Boron Quantum Dots Pillared Ti₃C₂T_x Membrane Electrode with High Rate Performance for Supercapacitor

A sonication-assisted liquid-phase preparation technique is developed to prepare boron quantum dots (BQDs) with a lateral size of 3 nm in a solution of NMP and NBA; it shows a direct bandgap semiconductor with a bandgap of 3 eV and a specific capacitance of 41 F g(-1). A BQDs(10)-Ti3C2Tx membrane electrode with excellent capacitance and high flexibility is prepared by using Ti3C2Tx nanosheets (NSs) as assembled units and BQDs as pillar; it gives a specific capacitance of 524 F g(-1) at 1 A g(-1) in 6 m H2SO4 electrolyte, a high capacity retention of 75%, and a minimum relaxation time of 0.51 s. An all-solid-state BQDs(10)-Ti3C2Tx flexibility supercapacitor is assembled by using a BQDs(10)-Ti3C2Tx membrane as electrodes and PVA/H2SO4 hydrogel as electrolyte; it not only shows an area specific capacitance of 552 mF cm(-2) at 1.25 mA cm(-2), a retention rate of 75%, a capacity retention of 93% after 5000 cycles, and an energy density of 40.4 Wh cm(-3) at a volume power density of 416 W cm(-3), but also provides superior flexibility and can be bent to different degrees, showing that the assembled BQDs(10)-Ti3C2Tx membrane electrode and BQDs(10)-Ti3C2Tx flexible supercapacitor display broad application prospects in field of portable/wearable electronic devices.