Nonhazardous in-situ exfoliation approach for Ta-Nb2CTx MXenes as sustainable supercapacitor electrode applications

Utilization of hydrofluoric acid (HF) for exfoliation of MXenes by etching is common but it is extremely hazardous due to its toxic and corrosive nature. Here, direct use of HF is avoided and an in-situ exfoliation approach has been developed which successfully exfoliates the MAX phase of Nb 2 AlC into multilayered Nb 2 CT x and Ta-doped Nb 2 CT x MXenes. Being MXene family, the Nb 2 CT x owing a set of characteristics with tunability by ions doping based material defects making it a promising contestant for supercapacitor electrodes applications. It has been observed that 6 wt % Ta-Nb 2 CT x exhibited enhanced specific capacity of 454.4 Cg -1 and highly sustainable cyclic stability of 88 % retention after 12000 CV cycles, attributed to additional active sites by Ta doping, intercalation, increased exfoliation and optimal surface terminations. The power law displays a pseudocapacitive nature (b = 0.61) and the Dunn method shows increasing trend of capacitive contribution with scan rate. The fabricated asymmetric 6 wt% Ta-Nb 2 CT x //AC (Activated Carbon) based supercapacitor showed energy density (ED) of 47.5 Whkg −1 and a power density (PD) of 500 Wkg -1 . These findings open up a perspective way of environment friendly and nonhazardous exfoliation, incorporation of metallic ions into Nb 2 CT x MXene, and their application in energy storage devices. • Nonhazardous in-situ exfoliation way for enhanced interlayer spacing in Ta-Nb 2 CT x . • Owing small R ct = 2.4 Ω, 6 % Ta–Nb 2 CT x revealed tremendous C s = 826.2 Fg -1 at 5 mVs −1 . • Incredible 88 % retention for 1200 CV cycles revealing its excellent sustainability. • Power law (b = 0.61) proved the suitability of 6 % Ta–Nb 2 CT x for supercapacitors. • The Ta-Nb 2 CT x //AC based supercapacitor exhibited ED = 47.5Whkg −1 and PD = 500 Wkg −1