K+ Intercalation of NH4HF2‐Exfoliated Ti3C2 MXene as Binder‐Free Electrodes with High Electrochemical Capacitance. Issue 8 (8th March 2020) - Li, Jingbo
Abstract : As a 2D material, Ti3 C2 (MXene) has been recently used as electrodes for electrochemical capacitors. Herein, a two‐step procedure is used to obtain a highly opened layer structure for Ti3 C2, which differs from the methods used in the literature for synthesizing exfoliated MXene. First, the mild NH4 HF2 etching agent is used to prepare the regular Ti3 C2 MXene. Second, KOH is added into the obtained solution for K + to intercalate the MXene. The K + intercalation is found to greatly increase the (002) crystal planar spacing of the Ti3 C2 from 10.8 to 12.4 Å. More importantly, this K + ‐intercalated MXene exhibits a highly opened layer structure, whereas the regular MXene only has a partially opened layer structure. Consequently, the former is expected to allow much more active sites exposed to liquid electrolyte, and also facilitates remarkably higher ion and electron transport efficiency. To investigate their electrochemical capacitance properties, the regular and K + ‐intercalated Ti3 C2 MXenes are used to fabricate binder‐free electrodes on nickel foams by an electrophoretic deposition method. The K + ‐intercalated MXene‐based electrode is found to have twice higher specific capacitance than the regular MXene. Furthermore, the K + ‐intercalated Ti3 C2 MXene‐based electrode exhibits an excellent cyclic stability. Abstract : A mild two‐step procedure is used to obtain K + intercalation of NH4 HF2 ‐exfoliated Ti3 C2 MXene. The highly opened layer structure K‐MXene is successfully used to fabricate binder‐free electrodes on nickel foams (NF) via electrophoretic deposition and the K‐MXene‐based NF electrode displays a high specific capacitance of 690.9 F g −1 and excellent cyclic stability.