Tantalum oxide become an important electrode material for supercapacitor due to multiple redox, high capacitance and structural stability, but low electrical conductivity prevents its practical applications. The study reports synthesis of Co and V-doped Ta1.1O1.05 using tryptophan and aspartic acid functionalized and boron doped graphene quantum dot (DWB-GQD). Ta5+, V5+ and Co3+ were combined with DWB-GQD to form water-soluble complex. Followed by sucking into cotton, drying and annealing at 850 °C in N2. The resulting Ta1.1O1.05 nanocrystals show a cube-like nanostructure. The self-doping of low valent Ta, V and Co species induces the production of oxygen vacancies. The presence of oxygen vacancies narrows the bandgap and creates new electron transfer pathways. The graphene surface modification accelerates the electron transfer from Ta1.1O1.05 to graphene and improves the structural stability. The unique structure achieves to a significantly improved conductivity and a wide safe voltage window of 1.9 V. The symmetrical supercapacitor with Co/V-Ta1.1O1.05@DWB-GQD electrodes and 1 M Li2SO4/PVA gel electrolyte exhibits high specific capacitance (560.9 F g-1 at current density of 1 A g-1), high-rate capacitance (365.55 F g-1 at current density of 10 A g-1), cycling stability (99.5% capacitance retention over 10000-cycle), and energy density (140.63 W h kg-1 at power density of 475 W kg-1). The soft supercapacitor also shows a wide application prospect in wearable electronic devices.

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