Phase and Morphology Control of Hexagonal MoO3Crystals via Na+Interactions: A Raman Spectroscopy Study

C. Ingram Vargas-Consuelos, Marco A. Camacho-López, Victor H. Ramos-Sanchez, Olivia A. Graeve

Research output: Contribution to journalArticlepeer-review

7 Scopus citations

Abstract

We present the effect of sodium ions (Na+) on the nucleation process and phase selectivity for the formation of hexagonal molybdenum trioxide crystals (h-MoO3). The phase selectivity during the reaction is attributed to the interaction of Na+ with the molecules in our precursor solution formed by metallic molybdenum dissolved in a mixture of hydrochloric and nitric acids. The vibrational characteristics of the precursor solutions were studied by Raman spectroscopy in combination with density functional theory modeling, showing the presence of [MoO2Cl3(H2O)]- ions within the solutions. The symmetric stretching vibration of the Mo-O bonds found at 962 cm-1 in [MoO2Cl3(H2O)]- proved that the addition of Na+ (in the form of dissolved NaCl) to the precursor solutions resulted only in an electrostatic interaction with the aquo (H2O) and chloro (Cl-) ligands in the complex. After heating the precursor solutions, X-ray diffraction, Raman spectroscopy, and scanning electron microscopy of the obtained powders showed that adding NaCl contributed to the phase selectivity of the reaction, with the Na+ ions playing a vital role in the formation of h-MoO3 over other crystalline phases. Based on the nature of the molybdenum complexes found in the precursor solutions and the structural characteristics of the powders, a formation mechanism to obtain h-MoO3 is proposed. Additionally, the phase stability of h-MoO3 crystals was studied by calorimetry techniques, showing that h-MoO3 transforms to α-MoO3 at ∼649 K. These results provide important insights into phase control to selectively form hexagonal MoO3.

Original languageEnglish (US)
Pages (from-to)13136-13148
Number of pages13
JournalJournal of Physical Chemistry C
Volume127
Issue number27
DOIs
StatePublished - Jul 13 2023

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • General Energy
  • Physical and Theoretical Chemistry
  • Surfaces, Coatings and Films

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