Water-gas shift activity on Pt-Re surfaces and the role of the support

Brandt, Amy J.; Maddumapatabandi, Thathsara D.; Shakya, Deependra M.; Xie, Kangmin; Seuser, Grant S.; Farzandh, Sharfa; Chen, Donna

doi:10.1063/1.5128735

Cited by 11 publications

(5 citation statements)

References 78 publications

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“…Brandt et al [75] studied the activity of Pt-Re surfaces, prepared with different methods. In one case Pt and Re surfaces were prepared by annealing Re films on Pt (111) to form Pt-Re surface alloys, in another case Pt was deposited on Re/Pt (111), finally Pt was deposited on Re clusters supported on highly oriented pyrolytic graphite (HOPG) surfaces.…”

Section: Comparative Studies Between Multiple Metalsmentioning

confidence: 99%

Platinum Based Catalysts in the Water Gas Shift Reaction: Recent Advances

Palma

Ruocco

Cortese

et al. 2020

Metals

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The water gas shift (WGS) is an equilibrium exothermic reaction, whose corresponding industrial process is normally carried out in two adiabatic stages, to overcome the thermodynamic and kinetic limitations. The high temperature stage makes use of iron/chromium-based catalysts, while the low temperature stage employs copper/zinc-based catalysts. Nevertheless, both these systems have several problems, mainly dealing with safety issues and process efficiency. Accordingly, in the last decade abundant researches have been focused on the study of alternative catalytic systems. The best performances have been obtained with noble metal-based catalysts, among which, platinum-based formulations showed a good compromise between performance and ease of preparation. These catalytic systems are extremely attractive, as they have numerous advantages, including the feasibility of intermediate temperature (250–400 °C) applications, the absence of pyrophoricity, and the high activity even at low loadings. The particle size plays a crucial role in determining their catalytic activity, enhancing the performance of the nanometric catalytic systems: the best activity and stability was reported for particle sizes < 1.7 nm. Moreover the optimal Pt loading seems to be located near 1 wt%, as well as the optimal Pt coverage was identified in 0.25 ML. Kinetics and mechanisms studies highlighted the low energy activation of Pt/Mo2C-based catalytic systems (Ea of 38 kJ·mol−1), the associative mechanism is the most encountered on the investigated studies. This review focuses on a selection of recent published articles, related to the preparation and use of unstructured platinum-based catalysts in water gas shift reaction, and is organized in five main sections: comparative studies, kinetics, reaction mechanisms, sour WGS and electrochemical promotion. Each section is divided in paragraphs, at the end of the section a summary and a summary table are provided.

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Section: Comparative Studies Between Multiple Metalsmentioning

confidence: 99%

Platinum Based Catalysts in the Water Gas Shift Reaction: Recent Advances

Palma

Ruocco

Cortese

et al. 2020

Metals

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“…HOPG crystals (SPI Supplies, 10 mm × 10 mm × 1 mm) were mounted on an Omicron Ta sample plate and supported with Ta foil straps, as previously described . Samples were heated via electron bombardment from a tungsten filament position directly behind the crystal, and temperatures were measured with an infrared pyrometer, which was calibrated against a type K thermocouple spotwelded to the Ta sample plate. , Before each STM experiment, the HOPG crystal was cleaved in air using adhesive tape and heated to 950 K for 12 min in UHV before metal deposition; surface cleanliness was confirmed by XPS and STM. For the modified HOPG surfaces, the crystal was sputtered with Ar + at 500 eV and 100 nA for 10 s and then annealed at 950 K for 10 min.…”

Section: Experimental Methodsmentioning

confidence: 99%

“…59 Samples were heated via electron bombardment from a tungsten filament position directly behind the crystal, and temperatures were measured with an infrared pyrometer, which was calibrated against a type K thermocouple spotwelded to the Ta sample plate. 59,60 Before each STM experiment, the HOPG crystal was cleaved in air using adhesive tape and heated to 950 K for 12 min in UHV before metal deposition; surface cleanliness was confirmed by XPS and STM. For the modified HOPG surfaces, the crystal was sputtered with Ar + at 500 eV and 100 nA for 10 s and then annealed at 950 K for 10 min.…”

