Yingzhe Yu

DFT study of In2O3-catalyzed methanol synthesis from CO2 and CO hydrogenation on the defective site

Research on the mechanism of methanol synthesis from CO2 hydrogenation on the defective surface of In2O3 catalyst plays a pivotal role in the promotion of its catalytic performance and the catalytic conversion of CO2. Methanol synthesis from the hydrogenation of CO2 and CO on the vacancy site, consisting of Ov1 and Ov2, of the defective In2O3(110) surface (D surface) has been studied using the density functional theory method in the present work. The calculated results indicate that the HCOO route and RWGS route both are possible reaction pathways for methanol synthesis on the D surface. In the HCOO route, the reaction of p-HCOO with the surface H atom to form H2COO species is the rate-determining step, with an activation barrier of 1.25 eV. In the RWGS route, the dissociation of CO2 to CO on the D surface with a barrier of 0.99 eV is the rate-determining step for methanol synthesis. The hydrogenation of CO and HCO species on the D surface both are kinetically and energetically favorable.

Water Adsorption and Decomposition on Co(0001) Surface: A Computational Study

Water adsorption and decomposition on the Co(0001) surface has been systematically studied by spin-polarized density functional theory calculations and atomic thermodynamics. H2O adsorption mechanism has been analyzed by partial density of states. The possible structure of adsorbed H2O molecules comprised of monomer-hexamer have been investigated and the phase diagram shows that only two configurations are stable thermodynamically: clean Co(0001) surface and H2O hexamer adsorption. The competition between the ability of a H2O molecule to bond with the substrate and its ability to act as a H-bond acceptor leads to the symmetry-breaking bond alteration in the hexamer structure. In addition, the interaction among adsorbed H2O molecules can help stabilize adsorption configurations by forming H-bonds. Presence of O species has a great influence on the decomposition of water and can significantly lower the activation barrier of H–OH bond cleavage.Graphical Abstract

Investigation on the conversion of ethylene to ethylidyne on Pt(100) and Pd(100) using density functional theory

The comprehensive formation network of ethylidyne (CH3C) from ethylene (CH2CH2) is investigated on Pt(100) and Pd(100) using the density functional theory method. The structural and energetic features of all intermediate products were considered. We found that the trend of the activation barriers in each pathway on Pt(100) and Pd(100) are the same, whereas the barriers on Pt(100) are higher than that on Pd(100). The activation barriers of 1,2-H shift reactions are relatively high compared with the other reactions. We screened three possible pathways and selected the optimal route as CH2CH2(ethylene) → CH2CH(vinyl) → CH2C(vinylidene) → CH3C(ethylidyne).

Comparison of the coupling of ethylene with acetate species and ethylene dehydrogenation on Pd–Au(100): a density functional study

In this work, two key reactions in vinyl acetate monomer (VAM) synthesis, i.e., the coupling of ethylene with acetate species and ethylene dehydrogenation, on three different Pd–Au(100) surface configurations – the second nearest neighbors (denoted as PdsnAu), the first nearest neighbors (denoted as PdfnAu), and the fourth nearest-neighbor palladium island (denoted as PdislAu) – were studied. The energy barriers of the transition state of ethylene dehydrogenation to vinyl and the coupling of ethylene with acetate species on three different Pd–Au (100) surfaces were calculated. The influence of the surface properties of Pd–Au(100) on the reaction performance was analyzed and discussed at the microscopic level. The results reveal that on PdsnAu and PdfnAu surfaces where the coverage of the surface Pd atoms is relatively low, it is more likely for the coupling of ethylene with acetate species to occur, while on the PdislAu surface where the coverage of the surface Pd atoms is relatively high, it is more likely for ethylene dehydrogenation to happen. This work will improve the comprehension of the catalytic mechanism of Pd–Au(100) at the molecular and electronic levels and provide theoretical guidance for further application and development of efficient commercial catalysts, and the control of the reaction.

Study on the Reaction Species of 1, 3-Butadiene Formation from Bio-ethanol on ZrO2

Catalytic conversion of bio-ethanol to 1, 3-butadiene is an attractive alternative to biomass energy utilization. In the present study, both the acid and basic properties have been investigated through the experimental and density functional theory methods. The possible products of ethanol reaction on surface of ZrO2 catalyst have been studied through impulse response and density functional theory was also applied in the investigation of the reaction species adsorption on the surface of ZrO2.The three terminated surfaces of ZrO2 (100), (111), (110) have been optimized. The adsorption performances of ethanol, acetaldehyde, acetaldehyde- acetaldehyde and crotondehyde-ethanol on ZrO2 (100), (111), (110) have been studied. The results show that the ZrO2 (111) is the best in the adsorption performance of reaction species and the high reactivity of ZrO2 (111) owns to its acid-basic bi-function.Graphical Abstract

