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MM: Fachverband Metall- und Materialphysik

MM 27: Hydrogen in Materials

MM 27.4: Vortrag

Mittwoch, 29. März 2023, 11:00–11:15, SCH A 215

Hydrogen interstitials in iron oxides using ab-initio calculations — •Ahmed Abdelkawy, Mira Todorova, and Jörg Neugebauer — Max-Planck-Institut für Eisenforschung, Max-Planck-Str.1, 40470 Düsseldorf

The steel making industry is responsible for more than 6% of CO2 emissions. These emissions come from the dependency on carbon and carbon monoxide as reducing agents. Hydrogen, on the other hand, can reduce iron oxides with water released instead. The reduction route from Magnetite to Hematite, then Wüstite, and finally to pure iron requires hydrogen to diffuse into and react with the different solid structures as well as with the multiple solid-solid interfaces. To optimize the reduction process, the mechanistic details of this process requires understanding to the role of hydrogen interstitials in the bulk iron oxides. We therefore computed the diffusion paths of hydrogen through the different iron oxide phases employing density functional theory (DFT) calculations for all three iron oxides - Magnetite, Hematite, and Wüstite. Analyzing the electronic structure of the studied oxides, we examine the reliability of the used exchange correlation functionals and how the electronic structure is affected by the inclusion of hydrogen, both as a neutral and a charged point defect. Finally, we utilize symmetrized plane waves to map the full 3D potential energy surfaces (PESs) for hydrogen interstitials within these iron oxides using a modest number of DFT calculations. Based on these calculations we identify the hydrogen preferential interstitial sites, diffusion barriers, and diffusion paths.