Investigation of charge recombination lifetime in y-WO₃ films modified with Ag and Pt nanoparticles and its influence on photocurrent density

Full text: Nowadays, water and energy issues have attracted sustainable interest from researches groups due to large population growth of urban centers. Photoelectrochemical water splitting based on semiconductors supported onto the conductor substrate is regarded as a potential strategy to solve the energy and environment problems. Several semiconductor oxides have used as photoelectrocatalyst for energy conversion. This work, we reported the growth of pure gamma-tungsten oxide (y-WO₃) films on conducting substrate (fluorine doped tin oxide, FTO-glass) and heat-treated at 500 °C for 2 h, which were modified with silver (Ag) and platinum (Pt) metallic nanoparticles. These y-WO₃ thin film were prepared using tungsten citrate solution by drop-coating method and its surface was modified with Ag and Pt nanoparticles by photoreduction method. The studies of structure, morphology and photoelectrochemical properties were investigated in details. X-ray diffraction (XRD) analysis indicates that all thin films have a monoclinic structure. Field emission gun - scanning electron microscopic (FEGSEM) analysis reveals that large and fine grains for pure y-WO₃ film and modified WO₃ film with an average grain size of ~ 48 nm and thickness about at ~ 986 nm. XRD patterns, FEG-SEM images and photoelectrochemical results confirm the incorporation of Ag or Pt element on the films surface. Finally, the enhancement photoelectrochemical performance was observed for modified y-WO₃ films about at 2.5 times, which was attributed to superior electron-hole charge recombination lifetime under polychromatic irradiation. It was observed that even under bias condition an exponential reduction in photocurrent intensity is associated to charge recombination instead of mass transport conditions like diffusion process. (author)