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

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, WO3 center dot H2O 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 center dot H2O are reported for the first time and NDR is explained with density of state approach.