Orange hydrogen production with fayalite slag: identifying reaction bottlenecks
- 1Faculty of Technology, Fiber and Particle Engineering Research Unit, University of Oulu, PO Box 4300, Finland, 90014
- 2Faculty of Science, University of Oulu, P.O. Box 3000, Finland, FI-90014
Abstract
Orange hydrogen (H2) is generated through stimulated water–rock reactions, analogous to natural hydrogen formation via serpentinization, and offers a potential pathway for clean H2 production from Fe(II)-bearing minerals and mineral side streams. Here, we investigate orange H2 production based on fayalite slag, an Fe(II)-rich metallurgical waste that has not previously been studied for this purpose. H2 generation from fayalite slag was evaluated in a stirred hydrothermal reactor pressurized with Ar and experiments were carried out at initial pressures of 5, 50, and 100 bar and temperatures of 160 and 230 °C. The highest H2 production was observed at 230 °C and an initial pressure of 5 bar in 1 M KOH (pH 14) after 48 h, reaching 0.45 g H2 kg-1 fayalite slag, corresponding to ⁓7.2% of the theoretical maximum H2 yield. During the reaction, the fayalite content decreased, while magnetite and a K-bearing mica phase formed as secondary products. These secondary phases may have limited further reaction by reducing water access to Fe(II)-bearing regions. This is evidenced by the fact that H2 generation plateaued after 48 h of reaction time. Overall, the results show that fayalite slag is a potential feedstock for orange H2 production under comparatively mild hydrothermal conditions, while also indicating that secondary phase formation and surface passivation are important reaction bottlenecks.
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BibTeX
@misc{marvasti2026orange,
title = {{Orange hydrogen production with fayalite slag: identifying reaction bottlenecks}},
author = {Somayeh Karandish Marvasti and Rossella Greco and Juho Yliniemi and Tero Luukkonen},
howpublished = {ChemRxiv},
year = {2026},
month = sep,
doi = {10.26434/chemrxiv.15009239/v1},
url = {https://chemrxiv.org/doi/full/10.26434/chemrxiv.15009239/v1},
note = {CC BY},
}
RIS
TY - UNPB
TI - Orange hydrogen production with fayalite slag: identifying reaction bottlenecks
AU - Somayeh Karandish Marvasti
AU - Rossella Greco
AU - Juho Yliniemi
AU - Tero Luukkonen
PY - 2026
DA - 2026/09/22
PB - ChemRxiv
DO - 10.26434/chemrxiv.15009239/v1
UR - https://chemrxiv.org/doi/full/10.26434/chemrxiv.15009239/v1
AB - Orange hydrogen (H2) is generated through stimulated water–rock reactions, analogous to natural hydrogen formation via serpentinization, and offers a potential pathway for clean H2 production from Fe(II)-bearing minerals and mineral side streams. Here, we investigate orange H2 production based on fayalite slag, an Fe(II)-rich metallurgical waste that has not previously been studied for this purpose. H2 generation from fayalite slag was evaluated in a stirred hydrothermal reactor pressurized with Ar and experiments were carried out at initial pressures of 5, 50, and 100 bar and temperatures of 160 and 230 °C. The highest H2 production was observed at 230 °C and an initial pressure of 5 bar in 1 M KOH (pH 14) after 48 h, reaching 0.45 g H2 kg-1 fayalite slag, corresponding to ⁓7.2% of the theoretical maximum H2 yield. During the reaction, the fayalite content decreased, while magnetite and a K-bearing mica phase formed as secondary products. These secondary phases may have limited further reaction by reducing water access to Fe(II)-bearing regions. This is evidenced by the fact that H2 generation plateaued after 48 h of reaction time. Overall, the results show that fayalite slag is a potential feedstock for orange H2 production under comparatively mild hydrothermal conditions, while also indicating that secondary phase formation and surface passivation are important reaction bottlenecks.
ER -