DOE OSTI · 2589233
Molecular H 2 as the Reducing Agent in Low-Temperature Oxide Reduction Using Calcium Hydride
Abstract
Low-temperature synthesis is crucial for advancing sustainable manufacturing and accessing novel metastable phases. Metal hydrides have shown great potential in facilitating the reduction of oxides at low temperatures, yet the underlying mechanism—whether driven by H - , H 2 , or atomic H—remains unclear. Here, in this study, we employ in situ electrical transport measurements and first- principles calculations to investigate the CaH 2 -driven reduction kinetics in epitaxial α-Fe 2 O 3 thin films. Intriguingly, samples in direct contact with or separated from CaH 2 powders exhibit similar apparent activation energies for H 2 reduction, although direct contact significantly increases the reduction rate. These findings indicate that molecular H 2 is the dominant reducing species in the low-temperature reduction of oxides using CaH 2 , with a key aspect of the hydrides' superior reducing power attributed to their ability to eliminate residual moisture. This work underscores the critical role of moisture control in enabling effective low-temperature oxide reduction for advanced material synthesis.
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Wang, Jiayue [SLAC National Accelerator Laboratory (SLAC), Menlo Park, CA (United States). Stanford Institute for Materials and Energy Science (SIMES); Stanford Univ., CA (United States)] (ORCID:0000000220273634), Yu, Yijun [SLAC National Accelerator Laboratory (SLAC), Menlo Park, CA (United States). Stanford Institute for Materials and Energy Science (SIMES); Stanford Univ., CA (United States)] (ORCID:0000000240068072), Abdelkawy, Ahmed [Max Planck Institute for Sustainable Materials, Dusseldorf (Germany)] (ORCID:0009000778657618), Li, Jiarui [SLAC National Accelerator Laboratory (SLAC), Menlo Park, CA (United States). Stanford Institute for Materials and Energy Science (SIMES)], Li, Jinlei [Stanford Univ., CA (United States)], Yang, Jing [Max Planck Institute for Sustainable Materials, Dusseldorf (Germany)] (ORCID:0000000318550708), Ko, Eun Kyo [SLAC National Accelerator Laboratory (SLAC), Menlo Park, CA (United States). Stanford Institute for Materials and Energy Science (SIMES); Stanford Univ., CA (United States)], Lee, Yonghun [SLAC National Accelerator Laboratory (SLAC), Menlo Park, CA (United States). Stanford Institute for Materials and Energy Science (SIMES); Stanford Univ., CA (United States)], Thampy, Vivek [SLAC National Accelerator Laboratory (SLAC), Menlo Park, CA (United States). Stanford Synchrotron Radiation Lightsource (SSRL)], Cui, Yi [SLAC National Accelerator Laboratory (SLAC), Menlo Park, CA (United States). Stanford Institute for Materials and Energy Science (SIMES); Stanford Univ., CA (United States)] (ORCID:0000000261036352), Todorova, Mira [Max Planck Institute for Sustainable Materials, Dusseldorf (Germany)] (ORCID:0000000280539350), Neugebauer, Jörg [Max Planck Institute for Sustainable Materials, Dusseldorf (Germany)], Hwang, Harold Y. [SLAC National Accelerator Laboratory (SLAC), Menlo Park, CA (United States). Stanford Institute for Materials and Energy Science (SIMES); Stanford Univ., CA (United States)]. 2025-01-14. Molecular H 2 as the Reducing Agent in Low-Temperature Oxide Reduction Using Calcium Hydride. https://doi.org/10.1021/jacs.4c17825
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