Controlled synthesis of WO3 nanostructures: optical, structural and electrochemical properties

We report herein the synthesis of WO3 nanostructures and their various physicochemical and electrochemical properties. X-ray diffraction and Raman investigations indicate that the as-synthesized materials crystallize into orthorhombic WO3 (o-WO3) and monoclinic WO3 (m-WO3) phase depending upon the synthesis procedure and annealing temperature. Further, a phase transition was observed from o-WO3 to m-WO3 after annealing the materials at 500 oC. The results indicate that the monoclinic phase of WO3 is more stable at a higher temperature compared to the orthorhombic WO3 phase. More interestingly, nearly 0.4 eV band gap tuning was observed by changing the synthesis parameters and/ precursors. The formation of nanostructure was confirmed using FESEM techniques. The cyclic voltammetry (CV) measurements indicate the pseudocapacitive nature of the as-synthesized materials.