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

Understanding the effect of H 2 O 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 D 2 O 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 D 2 O 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 D 2 O is partially dissociated on the MgO surface, D 2 can only dissociate at the remaining active sites until that dissociated −OD w groups from D 2 O occupy all active sites. These findings provide a fundamental understanding of the effect of water adsorption on D 2 activation on oxide catalysts.