Conditions and mechanisms for the formation of nano-sized Delafossite (CuFeO{sub 2}) at temperatures ≤90 °C in aqueous solution

Journal Article · Mon Feb 15 00:00:00 EST 2016 · Journal of Solid State Chemistry

DOI:https://doi.org/10.1016/J.JSSC.2015.11.033· OSTI ID:22577773

John, Melanie ^[1]; Heuss-Aßbichler, Soraya ^[1]; Ullrich, Aladin ^[2]

---

1. Department of Earth and Environmental Sciences, Ludwig-Maximilians -University Munich, Theresienstr. 41, 80333 München (Germany)
2. Department of Experimental Physics II, University Augsburg, Universitätsstr. 1, 86159 Augsburg (Germany)

In this study, we present the mechanism of CuFeO{sub 2} formation in aqueous solution at low temperatures ≤90 °C, using sulfate salts as reactants. Furthermore, we demonstrate the influence of experimental conditions (alkalization, reaction and ageing temperature and time) on the synthesized nanoparticles. In all cases, GR–SO{sub 4}, a Fe(II–III) layered double hydroxysulphate (Fe{sup 2+}{sub 4}Fe{sup 3+}{sub 2}(OH){sub 12}·SO{sub 4}) and Cu{sub 2}O precipitate first. During further OH{sup −} supply GR–SO{sub 4} oxidizes and forms Fe{sub 10}O{sub 14}(OH){sub 2}, Cu{sub 2}O and CuFeO{sub 2} crystals. Due to the high pH further CuFeO{sub 2} crystals grow at the cost of the unstable intermediate products. The reaction rate increases with increasing ageing temperature, reaction pH and, in particular, NaOH concentrations in the solution. As a result, highly crystalline CuFeO{sub 2} (3R and 2H polytypes) nanoparticles showing hexagonal morphology can be synthesized at 70 °C within 10 h or at 50 °C within 1 week. The formation of 2H polytype is favored by additional OH{sup −} supply during the pH-stat time and rather low temperatures. - Highlights: • We solve the formation mechanism of pure CuFeO{sub 2} using sulfates as reactants. • CuFeO{sub 2} nanoparticles crystallize on cost of green rust, Fe{sub 10}O{sub 14}(OH){sub 2} and Cu{sub 2}O. • The reaction rate increases with increasing temperature and OH- concentration. • CuFeO{sub 2} nanoparticles form at 50 °C within one week and at 70 °C within 10 h. • 2H-polytype of CuFeO{sub 2} is favored by additional NaOH supply during pH-stat-time.

• OSTI ID: 22577773
• Journal Information: Journal of Solid State Chemistry, Vol. 234; Other Information: Copyright (c) 2015 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; Country of input: International Atomic Energy Agency (IAEA); ISSN 0022-4596
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
77 NANOSCIENCE AND NANOTECHNOLOGY
AQUEOUS SOLUTIONS
CONCENTRATION RATIO
COPPER OXIDES
CRYSTALS
ELECTRON SCANNING
FOURIER TRANSFORM SPECTROMETERS
FOURIER TRANSFORMATION
IRON IONS
NANOPARTICLES
NANOSTRUCTURES
PH VALUE
POWDERS
REACTION KINETICS
SCANNING ELECTRON MICROSCOPY
SODIUM HYDROXIDES
SULFATES
SYNTHESIS
TRANSMISSION ELECTRON MICROSCOPY
X RADIATION
X-RAY DIFFRACTION