Raman spectroscopy-in situ characterization of reversibly intercalated oxygen vacancies in α-MoO3

This work reports on the in situ strategy to reversibly generate or suppress oxygen vacancies on α-MoO3 which were probed by Raman spectroscopy. Reversible changes in two features of the α-MoO3 Raman spectrum could be correlated to the generation of oxygen vacancies: displacement of the Tb band frequency and the intensity decrease of the symmetrical stretching (νs) band. These two features could be used to qualitatively describe oxygen vacancies. Raman results also indicate that oxygen vacancies are located in the interlayer region of the α-MoO3 lattice. This observation is corroborated by in situ X-ray diffraction, which also indicates the absence of nonstoichiometric phase transitions.