Dual-defects induced band edge reconstruction of tin dioxide via cobalt and nitrogen Co-Doping for wearable supercapacitor application

Dual-defects induced band edge reconstruction of tin dioxide (SnO2) via metal and non-metal ions co-doping strategy is applied to synthesize cobalt and nitrogen co-doped tin dioxide (Co, N-SnO2) on activated carbon fiber (ACF) for supercapacitor. N-doping contributes to upward shift of valence band edge through the hybridization of N-2p and O-2p and Co-doping contributes to downward shift of conduction band edge through the hybridization of Co-3d and O-2p. The bandgap is highly narrowed from 2.29 eV for SnO2 to 0.68 eV for Co, N-SnO2. The Co, N-SnO2/ACF electrode achieves specific capacitance of 361.2 F g−1 at 1 A g−1, rate capability of 61.1% from 1 to 10 A g−1 and cycling stability of 103.3% for 10,000 cycles. The density functional theory proves that Co-doping mainly promotes the capacity due to its easier deprotonation process in acid electrolyte, whereas N-doping mainly promotes the rate capability due to its narrower bandgap and thus facile electron transport. The wearable bracelet-supercapacitor based on Co, N-SnO2/ACF electrode delivers an energy density of 70.7 Wh Kg−1 under a wide potential window of 2.0 V. This finding provides a feasible route to regulate the band edge of metal oxide electrode for the promising energy storage.