Surface functional modification of Nb2CTx 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 Nb2CTx 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-Nb2C 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 Nb2CTx and the surface with lowest termination of -F and –OH group, promoting the delicate surface of Nb2CTx MXene and accelerating ion transport. Furthermore, the derivation of KNbO3 nanowires on 400-KOH-Nb2C 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 Nb2C, this effectively addressing challenges associated with desalination. This study offers a novel solution for improving Nb2CTx MXene electrochemical properties in CDI.