Determination of molybdenum oxidation state on the mechanochemically treated MoO3

Abstract

The molybdenum oxidation degree in the MoO 3 samples after mechanochemical treatment in various media (air, water, ethanol)

Structural Evolution of MoO3 Thin Films Deposited on Copper Substrates upon Annealing: An X-ray Absorption Spectroscopy Study

“…The as-deposited film and the one annealed at 300 • C exhibited only a large peak at around 1.7 Å, corresponding to the nearest oxygen neighbors (Mo-O) without additional shells. This is in agreement with previous XANES spectra of these same samples that pointed out the presence of disordered phases [23]. On the other hand, a structural ordering of the coating was observed at higher annealing temperatures (> 350 • C).…”

“…The latter has a well-defined pre-edge peak at 20,005.6 eV (peak A), with two other major components at 20,025.7 eV and 20,037.2 eV (peaks B and C). The broadened features of the as-deposited film, in comparison with the reference spectra of the α-MoO 3 spectrum, confirmed that this film was mainly disordered [23][24][25]. Within the initial annealing stage at 300 • C, the ordering process (flagged by peak C) started to appear, although the film remained disordered.…”

“…At the annealing temperature of 500 • C, the spectrum indicated the occurrence of a phase transformation: a clear shift of 3.8 eV of the third component at the energy of 20,033.4 eV (peak C) was observed. This dynamic can be also associated with the partial reduction of Mo ions due to oxygen loss [23,26,27]. A closer look to the XANES spectra also revealed changes in the pre-edge peak as a function of the annealing temperature.…”

Oxygen vacancies in oxidized and reduced vertically aligned α-MoO3 nanoblades

“…The broadening of the peaks suggests that they consist of several overlapping signals, which is in line with previously reported studies. 28,30,31,34,35 The lower values of the absorption g-tensor scalar around 2.003, which were detected in reduced samples (H 2 , vacuum, N 2 ), can be ascribed to single ionized oxygen vacancies O • ‾ (radical oxygen), 35 see Fig. 3b.…”

The microstrain-accompanied structural phase transition from h-MoO3 to α-MoO3 investigated by in situ X-ray diffraction

“…Molybdenum exhibits oxidation states ranging from +2 to +6 [ 1 – 2 ], leading to a range of molybdenum oxides. Molybdenum oxides include the fully stoichiometric MoO 3 with a large bandgap above 2.7 eV, the reduced oxides MoO 3− x with oxygen vacancies, and the semimetal MoO 2 .…”