Mechanistic Insight into the Modification of the Surface Stability of In2O3 Catalyst Through Metal Oxide Doping

AbstractThe surface stability of In2O3 catalyst, which can be modified through the doping of metal oxide, plays vital role in methanol synthesis from CO2 hydrogenation. The surface stability of In2O3 (110) surface doped by MgO, TiO2, ZnO, Ga2O3, Y2O3, ZrO2, SnO2 and CeO2 species are studied using the density functional theory calculations in present work. Under CO atmosphere, the desorption of CO2 on the vacancy site is the rate determining step of oxygen vacancy formation on the surface of In2O3 catalyst. The calculated results demonstrate that MgO, ZnO, Ga2O3, Y2O3, SnO2 and CeO2 doped In2O3 (110) surface are favorable to be reduced via the reaction of CO with surface O atoms, which worsen the surface stability of In2O3 catalyst. Ti- and Zr-doped In2O3 (110) surfaces enhance both the reaction barriers of CO with surface O atom and adsorption of CO2 molecules on the vacancy sites. TiO2 and ZrO2 are promising modifiers to improve the activity and stability of In2O3 catalyst. The modification of the density of electron cloud or fermi level of In2O3 catalyst plays pivotal role in promotion of the stability of In2O3 catalyst.Graphical AbstractTiO2 and ZrO2 are promising modifiers to enhance the surface stability of In2O3 catalyst and the adsorption of CO2.

Surface carbon species formation from ethylene decomposition on Pd(100): a first-principles-based kinetic Monte Carlo study

Based on the activation barriers and reaction energies from periodic density functional calculations, we conducted kinetic Monte Carlo (kMC) simulations of surface carbon species formation from ethylene decomposition on a Pd(100) surface. A comprehensive reaction network of ethylene decomposition involving such intermediates as CH2CH, CHCH, CH2C, CHC, CC, CH2 and CH was proposed. Our kMC simulations show that the most probable pathway of ethylene decomposition on Pd(100) is CH2CH2 → CH2CH → CH2C → CHC → CC, among which the dehydrogenation of CH2CH2 to CH2CH is the rate-limiting step with the activation barrier of 1.51 eV, followed by CH2CH2 → CH2CH → CHCH → CHC → CC, whose rate-limiting step is the dehydrogenation of CH2CH to CHCH with the activation barrier of 1.59 eV. The two most probable pathways produce a carbon dimer as the final product, since the activation barrier of the C–C bond cleavage reaction is so high (2.32 eV) that it is almost impossible for it to occur before the metal surface is totally poisoned by surface carbon species. Another three feasible pathways are: (i) CH2CH2 → CH2CH → CHCH → CH → C, (ii) CH2CH2 → CH2CH → CHCH → CHC → CH + C → C and (iii) CH2CH2 → CH2CH → CH2C → CHC → CH + C → C, whose final products contain surface carbon monomers. And the reactions involving C–C bond cleavage are the rate-limiting step of the three pathways. Simple as the reaction network of ethylene decomposition looks, it is still difficult to analyze the decomposition mechanism merely according to the activation barriers from DFT calculations. Our work here demonstrates that kMC simulations can nicely tackle the problem on competitive reaction pathways, each of which involves some reactions with relatively low activation barriers (e.g. the dehydrogenation reactions involved in ethylene decomposition) and some other reactions with relatively high activation barriers (e.g. the C–C bond cleavage reactions involved in ethylene decomposition).

The Influence of Surface Oxygen and Hydroxyl Groups on the Dehydrogenation of Ethylene, Acetic Acid and Hydrogenated Vinyl Acetate on Pd/Au(100): A DFT Study

On the basis of Langmuir–Hinshelwood mechanism, with density functional theory method, all the dehydrogenation reactions in both Samanos mechanism and Moiseev mechanism in acetoxylation of ethylene to vinyl acetate, i.e., the dehydrogenation of ethylene, acetic acid and hydrogenated vinyl acetate (VAH), on Pd/Au(100) surface consisting of two diagonal Pd atoms were taken into consideration to examine the influence of surface oxygen atoms and hydroxyl groups on these dehydrogenation reactions. Besides, the corresponding adsorption of relevant species was investigated and the energetics of the dehydrogenation reactions was compared. Our calculations show that the surface Os kinetically facilitate ethylene dehydrogenation, but surface OHs kinetically inhibit ethylene dehydrogenation; the surface Os and OHs can kinetically facilitate acetic acid dehydrogenation, while they are kinetically unpreferable for VAH dehydrogenation; both surface Os and OHs are thermodynamically favored for the dehydrogenation of ethylene, acetic acid and VAH.Graphical Abstract