Electronic Metal–Support Interactions and the Production of Hydrogen Through the Water-Gas Shift Reaction and Ethanol Steam Reforming: Fundamental Studies with Well-Defined Model Catalysts

The electronic properties of Ni and Pt nanoparticles deposited on CeO₂(111) have been examined using core and valence photoemission. The results of valence photoemission point to a new type of metal–support interaction which produces large electronic perturbations for small Ni and Pt particles in contact with ceria. The Ni/CeO₂(111) and Pt/CeO₂(111) systems exhibited a density of metal d states near the Fermi level that was much smaller than that expected for bulk metallic Ni or Pt. The electronic perturbations induced by ceria on Ni made this metal a very poor catalyst for CO methanation, but transformed Ni into an excellent catalyst for the production of hydrogen through the water-gas shift and the steam reforming of ethanol. Furthermore, the large electronic perturbations seen for small Pt particles in contact with ceria significantly enhanced the ability of the admetal to adsorb and dissociate water made it a highly active catalyst for the water-gas shift. The behaviour seen for the Ni/CeO₂(111) and Pt/CeO₂(111) systems illustrates the positive effects derived from electronic metal–support interactions and points to a promising approach for improving or optimizing the performance of metal/oxide catalysts.