Section: ■ Experimental Methodsmentioning

confidence: 99%

Growth of Uniquely Small Tin Clusters on Highly Oriented Pyrolytic Graphite

Beniwal,

Chai,

Qiao

et al. 2024

J. Phys. Chem. C

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Sn clusters have been grown on highly oriented pyrolytic graphite (HOPG) surfaces and investigated by scanning tunneling microscopy (STM), X-ray photoelectron spectroscopy (XPS), and density functional theory (DFT) calculations. At low Sn coverages ranging from 0.02 to 0.25 ML, Sn grows as small clusters that nucleate uniformly on the terraces. This behavior is in contrast with the growth of transition metals such as Pd, Pt, and Re on HOPG, given that these metals form large clusters with preferential nucleation for Pd and Pt at the favored low-coordination step edges. XPS experiments show no evidence of Sn−HOPG interactions, and the activation energy barrier for diffusion calculated for Sn on HOPG (0.06 eV) is lower or comparable to those of Pd, Pt, and Re (0.04, 0.22, and 0.61 eV, respectively), indicating that the growth of the Sn clusters is not kinetically limited by diffusion on the surface. DFT calculations of the binding energy/atom as a function of cluster size demonstrate that the energies of the Sn clusters on HOPG are similar to those of Sn atoms in the bulk for Sn clusters larger than 10 atoms, whereas the Pt, Pd, and Re clusters on HOPG have energies that are 1−2 eV higher than in the bulk. Thus, there is no thermodynamic driving force for Sn atoms to form clusters larger than 10 atoms on HOPG, unlike for Pd, Pt, and Re atoms, which minimize their energy by aggregating into larger, more bulk-like clusters. In addition, annealing the Sn/HOPG clusters to 800 and 950 K does not increase the cluster size, but instead removes the larger clusters, while Sn deposition at 810 K induces the appearance of protrusions that are believed to be from subsurface Sn. DFT studies indicate that it is energetically favorable for a Sn atom to exist in the subsurface layer only when it is located at a subsurface vacancy.

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“…The rutile TiO 2 (110) crystal (Princeton Scientific Corporation, 10 mm × 10 mm × 1 mm) was mounted onto a standard Omicron Ta sample plate as previously described. 45 Sample heating was carried out by electron bombardment of the Ta back plate that was directly in contact with the crystal, 45 and sample temperatures were measured using a calibrated infrared pyrometer (Heitronics). 45,46 The TiO 2 (110) crystal was cleaned by multiple cycles of Ar + ion sputtering at 1 kV for 20 min and annealing to 950−1000 K for 3 min; sample cleanliness and order were confirmed by a combination of STM, XPS, and LEED.…”

Section: ■ Methodsmentioning

confidence: 99%

Oxidation of Sn at the Cluster–Support Interface: Sn and Pt–Sn Clusters on TiO₂(110)

et al. 2021

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The growth of Sn and Pt–Sn clusters on TiO2(110) has been studied by scanning tunneling microscopy, X-ray photoelectron spectroscopy (XPS), low energy ion scattering (LEIS), and density functional theory (DFT). At low Sn coverages (0.02 ML), single-layer high clusters of SnO x are formed with a narrow size distribution and uniform spatial distribution. XPS experiments indicate that these clusters consist of oxidized Sn, and the corresponding reduction in the TiO2 substrate is observed. At higher Sn coverages, the surface is still dominated by two-dimensional clusters of SnO x , but larger three-dimensional clusters of metallic Sn also appear. As the Sn coverage is increased, the number of three-dimensional clusters increases, and the ratio of Sn/SnO x increases, suggesting that SnO x and reduced TiO x form at the cluster–support interface. When Pt is deposited on top of the Sn/SnO x clusters, the relatively mobile Pt atoms diffuse across the TiO2 surface and become incorporated into existing Sn/SnO x clusters. Furthermore, the addition of Pt to the Sn/SnO x clusters causes the reduction of SnO x to metallic Sn and the oxidation of Ti3+ to Ti4+; this behavior is attributed to the formation of Pt–Sn alloy clusters, which results in the diffusion of Sn away from the interface with the TiO2 support. In contrast, when Sn is deposited on an equal coverage of Pt clusters, new Sn/SnO x clusters are formed that coexist with Pt–Sn clusters. However, the surfaces of both Pt on Sn and Sn on Pt clusters are Sn-rich due to the lower surface free energy of Sn compared to Pt. DFT calculations demonstrate that M–TiO2 bonding is favored over M–M bonding for M = Sn, unlike for transition metals such as M = Pt, Au, Ni, and Co. Furthermore, the substantial charge transfer from Sn to TiO2 leads to dipole–dipole repulsion of Sn atoms that prevents agglomeration into the larger clusters that are observed for the mid-late transition metals. DFT studies also confirm that the addition of Pt to a Sn cluster results in strong Pt–Sn bond formation and diminished Sn–O interactions.

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Water-gas shift activity on Pt-Re surfaces and the role of the support

Cited by 11 publications

References 78 publications

Platinum Based Catalysts in the Water Gas Shift Reaction: Recent Advances

Platinum Based Catalysts in the Water Gas Shift Reaction: Recent Advances

Growth of Uniquely Small Tin Clusters on Highly Oriented Pyrolytic Graphite

Oxidation of Sn at the Cluster–Support Interface: Sn and Pt–Sn Clusters on TiO₂(110)

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Water-gas shift activity on Pt-Re surfaces and the role of the support

Cited by 11 publications

References 78 publications

Platinum Based Catalysts in the Water Gas Shift Reaction: Recent Advances

Platinum Based Catalysts in the Water Gas Shift Reaction: Recent Advances

Growth of Uniquely Small Tin Clusters on Highly Oriented Pyrolytic Graphite

Oxidation of Sn at the Cluster–Support Interface: Sn and Pt–Sn Clusters on TiO2(110)

Contact Info

Product

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Oxidation of Sn at the Cluster–Support Interface: Sn and Pt–Sn Clusters on TiO₂(110)