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

• Excessive nitrogen doping of SnO 2 forms SnO x N y with micro-phase separation of SnN x. • SnN x contributes to high electron transfer and electronic conductivity of SnO x N y. • SnO x N y has high capacity of 637.3 F g−1 at 1 A g−1 & cyclability of 99.2% at 5 A g−1. • Density functional theory calculation proves high capacitive performance of SnO x N y. • Wire-shaped microsupercapacitor is formed using SnO x N y /ACFs and TiN wire electrodes. Tin dioxide (SnO 2) nanorod array has been vertically grown on activated carbon fibers (ACFs) substrate by seed-assisted hydrothermal synthesis. Well-aligned tin oxynitride (SnO x N y) nanorod array can be accordingly formed by excessive nitrogen doping of SnO 2 via nitriding treatment under an ammonia atmosphere. SnO x N y shows the micro-phase seperation of SnN x in SnO 2. The lower band gap energy of SnN x is advantageous to accelerate the electrons transfer and enhance the electronic conductivity of SnO 2 electrode material. The density functional theory calculation results prove that SnO x N y exhibits higher electronic donation at its interface for electrochemical reaction than SnO 2. Hence, the free-standing SnO x N y /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 H 2 SO 4 electrolyte than SnO 2 /ACFs (275.5 F g−1; 85.2%). The asymmetric wire-shaped microsupercapacitor using SnO x N y /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 W h L−1. So, SnO x N y /ACFs can act as the promissing positive electrode material for effective energy storage application. [ABSTRACT FROM AUTHOR]