Synthesis of NiO Crystals Exposing Stable High‐Index Facets

Metal oxides exposing high‐index facets are potentially impactful in catalysis and adsorption processes owing to under‐coordinated ions and polarities that alter their interfacial properties compared to low‐index facets. Here, we report molten‐salt syntheses of NiO particles exposing a variety of cr...

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Bibliographic Details
Published in:Angewandte Chemie 2020-08, Vol.132 (35), p.15231-15235
Main Authors: Susman, Mariano D., Pham, Hien N., Zhao, Xiaohui, West, David H., Chinta, Sivadinarayana, Bollini, Praveen, Datye, Abhaya K., Rimer, Jeffrey D.
Format: Article
Language:English
Subjects:
Anions
Catalysis
Cations
Chemistry
Chlorides
Coordination compounds
Coordination numbers
crystal growth
crystal habit
Crystallization
Crystals
Exposure
flux-mediated method
Interfacial properties
Metal oxides
molten-salt route
nickel oxide
Nickel oxides
Parametric analysis
Synthesis
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Summary:Metal oxides exposing high‐index facets are potentially impactful in catalysis and adsorption processes owing to under‐coordinated ions and polarities that alter their interfacial properties compared to low‐index facets. Here, we report molten‐salt syntheses of NiO particles exposing a variety of crystal facets. We show that for a given anion (nitrate or chloride), the alkali cation has a notable impact on the formation of crystals exposing {311}, {611}, {100}, and {111} faces. Based on a parametric analysis of synthesis conditions, we postulate that the crystallization mechanism is governed by the formation of growth units consisting of NiII complexes whose coordination numbers are determined by temperature and the selection of anion (associated to the coordination sphere) and alkali cation (associated with the outer coordination sphere). Notably, our findings reveal that high‐index facets are particularly favored in chloride media and are stable under prolonged periods of catalysis and steaming. Getting into shape: The role of chloride, nitrate, and alkali ions during metal‐oxide crystallization via molten salt routes has been thoroughly explored. It is shown that various ion combinations direct the NiO crystal morphology with nitrates acting as oxygen donors. Findings reveal the generation of unique high‐index {311} facets in media containing Cl− and K+ ions.
ISSN:0044-8249
1521-3757
DOI:10.1002/ange.202003390