Temperature-dependent ethylene dissociative adsorption on ruthenium

The dissociative adsorption of ethylene onto Ru(1 1 1) at different temperatures was computed systematically at the first time. At 105 K, ethylene dissociative adsorption has the co-adsorbed CH2C*+2H* and CH3C*+H* as the first and second stable surface intermediates. At over 330 K, CH3C*+H* is converted back into CH2C* accom-panied by H2 desorption and the subsequent dissociation of CH2C* into HCC*, HC*+C* and 2C*. The computed Arrhenius activation barriers of the dissociation of CH2CH2 (0.18 vs. 0.22 & PLUSMN; 0.04 eV) and CH3C (0.54 vs. 0.52 & PLUSMN; 0.04 eV) agree perfectly with the available experimental values, and CH3C* represents the most stable surface species. Under CO co-adsorption, the most stable surface species are the co-adsorbed CH3C*+H*+3CO*. It is found that CO co-adsorption promotes H2 desorption and stabilizes CH3C* by blocking the surface sites for dissociation and raises the dissociation barrier compared to the clean surface (0.78 vs 0.54 eV). Bronsted-Evans-Polanyi relationship between the activation Gibbs free energy barrier and reaction Gibbs free energy is found for CH2C*+2H*+nCO* = CH3C*+H*+nCO* and CH2C*+2H*+nCO* = HCC*+3H*+nCO* (n = 0-3). Ethylene adsorption has di-& sigma; and & pi; adsorption configurations in very close energy, and H2 has adsorption energy of about 0.90 eV.