deionization (CDI) due to their elevated conductivity and hydrophilic surface characteristics. Despite optimal electrochemical reaction conditions, MXene still exhibits unsatisfactory capacity. Enhancing capacitance in Nb 2 CT x MXene poses a key challenge, and addressing this involves leveraging pseudocapacitance through increased active site concentration. This study reports a method to notably improve the capacitance by incorporating cation intercalation and surface modification. After alkali treatment and thermal annealing, the obtained 400-KOH-Nb 2 C as a cathode in capacitive deionization, exhibiting notable salt adsorption capacity of 104.2 mg g -1 at 1.6 V and an efficient removal rate of 1.73 mg g -1 min -1 , cyclic stability maintained over 200 cycles. This optimized electrochemical and desalination performance is due to the large interlayer spaces of Nb 2 CT x and the surface with lowest termination of -F and - OH group, promoting the delicate surface of Nb 2 CT x MXene and accelerating ion transport. Furthermore, the derivation of KNbO 3 nanowires on 400-KOH-Nb 2 C surface further expands the layer spacing of MXene and enhances the active sites, and also acts as a protective layer to improve the stability of Nb 2 C, this effectively addressing challenges associated with desalination. This study offers a novel solution for improving Nb 2 CT x MXene electrochemical properties in CDI.