Excessive nitrogen doping of tin dioxide nanorod array grown on activated carbon fibers substrate for wire-shaped microsupercapacitor

Tin dioxide (SnO2) nanorod array has been vertically grown on activated carbon fibers (ACFs) substrate by seed-assisted hydrothermal synthesis. Well-aligned tin oxynitride (SnOxNy) nanorod array can be accordingly formed by excessive nitrogen doping of SnO2 via nitriding treatment under an ammonia atmosphere. SnOxNy shows the micro-phase seperation of SnNx in SnO2. The lower band gap energy of SnNx is advantageous to accelerate the electrons transfer and enhance the electronic conductivity of SnO2 electrode material. The density functional theory calculation results prove that SnOxNy exhibits higher electronic donation at its interface for electrochemical reaction than SnO2. Hence, the free-standing SnOxNy/ACFs electrode delivers greatly improved electrochemical performance including higher specific capacitance (637.3 F g(-1) at 1 A g(-1)) and cycling stability (99.2% at 5 A g(-1) for 2000 cycles) in 1.0 M H2SO4 electrolyte than SnO2/ACFs (275.5 F g(-1); 85.2%). The asymmetric wire-shaped microsupercapacitor using SnOxNy/ACFs as a positive electrode, TiN wire as a negative electrode and sulfuric acid-polyvinyl alcohol gel as the electrolyte has also achieved high output voltage of 1.6 V, high specific capacitance of 1.2 F cm(-3) at 10 mA cm(-3) and high energy density of 0.43 Wh L-1. So, SnOxNy/ACFs can act as the promissing positive electrode material for effective energy storage application.