Scalable synthesis of Ta1.1O1.05/biomass carbon composite with multiple structure engineering by boron-doped graphene quantum dot for high-energy supercapacitor

Abstract

Low intrinsic conductivity and insufficient electroactive sites hinder wide applications of tantalum oxide in supercapacitors. The study reports scalable synthesis of Ta1.1O1.05/biomass carbon (C) composite with multiple structure engineering by boron-doped graphene quantum dot (B-GQD). B-GQD was orderly coordinated with Ta(V) ion to produce Ta-B-GQD complex, sucked into cotton and dried. Followed by annealing at 900 °C in N2 to obtain B-GQD-Ta1.1O1.05/C. Experimental result and theoretical calculation demonstrate that the introduction of B-GQD results in formation of Ta1.1O1.05 nanorods with low valence, small size, highly exposed high-index crystal faces, oxygen vacancies and PN junction. The structure dramatically improves the intrinsic conductivity, electroactive sites and voltage window range. The B-GQD-Ta1.1O1.05/C electrode exhibits high capacitance of 528.3 F g−1 at 0.5 A/g, which is more than that of Ta1.1O1.05 electrode (130.9 F g−1). The flexible symmetrical supercapacitor provides ultrahigh capacitance of 374.1 F g−1 at 1 A/g, high-rate capacity of 207.8 F g−1 at 50 A/g, capacity retention of 98.7 % after 10,000 cycles at 10 A/g and energy density of 113.9 W h Kg−1 at 521.2 W kg−1. The supercapacitor has been successfully applied in the self-powered attitude sensor driven via friction nanogenerator to monitor human walking posture.