| Abstract
| - Hydrogen is dissociatively adsorbed on the gold particles in Au/Al2O3 catalysts, as demonstrated by acombination of in-situ X-ray absorption spectroscopy, chemisorption, and H/D exchange experiments. Thischemisorption of hydrogen induces changes in the Au L3 and L2 X-ray absorption near-edge structures. Thegold atoms on corner and edge positions dissociate the hydrogen, which does not spill over to the face sites.Therefore, the average number of adsorbed hydrogen atoms per surface gold atom increases with decreasingparticle size. With temperature, the hydrogen uptake by supported gold increases or remains constant, whereasit decreases for platinum. Furthermore, in H/D exchange experiments, the activity of Au/Al2O3 increasesstrongly with temperature. Thus, the dissociation and adsorption of hydrogen on gold is activated.
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