XAFS spectroscopy in catalysis research: AXAFS and shape resonances

Two new techniques in X-ray absorption spectroscopy (XAS) have recently bee n developed which provide previously unobtainable information on supported noble metal catalysts. Atomic X-ray absorption fine structure (AXAFS) provi des direct information on the average changes in interatomic potential of t he metal particles induced by metal-support effects. Changes in the interat omic potential can now be directly related to changes in catalytic reactivi ty. Analysis of shape resonances near the X-ray absorption edge provides in formation on the changes in the nature of the bonding of adsorbates (like h ydrogen) to the metal cluster as induced by the properties of the support. The strong decrease in activity of supported platinum clusters for neo-pent ane hydrogenolysis with increasing alkalinity of the support can be ascribe d to a decrease in ionization potential of the metal particles directly inf luenced by the alkalinity of the support.