For D2-dosed Pt4/alumina, desorption started near 200 K, peaked near 330 K, and was complete by ~450 K, similar to hydrogen recombinative desorption reported for both Pt clusters and bulk Pt surfaces. Desorption of D2 during C2D4 TPD began near 300 K, peaked near 470 K, and continued to 750 K, with integrated intensity roughly double that observed during D2 TPD. The higher D2 onset temperature during C2D4 TPD supports the conclusion that D2 desorption is rate-limited by the C2D4 decomposition step, rather than D-D recombinative desorption.