Polyoxometalate-coupled MXene nanohybrid: Via poly(ionic liquid) linkers and its electrode for enhanced supercapacitive performance

MXenes are novel 2D transition metal carbides with metallic conductivity and hydrophilic surfaces, which have highly active 2D surfaces and can act as a promising new type of electrode material; however, their low capacity and irreversible self-restacking limit their practicality and development. This paper presents a novel method for preparing an MXene-polyoxometalate (POM) nanohybrid using poly(ionic liquid) (PIL) as the linker. The electrostatic interactions, chemical structure, and morphology of this nanohybrid are systematically characterized and have indicated that the MXene-PIL-POM nanohybrid provides the uniform distribution of POM nanoparticles on the MXene nanosheets and exhibits excellent electrochemical activity and stability due to the use of PIL as the linker and stabilizer. The prepared MXene-PIL-POM nanohybrid, used as an electrode, displayed a definite improvement in electrochemical performance with the specific capacitance of 384.6 F g^-1 at a current density of 1 A g^-1, which is about three-fold higher than that of the MXene electrode. The MXene-PIL-POM electrode also achieved a good rate performance (90.5% retention at 10 A g^-1) and a long cycling life (91.7% maintenance of specific capacitance at a constant current density of 4 A g^-1 after 2000 cycles). The proposed nanohybrid structure capitalizes on the enhancement of the redox reactions of POM through the PIL linkers to facilitate charge transfer and provide efficient ion transfer channels in the nanohybrid.