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

Abstract 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)‐Ti₃C₂T_x membrane electrode with excellent capacitance and high flexibility is prepared by using Ti₃C₂T_x 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)‐Ti₃C₂T_x flexibility supercapacitor is assembled by using a BQDs(10)‐Ti₃C₂T_x 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)‐Ti₃C₂T_x membrane electrode and BQDs(10)‐Ti₃C₂T_x flexible supercapacitor display broad application prospects in field of portable/wearable electronic devices.