Dresden 2026 – scientific programme

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MM: Fachverband Metall- und Materialphysik

MM 35: Additive Manufacturing / Transport in Materials III

MM 35.7: Talk

Thursday, March 12, 2026, 17:15–17:30, SCH/A216

Hydrogen Diffusion in ß-MoO₃ Thin Films Governed by Structural Changes — •Tim K. Hecker, Martin Becker, and Peter J. Klar — Institute of Experimental Physics I and Center for Materials Research, Justus Liebig University Giessen, Giessen, Germany

Hydrogen incorporation strongly alters the electronic, optical and structural properties of transition-metal oxides. In MoO₃, hydrogen intercalation forms H_xMoO₃ bronzes that exhibit reversible color changes, lattice distortions and notably higher hydrogen diffusion coefficients. Although these effects are central to electrochromic, catalytic, sensing and energy storage applications, the mechanisms of hydrogen transport remain poorly understood, especially in the metastable ß-phase. To address this, we performed electrochemical hydrogen insertion into ß-MoO₃ thin films covered by a PMMA layer, only allowing incorporation in a small, well-defined uncovered stripe. Hydrogen only enters through this gap and then diffuses laterally beneath the PMMA in a semi-infinite space. Using the electrochromic response of MoO₃ in combination with the Beer-Lambert law, we monitored the hydrogen concentration in-situ. These diffusion profiles were then analyzed with a deep-learning algorithm to extract concentration dependent diffusion coefficients. We identify two distinct increases in the diffusion coefficient as hydrogen concentration rises. Complementary Raman measurements during intercalation and deintercalation link these changes to partial structural transformations, each increasing the hydrogen diffusion coefficient by nearly one order of magnitude.

Keywords: concentation dependent diffusion; hydrogen diffusion; in situ transmission spectroscopy; deep learning; molybdenum trioxide