PtnGex/alumina samples were prepared by exposing freshly deposited size-selected Ptn/alumina samples to 60 L of GeCl4 vapor at 300 K, followed by a 300 K 6000 L exposure to H2, resulting in HCl desorption. To avoid contaminating the UHV chamber, both alumina growth and GeCl4/H2 exposures were carried out with the sample sealed into a separately pumped UHV antechamber. Following the H2 exposure, the PtnGex clusters are saturated with Hads and have some residual Cl coverage, thus the final step was to ramp the sample temperature to 750 K, desorbing HCl and H2.