Print Email Facebook Twitter Neutron Diffraction Study of a Sintered Iron Electrode In Operando Title Neutron Diffraction Study of a Sintered Iron Electrode In Operando Author Weninger, B. (TU Delft ChemE/Materials for Energy Conversion and Storage) Thijs, M.A. (TU Delft RST/Neutron and Positron Methods in Materials) Nijman, Jeroen A.C. (Independent researcher) van Eijck, L. (TU Delft RST/Neutron and Positron Methods in Materials) Mulder, F.M. (TU Delft ChemE/Materials for Energy Conversion and Storage) Date 2021 Abstract Iron is a promising, earth-abundant material for future energy applications. In this study, we use a neutron diffractometer to investigate the properties of an iron electrode in an alkaline environment. As neutrons penetrate deeply into materials, neutron scattering gives us a unique insight into what is happening inside the electrode. We made our measurements while the electrode was charging or discharging. Our key questions are: Which phases occur for the first and second discharge plateaus? And why are iron electrodes less responsive at higher discharge rates? We conclude that metallic iron and iron hydroxide form the redox pair for the first discharge plateau. For the second discharge plateau, we found a phase similar to feroxyhyte but with symmetrical and equally spaced arrangement of hydrogen atoms. The data suggest that no other iron oxide or iron (oxy)hydroxide formed. Remarkable findings include the following: (1) substantial amounts of iron hydroxide are always present inside the electrode. (2) Passivation is mostly caused by iron hydroxide that is unable to recharge. (3) Iron fractions change as expected, while iron hydroxide fractions are delayed, resulting in substantial amounts ofamorphous, undetectable iron phases. About 40% of the participating iron of the first plateau and about 55% of the participating iron for the second plateau are undetectable. (4) Massive and unexpected precipitation of iron hydroxide occurs in the transition from discharging to charging. (2), (3), and (4) together cause accumulation of iron hydroxide inside the electrode. To reference this document use: http://resolver.tudelft.nl/uuid:74d45c2f-1532-4455-9c8b-ea6358706910 DOI https://doi.org/10.1021/acs.jpcc.1c03263 ISSN 1932-7455 Source The Journal of Physical Chemistry C, 125 (30), 16391-16402 Part of collection Institutional Repository Document type journal article Rights © 2021 B. Weninger, M.A. Thijs, Jeroen A.C. Nijman, L. van Eijck, F.M. Mulder Files PDF acs.jpcc.1c03263.pdf 5.44 MB Close viewer /islandora/object/uuid:74d45c2f-1532-4455-9c8b-ea6358706910/datastream/OBJ/view