Surface structure and chemistry of Pt/Cu/Pt(1 1 1) near surface alloy model catalyst in CO

Zeng, Shibi; Nguyen, Luan; Cheng, Fang; Liu, Lacheng; Yu, Ying; Tao, Franklin Feng

doi:10.1016/j.apsusc.2014.09.090

Cited by 16 publications

(8 citation statements)

References 28 publications

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“…Within 25 min, approximately 40% of the surface is restructured to (1 × 1). These simultaneous measurements of partial pressure of CO 2 in the reaction cell using the online mass spectrometer installed on our HP-STM system ,, confirmed that Rh(110) was catalyzing CO oxidation to form CO 2 at 25 °C.…”

Section: Resultssupporting

confidence: 64%

Atomic-Scale Structural Evolution of Rh(110) during Catalysis

et al. 2016

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We report direct observation at the atomic scale of the pressure- and temperature-dependent evolution of a model Rh(110) catalyst surface during transient and steady-state CO oxidation, using high-pressure scanning tunneling microscopy (HP-STM) and ambient-pressure X-ray photoelectron spectroscopy (AP-XPS) correlated against density functional theory (DFT) calculations. Rh(110) is susceptible to the well-known missing row (MR) reconstruction. O2 dosing produces a MR structure and an O coverage of 1/2 monolayer (ML), the latter limited by the kinetics of O2 dissociation. In contrast, CO dosing retains the (1 × 1) structure and a CO coverage of 1 ML. We show that CO dosing titrates O from the (2 × 1) structure and that the final surface state is a strong function of temperature. Adsorbed CO accelerates and O inhibits the (2 × 1) to (1 × 1) transition, an effect that can be traced to the influence of the adsorbates on the energy landscape for moving metal atoms from filled to empty rows. During simultaneous dosing of CO and O2, we observed steady-state CO oxidation as well as a transition to the (1 × 1) structure at temperatures more modest than in the titration experiments. This difference may reflect surface heating generated during CO oxidation. At more elevated temperatures the metallic surface transforms to a surface oxide, also active for CO oxidation. Being one of the first examples, these results demonstrate how operando experiment exploration in terms of correlation between surface structure dominated by reaction conditions and activity of a catalytic material and first-principles models can be integrated to disentangle the underlying thermodynamic and kinetic factors that influence the dependence of catalytic activity on surface structure at nano and atomic scales.

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Section: Resultssupporting

confidence: 64%

Atomic-Scale Structural Evolution of Rh(110) during Catalysis

et al. 2016

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“…The Pt 4f 7/2 binding energy values are 0.3–0.5 eV higher than the reported literature values for Pt(111), as summarized in Table . A positive shift of the Pt 4f binding energy has been reported in the literature for various Pt alloys, and it can be attributed to compressive strain and/or electronic effects. − …”

Section: Results and Discussionmentioning

confidence: 85%

Enhanced Stability of Pt-Cu Single-Atom Alloy Catalysts: In Situ Characterization of the Pt/Cu(111) Surface in an Ambient Pressure of CO

et al. 2018

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The interaction between a catalyst and reactants often induces changes in the surface structure and composition of the catalyst, which, in turn, affect its reactivity. Therefore, it is important to study such changes using in situ techniques under well-controlled conditions. We have used ambient pressure X-ray photoelectron spectroscopy to study the surface stability of a Pt/Cu(111) single-atom alloy in an ambient pressure of CO. By directly probing the Pt atoms, we found that CO causes a slight surface segregation of Pt atoms at room temperature. In addition, while the Pt/Cu(111) surface demonstrates poor thermal stability in ultrahigh vacuum conditions, where surface Pt starts to diffuse to the subsurface layer above 400 K, the presence of adsorbed CO enhances the thermal stability of surface Pt atoms. However, we also found that temperatures above 450 K cause restructuring of the subsurface layer, which consequently strengthens the CO binding to the surface Pt sites, likely because of the presence of neighboring subsurface Pt atoms.

