Ethylene decomposition on Rh(100): Theory and experiment

The decomposition of ethylene on a Rh(100) single crystal has been studied by a combination of experimental techniques: static secondary ion mass spectrometry (SSIMS), temperature-programmed desorption (TPD), low-energy electron diffraction (LEED), and high-resolution electron energy loss spectroscopy (HREELS), to gain insight into the nature of the reaction intermediates during the decomposition process. These experimental techniques were combined with a computational approach using density functional theory (DFT). Ethylene adsorbs irreversibly on the Rh(100) surface and eventually decomposes to atomic carbon and gas phase hydrogen. The type of intermediate species depends strongly on the initial surface coverage of ethylene. At low coverage, ethynyl (CCH) is the main intermediate species, whereas at high coverage a mixture of ethynyl, acetylene (CHCH), and ethylidyne (CCH3) forms. The rate of decomposition is significantly slower at higher coverages, indicative of lateral interactions between coadsorbed species and site-blocking effects.