As noted, the Ge treatment process resulted in significant numbers of alumina-bound Ge atoms in the Ge-treated samples, i.e., the PtnGem/alumina samples had Ge bound to the Pt clusters with additional Ge in nearby alumina sites. Ge-treated, Pt-free alumina was found to have ~5.9 x 10 13 Ge/cm 2 (~4% of a Ge monolayer), and the alumina-bound Ge coverage on the PtnGem/alumina samples would have been during the 1 st C2D4 TPD experiment on Pt4/alumina (Fig. ). A small HD signal was observed for the as-deposited Pt4 sample, attributed to adventitious H2 adsorption during deposition, and the "D2" signal for that sample is the sum of the HD and D2 signals.