Surface alloys and alloy surfaces: the platinum-tin system

Speller, S.; Bardi, Ugo

doi:10.1016/s1571-0785(02)80093-1

Cited by 8 publications

(6 citation statements)

References 101 publications

(170 reference statements)

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“…Although only SnO 2 and no crystalline Pt-Sn alloy could be found by XRD, this evidence alone is insufficient to assert that no Pt-Sn alloy phase exists in Pt-SnO 2 /C. If there were alloyed Sn species, they might be oxidized after exposure to air, [14] and/ or at concentrations below the detection limit of XRD. Thus, the Sn speciation of Pt-SnO 2 /C was further characterised from aspects of local coordination environment and oxidation state and by combining XAS spectra obtained at the Pt L 3 and Sn K edges.…”

Section: Resultsmentioning

confidence: 93%

“…[11] This relationship is supported by other studies on Pt-Sn bimetallic catalysts, [12] and the promoted CO oxidation can be also found on Sn modified Pt nanoparticles, in which the Sn was suggested to exist as SnO 2 . [9b,13] In addition, the surfaces of Pt-Sn alloys tend to segregate into Pt-Sn 4 + or Pt-SnO 2 due to the instability to air exposure, [14] as observed during low-temperature CO oxidation, [15] suggesting that the bifunctional effects reported on Pt-Sn bimetallic catalysts may be partly attributed to SnO 2 .…”

Section: Introductionmentioning

confidence: 99%

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Role of SnO₂ in the Bifunctional Mechanism of CO Oxidation at Pt‐SnO₂ Electrocatalysts

et al. 2021

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Pt-Sn bimetallic catalysts, especially Pt-Sn alloys, are considered highly CO-tolerant and are thus candidates for reformate derived hydrogen oxidation and for direct oxidation of fuel cell molecules. However, it remains unclear if this CO-tolerance originates from Sn in the Pt-Sn alloy or whether SnO 2 , present as a separate phase, also contributes. In this work, a carbonsupported Pt-SnO 2 was carefully synthesized to avoid the formation of Pt-Sn alloy phases. The resulting structure was analysed by scanning transmission electron microscopy (STEM) and detailed X-ray absorption spectroscopy (XAS). CO oxidation voltammograms of the Pt-SnO 2 /C and other SnO 2 -modified Pt surfaces unambiguously suggest that a bifunctional mechanism is indeed operative at such Pt-SnO 2 catalysts for stable CO oxidation at low overpotentials. The results from these studies suggest that the bifunctional mechanism can be attributed to the co-catalysis role of SnO 2 , in which the surface hydroxide of SnO 2 (Sn-OH) reacts with CO adsorbed on Pt surface (Pt-CO ads ) and regenerates via a Sn II /Sn IV reversible redox couple (À 0.2-0.3 V vs. reversible hydrogen electrode).

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Section: Resultsmentioning

confidence: 93%

Section: Introductionmentioning

confidence: 99%

Role of SnO₂ in the Bifunctional Mechanism of CO Oxidation at Pt‐SnO₂ Electrocatalysts

et al. 2021

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“…The cyclic voltammograms indicate the electrocatalytic superiority of the (111) over the (110) surface, as apparent from the high CO oxidation currents observed at low potentials. However, a thorough analysis of the influence of the preparation procedure on the structure and composition was only performed in a subsequent study, after the electrocatalytic experiments had been performed [108,109]. Low Energy Electron Diffraction (LEED) [108] revealed that with increasing temperature, the Pt 3 Sn(111) surface became increasingly dominated by a p(2 x 2) pattern, with Sn surface content = ¼.…”

Section: Electrochemistry At Uhv Prepared Bulk Alloy Surfaces: Pt3snmentioning

confidence: 99%

Ultrahigh vacuum and electrocatalysis – The powers of quantitative surface imaging

Mercer

Hoster

2016

Nano Energy

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We highlight the impact of Ultrahigh Vacuum (UHV)-born surface science on modern electrocatalysis. The microscopic, atomic level picture of surface adsorption and reaction, which was developed in the surface science community in decades of systematic research on single crystals in UHV, has meanwhile become state-of-the-art also in electrochemistry. For the example of CO on Pt(111) single crystals, which has been extensively studied at the solid/gas and the solid/liquid interface using atomic resolution scanning tunnelling microscopy (STM), we highlight how both interfaces may have even more in common than often assumed. We then illustrate how planar model surfaces such as mono-and bimetallic single crystals and surface alloys, prepared and thoroughly analysed in UHV, enabled a systematic search for improved electrocatalysts. Surface alloys, thermodynamically more stable than foreign metal islands, are a particularly important subgroup of model surfaces, which so far have only been fabricated in UHV. We also flag that model surfaces may not always assume the structure anticipated for the respective experiment, regardless of their preparation in UHV or by electrochemical methods. "Accidental" surface alloying may be more common than often assumed, leading to misinterpretations of the structure-property relationships targeted in many model studies. We highlight that controlled surface alloy formation should be a key step in any model study looking at bimetallic systems in order to get an idea what the effect of unintended alloying could possibly be, and to cross-check whether alloyed surfaces may potentially be the better electrocatalysts in the first place.

