MXene-based binary composite material for flexible energy storage devices

This research work uses in-situ oxidation of HF-etched Ti₃C₂ MXene with laser-ablated black TiO₂ (B-TiO₂) nanospheres to produce a novel B-TiO₂/Ti₃C₂ MXene. This composite formation effectively reduces the tendency for restacking of Ti₃C₂ by evenly dispersing TiO₂ nanoparticles with enhanced electrochemical properties. Electrochemical analyses in 1 M KOH show impressive capacitive behavior, with the composite delivering 902 F g⁻¹ at 1 A g⁻¹, giving much higher capacitance than B-TiO₂ (380 F g⁻¹) and Ti₃C₂ (369 F g⁻¹) components. Moreover, a two-electrode symmetric flexible device constructed using the composite has an energy density of 33 Wh kg⁻¹ and a power density of 300 W kg⁻¹. Calculations within the complementary density functional theory with the GGA-PBE functional indicate that pristine and heterostructure MXene are metallic in nature, and Ti-3d orbitals prevail in and around the Fermi level. Hydroxyl functionalization indirectly decreases the Fermi-level DOS and alters the charge distribution, thereby improving charge separation and favoring electrochemical activity.