A comprehensive review of the MXene-PANI nanohybrids: Preparation, characterization, and electrochemical performances for supercapacitor applications

The novel promising materials of the transition metal carbonitrides, especially MXenes, have been attracting great attention, due to the extraordinary electrochemical and optoelectronic properties of their inorganic 2D layers. However, the potential properties of single-layered MXene nanoflakes, which are crucial, remain unexplored. Restacking of exfoliated MXene nanoflakes, driven by the strong van der Waals interactions, diminishes the surface area, leading to the reduction of ion transport, which results in low charge storage capacity below the theoretical value of 615 C·g or 1200 F·g. In addition, the MXene surface with the most electronegative −F functional groups hinders the ionic transport of electrolytes. The synergistic combination of intrinsically conducting polymers, such as PANI, and the two-dimensional transition metal carbides, MXenes, which can store higher energy, offers better volumetric and areal capacitance resulting in superior pseudocapacitance. Due to the high energy density, exfoliation of polyaniline restricts the restacking of MXene layers, thereby improving the electrochemical performance of the energy storage electrode materials. This review addresses the preparation, and characterization of the MXene-PANI nanohybrids, and their electrochemical behavior as energy storage materials for supercapacitor applications.