Study on the role of oxygen vacancy in the catalytic dissociation of H2 on MoO3 and the formation mechanism of HxMoO3

This study focuses on the effect of oxygen vacancies on the dissociation of H2 from MoO3 and the consequent formation of HxMoO3. Furthermore, a comparison of the properties of three distinct MoO3 (bulk-MoO3, Pd/MoO3 and mesoporous MoO3) after hydrogenation is conducted in order to develop a deeper understanding of the intrinsic activity of MoO3. Both the experimental and DFT findings demonstrate that the breaking rate of an H-H bond extremely restrained the hydrogen spillover on bulk-MoO3, while the Mo acid site caused by the abundant O defects on mesoporous MoO3 greatly enhanced its inherent catalytic activity, leading to its remarkable ability to dissociate H2. The active barrier energy of H2 dissociation on MoO3 decreased significantly from 3.82 eV (perfect MoO3 surface) to 0.52 eV (Mo acid site), which is comparable to that of noble metals. Our results may provide useful insights into the mechanism by which H2 dissociates from MoO3 to form HxMoO3.