EGU24-20271, updated on 11 Mar 2024
EGU General Assembly 2024
© Author(s) 2024. This work is distributed under
the Creative Commons Attribution 4.0 License.

New thermodynamic and kinetic constraints on H2 production during ferroan brucite reaction at low temperature

Benjamin Malvoisin1, William Carlin1,2, Fabrice Brunet1, Bruno Lanson1, Nathaniel Findling1, Martine Lanson1, Laurent Jeannin2, Tiphaine Fargetton2, and Olivier Lhote3
Benjamin Malvoisin et al.
  • 1Univ. Grenoble Alpes, Univ. Savoie Mont Blanc, CNRS, IRD, Univ. Gustave Eiffel, ISTerre, 38000 Grenoble, France (
  • 2Storengy (ENGIE), France
  • 3Engie Research, ENGIE, France

The alteration of ferroan brucite, a common by-product of serpentinization, has been proposed as a H2 source at low temperature. Here, synthetic ferroan brucite with Fe/(Fe+Mg) = 0.2 was reacted with pure water at temperatures ranging from 348 to 573 K in 29 experiments either conducted in gold capsules or Ti-based reactors. H2 production monitoring with time and characterization of the reaction products revealed the occurrence of the following reaction: 3 Fe(OH)2brucite = Fe3O4 + H2 + 2 H2O. This reaction proceeds completely in ~ 2 months at 378 K and is thermally activated. The small grain size of the synthetic brucite (40-100 nm) is similar to observations in natural samples, and is probably responsible for the high reaction rate measured. H2 production reached a plateau and Fe-bearing brucite also precipitated as a reaction product, suggesting the achievement of equilibrium. The thermodynamic properties of Fe(OH)2 were refined based on the experimental dataset and differ by less than 5 % from previous estimates. However, ferroan brucite is predicted to be stable at an hydrogen activity one order of magnitude lower than previously calculated. As a result, significant H2 production during ferroan brucite alteration at low temperature requires efficient fluid renewal. Such a mechanism strongly differs from olivine serpentinization which can occur even at high activity in H2 and thus with limited water renewal.

How to cite: Malvoisin, B., Carlin, W., Brunet, F., Lanson, B., Findling, N., Lanson, M., Jeannin, L., Fargetton, T., and Lhote, O.: New thermodynamic and kinetic constraints on H2 production during ferroan brucite reaction at low temperature, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20271,, 2024.