Detection of hydrogen distribution in pure iron using WO₃ thin film

The usefulness of a new approach to detecting the distribution of hydrogen absorbed into pure iron utilizing a WO₃ thin film was demonstrated in this study. A WO₃ film with an electrochromic property was formed on the hydrogen detection side of iron sheet by reactive magnetron sputtering. After hydrogen was absorbed into the iron sheet by cathodic polarization on the hydrogen absorption side, the color of the WO₃ film corresponding to the electrode area changed from light blue to dark blue. The WO₃ film was found to reflect the distribution of hydrogen absorbed into the pure iron sheet. No color change occurred on the hydrogen detection side unless a Pd film was inserted between the WO₃ film and the iron specimen. The reflectance of the WO₃ film in the visible region was reduced by hydrogen charging, with a marked reduction in the RGB color values after the start of hydrogen charging. The results of an XPS analysis suggested that the phase transition from WO₃ to H_xWO₃ resulted in the color change of the WO₃ film during hydrogen charging. Because of the simplicity of this approach to detecting hydrogen compared to other hydrogen detection methods, it is expected to have various applications.