Browse
Submit Data
Databases
API
Help

Dataset Information

28 Views

0 Connections

0 Citations

0 Reanalyses

0 Downloads

Omics score: 0

Structural Evolution of Ga-Cu Model Catalysts for CO₂ Hydrogenation Reactions.

ABSTRACT: We studied the initial stages of Ga interaction with the Cu(001) surface and environment-induced surface transformations in an attempt to elucidate the surface chemistry of the Cu-Ga catalysts recently proposed for CO₂ hydrogenation to methanol. The results show that Ga readily intermixes with Cu upon deposition in vacuum. However, even traces of oxygen in the gas ambient cause Ga oxidation and the formation of two-dimensional ("monolayer") Ga oxide islands uniformly covering the Cu surface. The surface morphology and the oxidized state of Ga remain in H₂ as well as in a CO₂ + H₂ reaction mixture at elevated pressures and temperatures (0.2 mbar, 700 K). The results indicate that the Ga-doped Cu surface under reaction conditions exposes a variety of structures including GaO _x /Cu interfacial sites, which must be taken into account for elucidating the reaction mechanism.

SUBMITTER: Zhong JQ

PROVIDER: S-EPMC7830109 | biostudies-literature | 2021 Jan

REPOSITORIES: biostudies-literature

ACCESS DATA

Json Xml

Publications

Structural Evolution of Ga-Cu Model Catalysts for CO2 Hydrogenation Reactions.

Zhong Jian-Qiang JQ Shaikhutdinov Shamil S Roldan Cuenya Beatriz B

The journal of physical chemistry. C, Nanomaterials and interfaces 20210106 2

We studied the initial stages of Ga interaction with the Cu(001) surface and environment-induced surface transformations in an attempt to elucidate the surface chemistry of the Cu-Ga catalysts recently proposed for CO2 hydrogenation to methanol. The results show that Ga readily intermixes with Cu upon deposition in vacuum. However, even traces of oxygen in the gas ambient cause Ga oxidation and the formation of two-dimensional ("monolayer") Ga oxide islands uniformly covering the Cu s ...[more]

PMID: 33510828

Similar Datasets

Structural evolution and strain generation of derived-Cu catalysts during CO2 electroreduction.

Project description:Copper (Cu)-based catalysts generally exhibit high C2+ selectivity during the electrochemical CO2 reduction reaction (CO2RR). However, the origin of this selectivity and the influence of catalyst precursors on it are not fully understood. We combine operando X-ray diffraction and operando Raman spectroscopy to monitor the structural and compositional evolution of three Cu precursors during the CO2RR. The results indicate that despite different kinetics, all three precursors are completely reduced to Cu(0) with similar grain sizes (~11 nm), and that oxidized Cu species are not involved in the CO2RR. Furthermore, Cu(OH)2- and Cu2(OH)2CO3-derived Cu exhibit considerable tensile strain (0.43%~0.55%), whereas CuO-derived Cu does not. Theoretical calculations suggest that the tensile strain in Cu lattice is conducive to promoting CO2RR, which is consistent with experimental observations. The high CO2RR performance of some derived Cu catalysts is attributed to the combined effect of the small grain size and lattice strain, both originating from the in situ electroreduction of precursors. These findings establish correlations between Cu precursors, lattice strains, and catalytic behaviors, demonstrating the unique ability of operando characterization in studying electrochemical processes.

| S-EPMC9388520 | biostudies-literature

Dynamic structural evolution of iron catalysts involving competitive oxidation and carburization during CO2 hydrogenation.

Project description:Identifying the dynamic structure of heterogeneous catalysts is crucial for the rational design of new ones. In this contribution, the structural evolution of Fe(0) catalysts during CO2 hydrogenation to hydrocarbons has been investigated by using several (quasi) in situ techniques. Upon initial reduction, Fe species are carburized to Fe3C and then to Fe5C2. The by-product of CO2 hydrogenation, H2O, oxidizes the iron carbide to Fe3O4. The formation of Fe3O4@(Fe5C2+Fe3O4) core-shell structure was observed at steady state, and the surface composition depends on the balance of oxidation and carburization, where water plays a key role in the oxidation. The performance of CO2 hydrogenation was also correlated with the dynamic surface structure. Theoretical calculations and controll experiments reveal the interdependence between the phase transition and reactive environment. We also suggest a practical way to tune the competitive reactions to maintain an Fe5C2-rich surface for a desired C2+ productivity.

| S-EPMC8816344 | biostudies-literature

The active sites of Cu-ZnO catalysts for water gas shift and CO hydrogenation reactions.

