Preprint article · Journal article
Impact of cation redox chemistry on continuous hydrothermal synthesis of 2D-Ni(Co/Fe) hydroxides
Department of Energy Conversion and Storage, Technical University of Denmark1
Universidade Federal do ABC2
University of Padua3
Imaging and Structural Analysis, Department of Energy Conversion and Storage, Technical University of Denmark4
Solid State Chemistry, Department of Energy Conversion and Storage, Technical University of Denmark5
Swiss Federal Institute of Technology Lausanne6
Functional Oxides, Department of Energy Conversion and Storage, Technical University of Denmark7
Continuous hydrothermal flow synthesis (CHFS) is a facile, upscalable and cost-efficient synthetic method enabling the nanostructuring of advanced functional materials in steady conditions, i.e. not in batch synthesis. In this paper, we use CHFS to crystallize NiCo- and NiFe-hydroxides in water solution with 2D nanofeatures.
By tuning the synthetic parameters, we disclose the key role of the cation redox chemistry in the transition between two competitive phases: from 2D-nanoplatelets of brucite to layered double hydroxides (LDH). For controlling the precipitation of different Ni, Fe, Co-hydroxide phases, we propose the combined use of an oxidizing (H2O2) and a complexing (NH3) agent.
At temperatures as low as 80 °C, the presence of H2O2 and a low concentration of NH3 favour the Ni2+/Co3+ over Ni2+/Co2+ oxidation states, shifting the product structure from brucite phase (temperatures > 80 °C) to LDH. Conversely, for the NiFe-hydroxides the transition from LDH (temperatures ≤ 80 °C) to brucite phase (temperatures > 80 °C) is controlled by the reaction temperature only.
Due to the high stability of Fe3+, the synthesis of NiFe products by CHFS does not require oxidizing and complexing agents, resulting in a robust process for large-scale production.
Language: | English |
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Year: | 2019 |
Pages: | 2060-2073 |
ISSN: | 20589883 |
Types: | Preprint article and Journal article |
DOI: | 10.1039/C9RE00334G |
ORCIDs: | 0000-0003-0558-4554 , Simonsen, Søren Bredmose , 0000-0003-4334-2150 , Esposito, Vincenzo , Zielke, Philipp and Kiebach, Ragnar |