Controlled N-doped Fe3O4@C arrays: Achieving enhanced donor density and capacity for hybrid supercapacitors

Carbon modified nitrogen-doped Fe 3 O 4 (N–Fe 3 O 4 @C) nanorod array directly grown on carbon cloth was fabricated. Nitrogen-doping and carbon shell effectively decrease the potential barrier of ion migration of the oxides and improve the electrochemical performance. An enhanced donor density of N-Fe 2 O 3 (7.6 × 10 15  cm −3 ) is achieved with optimized doping temperature. Following with carbon coated, the optimized N–Fe 3 O 4 @C electrode showed ultrahigh capacitance over an extended potential window and remarkable cycling performance. A new quasi-solid-state supercapacitor with N–Fe 3 O 4 @C and NiCoP@Ni(OH) 2 achieved high voltage to 2.0 V and high energy density (72.37 Wh kg −1 , 2.36 mWh cm −3 ).