Promoter Effect of Early Stage Grown Surface Oxides: A Near-Ambient-Pressure XPS Study of CO Oxidation on PtSn Bimetallics.

The knowledge of the catalyst active phase on the atomic scale under realistic working conditions is the key for designing new and more efficient materials. In this context, the investigation of CO oxidation on the bimetallic Pt3Sn(111) surfaces by near-ambient-pressure X-ray photoelectron spectroscopy and density functional theory calculations illustrates how combining advanced methodologies allows the determination of the nature of the active phase. Starting from 300 K and 500 mTorr of oxygen, the progressive formation of surface oxides is observed with increasing temperature: SnO, PtO units first, and SnO2, PtO2 units afterward.

Restructuring of the Pt3Sn(111) surfaces induced by atomic and molecular oxygen from first principles.

The surface restructuring of Pt(3)Sn(111) induced by oxygen chemisorption is examined by means of density-functional theory calculations. Molecular and atomic oxygen chemisorption is investigated on the two available terminations of the bulk alloy--(2 x 2) and (square root(3) x square root(3))R30 degrees--these two surfaces differing by the tin content and the nature of chemical sites. An extensive geometric, energetic, and vibrational analysis is performed including the influence of oxygen coverage in the case of atomic adsorption.

Interaction of self-assembled monolayers of DNA with electrons: HREELS and XPS studies.

We present results from high-resolution electron energy loss spectroscopy (HREELS) and XPS studies of self-assembled monolayers of DNA. The monolayers are well-organized and display sharp vibrational peaks in the HREEL spectra. The electrons interact mainly with the backbone of the DNA.

Theoretical evidence of PtSn alloy efficiency for CO oxidation.

The efficiency of PtSn alloy surfaces toward CO oxidation is demonstrated from first-principles theory. Oxidation kinetics based on atomistic density-functional theory calculations shows that the Pt3Sn surface alloy exhibits a promising catalytic activity for fuel cells. At room temperature, the corresponding rate outstrips the activity of Pt(111) by several orders of magnitude.