Impact of annealing on the electrodeposited WS2 thin films: Enhanced photodegradation of coupled semiconductor

Polycrystalline WS2 thin films were electrodeposited on ITO coated glass substrate using sodium tungastate (Na2WO4 center dot 2H(2)O) 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 degrees C generates a mix phase of WS2/WO3 and annealing the same film at 650 degrees 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. (C) 2014 Elsevier B.V. All rights reserved.