Nucleation of hematite : A non-classical mechanism

Hematite (α-Fe2O3) is thermodynamically stable at ambient conditions, of vast geological importance, and widely used in applications. It forms at elevated temperatures, while room temperature reactions typically yield metastable akaganéite or ferrihydrite. The mechanistic key changes underlying this observation were explored in the present study. The entropic contribution to the pre-nucleation hydrolysis reaction categorically implies the presence of pre-nucleation clusters (PNCs) as fundamental precursors. The formation of hematite is then due to a change in the reaction mechanism above ~50 °C, where the reaction limitation towards oxolation within phase separated clusters is overcome. We propose a model that rationalizes the occurrence of hematite, akagenéite and ferrihydrite based upon the chemistry of olation PNCs. Supersaturation, or the temperature dependencies of olation and oxolation rates from monomeric precursors are irrelevant in this non-classical mechanism.

Fachgebiet (DDC)

540 Chemie

Schlagwörter

entropy, Hematite, Iron oxide, Non-classical Nucleation, Pre-nucleation Clusters

Zitieren

ISO 690

SCHECK, Johanna, Lisa FUHRER, Baohu WU, Markus DRECHSLER, Denis GEBAUER, 2019. Nucleation of hematite : A non-classical mechanism. In: Chemistry - A European Journal. 2019, 25(56), pp. 13002-13007. ISSN 0947-6539. eISSN 1521-3765. Available under: doi: 10.1002/chem.201902528

BibTex

@article{Scheck2019-10-08Nucle-46370,
  year={2019},
  doi={10.1002/chem.201902528},
  title={Nucleation of hematite : A non-classical mechanism},
  number={56},
  volume={25},
  issn={0947-6539},
  journal={Chemistry - A European Journal},
  pages={13002--13007},
  author={Scheck, Johanna and Fuhrer, Lisa and Wu, Baohu and Drechsler, Markus and Gebauer, Denis}
}

RDF

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    <dcterms:abstract xml:lang="eng">Hematite (α-Fe2O3) is thermodynamically stable at ambient conditions, of vast geological importance, and widely used in applications. It forms at elevated temperatures, while room temperature reactions typically yield metastable akaganéite or ferrihydrite. The mechanistic key changes underlying this observation were explored in the present study. The entropic contribution to the pre-nucleation hydrolysis reaction categorically implies the presence of pre-nucleation clusters (PNCs) as fundamental precursors. The formation of hematite is then due to a change in the reaction mechanism above ~50 °C, where the reaction limitation towards oxolation within phase separated clusters is overcome. We propose a model that rationalizes the occurrence of hematite, akagenéite and ferrihydrite based upon the chemistry of olation PNCs. Supersaturation, or the temperature dependencies of olation and oxolation rates from monomeric precursors are irrelevant in this non-classical mechanism.</dcterms:abstract>
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