Effects of water adsorption on active site-dependent H2 activation over MgO nanoflakes

Understanding the effect of H2O adsorption on reactant activation is of great importance in heterogeneous catalysis, which remains a grand challenge particularly in oxide catalyst systems with structural complexity. Herein, the effect of D2O adsorption on D-2 activation over MgO nanocatalysts at different temperatures has been investigated by transmission Fourier transform infrared (FT-IR) and temperature-programmed desorption (TPD). Two sets of hydride and hydroxyl species produced from D-2 dissociation at more active and less active Mg-O pairs can be observed by FT-IR, which all desorb via the product of D-2 as confirmed by TPD experiments. We find that the physically adsorbed D2O overlayer does not affect the dissociation of D-2 since D-2 may pass through the molecular layer and access the surface-active sites. When D2O is partially dissociated on the MgO surface, D-2 can only dissociate at the remaining active sites until that dissociated -ODw groups from D2O occupy all active sites. These findings provide a fundamental understanding of the effect of water adsorption on D-2 activation on oxide catalysts.

Automated summary

The effect of D2O adsorption on D-2 activation over MgO nanocatalysts was investigated using FT-IR and TPD techniques. It was found that two sets of hydride and hydroxyl species produced from D-2 dissociation at more active and less active Mg-O pairs could be observed by FT-IR and desorb via the product of D-2. The physically adsorbed D2O overlayer was found to not affect the dissociation of D-2, as D-2 could pass through the molecular layer and access the surface-active sites.