Effect of growth temperature on the nanostructure and electrochemical properties of in-situ deposited WO3 thin films

Thin films of tungsten trioxide (WO3) have widespread applications such as in photocatalysis, electrochromism, photochromism, etc. Tuning the nanostructure of WO3 thin films has a notable impact on their electro/photocatalytic properties. In this work, WO3 thin films were prepared on FTO glass employing the in-situ hydrothermal method. Amongst other parameters of thin-film growth, the hydrothermal growth temperature is crucial toward WO3 thin film characteristics. The reaction temperature for the preparation of WO3 thin films in this study varied from 120 to 180 degrees C. XRD analysis revealed that WO3 thin films prepared at reaction temperatures of 120 (W120) and 150 degrees C (W150) have a hexagonal structure, whereas thin film prepared at 180 degrees C (W180) has a mixed hexagonal and monoclinic structure. The morphology of thin films changed with reaction temperature, as evidenced by FE-SEM analysis. Cyclic voltammetry analysis indicated that W120 exhibited fast Li+ ions insertion and extraction kinetics as compared to thin films synthesized at other temperatures. Finally, a correlation was made between the better electrochemical performance of W120 with its structure and morphology.