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[Display omitted] • CO 2 hydrogenation over inverse supported Zr 9 O 18 /Ni(1 1 1) nanocatalyst was computed. • Charge transfer from Ni(1 1 1) to supported Zr 9 O 18 nanoparticle has been found. • Supported Zr 9 O 18 nanoparticle has coordinatively unsaturated Zr sites at interface. • H 2 prefers dissociative adsorption on Ni(1 1 1) and CO 2 activation prefers interface Zr sites. • Surface HCOO is the most important intermediate and methanol is the selective product. To tune the activity and selectivity of CO 2 hydrogenation, inverse supported Zr 9 O 18 /Ni(1 1 1) catalysts are designed based on ab initio molecular dynamics simulation and density functional theory calculation under the consideration of the number of interfacial O and Zr atoms as well as the interaction between O and Zr atoms. For the most stable catalyst with coordinatively unsaturated interface Zr sites, charge transfer from surface to oxide has been found. The Ni(1 1 1) surface is pre-covered by H atoms and the interface Zr sites can activate CO 2 to a large extent, and their interaction results in the spontaneous formation of surface formate. Further hydrogenation of surface formate leads to the selective formation of methanol with an apparent Gibbs free energy barrier of 0.62 eV, lower than that of methane formation (1.09 eV). On the contrary to metallic nickel and supported nickel catalysts, the most favoured methanol formation route [HCOO → CHO → CH 2 O → CH 3 O → CH 3 OH] does not involve CO as intermediate, revealing the mediated interface effect. [ABSTRACT FROM AUTHOR]

[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]

[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]

[Display omitted] • The morphology evolution of Hägg carbide Fe 5 C 2 under hydrogen conditions was explored. • Carbon-rich facets expose more area surface in Wulff construction with decreasing hydrogen chemical potential, while iron-rich facets are in contrast. • The reduction of surface carbon to methane for (1 1 1) and (11-1) facets is more facile than other facets. In heterogeneous catalysis, the interaction between adsorbates and substrate surface plays an important role on surface structure evolution and even the reaction mechanism. Herein, unified DFT calculation and ab initio atomistic thermodynamics were adopted to explore the interaction between hydrogen and multiple Fe 5 C 2 surfaces. The computation indicates that the dissociation of hydrogen molecule is both thermodynamically and kinetically favorable on Fe 5 C 2 surfaces. The adsorption energy of hydrogen atoms is related to the summed H bond valance (SBV H), a higher SBV H corresponding to a more stable adsorption strength. Based on calculated surface free energy with different hydrogen coverage, the equilibrium crystalline morphology evolution of Fe 5 C 2 under dynamic conditions was constructed with Wulff theorem. C-rich facets expose more area in Wulff construction with decreasing hydrogen chemical potential. The generation of carbon vacancy through reducing to methane has also been investigated, and the reduction of (1 1 1) and (11-1) facets is more facile than other facets. We anticipate this work could complement some knowledge to help understanding the surface structure and performance of iron carbide catalysts under experimental conditions. [ABSTRACT FROM AUTHOR]

[Display omitted] • Main features of GDOES, XPS and ToF-SIMS depth profiling of the thin amine polymer film are compared. • GDOES depth profiling in Ar/O 2 mixture increases etching rate and depth resolution for amine polymer film compared to pure Ar gas. • Etching of polymer surface by glow discharge of Ar/O 2 mixture is based on the synergy of ion sputtering and reactive chemical etching. • GDOES depth profiling is suitable for fast analyses of polymer layers up to a few μm in thickness. Thin polymer films were deposited on polished stainless-steel samples by PECVD from a cyclopropylamine precursor and characterized by X-ray photoelectron spectroscopy, secondary-ion mass spectrometry and glow-discharge optical emission spectroscopy (GDOES) depth profiling. These depth profiles exhibited reasonable agreement. The GDOES involved the erosion of the polymer films in plasma sustained by an asymmetric RF capacitively coupled discharge using both Ar and Ar-O 2 gases. The application of pure Ar caused unwanted effects, such as the broadening of the polymer-film/substrate interface, which were suppressed when using the mixture with oxygen. Another benefit of oxygen was a significant increase in the etching rate by a factor of about 15 as compared to pure argon. The mechanisms involved in the depth profiling using the mixture of gases were elaborated in some detail, taking into account plasma parameters typical for an asymmetric, capacitively coupled RF discharge in a small volume. The main benefit of using the Ar/O 2 GDOES profiling with respect to XPS and SIMS depth profiling is the increased sputtering rate for polymer films. Comparing the GDOES depth profiling with the Ar/O 2 mixture with profiling in pure Ar, the benefits are a higher sputtering rate and better depth resolution at the polymer/substrate interface. [ABSTRACT FROM AUTHOR]

The CO 2 formation mechanism on Fe x C y and its structure–reactivity relationship during sintering process were systemically elucidated using the ReaxFF. [Display omitted] • Investigate the structure-activity relationship of different Fe-based nanoparticles in the sintering process. • Formation of low-coordination-number atoms may be the real reason for promoted TOF of the sintering structures. • The increased amplitude of surface area of sintered Fe x C y varies with its content of carbon. • The main CO 2 formation varies with the Fe x C y : Eley-Rideal VS. Langmuir-Hinshelwood mechanism. The sintering of nanostructured catalysts poses a grand challenge in understanding the complex mechanism in the experimental phenomena, as well as the structure-activity relationship. Here, we systematically investigate the structure-activity relationship of sintered Fe-based catalysts, including Fe 2 C, Fe 5 C 2 , Fe 3 C and pure Fe, in the CO activation by reactive molecular dynamics simulations. The results show that the sintering structures can promote the turn-over frequency of Fe 3 C compared with its un-sintered near-size structures, which might be attributed to the formation of low-coordination-number atoms. The change of surface area shows a similar trend for Fe x C y and pure Fe, and its increased magnitude varies with the content of carbon in the Fe x C y bulk. For size effect, the Fe 2 C displays the largest turn-over frequency for the 4.34 nm particle. The CO 2 formation mechanism has also been compared for different Fe x C y , which may provide critical theoretical insights for industrial reduction of CO 2 emission. [ABSTRACT FROM AUTHOR]