State and action of the tin atoms in platinum-tin catalysts for methanol fuel cells

Janssen, M.M.P.; Moolhuysen, J.

doi:10.1016/0021-9517(77)90212-3

Cited by 104 publications

(8 citation statements)

References 15 publications

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“…Sn adatoms have long been known to inhibit H adsorption onto Pt, thus suppressing the hydride adsorption waves in the Pt cyclic voltammogram in aqueous acid. − In our catalysts, the Sn source is Sn(0) from the bulk of the electrodeposited electrodes or from the Sn structures in the microfabricated samples. However, inhibition of H or organic adsorption onto Pt is presumably accomplished by oxidized Sn, because redistribution of Sn to Pt background regions in the microfabricated catalysts is accompanied by a dramatic increase in the O signal on these regions in the Auger analysis (Figure ), and Sn is present in an oxidized state at the surface of the electrodeposited catalysts, as determined by XPS .…”

Section: Resultsmentioning

confidence: 99%

Pt−Sn Microfabricated Surfaces as Catalysts for Organic Electro-oxidation

2001

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Microfabrication techniques have been used to prepare electrode surfaces reproducibly with well-defined composition and active area. Characterization of surfaces thus prepared leads to straightforward compositionactivity and structure-activity relations. Conventional ebeam deposition/lift-off techniques were used to fabricate the catalysts from a photopatterned resist on Pt. Catalysts consist of an array of closely spaced microstructures (circles or squares, 0.1 µm thick, 10-200 µm wide) of Sn on Pt. Characterization of these structures by Auger electron spectroscopy shows that the Pt areas are relatively rich in C, whereas the Sn is relatively rich in O, before and after exposure to aqueous solutions containing the organic fuel. After 3-5 min of use in 0.5 M H 2 SO 4 /MeOH, at potentials at which fuel oxidation occurs, redistribution of Sn to the Pt regions was observed. Sn redistribution on the time scale of the experiments is inhibited by capping the Sn with a Pt layer. In samples with capped Sn squares, the length of the Pt-Sn contact line was varied by changing the size of the structures while the exposed area of the electrode was kept constant. The activity of the capped Pt-Sn structures depends linearly on the Pt-Sn contact edge length. Thus, it is possible to confine the catalytic area of Pt-Sn electrodes by working with the appropriate structure design. The catalytic area of microfabricated Pt-Sn is located in the zone of intimate contact between the Pt and the Sn layers.

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Section: Resultsmentioning

confidence: 99%

Pt−Sn Microfabricated Surfaces as Catalysts for Organic Electro-oxidation

2001

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“…As for the Sn3.0Ag0.5Cu alloy, the standard redox potential of Ag/Ag + , Cu/Cu 2+ and Sn/Sn 2+ , was 0.8 V (versus SHE) [24,33], 0.339 V (versus SHE) [35,36], and −0.14 V (versus SHE) [34], respectively. So, the oxidizing abilities of the metal cations in order were Ag + , Cu 2+ , and Sn 2+ .…”

Section: Formation Process Of the Primary Nanoparticles Of The Snagcumentioning

confidence: 89%

“…The reduction rate of cations increased with the standard redox potentials increase [32]. The standard redox potential of Ag/Ag + and Sn/Sn 2+ was 0.8 V (versus SHE) [24,33] and 0.14 V (versus SHE) [34], respectively. The principles were…”

Section: Formation Process Of Snag Nanoparticlesmentioning

confidence: 92%

Investigating the Formation Process of Sn‐Based Lead‐Free Nanoparticles with a Chemical Reduction Method

Zhang

Zhao

Zou

et al. 2013

Journal of Nanomaterials

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Nanoparticles of a promising lead-free solder alloy (Sn3.5Ag (wt.%, SnAg) and Sn3.0Ag0.5Cu (wt.%, SAC)) were synthesized through a chemical reduction method by using anhydrous ethanol and 1,10-phenanthroline as the solvent and surfactant, respectively. To illustrate the formation process of Sn-Ag alloy based nanoparticles during the reaction, X-ray diffraction (XRD) was used to investigate the phases of the samples in relation to the reaction time. Different nucleation and growth mechanisms were compared on the formation process of the synthesized nanoparticles. The XRD results revealed different reaction process compared with other researchers. There were many contributing factors to the difference in the examples found in the literature, with the main focus on the formation mechanism of crystal nuclei, the solubility and ionizability of metal salts in the solvent, the solid solubility of Cu in Ag nuclei, and the role of surfactant on the growth process. This study will help define the parameters necessary for the control of both the composition and size of the nanoparticles.

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“…We use this opportunity to study the reactions of this intermediate on two well-defined Pt−Sn surface alloys. Pt−Sn alloys generated interest in the past as possible electrocatalysts for methanol oxidation, , even though recent studies show that the use of these alloys inhibits the rate of methanol oxidation. Our new method is an important development for surface science studies of methoxy on Pt−Sn surfaces because methanol does not decompose on these alloys under UHV conditions 9 and because it is very difficult to generate preadsorbed oxygen on the surface owing to the fact that dioxygen does not dissociatively adsorb on these surfaces …”

Section: Introductionmentioning

confidence: 99%

Methyl Nitrite Adsorption as a Novel Route to the Surface Methoxy Intermediate

et al. 1998

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Surface-bound methoxy species are intermediates in a variety of surface processes, ranging from heterogeneous catalysis to advanced fuel cells, yet their chemistry on many metals remains elusive because of the difficulty of cleanly preparing adsorbed layers of these species. We propose that thermal dissociation of an adsorbed precursor, methyl nitrite (CH3ONO), can be used to produce methoxy species on reactive metal surfaces at low temperatures. On two Pt−Sn alloys, the methoxy intermediate is strongly stabilized (to 300 K) against thermal decomposition compared to Pt(111), where dissociation occurs at below 140 K, and there is a high selectivity to produce formaldehyde. These Pt−Sn alloys do not form the CO and H2 dissociation products characteristic of methoxy chemistry on Pt(111).

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State and action of the tin atoms in platinum-tin catalysts for methanol fuel cells

Cited by 104 publications

References 15 publications

Pt−Sn Microfabricated Surfaces as Catalysts for Organic Electro-oxidation

Pt−Sn Microfabricated Surfaces as Catalysts for Organic Electro-oxidation

Investigating the Formation Process of Sn‐Based Lead‐Free Nanoparticles with a Chemical Reduction Method

Methyl Nitrite Adsorption as a Novel Route to the Surface Methoxy Intermediate

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