"Toward understanded the electrochemical capacitance mechanism of MXene by intercalation of inorganic ions and organic macromolecular ions" [Appl. Surf. Sci. 578 (2022) 152030]

Interlayer ion modification of MXene is one of the effective ways to improve the pseudocapacitance performance. However, the origin of electrochemical capacitance mechanism still remains elusive due to the effect of different kinds of ion interlayer modification. In this work, interlayer modification of MXene (Ti3C2Cl2) with inorganic ions (NaCl) and organic macromolecular ions (cetyl trimethyl ammonium bromide cation, CTAB) were carried out by ion ultrasonic intercalation and the electrochemical capacitance mechanism was investigated. It was found that MXene- CTAB has higher specific capacitance (258.28F g-1 Vs 225.55F g-1) and better cycle stability (93% retention Vs 85% retention after 3000 cycles) than MXene-NaCl. Such a large difference in electrochemical energy storage performance is mainly due to two points : (1) Organic macromolecular CTAB can effectively expand the layer spacing of MXene, which is conducive to the storage of electrolyte ions. (2) Compared with inorganic ions, organic macromolecular ions not only have redox reaction with interlayer ions of MXene, but also can adsorb counter ions in the electrolyte, thus providing additional pseudocapacitance. This work opens up a new way for the development of high-performance MXene based electrode materials.