MgO Nanostructures on Cu(111): Understanding Size- and Morphology-Dependent CO<sub>2</sub> Binding and Hydrogenation

Reddy, Kasala Prabhakar; Islam, Arephin; Tian, Yi; Lim, Hojoon; Kim, Jeongjin; Kim, Dongwoo; Hunt, Adrian; Waluyo, Iradwikanari; Rodriguez, José A.

doi:10.1021/acs.jpcc.4c02049

Cited by 3 publications

(1 citation statement)

References 74 publications

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“…Due to the high stability of its C–O bonds and its nonpolar nature, the activation of CO 2 is not an easy task. In general, it is difficult to bind the CO 2 molecule well. ,, However, the formation of a metal-oxide interface can produce compounds that bind and activate CO 2 at room temperature. , From our results, it is clear that when dealing with a system that is efficient for the binding and conversion of CO 2 , one must consider the effects of the molecule on the surface morphology of the system.…”

Section: Resultsmentioning

confidence: 81%

Observing Chemical and Morphological Changes in a Cu@TiO_x Core@Shell Catalyst: Impact of Reversible Metal-Oxide Interactions on CO₂ Activation and Hydrogenation

Deng,

Chen,

Moncada

et al. 2024

ACS Catal.

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A combination of several in situ techniques (XRD, XAS, AP-XPS, and E-TEM) was used to explore links between the structural and chemical properties of a Cu@ TiO x catalyst under CO 2 hydrogenation conditions. The active phase of the catalyst involved an inverse oxide/metal configuration, but the initial core@shell motif was disrupted during the pretreatment in H 2 . As a consequence of strong metal−support interactions, the titania shell cracked, and Cu particles migrated from the core to on top of the oxide with the simultaneous formation of a Cu−Ti−O x phase. The generated Cu particles had a diameter of 20−40 nm and were decorated by small clusters of TiO x (<5 nm in size). Results of in situ XAS and XRD and images of E-TEM showed a very dynamic system, where the inverse oxide/metal configuration promoted the reactivity of the system toward CO 2 and H 2 . At room temperature, CO 2 oxidized the Cu nanoparticles (CO 2,gas → CO gas + O oxide ) inducing a redistribution of the TiO x clusters and big modifications in catalyst surface morphology. The generated oxide overlayer disappeared at elevated temperatures (>180 °C) upon exposure to H 2, producing a transient surface that was very active for the reverse water−gas shift reaction (CO 2 + H 2 → CO + H 2 O) but was not stable at 200−350 °C. When oxidation and reduction occurred at the same time, under a mixture of CO 2 and H 2 , the surface structure evolved toward a dynamic equilibrium that strongly depended on the temperature. Neither CO 2 nor H 2 can be considered as passive reactants. In the Cu@ TiO x system, morphological changes were linked to variations in the composition of metal-oxide interfaces which were reversible with temperature or chemical environment and affected the catalytic activity of the system. The present study illustrates the dynamic nature of phenomena associated with the trapping and conversion of CO 2 .

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Section: Resultsmentioning

confidence: 81%

Observing Chemical and Morphological Changes in a Cu@TiO_x Core@Shell Catalyst: Impact of Reversible Metal-Oxide Interactions on CO₂ Activation and Hydrogenation

Deng,

Chen,

Moncada

et al. 2024

ACS Catal.

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Insights into the Surface Electronic Structure and Catalytic Activity of InO_x/Au(111) Inverse Catalysts for CO₂ Hydrogenation to Methanol

Prabhakar Reddy,

Tian,

Ramírez

et al. 2024

ACS Catal.

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The direct conversion of carbon dioxide (CO 2 ) into methanol (CH 3 OH) via low-temperature hydrogenation is crucial for recycling anthropogenic CO 2 emissions and producing fuels or high value chemicals. Nevertheless, it continues to be a great challenge due to the trade-off between selectivity and catalytic activity. For CO 2 hydrogenation, In 2 O 3 catalysts are known for their high CH 3 OH selectivity. Subsequent studies explored depositing metals on In 2 O 3 to enhance CO 2 conversion. Despite extensive research on metal (M) supported In 2 O 3 catalysts, the role of In−M alloys and M/In 2 O 3 interfaces in CO 2 activation and CH 3 OH selectivity remains unclear. In this work, we have examined the behavior of In/ Au(111) alloys and InO x /Au(111) inverse systems during CO 2 hydrogenation using synchrotron-based ambient-pressure X-ray photoelectron spectroscopy (AP-XPS) and catalytic tests in a batch reactor. Indium forms alloys with Au(111) after deposition. The In−Au(111) alloys display high reactivity toward CO 2 and can dissociate the molecule at room temperature to generate InO x nanostructures. At very low coverages of In (≤0.05 ML), the InO x nanostructures are not stable under CO 2 hydrogenation conditions and the active In−Au(111) alloys produces mainly CO and little methanol. An increase in indium coverage to 0.3 ML led to stable InO x nanostructures under CO 2 hydrogenation conditions. These InO x /Au(111) catalysts displayed a high selectivity (∼80%) toward CH 3 OH production and an activity for CO 2 conversion that was at least 10 times larger than that of plain In 2 O 3 or Cu(111) and Cu/ZnO(0001̅ ) benchmark catalysts. The results of AP-XPS show that InO x /Au(111) produces methanol via methoxy intermediates. Inverse oxide/metal catalysts containing InO x open up a possibility for improving CO 2 → CH 3 OH conversion in processes associated with the control of environmental pollution and the production of high value chemicals.

