Defect-induced recombination mechanism and electrochemical properties of green synthesised Ti2NTxand V2NTx MXene

Ti 2 NT x and V 2 NT x MXene were synthesised by green routes using NaF and HCl from the Ti 2 AlN and V 2 AlN MAX phases, respectively. SEM and HRTEM results confirmed thin transparent MXene sheets with a larger lateral sheet dimension of 0.7–2.4 µm for Ti 2 NT x MXene. EDX revealed the residual of Al remains 16.59 and 7 wt% after exfoliation from their respective MAX phases. The highest intense XRD peak shifted to a lower 2θ value, indicating increased d -spacing to 2.1 and 2.16 Å in Ti 2 NT x and V 2 NT x MXenes, respectively. Tauc optical band gaps were estimated to be 4.74 and 4.23 eV for Ti 2 NT x and V 2 NT x MXene, respectively. Due to uniform functionalization, Ti 2 NT x MXene showed narrower stretching vibrations for –OH, -F, and –O surface terminations. The excitation-dependent defect state distribution and electrochemical properties of Ti 2 NT x and V 2 NT x MXenes for electrode material were investigated. The surface and bulk states of Ti 2 NT x and V 2 NT x MXene were investigated by photoluminescence at 230–290 nm and 290–390 nm excitation wavelength, respectively. The highest specific capacitance of 15.47 and 15.85 F/g at 0.25 V/s were from Ti 2 NT x and V 2 NT x MXene in 1 M H 2 SO 4 within a range of −1.0–1.0 V wide potential window. The charge stored in the Ti 2 NT x multilayer was higher, i.e. 1031.25 C/cm 2 , than V 2 NT x MXene due to more layer spacing. Lower R e and R CT were observed, i.e. 6 and 445.4 ohms for the V 2 NT x electrode, suggesting the high conductivity and charge transfer capability even in the acidic electrolyte.