A New Facile Synthesis of Tungsten Oxide from Tungsten Disulfide: Structure Dependent Supercapacitor and Negative...

Tungsten oxide (WO₃ ) is an emerging 2D nanomaterial possessing unique physicochemical properties extending a wide spectrum of novel applications which are limited due to lack of efficient synthesis of high-quality WO₃ . Here, a facile new synthetic method of forming WO₃ from tungsten sulfide, WS₂ is reported. Spectroscopic, microscopic, and X-ray studies indicate formation of flower like aggregated nanosized WO₃ plates of highly crystalline cubic phase via intermediate orthorhombic tungstite, WO_3. H₂ O phase. The charge storage ability of WO₃ is extremely high (508 F g^-1 at current density of 1 A g^-1 ) at negative potential range compared to tungstite (194 F g^-1 at 1 A g^-1 ). Moreover, high (97%) capacity retention after 1000 cycles and capacitive charge storage nature of WO₃ electrode suggest its supremacy as a negative electrode of supercapacitors. The asymmetric supercapacitor, based on the WO₃ as a negative electrode and mildly reduced graphene oxide as a positive electrode, manifests high energy density of 218.3 mWhm^-2 at power density 1750 mWm^-2 , and exceptionally high power density, 17 500 mW m^-2 , with energy density of 121.5 mWh m^-2 . Furthermore, the negative differential resistance (NDR) property of both WO₃ and WO₃ .H₂ O are reported for the first time and NDR is explained with density of state approach.