Noble Metal Segregation and Cluster Size of Pt/Rh/CeO2/γ-Al2O3 Automotive Three-Way Catalysts Studied with Low-Energy Ion Scattering

Jansen, Wpa Wim; Harmsen, Jma Jan; Gon, AW Arnoud Denier van der; Hoebink, Jhbj Jozef; Schouten, JC Jaap; Brongersma, H.H.

doi:10.1006/jcat.2001.3391

Cited by 29 publications

(6 citation statements)

References 24 publications

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“…It has been used, for example, to determine metal segregation and the average cluster size of Pt/Rh/CeO 2 /γ-Al 2 O 3 supported catalysts. The cluster size measurement has been applied to atomically dispersed metals in a nanostructured catalyst and can be used to determine cluster size for particles up to 10 nm [59]. …”

Section: Ion-based Surface Analysis Methodsmentioning

confidence: 99%

Application of surface chemical analysis tools for characterization of nanoparticles

et al. 2010

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The important role that surface chemical analysis methods can and should play in the characterization of nanoparticles is described. The types of information that can be obtained from analysis of nanoparticles using Auger electron spectroscopy (AES); X-ray photoelectron spectroscopy (XPS); time of flight secondary ion mass spectrometry (TOF-SIMS); low energy ion scattering (LEIS); and scanning probe microscopy (SPM), including scanning tunneling microscopy (STM) and atomic force microscopy (AFM), are briefly summarized. Examples describing the characterization of engineered nanoparticles are provided. Specific analysis considerations and issues associated with using surface analysis methods for the characterization of nanoparticles are discussed and summarized, along with the impact that shape instability, environmentally induced changes, deliberate and accidental coating, etc., have on nanoparticle properties.

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Section: Ion-based Surface Analysis Methodsmentioning

confidence: 99%

Application of surface chemical analysis tools for characterization of nanoparticles

et al. 2010

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“…32 The diameter is derived from the ratio of the bulk loading (volume) to the LEIS signal (surface area) as described in more detail previously. 33 CO chemisorption isotherms were measured with ASAP2020 Plus (Micromeritics Instrument Corporation) adsorption volume analyzer. Before adsorption measurements the samples were reduced at 300 °C with H 2 for 30 min, followed by evacuation for 30 min at the same temperature.…”

Section: ■ Experimental Sectionmentioning

confidence: 99%

“…Surface roughness correction factors were introduced for the data analysis ( R support = 0.6, R metallic cluster = 0.7, R oxidic cluster = 0.9), and the average nanoparticle sizes were calculated by using the surface quantification data of the reduced and oxidized samples assuming a cluster contact angle of 120° and 90°, respectively . The diameter is derived from the ratio of the bulk loading (volume) to the LEIS signal (surface area) as described in more detail previously …”

Section: Experimental Sectionmentioning

confidence: 99%

Characterization of Surface Structure and Oxidation/Reduction Behavior of Pd–Pt/Al₂O₃Model Catalysts

et al. 2016

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Structural and morphological characterisation of bimetallic Pd-Pt/Al 2 O 3 model catalysts are performed using X-ray diffraction, X-ray absorption spectroscopy, transmission electron microscopy and CO chemisorption. Further, the catalysts were studied under oxidising and reducing conditions using both X-ray absorption spectroscopy and low-energy ion scattering spectroscopy. For the as-prepared catalysts, the existence of alloyed bimetallic Pd-Pt particles and of (tetragonal) PdO were found for the samples calcined at 800 C. PdO is present in form of crystals at the surface of the Pd-Pt particles or as isolated PdO crystals on the support oxide. Bimetallic Pd-Pt nanoparticles were only formed on the Pd-Pt catalysts after calcination at 800 C. The results show that the Pd-Pt nanoparticles undergo reversible changes in surface structure composition and chemical state in response to oxidising or reducing conditions. Under oxidising conditions Pd segregates to the shell and oxidises forming PdO, while under reducing conditions regions with metallic Pd and Pd-Pt alloys were observed at the surface.No bimetallic Pd-Pt nanoparticles were observed for the sample initially calcined at 500 C, but instead isolated monometallic particles, where small Pt particles are easily oxidised under O 2 treatment. In the monometallic catalysts, the Pd is found to be completely oxidised already after calcination and to consist of metallic Pd after reductive treatment.

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“…LEIS has been used to study heterogeneous catalysts for over 20 years [17,18]. Quantification is not significantly affected by surface roughness [19] so, with suitable reference samples, the technique is a very useful tool for quantitative studies of heterogeneous catalysts [20,21].…”

Section: Ex-situ-characterisationmentioning

confidence: 99%

Activity and Stability of Pt Monolayer Core Shell Catalysts

et al. 2009

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Pt and Pt alloy catalysts for the PEMFC cathode fall short of the high activities per gram of Pt required to enable large scale automotive PEMFC commercialization. Thrifting of the active Pt component in the ORR catalyst via the formation of core shell catalysts is an exciting approach to resolve this issue. Pt monolayers have been deposited onto Pd3Co, Pd3Fe and Ir cores using scaleable proprietary methods. Characterisation of these materials, via cyclic voltammetry, LEIS and XPS, showed successful Pt coating of the surface and enhanced catalyst stability in liquid electrolyte cycling tests compared to the bare cores. Electrolyte analysis indicated leaching of base metals and Pd/Ir, so further optimisation is required to generate a uniform pinhole free Pt shell. RDE testing showed 3.7 x Pt activity for PtML/Pd3Co and preliminary MEA tests show great promise, with mass activity up to 2 x that of Pt only.

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Noble Metal Segregation and Cluster Size of Pt/Rh/CeO2/γ-Al2O3 Automotive Three-Way Catalysts Studied with Low-Energy Ion Scattering

Cited by 29 publications

References 24 publications

Application of surface chemical analysis tools for characterization of nanoparticles

Application of surface chemical analysis tools for characterization of nanoparticles

Characterization of Surface Structure and Oxidation/Reduction Behavior of Pd–Pt/Al₂O₃Model Catalysts

Activity and Stability of Pt Monolayer Core Shell Catalysts

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Noble Metal Segregation and Cluster Size of Pt/Rh/CeO2/γ-Al2O3 Automotive Three-Way Catalysts Studied with Low-Energy Ion Scattering

Cited by 29 publications

References 24 publications

Application of surface chemical analysis tools for characterization of nanoparticles

Application of surface chemical analysis tools for characterization of nanoparticles

Characterization of Surface Structure and Oxidation/Reduction Behavior of Pd–Pt/Al2O3Model Catalysts

Activity and Stability of Pt Monolayer Core Shell Catalysts

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Product

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Characterization of Surface Structure and Oxidation/Reduction Behavior of Pd–Pt/Al₂O₃Model Catalysts