TY - GEN A1 - Morales, Carlos A1 - Tschammer, Rudi A1 - Pożarowska, Emilia A1 - Kosto, Julia A1 - Villar‐Garcia, Ignacio J. A1 - Pérez‐Dieste, Virginia A1 - Favaro, Marco A1 - Starr, David E. A1 - Kapuścik, Paulina A1 - Mazur, Michał A1 - Wojcieszak, Damian A1 - Domaradzki, Jarosław A1 - Alvarado, Carlos A1 - Wenger, Christian A1 - Henkel, Karsten A1 - Flege, Jan Ingo T1 - Hydrogen sensing via heterolytic H₂ activation at room temperature by atomic layer deposited ceria T2 - ChemSusChem : chemistry, sustainability, energy, materials N2 - Ultrathin atomic layer deposited ceria films (<20 nm) are capable of H2 heterolytic activation at room temperature, undergoing a significant reduction regardless of the absolute pressure, as measured under in‐situ conditions by near ambient pressure X‐ray photoelectron spectroscopy. ALD‐ceria can gradually reduce as a function of H2 concentration under H2/O2 environments, especially for diluted mixtures below 10 %. At room temperature, this reduction is limited to the surface region, where the hydroxylation of the ceria surface induces a charge transfer towards the ceria matrix, reducing Ce4+ cations to Ce3+. Thus, ALD‐ceria replicates the expected sensing mechanism of metal oxides at low temperatures without using any noble metal decorating the oxide surface to enhance H2 dissociation. The intrinsic defects of the ALD deposit seem to play a crucial role since the post‐annealing process capable of healing these defects leads to decreased film reactivity. The sensing behavior was successfully demonstrated in sensor test structures by resistance changes towards low concentrations of H2 at low operating temperatures without using noble metals. These promising results call for combining ALD‐ceria with more conductive metal oxides, taking advantage of the charge transfer at the interface and thus modifying the depletion layer formed at the heterojunction. KW - Atomic Layer Deposition KW - Ceria KW - Hydrogen Sensing KW - X-Ray photoelectron spectroscopy KW - Raman spectroscopy KW - Resitive sensor Y1 - 2025 U6 - https://doi.org/10.1002/cssc.202402342 SN - 1864-5631 VL - 18 IS - 13 SP - 1 EP - 13 PB - Wiley-VCH CY - Weinheim ER - TY - GEN A1 - Weichbrodt, Wiktoria A1 - Domaradzki, Jaroslaw A1 - Obstarczyk, Agata A1 - Kot, Malgorzata A1 - Flege, Jan Ingo A1 - Mazur, Michal T1 - Influence of thermal modification on the gasochromic properties of WO₃ thin films fabricated by electron beam evaporation T2 - Applied optics N2 - This paper describes the effect of post-deposition annealing on the structural and gasochromic properties of WO3 thin films deposited by electron beam evaporation and additionally decorated with a Pd catalyst layer of varying thickness. The WO3 layers were annealed at 800°C, which led to a phase transition from an amorphous to a monoclinic crystal structure, accompanied by an increase in surface roughness from 1.3 to 66 nm and the formation of a discontinuous island-like morphology with grain sizes up to 3 µm. The structural changes had a significant effect on the optical response of the layers to hydrogen. For the annealed samples, the absolute change in light transmission reached 20.2–20.9% for the 1.5 nm thick Pd catalyst and 7.7–9.2% for the 5 nm thick Pd catalyst at a wavelength of 850 nm. The corresponding optical response was 184–186% for the thin Pd layer and 353–396% for the thick Pd layer, depending on the hydrogen concentration (25–1000 ppm). The response time was reduced from 10 min at 25 ppm to < 4 min at 1000 ppm, while the recovery time to the original state in air remained below 66 s under all conditions. XPS studies confirmed the reduction of W6+ to W5+ under the influence of hydrogen and reversible transition PdO - Pd, which correlates with the observed optical changes. The results show that annealing increases crystallinity and modifies porosity, which, in combination with the Pd catalyst directly affects the kinetics and magnitude of the gasochromic response. Y1 - 2025 U6 - https://doi.org/10.1364/AO.574918 SN - 1559-128X VL - 65 IS - 5 SP - A58 EP - A67 PB - Optica Publishing Group CY - Washington, DC ER -