Multilayer Ti3C2Tx MXene electrode decorated with polypyridine for efficient symmetric supercapacitors†

MXenes are unique two-dimensional nanomaterials and have the advantages of large interlayer spacings and conductive layered structures, providing great potential for enhancing the electrochemical properties of supercapacitors. However, van der Waals forces may cause the re-stacking of sheets in MXenes, which further reduces the specific surface area and restricts the transport of ions/electrolytes within the electrode, thus resulting in an unfavorable electrochemical performance. In this paper, a heteropoly acid was used as a dopant to oxidize pyridine for the preparation of conductive polypyridine (PPY). By doping MXene with PPY, the resulting MXene/PPY composite exhibits significant advantages for averting the self-stacking of the MXene nanosheets induced by van der Waals forces, promoting electron migration, and the improving specific capacitance. Under the synergistic effect of the highly conductive MXene and electrochemically active PPY, a symmetric supercapacitor fabricated from MXene/PPY attains an energy density of 8.77 W h kg⁻¹ at a power density of 750 W kg⁻¹. More importantly, the supercapacitor maintains a capacity retention rate of 75% after 4000 cycles of continuous charging and discharging. The favorable energy density and power density, along with its excellent electrochemical stability, suggest that the fabricated MXene/PPY composite has considerable potential for practical applications.