Polycrystalline WS₂ thin films were electrodeposited on ITO coated glass substrate using sodium tungastate (Na₂WO₄·2H₂O) and thioacetamide (CH₃C(S)NH₂) as metal and sulfur sources. The deposited WS₂ thin films were air annealed at different temperatures and the changes in phase, morphology, optical property were studied. It has been observed that annealing WS₂ films at 450 °C generates a mix phase of WS₂/WO₃ and annealing the same film at 650 °C results 100% conversion of WS₂ to WO₃. These phases are absolutely different from each other. Their applicability has also been tested by photodegradation of phenol. It has been found that among the different phases, mix phase i.e WS₂/WO₃ shows better catalytic activity. Presence of two semiconductors with different energy levels in conduction and valence bands enhance displacement of electrons and holes from one semiconductor to another. The better charge separation in the coupled semiconductor is the key factor for interfacial charge transfer to the adsorbed substrate.