XPS and UPS study of Pb monolayers on polycrystalline Pd

Chadwick, David; Karolewski, M.A.

doi:10.1016/0039-6028(83)90693-3

Cited by 14 publications

(8 citation statements)

References 17 publications

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“…7͒, and this is consistent with the value of 0.04 reported in Ref. 69. On the other hand, they 69 report that the Pb 4 f 7/2 BE increase between coverages of 0.1 to 2 ML was ϳ0.16 eV, considerably smaller than the increase of 0.55 eV that we found; see Fig.…”

Section: Discussionsupporting

confidence: 93%

“…10͒, is significantly larger than 0.5 eV for Pb overlayers reported in Ref. 69. Furthermore, Chadwick and Karolewski 69 used data on alloy heats of formation to estimate core level BE shifts in dilute Pb-Pd alloys; these estimates are based on the use of Born-Haber cycles.…”

Section: Discussionmentioning

confidence: 98%

“…Chadwick and Karolewski 69 studied the adsorption of Pb on polycrystalline Pd including measurements of core level BE shifts and concluded that Pb-rich intermediate alloy phases, PdPb 2 and or PdPb, were formed. There are significant similarities between their XPS results and our results; however, there are also differences, in particular for the magnitudes of the BE shifts with Pd coverage.…”

Section: Discussionmentioning

confidence: 99%

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Interactions of ultrathin Pb films with Ru(0001) and Pd(111)

et al. 2003

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The interaction of ultrathin Pb films with Ru͑0001͒ and Pd͑111͒ has been studied with x-ray photoelectron spectroscopy ͑XPS͒ and thermal desorption spectroscopy ͑TDS͒. XPS and TDS show that at room temperature Pb grows on Ru͑0001͒ via a Stranski-Krastanov mechanism, i.e., after completion of the first adlayer of Pb on Ru͑0001͒, further Pb deposition leads to the formation of three-dimensional islands. Upon annealing to 500 K, the overlayer Pb undergoes significant clustering with the extent dictated by the initial coverages. XPS results show that the Pb 4 f 7/2 core level binding energy ͑BE͒ increases slightly (ϩ0.3 eV) as the Pb coverage increases from 0.07 ML to multilayers. When the first monolayer of Pb/Ru͑0001͒ has been completed, the Pb 4 f 7/2 BE has nearly reached the BE value for bulk Pb; it is only 0.1 eV lower. At ϳ2 ML, the Pb 4 f 7/2 BE is equivalent to that of bulk Pb. In contrast, at room temperature, Pb alloys with the Pd͑111͒ surface, the Pd 3d 5/2 BE increasing ϳ0.8 eV with coverage from 0.07-to 4.3-ML Pb. The Pb 4 f 7/2 BEs also increase with increasing coverage reaching the bulk value of Pb at a coverage of ϳ2 ML. The Pb 4 f 7/2 BE at 0.07 ML is 0.55 eV smaller than that of bulk Pb. The lineshape and position of the x-ray induced Pd Auger features (M 4,5 VV) also display significant changes upon alloying. For Pb/Pd alloys, annealing to 500 K does not induce further changes in the Pd (M 4,5 VV) Auger features. The core level BE shifts are discussed in terms of possible initial and final state contributions. In particular, the initial state BE shift mechanisms of hybridization and environmental conduction band charge density are explained in the context of prior theoretical studies. It is shown that 6s→6p hybridization in Pb can be expected to be sufficiently large to contribute to the observed BE shifts.

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Section: Discussionsupporting

confidence: 93%

Section: Discussionmentioning

confidence: 98%

Section: Discussionmentioning

confidence: 99%

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Interactions of ultrathin Pb films with Ru(0001) and Pd(111)

et al. 2003

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“…The XPS results reveal a higher Pd percentage on the catalyst surface than in the bulk (Table S1 in the Supporting Information). The main Pb 4f and Pd 3d peaks shift to lower binding energies after the anodic treatment, which is consistent with a prior report that a lower Pb content in the Pb–Pd alloy system would lower the binding energies of the core‐level electrons for both elements . We also note the emergence of two new shoulder peaks in the Pd 3d 5/2 and 3d 3/2 components (Figure h), which can be assigned to oxidized Pd species formed on the catalyst surface under the anodic condition.…”

Section: Figuresupporting

confidence: 91%

An Integrated CO₂ Electrolyzer and Formate Fuel Cell Enabled by a Reversibly Restructuring Pb–Pd Bimetallic Catalyst

