Test of structural models for the (4 4) phase formed by oxygen adsorption on the Pt3Sn(1 1 1) surface

Exposure of the Pt3Sn(1 1 1) surface to oxygen at a pressure in the 10-6 mbar range at 800 K leads to the formation of a chemisorbed phase with a (4 × 4) periodicity. In previous works we investigated the structure of the (4 × 4) phase by means of scanning tunneling microscopy (STM) and XPD. STM images show that the (4 × 4) periodicity results from an array of protrusions and holes. XPD data suggest that oxygen adsorption induces the reconstruction of the substrate with the formation of a Sn-O overlayer. In the present work, several structural models compatible with the STM and XPD results were tested by tensor LEED analysis. The best agreement with the experimental I-V curves was obtained for a model similar to that proposed to interpret the STM images of the Ag(1 1 1)(4 × 4)-O phase. According to this structure, the protrusions observed in STM would correspond to tin atoms occupying on-top positions

Adsorption of oxygen on Pt3Sn(110) studied by STM and LEED

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Magnetite nanoparticles functionalized with citrate: A surface science study by XPS and ToF-SIMS

The surface composition of magnetite nanoparticles, bare and functionalized with citrate, was investigated by means of XPS and ToF-SIMS. Magnetite nanoparticles were prepared by co-precipitation and two different procedures were used to functionalize them with citrate ions. By means of XPS we found that the composition of the oxide is not modified, within the uncertainty of the analysis, by the functionalization swith citrate. Moreover, the amount of citrate ions adsorbed at the surface of the nanoparticles is the same, independently on the functionalization procedure. The thickness of the citrate shell is consistent with that of a single layer of citrate ions covering only partially the surface of the nanoparticles. XPS and ToF-SIMS analyses revealed the presence of ammonia molecules, resulting from the Fe(II) salt used to prepare the oxide nanoparticles, adsorbed at the surface of nanoparticles

Sistema integrato per la produzione di energia elettrica tramite celle a combustibile alimentate con idrogeno ottenuto da etanolo o altro alcool a seguito di reforming catalitico

L'idea brevettuale, attuabile industrialmente ed originale, è relativa alla produzione, a bordo (autoveicolo, generatore portatile di energia etc.) di idrogeno, con una purezza tale da essere efficacemente utilizzabile per alimentare una cella a combustibile, partendo da etanolo. Il processo per la produzione in continuo di idrogeno si basa sul reforming catalitico dell’etanolo in presenza di acqua e/o ossigeno