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 °C. XRD analysis revealed that WO₃ thin films prepared at reaction temperatures of 120 (W120) and 150 °C (W150) have a hexagonal structure, whereas thin film prepared at 180 °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.