Yuan

et al. 2019

Angew Chem Int Ed

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A single device combining the functions of a CO2 electrolyzer and a formate fuel cell is a new option for carbon‐neutral energy storage but entails rapid, reversible and stable interconversion between CO2 and formate over a single catalyst electrode. We report a new catalyst with such functionalities based on a Pb–Pd alloy system that reversibly restructures its phase, composition, and morphology and thus alters its catalytic properties under controlled electrochemical conditions. Under cathodic conditions, the catalyst is relatively Pb‐rich and is active for CO2‐to‐formate conversion over a wide potential range; under anodic conditions, it becomes relatively Pd‐rich and gains stable catalytic activity for formate‐to‐CO2 conversion. The bifunctional activity and superior durability of our Pb–Pd catalyst leads to the first proof‐of‐concept demonstration of an electrochemical cell that can switch between the CO2 electrolyzer/formate fuel cell modes and can stably operate for 12 days.

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“…To model the Lindlar catalyst, single Pd atoms were substituted by Pb with a 0.25 monolayer coverage, considering that earlier experimental studies on the interaction of Pb with Pd in the Lindlar catalyst suggested the formation of a surface Pd 3 Pb alloy 15. 54 Pd–Zn10 and Pd–Ga25 alloys, which are also selective catalysts for alkyne hydrogenation, were represented similarly to Pd–Pb. The crystal structure of the HHDMA ligand had been derived from the structure of hexadecyltrimethylammomium bromide 55.…”

Section: Experimental and Computational Sectionmentioning

confidence: 99%

From the Lindlar Catalyst to Supported Ligand‐Modified Palladium Nanoparticles: Selectivity Patterns and Accessibility Constraints in the Continuous‐Flow Three‐Phase Hydrogenation of Acetylenic Compounds

Vilé

Almora‐Barrios

Mitchell

et al. 2014

Chemistry A European J

147

127

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Site modification and isolation through selective poisoning comprise an effective strategy to enhance the selectivity of palladium catalysts in the partial hydrogenation of triple bonds in acetylenic compounds. The recent emergence of supported hybrid materials matching the stereo- and chemoselectivity of the classical Lindlar catalyst holds promise to revolutionize palladium-catalyzed hydrogenations, and will benefit from an in-depth understanding of these new materials. In this work, we compare the performance of bare, lead-poisoned, and ligand-modified palladium catalysts in the hydrogenation of diverse alkynes. Catalytic tests, conducted in a continuous-flow three-phase reactor, coupled with theoretical calculations and characterization methods, enable elucidation of the structural origins of the observed selectivity patterns. Distinctions in the catalytic performance are correlated with the relative accessibility of the active site to the organic substrate, and with the adsorption configuration and strength, depending on the ensemble size and surface potentials. This explains the role of the ligand in the colloidally prepared catalysts in promoting superior performance in the hydrogenation of terminal and internal alkynes, and short-chain alkynols. In contrast, the greater accessibility of the active surface of the Pd-Pb alloy and the absence of polar groups are shown to be favorable in the conversion of alkynes containing long aliphatic chains and/or ketone groups. These findings provide detailed insights for the advanced design of supported nanostructured catalysts.

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XPS and UPS study of Pb monolayers on polycrystalline Pd

Cited by 14 publications

References 17 publications

Interactions of ultrathin Pb films with Ru(0001) and Pd(111)

Interactions of ultrathin Pb films with Ru(0001) and Pd(111)

An Integrated CO₂ Electrolyzer and Formate Fuel Cell Enabled by a Reversibly Restructuring Pb–Pd Bimetallic Catalyst

From the Lindlar Catalyst to Supported Ligand‐Modified Palladium Nanoparticles: Selectivity Patterns and Accessibility Constraints in the Continuous‐Flow Three‐Phase Hydrogenation of Acetylenic Compounds

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XPS and UPS study of Pb monolayers on polycrystalline Pd

Cited by 14 publications

References 17 publications

Interactions of ultrathin Pb films with Ru(0001) and Pd(111)

Interactions of ultrathin Pb films with Ru(0001) and Pd(111)

An Integrated CO2 Electrolyzer and Formate Fuel Cell Enabled by a Reversibly Restructuring Pb–Pd Bimetallic Catalyst

From the Lindlar Catalyst to Supported Ligand‐Modified Palladium Nanoparticles: Selectivity Patterns and Accessibility Constraints in the Continuous‐Flow Three‐Phase Hydrogenation of Acetylenic Compounds

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An Integrated CO₂ Electrolyzer and Formate Fuel Cell Enabled by a Reversibly Restructuring Pb–Pd Bimetallic Catalyst