To prepare Nb2CTx MXene, 1.0 g of Nb2AlC powder was transferred into 20 mL of HF (aqueous, 49%, Millipore-Sigma) over 60 s and stirred for 48 h at 50 °C. The mixture was washed several times by centrifugation at 3500 rpm (5 min/cycle), the supernatant was decanted, and deionized (DI) water was added until the supernatant reached a pH >6.