Electrochemical Behavior Of Vanadium Carbide In Neutral Aqueous Electrolytes

The V2C compound, belonging to the group of two-dimensional transition metal carbonitrides, or MXenes, has demonstrated a promising electrochemical performance in capacitor applications in acidic electrolytes; however, there is evidence to suggest that V2C is unstable in an acidic environment. On the other hand, the performance of V2C in neutral aqueous electrolytes is still moderate, and has not yet been systematically studied. The charge storage mechanism in a V2C electrode, employed in neutral aqueous electrolytes, is investigated via cyclic voltammetry testing and in situ x-ray diffraction (XRD). Good specific capacitances are achieved, specifically 208 F/g in 0.5 M Li2SO4, 225 F/g in 1 M MgSO4, 120 F/g in 1M Na2SO4, and 104 F/g in 0.5 M K2SO4. Using in situ XRD, we observe that, during the charge and discharge process, the c-lattice parameter shrinks or expands by up to 0.25 angstrom in MgSO4, and 0.29 angstrom in Li2SO4 which demonstrates the intercalation/de-intercalation of cations into the d-V2C layer.