Activated carbon induced oxygen vacancies-engineered nickel ferrite with enhanced conductivity for supercapacitor application

NiFe_(2)O_(4) is a kind of bimetallic oxide possessing excellent theoretical capacity and application prospect in the field of supercapacitors.Whereas,due to the inherent poor conductivity of metal oxides,the performance of NiFe_(2)O_(4) is not ideal in practice.Oxygen vacancies can not only enhance the conductivities of NiFe_(2)O_(4) but also provide better adsorption of OH,which is beneficial to the electrochemical performances.Hence,oxygen vacancies engineered NiFe_(2)O_(4)(NiFe_(2)O_(4)‒δ)is obtained through a two-step method,including a hydrothermal reaction and a further heat treatment in activated carbon bed.Results of electron paramagnetic resonance spectra indicate that more oxygen vacancies exist in the treated NiFe_(2)O_(4)‒δthan the original one.UV-Vis diffuse reflectance spectra prove that the treated NiFe_(2)O_(4)‒δowns better conductivity than the original NiFe_(2)O_(4).As for the electrochemical performances,the treated NiFe_(2)O_(4)‒δperforms a high specific capacitance of 808.02 F∙g^(‒1) at 1 A∙g^(‒1).Moreover,the asymmetric supercapacitor of NiFe_(2)O_(4)‒δ//active carbon displays a high energy density of 17.7 Wh∙kg^(‒1) at the power density of 375 W∙kg^(‒1).This work gives an effective way to improve the conductivity of metal oxides,which is beneficial to the application of metal oxides in supercapacitors.