Fig. shows TPD data for Pt4Ge/alumina, Pt7Ge2/alumina, and Pt11Ge4/alumina measured using the same protocol used for Ptn/alumina (Fig. ). Both C2D4 and D2 were observed to desorb, but the Note that the 1 st TPD run for the PtnGem samples was different from the 2 nd -6 th runs. As noted, the final step in the Ge-treatment process was to ramp the sample temperature to 750 K to desorb H and residual Cl as HCl and H2. For the experiments in Fig. the samples were dosed with C2D4 at 150 K prior to this heat ramp, thus the 1 st C2D4 TPD run was also the final step of the Ge treatment. Because H and Cl were present when the C2D4 was dosed, less C2D4 adsorbed, and the desorption products also changed, as shown in Fig. for Pt7Ge2/alumina. No D2 was observed, and in addition to small signals for HCl and C2D4 desorption, signal for C2D4H2 + was observed, resulting from reaction between adsorbed C2D4 and H. The important point is that after this first heat ramp, only C2D4 and D2 were observed in subsequent C2D4 TPD runs, and the intensities were essentially identical if the 1 st heat ramp was done without the 150 K C2D4 dose (Table ). Thus, the first heating, with or without C2D4 present, generated clean PtnGem/alumina samples that were then probed in the 2 nd -6 th C2D4 TPD runs. This numbering scheme was used to keep the thermal history of the PtnGem/alumina and Ptn/alumina samples consistent, but analysis of the PtnGem/alumna TPD data is focused on runs 2 -6. Note that for Ge/alumina the TPD results were identical in runs 2 -6, and Fig. shows the 2 nd run signal.