Phase transitions and morphology evolutions during hydrogen reduction of MoO3 to MoO2

Abstract

In the present work, studies of phase transitions and morphology evolutions during hydrogen reduction of MoO3 to MoO2 were carried out in the temperature range from 678 to 829 K. It was found that no intermediate phase was formed and MoO2 was the unique detectable product during the reduction at 678 K. While above 713 K, an intermediate phase of Mo4O11 was formed. The formation of Mo4O11 was found to obey the consecutive mechanism under the experimental condition. Regarding the morphology evolution of MoO2 during reduction, it was found that in the temperature range from 713 to 733 K, MoO3 was firstly reduced to large spherical or oval Mo4O11 grains, then to small spherical or oval MoO2 ones. From 793 to 829 K, most of MoO3 grains were firstly reduced to large plate-shaped Mo4O11 grains, subsequently to small plateshaped MoO2 ones.