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

Tungsten oxide (WO ) 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 WO . Here, a facile new synthetic method of forming WO from tungsten sulfide, WS is reported. Spectroscopic, microscopic, and X-ray studies indicate formation of flower like aggregated nanosized WO plates of highly crystalline cubic phase via intermediate orthorhombic tungstite, WO H O phase. The charge storage ability of WO is extremely high (508 F g at current density of 1 A g ) at negative potential range compared to tungstite (194 F g at 1 A g ). Moreover, high (97%) capacity retention after 1000 cycles and capacitive charge storage nature of WO electrode suggest its supremacy as a negative electrode of supercapacitors. The asymmetric supercapacitor, based on the WO as a negative electrode and mildly reduced graphene oxide as a positive electrode, manifests high energy density of 218.3 mWhm at power density 1750 mWm , and exceptionally high power density, 17 500 mW m , with energy density of 121.5 mWh m . Furthermore, the negative differential resistance (NDR) property of both WO and WO .H O are reported for the first time and NDR is explained with density of state approach.