Time-resolved XAFS study on the supporting process of Rh6(CO)16 cluster on γ-Al2O3

The structural change during the supporting process of rhodium cluster [Rh6(CO)16] on Al2O3 has been studied by time-resolved energy-dispersive XAFS. With the increase of temperature, the bridging CO desorbs continuously at first and almost completely desorbs until 460 K. However, less than 20% terminal CO desorbs until 420 K. About 60% terminal CO desorbs between 420 and 500 K and remaining terminal CO desorbs above 500 K. The Rhsingle bondRh distance decreases from 0.277 to 0.268 nm suddenly between 470 and 490 K then gradually decreases to 0.264 nm. About a half Rhsingle bondO interaction grew at the same temperature as the change of Rhsingle bondRh distance and remaining Rhsingle bondO grows up above 490 K. The support of rhodium cluster on alumina is controlled by the desorption of bridging CO and the Rhsingle bondRh distance changes simultaneously.