Project description:Cu-ZnO-Al2O3 catalysts are used as the industrial catalysts for water gas shift (WGS) and CO hydrogenation to methanol reactions. Herein, via a comprehensive experimental and theoretical calculation study of a series of ZnO/Cu nanocrystals inverse catalysts with well-defined Cu structures, we report that the ZnO-Cu catalysts undergo Cu structure-dependent and reaction-sensitive in situ restructuring during WGS and CO hydrogenation reactions under typical reaction conditions, forming the active sites of CuCu(100)-hydroxylated ZnO ensemble and CuCu(611)Zn alloy, respectively. These results provide insights into the active sites of Cu-ZnO catalysts for the WGS and CO hydrogenation reactions and reveal the Cu structural effects, and offer the feasible guideline for optimizing the structures of Cu-ZnO-Al2O3 catalysts.

| S-EPMC8282834 | biostudies-literature

Enhanced CH3OH selectivity in CO2 hydrogenation using Cu-based catalysts generated via SOMC from GaIII single-sites.

Project description:Small and narrowly distributed nanoparticles of copper alloyed with gallium supported on silica containing residual GaIII sites can be obtained via surface organometallic chemistry in a two-step process: (i) formation of isolated GaIII surface sites on SiO2 and (ii) subsequent grafting of a CuI precursor, [Cu(O t Bu)]4, followed by a treatment under H2 to generate CuGa x alloys. This material is highly active and selective for CO2 hydrogenation to CH3OH. In situ X-ray absorption spectroscopy shows that gallium is oxidized under reaction conditions while copper remains as Cu0. This CuGa material only stabilizes methoxy surface species while no formate is detected according to ex situ infrared and solid-state nuclear magnetic resonance spectroscopy.

| S-EPMC8159433 | biostudies-literature

Differences in Deterioration Behaviors of Cu/ZnO/Al2O3 Catalysts with Different Cu Contents toward Hydrogenation of CO and CO2.

Project description:The deterioration behaviors of Cu/ZnO/Al2O3 (CZA) catalysts upon different Cu contents were elucidated. The fresh and spent catalysts after being used in CO and CO2 hydrogenation at 250 °C under atmospheric pressure were properly characterized using various techniques including X-ray powder diffraction, X-ray photoelectron spectroscopy, and temperature-programmed reduction for the changes of metal sites, while the textural and chemical properties and carbon deposition on spent CZA catalysts were analyzed by N2 physisorption, energy-dispersive X-ray spectroscopy, and temperature-programmed oxidation. During the hydrogenation reaction for both CO and CO2, the unstable Cu0 site on the spent CZA catalyst having a low Cu loading (sCZA-L) was oxidized to CuO and the aggregation of metal crystallite sites (Cu-ZnO and ZnO) was observed. Moreover, the amount of carbon deposition on sCZA-L (ca. >2%) is higher than the spent CZA catalyst having a high Cu loading (sCZA-H, ca. <0.5%). These phenomena led to a decrease in the surface area and the blockage of active sites. These findings can be determined on the catalytic deactivation and the obvious decrease in the catalytic activity of the CZA catalyst having a low Cu content (CZA-L, Cu:Zn = 0.8).

| S-EPMC9330176 | biostudies-literature

Exploring the ternary interactions in Cu-ZnO-ZrO2 catalysts for efficient CO2 hydrogenation to methanol.

Project description:The synergistic interaction among different components in complex catalysts is one of the crucial factors in determining catalytic performance. Here we report the interactions among the three components in controlling the catalytic performance of Cu-ZnO-ZrO2 (CZZ) catalyst for CO2 hydrogenation to methanol. The in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) measurements under the activity test pressure (3 MPa) reveal that the CO2 hydrogenation to methanol on the CZZ catalysts follows the formate pathway. Density functional theory (DFT) calculations agree with the in situ DRIFTS measurements, showing that the ZnO-ZrO2 interfaces are the active sites for CO2 adsorption and conversion, while the presence of metallic Cu is also necessary to facilitate H2 dissociation and to provide hydrogen resource. The combined experiment and DFT results reveal that tuning the interaction between ZnO and ZrO2 can be considered as another important factor for designing high performance catalysts for methanol generation from CO2.

| S-EPMC6411953 | biostudies-literature

Cu2In alloy-embedded ZrO2 catalysts for efficient CO2 hydrogenation to methanol: promotion of plasma modification.

Project description:Cu1In2Zr4-O-C catalysts with Cu2In alloy structure were prepared by using the sol-gel method. Cu1In2Zr4-O-PC and Cu1In2Zr4-O-CP catalysts were obtained from plasma-modified Cu1In2Zr4-O-C before and after calcination, respectively. Under the conditions of reaction temperature 270°C, reaction pressure 2 MPa, CO2/H2 = 1/3, and GHSV = 12,000 mL/(g h), Cu1In2Zr4-O-PC catalyst has a high CO2 conversion of 13.3%, methanol selectivity of 74.3%, and CH3OH space-time yield of 3.26 mmol/gcat/h. The characterization results of X-ray diffraction (XRD), scanning electron microscopy (SEM), and temperature-programmed reduction chemisorption (H2-TPR) showed that the plasma-modified catalyst had a low crystallinity, small particle size, good dispersion, and excellent reduction performance, leading to a better activity and selectivity. Through plasma modification, the strong interaction between Cu and In in Cu1In2Zr4-O-CP catalyst, the shift of Cu 2p orbital binding energy to a lower position, and the decrease in reduction temperature all indicate that the reduction ability of Cu1In2Zr4-O-CP catalyst is enhanced, and the CO2 hydrogenation activity is improved.

| S-EPMC10242014 | biostudies-literature

Iron catalyzed CO2 hydrogenation to formate enhanced by Lewis acid co-catalysts.

