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[Display omitted] • Temperature-dependent ethylene dissociative adsorption on ruthenium was computed quantitatively. • Revised PBE can best quantify the adsorption energy of ethylene, H 2 and CO. • Computed activation barriers of the dissociation of CH 2 CH 2 * and CH 3 C* agree quantitively with experiments. • CO co-adsorption stabilizes CH 3 C* by blocking surface sites and raising the dissociation barrier. • BEP relationship is found for the formation of CH 3 C* and HCC under the co-adsorbed CO and hydrogen. 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 CH 2 C*+2H* and CH 3 C*+H* as the first and second stable surface intermediates. At over 330 K, CH 3 C*+H* is converted back into CH 2 C* accompanied by H 2 desorption and the subsequent dissociation of CH 2 C* into HCC*, HC*+C* and 2C*. The computed Arrhenius activation barriers of the dissociation of CH 2 CH 2 (0.18 vs. 0.22 ± 0.04 eV) and CH 3 C (0.54 vs. 0.52 ± 0.04 eV) agree perfectly with the available experimental values, and CH 3 C* represents the most stable surface species. Under CO co-adsorption, the most stable surface species are the co-adsorbed CH 3 C*+H*+3CO*. It is found that CO co-adsorption promotes H 2 desorption and stabilizes CH 3 C* by blocking the surface sites for dissociation and raises the dissociation barrier compared to the clean surface (0.78 vs 0.54 eV). Brønsted–Evans–Polanyi relationship between the activation Gibbs free energy barrier and reaction Gibbs free energy is found for CH 2 C*+2H*+ n CO* = CH 3 C*+H*+ n CO* and CH 2 C*+2H*+ n CO* = HCC*+3H*+ n CO* (n = 0–3). Ethylene adsorption has di-σ and π adsorption configurations in very close energy, and H 2 has adsorption energy of about 0.90 eV. [ABSTRACT FROM AUTHOR]

Abstract The surface energies and the morphologies of three iron oxides (α-Fe 2 O 3 , Fe 3 O 4 , and FeO) are systematically investigated by Density Functional Theory (DFT) employing PBE and PBE+U methods. The surface energies are computed under various O chemical potential which is directly related to atmosphere condition. Compared with available experimental observations, PBE provides reasonable prediction on surface stability of all three oxides while the results of PBE+U are not well consistent with experiments for Fe 2 O 3. Based on the Wulff construction and calculated surface energies, the micro-crystal morphologies of three iron oxides are predicted at various oxygen chemical potential. Subsequently, on basis of the data of surface energies, the effect of surface free energies on phase equilibrium of iron oxides nanoparticles are investigated. These results suggest that particle sizes of nanometer have a significant influence on the thermodynamic equilibrium shifting due to their large surfaces energies contributions. This principle can guide people control the phase transition of iron oxides by adjusting surface energies contributions by changing the sizes of particles. Graphical abstract Unlabelled Image Highlights • PBE provides more reasonable prediction on surface stability of three iron oxides (α-Fe 2 O 3 , Fe 3 O 4 , and FeO) than PBE+U. • O-terminations are generally more stable than the Fe-terminations over a wide range of Δμ O for three iron oxides. • The Wulff morphology of iron oxides is a function of O chemical potential. • Particle sizes of nanometer have a significant influence on the thermodynamic equilibrium shifting. [ABSTRACT FROM AUTHOR]

[Display omitted] • Real space evidence of p4g(2 × 2) Fe 2 C and Co 2 C surface carbides. • Tip-sample distance dependent STM imaging of Fe 2 C. • Fe 2 X (X = B, C, N, O) with increasing electrons the reconstruction becomes less favourable. Thin FCC (1 0 0) iron and cobalt carbide films were prepared on Cu(1 0 0) to study the connection between their structure, electronic properties and stability. We present the first detailed, real space experimental confirmation of the C-induced clock reconstruction on the FCC(1 0 0) surfaces of iron and cobalt. Both Fe and Co surface carbides show p4g (2 × 2) surface reconstruction with tetracoordinated square planar carbon and pure FCC (1 0 0) metal layers underneath. Combining tip-sample distance dependent STM imaging with theoretical calculations we present different imaging modes of Fe 2 C. Using a combination of angle-resolved x-ray photoelectron spectroscopy (AR-XPS), Auger electron spectroscopy (AES), low energy electron diffraction (LEED), scanning tunneling microscopy (STM), and theoretical calculations we provide detailed electronic and structural models for Fe 2 C and Co 2 C p4g (2 × 2) surface carbides and other 2D Fe 2 X interstitial compound systems. In various Fe 2 X (X = B, C, N, O) surface compounds moving to the right in the periodic table with increasing electrons the reconstruction becomes less favorable, while iron carbide shows the highest stability. [ABSTRACT FROM AUTHOR]

[Display omitted] • CO 2 Conversion to CH 4 and CH 3 OH on ZrO 2 support Ni catalysis was computed. • Metal-Metal and Metal-support Interaction was analysed. • Reaction Mechanisms, differently from metallic Ni, were identified. • Metal interaction determines structure of support Ni and reaction mechanisms. To better understand the metal-support interaction and structure–activity relationship, we computed the mechanisms of CO 2 hydrogenation to CH 4 and CH 3 OH on ZrO 2 supported Ni catalyst. On a supported irregular Ni 13 cluster, which exhibits a balanced metal–metal and metal-support interaction with surface Zr and O atoms covered, two preferred routes [CO 2 → CO → CHO → CH/CH 3 O → CH 3 → CH 4 /CH 3 OH] are found, and the rate-determining step is the CO 2 direct dissociation. Such mechanisms differ very strongly from those reported on flat metallic Ni(1 1 1) surface and Ni clusters supported on different metal oxides, demonstrating that different supports generate different metal-support interaction that simultaneously changes the metal structures and the reaction mechanisms. [ABSTRACT FROM AUTHOR]