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“…No significant diffraction pattern change was observed in the catalyst annealed at 200°C, which might have been expected due to phase segregation of PtSn alloys at low temperatures. A platinum-tin phase diagram, reported by Srinivasan et al [34] and Sylvia et al, [35] shows that both Pt 3 Sn and PtSn alloys exist at room temperature and are stable up to 1000°C. In that study, XPS measurements also confirmed that a small fraction of the surface SnO 2 was reduced under hydrogen to metallic tin which forms an alloy with Pt.…”

Section: X-ray Diffractionmentioning

confidence: 99%

“…[33] The diffraction pattern of the catalyst annealed at 400°C ( Figure 1) displays a much more diverse phase distribution. A platinum-tin phase diagram, reported by Srinivasan et al [34] and Sylvia et al, [35] shows that both Pt 3 Sn and PtSn alloys exist at room temperature and are stable up to 1000°C. The phase transition of PtSn to Pt 3 Sn occurs only above 1300°C.…”

Section: X-ray Diffractionmentioning

confidence: 99%

Dimethyl Ether Oxidation on an Active SnO₂/Pt/C Catalyst for High‐Power Fuel Cells

2019

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Dimethyl ether (DME) has been considered a potential fuel for direct-feed proton exchange membrane fuel cells, owing to its high energy density, low toxicity, and low crossover through a Nafion® membrane in comparison to commonly reported fuels such as methanol, ethanol, and formic acid. The main hurdle in the implementation of direct DME fuel cells is the sluggish oxidation kinetics on state-of-the-art PtÀ based catalysts (e. g. Pt and PtRu). In this work, DME oxidation on a platinum-coated tin oxide catalyst (Pt/SnO 2 ) supported on carbon is reported and compared with commercial Pt/C catalysts. Our catalyst was synthesized by using the polyol method, and structural characterization was performed by using transmission electron microscopy and X-ray diffraction. Electrochemical analysis in acid solution showed overpotentials that are 50 mV lower than commercial Pt/C, as well as a higher oxidation current ( 44 mA À 1 Pt ). The peak power obtained using a 4 cm 2 laboratory prototype fuel cell (loading of 1.23 mg Pt cm À 2 on anode at 0.40 V) was 105 mW cm À 2 at 70°C. Online mass spectrometry analysis of the oxidation products gives insights into the new pathways of the electro-oxidation mechanism on this promising catalyst.

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Surface alloys and alloy surfaces: the platinum-tin system

Cited by 8 publications

References 101 publications

Role of SnO₂ in the Bifunctional Mechanism of CO Oxidation at Pt‐SnO₂ Electrocatalysts

Role of SnO₂ in the Bifunctional Mechanism of CO Oxidation at Pt‐SnO₂ Electrocatalysts

Ultrahigh vacuum and electrocatalysis – The powers of quantitative surface imaging

Dimethyl Ether Oxidation on an Active SnO₂/Pt/C Catalyst for High‐Power Fuel Cells

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Surface alloys and alloy surfaces: the platinum-tin system

Cited by 8 publications

References 101 publications

Role of SnO2 in the Bifunctional Mechanism of CO Oxidation at Pt‐SnO2 Electrocatalysts

Role of SnO2 in the Bifunctional Mechanism of CO Oxidation at Pt‐SnO2 Electrocatalysts

Ultrahigh vacuum and electrocatalysis – The powers of quantitative surface imaging

Dimethyl Ether Oxidation on an Active SnO2/Pt/C Catalyst for High‐Power Fuel Cells

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Role of SnO₂ in the Bifunctional Mechanism of CO Oxidation at Pt‐SnO₂ Electrocatalysts

Role of SnO₂ in the Bifunctional Mechanism of CO Oxidation at Pt‐SnO₂ Electrocatalysts

Dimethyl Ether Oxidation on an Active SnO₂/Pt/C Catalyst for High‐Power Fuel Cells