Project description:A family of iron(ii) carbonyl hydride complexes supported by either a bifunctional PNP ligand containing a secondary amine, or a PNP ligand with a tertiary amine that prevents metal-ligand cooperativity, were found to promote the catalytic hydrogenation of CO2 to formate in the presence of Brønsted base. In both cases a remarkable enhancement in catalytic activity was observed upon the addition of Lewis acid (LA) co-catalysts. For the secondary amine supported system, turnover numbers of approximately 9000 for formate production were achieved, while for catalysts supported by the tertiary amine ligand, nearly 60 000 turnovers were observed; the highest activity reported for an earth abundant catalyst to date. The LA co-catalysts raise the turnover number by more than an order of magnitude in each case. In the secondary amine system, mechanistic investigations implicated the LA in disrupting an intramolecular hydrogen bond between the PNP ligand N-H moiety and the carbonyl oxygen of a formate ligand in the catalytic resting state. This destabilization of the iron-bound formate accelerates product extrusion, the rate-limiting step in catalysis. In systems supported by ligands with the tertiary amine, it was demonstrated that the LA enhancement originates from cation assisted substitution of formate for dihydrogen during the slow step in catalysis.

| S-EPMC5707511 | biostudies-literature

Copper-Based Catalysts for Selective Hydrogenation of Acetylene Derived from Cu(OH)2.

Project description:Replacing precious metals with cheap metals in catalysts is a topic of interest in both industry and academia but challenging. Here, a selective hydrogenation catalyst was prepared by thermal treatment of Cu(OH)2 nanowires with acetylene-containing gas at 120 °C followed by hydrogen reduction at 150 °C. The characterization by means of transmission electron microscopy observation, X-ray diffraction, and X-ray photoelectron spectroscopy revealed that two crystallites were present in the resultant catalyst. One of the crystal phases was metal Cu, whereas the other crystal phase was ascribed to an interstitial copper carbide (Cu x C) phase. The reduction of freshly prepared copper (II) acetylide (CuC2) at 150 °C also afforded the formation of Cu and Cu x C crystallites, indicating that CuC2 was the precursor or an intermediate in the formation of Cu x C. The prepared catalysts consisting of Cu and Cu x C exhibited a considerably high hydrogenation activity at low temperatures in the selective hydrogenation of acetylene in the ethylene stream. In the presence of a large excess of ethylene, acetylene was completely converted at 110 °C and atmospheric pressure with an ethane selectivity of <15%, and the conversion and selectivity were constant in a 260 h run.

| S-EPMC7860242 | biostudies-literature

Flame Synthesis of Cu/ZnO-CeO2 Catalysts: Synergistic Metal-Support Interactions Promote CH3OH Selectivity in CO2 Hydrogenation.

Project description:The hydrogenation of CO2 to CH3OH is an important reaction for future renewable energy scenarios. Herein, we compare Cu/ZnO, Cu/CeO2, and Cu/ZnO-CeO2 catalysts prepared by flame spray pyrolysis. The Cu loading and support composition were varied to understand the role of Cu-ZnO and Cu-CeO2 interactions. CeO2 addition improves Cu dispersion with respect to ZnO, owing to stronger Cu-CeO2 interactions. The ternary Cu/ZnO-CeO2 catalysts displayed a substantially higher CH3OH selectivity than binary Cu/CeO2 and Cu/ZnO catalysts. The high CH3OH selectivity in comparison with a commercial Cu-ZnO catalyst is also confirmed for Cu/ZnO-CeO2 catalyst prepared with high Cu loading (∼40 wt %). In situ IR spectroscopy was used to probe metal-support interactions in the reduced catalysts and to gain insight into CO2 hydrogenation over the Cu-Zn-Ce oxide catalysts. The higher CH3OH selectivity can be explained by synergistic Cu-CeO2 and Cu-ZnO interactions. Cu-ZnO interactions promote CO2 hydrogenation to CH3OH by Zn-decorated Cu active sites. Cu-CeO2 interactions inhibit the reverse water-gas shift reaction due to a high formate coverage of Cu and a high rate of hydrogenation of the CO intermediate to CH3OH. These insights emphasize the potential of fine-tuning metal-support interactions to develop improved Cu-based catalysts for CO2 hydrogenation to CH3OH.

| S-EPMC8057230 | biostudies-literature