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“…In situ studies of surface chemistry of catalysts were performed on the lab-based AP-XPS system in our group. The function of this in-house AP-XPS was demonstrated in our recent work. − Catalyst samples were transferred to a fixed-bed flow reactor which has gas inlet and outlet for in situ studies with a flowing mode. Reactant environment of in situ studies of Pt 1 /Co 3 O 4 and Pd 1 /Co 3 O 4 catalysts is a mixture of 1 Torr NO and 1 Torr of H 2 .…”

Section: Methodsmentioning

confidence: 99%

Reduction of Nitric Oxide with Hydrogen on Catalysts of Singly Dispersed Bimetallic Sites Pt₁Co_m and Pd₁Co_n

et al. 2016

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The bimetallic catalyst has been one of the main categories of heterogeneous catalysts for chemical production and energy transformation. Isolation of the continuously packed bimetallic sites of a bimetallic catalyst forms singly dispersed bimetallic sites which have distinctly different chemical environment and electronic state and thus exhibit a different catalytic performance. Two types of catalysts consisting of singly dispersed bimetallic sites Pt1Co m or Pd1Co n (m and n are the average coordination numbers of Co to a Pt or Pd atom) were prepared through a deposition or impregnation with a following controlled calcination and reduction to form Pt1Co m or Pd1Co n sites. These bimetallic sites are separately anchored on a nonmetallic support. Each site only consists of a few metal atoms. Single dispersions of these isolated bimetallic sites were identified with scanning transmission electron microscopy. Extended X-ray absorption fine structure spectroscopy (EXAFS) revealed the chemical bonding of single atom Pt1 (or Pd1) to Co atoms and thus confirmed the formation of bimetallic sites, Pt1Co m and Pd1Co n . Reduction of NO with H2 was used as a probing reaction to test the catalytic performance on this type of catalyst. Selectivity in reducing nitric oxide to N2 on Pt1Co m at 150 °C is 98%. Pd1Co n is active for reduction of NO with a selectivity of 98% at 250 °C. In situ studies of surface chemistry with ambient-pressure X-ray photoelectron spectroscopy and coordination environment of Pt and Pd atoms with EXAFS showed that chemical state and coordination environment of Pt1Co m and Pd1Co n remain during catalysis up to 250 and 300 °C, respectively. The correlation of surface chemistries and structures of these catalysts with their corresponding catalytic activities and selectivities suggests a method to develop new bimetallic catalysts and a new type of single site catalysts.

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Surface structure and chemistry of Pt/Cu/Pt(1 1 1) near surface alloy model catalyst in CO

Cited by 16 publications

References 28 publications

Atomic-Scale Structural Evolution of Rh(110) during Catalysis

Atomic-Scale Structural Evolution of Rh(110) during Catalysis

Enhanced Stability of Pt-Cu Single-Atom Alloy Catalysts: In Situ Characterization of the Pt/Cu(111) Surface in an Ambient Pressure of CO

Reduction of Nitric Oxide with Hydrogen on Catalysts of Singly Dispersed Bimetallic Sites Pt₁Co_m and Pd₁Co_n

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Surface structure and chemistry of Pt/Cu/Pt(1 1 1) near surface alloy model catalyst in CO

Cited by 16 publications

References 28 publications

Atomic-Scale Structural Evolution of Rh(110) during Catalysis

Atomic-Scale Structural Evolution of Rh(110) during Catalysis

Enhanced Stability of Pt-Cu Single-Atom Alloy Catalysts: In Situ Characterization of the Pt/Cu(111) Surface in an Ambient Pressure of CO

Reduction of Nitric Oxide with Hydrogen on Catalysts of Singly Dispersed Bimetallic Sites Pt1Com and Pd1Con

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Reduction of Nitric Oxide with Hydrogen on Catalysts of Singly Dispersed Bimetallic Sites Pt₁Co_m and Pd₁Co_n