Figure 1. TPR of ethylene hydrogenation on Pt_n clusters and Pt(111).

(a) The measured ethane ion signals (m/z=30) for Pt₉, Pt₁₀, Pt₁₃ and Pt(111) as a function of substrate temperature are shown. (b) The integrated signal from the curves in a as well as for cluster sizes up to Pt₄₀ normalized to the number of Pt atoms, are displayed. The TPR experiments were performed by first dosing 0.4 H₂ molecules per MgO surface atom (1 cm²=2.25 × 10¹⁵ surface atoms) followed by 0.4 C₂H₄ ethylene molecules per MgO surface atom at 100 K followed by applying a temperature ramp of 2 K s⁻¹. The error bars represent a 16% error, which was determined from multiple measurements on a single cluster size.