Effect of large-sized hydrophilic polypyrrole on electrochemical properties of MXene films

Abstract

Two-dimensional (2D) Ti3C2Tx MXene has triggered intensive research interest in supercapacitors applications due to its tunable surface chemistry and high specific capacitance. However, as with other 2D materials, the self-stacking phenomenon of flakes seriously hinders the transport dynamics of ions in the vertical direction since van der Waals attractions, which is a major challenge. Here, the work reports the fabrication of Ti3C2Tx/polypyrrole composite films using large-sized hydrophilic polypyrrole (PPy) as filler by mixing with Ti3C2Tx solution, in which PPy is freely distributed in the Ti3C2Tx substrate to improve the exposed surface area instead of expanding the interlayer spacing of nanosheets. Further, the electrochemical energy storage mechanism analysis indicates that the surface-controlled capacitance of Ti3C2Tx/polypyrrole film is remarkablely higher than that of Ti3C2Tx, and the surface-controlled capacitance is independent of the scan rate (<20 mV s−1), depending on the inherent microstructure characteristics of the electrode materials. The free-standing film electrode with gravimetric capacitance of 369.6 F g−1 is demonstrated. It provides a new insight into the design and fabrication of novel MXene composite film electrodes, and strengthens the basic understanding of the energy storage mechanism that is often overlooked.