Abstract:
Transition metals oxides and their composites with transition metal dichalcogenides
(TMDs) and carbonaceous materials have proved good electrochemical properties for
supercapacitor application. In this study, we synthesized WS2 nanosheets via liquid phase
exfoliation, ZnCo2O4, binary composites of ZnCo2O4/WS2 and ZnCo2O4/FCNTs; and a
ternary composite of ZnCo2O4/WS2/FCNTs hydrothermally. ZnCo2O4/WS2/FCNTs
showed a higher specific capacitance of 1421.93F/g at 5mV/s. The capacitance shown by
ZnCo2O4/FCNTs, ZnCo2O4/WS2, ZnCo2O4, FCNTs and WS2 at 5mV/s are 1308.45,
1028.59, 788.63, 646.29 and 227.53F/g respectively. The redox current increases with the
increasing scan rates. The ternary composite showed the highest integral area and redox
peak current values which indicates the availability of more electroactive sites than the
binary composites and the individual constituents. The shape of the CV curve suggested a
pseudocapacitive nature of the ternary composite. Galvanostatic charge discharge (GCD)
was done at current densities of 0.5A/g, 1A/g, 2A/g, and 5A/g. The capacitances shown by
ZnCo2O4/WS2/FCNTs, ZnCo2O4/FCNTs, ZnCo2O4/WS2, ZnCo2O4, FCNTs and WS2 at a
current density of 0.5A/g are 1571, 1210, 1125, 756, 525, and 241 F/g respectively. The
electrochemical results suggested the ternary electrode ZnCo2O4/WS2/FCNTs as a better
electrode material for supercapacitor applications. The better performance of the ternary
composite can be attributed to the synergistic effect of WS2, FCNTs and ZnCo2O4. The
integration of functionalized CNTs with ZnCo₂O₄ and WS₂ creates a conductive network
that facilitates efficient charge transport, reducing the internal resistance of the electrode.
The combination of ZnCo₂O₄'s pseudocapacitance with the double-layer capacitance
provided by CNTs and WS₂ results in a higher overall capacitance. WS₂ also contributes
additional pseudocapacitance due to its surface redox reactions. CNTs and WS2 also give
mechanical stability preventing the degradation of ZnCo2O4. It is also due to the multiple
oxidation states of the transition metals W, Co, and Zn.
