Observation of a hydrogen-induced shape resonance on Pt/LTL catalysts and its relation with support acidity/alkalinity

A novel analysis method of the platinum L-3 and L-2 X-ray absorption edges of Pt/LTL catalysts indicates that chemisorbed hydrogen induces an antibond ing resonance state just above the Fermi level at the Pt L-3 edge. The diff erence in energy of this antibonding state (E-res) with respect to the Ferm i level is strongly influenced by the acidity/alkalinity of the LTL support : E-res decreases with increasing alkalinity. The decrease in E-res can als o be correlated with the decrease of the neopentane hydrogenolysis turnover frequency of Pt/LTL with increasing support alkalinity. These results prov ide the most direct experimental evidence that the support acidity/alkalini ty alters the actual chemical bond between the surface platinum atoms and t he reacting molecule.