Article ID: ISIJINT-2025-340
A hydrogen visualization technique based on Prussian blue (PB), a fully reversible hydrogenochromic material, was developed for detecting hydrogen distribution in a pure Fe sheet. A PB layer was electrochemically formed on a Pd-coated Fe sheet. The Pd intermediate layer acted as a catalyst for the reduction of PB by hydrogen atoms diffusing through the Fe sheet. During hydrogen charging, the PB layer exhibited a color change from deep blue to light blue, effectively visualizing the hydrogen distribution in the Fe sheet. The color gradually recovered in air via oxidation by O2 in air, and the color restoration was significantly accelerated by heating at 70°C. The PB layer exhibited excellent reversibility of color change over multiple hydrogen charging and heating cycles. This study highlights the potential of PB as a reusable sensor for the in situ monitoring of hydrogen distribution in metals.
