Fig. 2: Temperature-programmed reaction spectroscopy.

Ethylene (black line) and hydrogen desorption (red line) during heating (0.2 K s−1) of a an ethylene-saturated Co(0001) in vacuum and b a 0.12 ML C2H2ad/0.24 ML Had-covered surface in 1 × 10−7 mbar CO. H2 desorption from a 0.5 ML Had-covered surface heated in CO (light blue and divided by 4 to facilitate comparison) and H2 desorption due to 2-butyne decomposition (grey line, in 1 × 10−7 mbar CO) are added for reference. The dark blue lines show the integral of the H2 desorption traces in the absence and presence of CO, normalized to the number of H atoms in the ethylene precursor.