In-situ observation of Mo-O stretching vibrations during the reduction of MoO3 with hydrogen by diffuse reflectance FTIR spectroscopy

Using diffuse reflectance FTIR spectroscopy, the stretching vibrations of the terminal Mo=O (995 cm−1) and the bridging Mo-O-Mo (820 cm−1) bands were monitored while MoO3 powders are heated from 25 to 350°C at a hydrogen pressure of 6 atm. It was found that some discernible change is observed in the band at 820 cm−1 with temperature. The “difference spectrum”, obtained after subtracting the high temperature spectrum from the low temperature spectrum, reveals that the band at 995 cm−1 changes as well, indicating that oxide anion vacancies are formed in MoO3 during the reduction process; the percentage change of both bands in MoO3 powder is determined as a function of temperature.