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Low-Temperature Activation and Coupling of Methane on MgO Nanostructures Embedded in Cu₂O/Cu(111)

Islam,

Huang,

Tian

et al. 2024

ACS Nano

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The efficient conversion of methane into valuable hydrocarbons, such as ethane and ethylene, at relatively low temperatures without deactivation issues is crucial for advancing sustainable energy solutions. Herein, AP-XPS and STM studies show that MgO nanostructures (0.2−0.5 nm wide, 0.4−0.6 Å high) embedded in a Cu 2 O/Cu(111) substrate activate methane at room temperature, mainly dissociating it into CH x (x = 2 or 3) and H adatoms, with minimal conversion to C adatoms. These MgO nanostructures in contact with Cu 2 O/Cu(111) enable C−C coupling into ethane and ethylene at 500 K, a significantly lower temperature than that required for bulk MgO catalysts (>700 K), with negligible carbon deposition and no deactivation. DFT calculations corroborate these experimental findings. The CH 4,gas → *CH 3 + *H reaction is a downhill process on MgO/Cu 2 O/Cu(111) surfaces. The activation of methane is facilitated by electron transfer from copper to MgO and the existence of Mg and O atoms with a low coordination number in the oxide nanostructures. The formation of O−CH 3 and O−H bonds overcomes the energy necessary for the cleavage of a C−H bond in methane. DFT studies reveal that smaller Mg 2 O 2 model clusters provide stronger binding and lower activation barriers for C−H dissociation in CH 4 , while larger Mg 3 O 3 clusters promote C−C coupling due to weaker *CH 3 binding. All of these results emphasize the importance of size when optimizing the catalytic performance of MgO nanostructures in the selective conversion of methane.

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MgO Nanostructures on Cu(111): Understanding Size- and Morphology-Dependent CO₂ Binding and Hydrogenation

Cited by 3 publications

References 74 publications

Observing Chemical and Morphological Changes in a Cu@TiO_x Core@Shell Catalyst: Impact of Reversible Metal-Oxide Interactions on CO₂ Activation and Hydrogenation

Observing Chemical and Morphological Changes in a Cu@TiO_x Core@Shell Catalyst: Impact of Reversible Metal-Oxide Interactions on CO₂ Activation and Hydrogenation

Insights into the Surface Electronic Structure and Catalytic Activity of InO_x/Au(111) Inverse Catalysts for CO₂ Hydrogenation to Methanol

Low-Temperature Activation and Coupling of Methane on MgO Nanostructures Embedded in Cu₂O/Cu(111)

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MgO Nanostructures on Cu(111): Understanding Size- and Morphology-Dependent CO2 Binding and Hydrogenation

Cited by 3 publications

References 74 publications

Observing Chemical and Morphological Changes in a Cu@TiOx Core@Shell Catalyst: Impact of Reversible Metal-Oxide Interactions on CO2 Activation and Hydrogenation

Observing Chemical and Morphological Changes in a Cu@TiOx Core@Shell Catalyst: Impact of Reversible Metal-Oxide Interactions on CO2 Activation and Hydrogenation

Insights into the Surface Electronic Structure and Catalytic Activity of InOx/Au(111) Inverse Catalysts for CO2 Hydrogenation to Methanol

Low-Temperature Activation and Coupling of Methane on MgO Nanostructures Embedded in Cu2O/Cu(111)

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MgO Nanostructures on Cu(111): Understanding Size- and Morphology-Dependent CO₂ Binding and Hydrogenation

Observing Chemical and Morphological Changes in a Cu@TiO_x Core@Shell Catalyst: Impact of Reversible Metal-Oxide Interactions on CO₂ Activation and Hydrogenation

Observing Chemical and Morphological Changes in a Cu@TiO_x Core@Shell Catalyst: Impact of Reversible Metal-Oxide Interactions on CO₂ Activation and Hydrogenation

Insights into the Surface Electronic Structure and Catalytic Activity of InO_x/Au(111) Inverse Catalysts for CO₂ Hydrogenation to Methanol

Low-Temperature Activation and Coupling of Methane on MgO Nanostructures Embedded in Cu₂O/Cu(111)