Ni0.85Co0.15WO4 nanosheet electrodes for supercapacitors with excellent electrical conductivity and capacitive performance

Monoclinic wolframite Ni1-xCoxWO4 (x = 0 and 0.15) nanosheets are synthesized successfully through chemical co-precipitation. The specific surface area increases appreciably with reduced pore radius when Co2+ ions are incorporated into the NiWO4 lattice. In comparison with NiWO4, the band gap of Ni0.85Co0.15WO4 reduces with the electrical conductivity increased threefold. The electrochemical properties and the device performance of supercapacitors with Ni1-xCoxWO4 as electrodes are characterized via the potentiostatic and galvanostatic cycle measurements, and electrochemical impedance spectroscopy (EIS). The Ni0.85Co0.15WO4 electrode exhibits an obvious increase in specific capacitance, six-fold higher than that of NiWO4 electrode at a current density of 0.5 A g−1. Ni0.85Co0.15WO4 electrode also shows excellent rate performance with ~78% capacitive retention while the current density is enhanced fivefold. The possible mechanism for the improved electrical conductivity and capacitive performance due to the incorporation of Co2+ to NiWO4 lattice has been discussed.