A MXene-BiFeO 3 -ZnO nanocomposite photocatalyst served as a high-performance supercapacitor electrode.

MXenes have attracted considerable attention in the field of energy storage and conversion due to their high surface area, excellent electrical conductivity, and ability to intercalate various ions. However, simultaneously achieving high capacitance, rate capability, cycling stability, and mechanical flexibility is a significant challenge for designing MXene-based supercapacitors. In this article, we explored MXene-BiFeO 3 -ZnO nanocomposites for both photocatalytic and electric double-layer supercapacitor applications. While the BiFeO 3 -ZnO nanohybrid heterostructure improves the charge separation properties in nanocomposite photocatalysts, it was applied as an interlayer spacer between the MXene layers to prevent the stacking effect of electrodes in the supercapacitor. Furthermore, the optimization of MXene content in the nanocomposite was established by photocatalytic studies on methylene blue dye, which revealed a maximum of 98.72% degradation under direct sunlight with superior stability. The electrochemical studies on the best composition material reveal a maximum areal capacitance ( C cv ) of 142.8 mF cm -2 , an energy density ( E ) of 1.65 μW h cm -2 , and a capacitive retention of 99.98% after 8000 cycles at 7 μA cm -2 . Additionally, the flexible solid-state supercapacitor fabricated with the same material demonstrates an areal capacitance of 47.6 mF cm -2 and a capacitive retention of 66% after 8000 cycles at 7 μA cm -2 , with potential for high-performance flexible supercapacitors.