Titanium–Tantalum Double-Ordered MXene Nanosheets as Supercapacitor Electrodes

Double-ordered titanium tantalum carbide MXene nanosheets (TixTa4–xC3) were synthesized by selectively etching the intermediate aluminum element from the parental titanium tantalum aluminum carbide MAX phase. The phase, structural, and vibrational studies confirmed the successful synthesis of MXene and revealed that the MXene layers were in the hexagonal crystal system. Morphological studies indicated that the MXene layers have a 2D layered morphology, and HF etching effectively removed the aluminum intermediate layers. Thermogravimetric analysis revealed that the synthesized MXenes were more thermally stable in both air and N2 atmospheres. X-ray photoelectron spectroscopy analysis confirmed the elemental composition of the synthesized MXene samples. The thermal and electrical properties of the MXene nanosheets were studied, and the results indicated that the MXene nanosheets are highly conductive and exhibit a decrease in thermal diffusivity with temperature. The electrochemical properties of the MXene nanosheets were investigated using 1 M H2SO4, and cyclic voltammetry results demonstrated that the synthesized double-ordered MXene nanosheets could operate within the range of −2 to +2 V. The specific capacitance of the two-electrode symmetric device was estimated to be around 200 F/g, with a capacitance retention of 80% over 30 days.