Solution-Processing of Topochemically Converted Layered WO3 for Multifunctional Applications.

Abstract

Solution processing of nanomaterials is a promising technique to utilize in various applications owing to its simplicity and scalability. However, the studies on liquid phase exfoliation (LPE) of tungsten oxide (WO3) are limited, unlike others due to lack of commercial availability of bulk WO3 with layered structures. Herein, we report a one-step topochemical synthesis approach to obtain bulk layered WO3 from commercially available layered tungsten disulfide (WS2) by optimizing various parameters like reaction time and temperature. Detailed microscopic and spectroscopic techniques have confirmed the conversion process. Further, LPE has been carried out on topochemically converted bulk layered WO3 in twenty-two different solvents, and among studied solvents isopropyl alcohol-water (1:1) co-solvent system appears to be the best. This indicates that the possible values of surface tension and Hansen solubility parameters for bulk WO3 could be close to that of co-solvent system. The obtained WO3 dispersions in a low boiling point solvent enable to fabricate thin films with varying thickness using spray deposition method. The obtained thin films are used as active materials in supercapacitors without any conductive additives/binders and exhibited an areal capacitance of 31.7 mF cm-2 at 5 mV s-1. The photoelectrochemical measurements reveal that these thin films can also be used as photoanodes for photoelectrochemical water oxidation.