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Abstract: Alloys of platinum and gadolinium present significant activity enhancement over pure Pt for the oxygen reduction reaction (ORR), both in the form of extended electrode surfaces and nanoparticulate catalysts. The active phase consists of a compressed Pt overlayer formed on Pt5Gd electrodes upon exposure to the electrolyte by acid leaching. Here, we investigate the formation, strain and correlation lengths of the active Pt overlayer by using in situ synchrotron grazing incidence X‐ray diffraction on Gd/Pt(111) single‐crystalline electrodes. The overlayer forms upon exposure to electrolyte under open circuit conditions; the compressive strain relaxes slightly upon repeated electrochemical cycling in the potential range 0.6 to 1.0 V versus the reversible hydrogen electrode (RHE). In addition, the strain relaxes strongly when exposing the electrode to 1.2 V versus RHE, and the thickness of the crystalline portion of the overlayer increases with potential above 1.3 V versus RHE. [ABSTRACT FROM AUTHOR]

Abstract: The relationship between the binding of the reaction intermediates and oxygen reduction activity in alkaline media was experimentally explored. By introducing Cu into the 2nd surface layer of a Pt(111) single crystal, the surface reactivity was tuned. In both 0.1  m NaOH and 0.1  m KOH, the optimal catalyst should exhibit OH binding circa 0.1 eV weaker than Pt(111), via a Sabatier volcano; this observation suggests that the reaction is mediated via the same surface bound intermediates as in acid, in contrast to previous reports. In 0.1  m KOH, the alloy catalyst at the peak of the volcano exhibits a maximum activity of 101±8 mA cm−2 at 0.9 V vs. a reversible hydrogen electrode (RHE). This activity constitutes a circa 60‐fold increase over Pt(111) in 0.1  m HClO4. [ABSTRACT FROM AUTHOR]

Platinum-lanthanide alloys are very promising as active and stable catalysts for the oxygen reduction reaction (ORR) in low-temperature fuel cells. We have fabricated Pt and Pt 5 Gd metallic thin films via (co-)sputtering deposition in an ultra-high vacuum (UHV) chamber. The electrochemical ORR activity, stability, as-well as chemical composition and crystallographic structure of Pt 5 Gd thin film catalysts have been investigated using a combination of electrochemical measurements, X-ray photoemission spectroscopy (XPS) and X-ray diffraction (XRD) techniques. We describe the measurement procedures, with the aim of benchmarking electrochemical characterization of Pt-based thin film catalysts for ORR. Pt 5 Gd thin films present an activity enhancement by a factor of 4.5 and 2.5 over polycrystalline Pt and Pt thin films, respectively. [ABSTRACT FROM AUTHOR]

Pt x Y and Pt x Gd exhibit exceptionally high activity for oxygen reduction, both in the polycrystalline form and the nanoparticulate form. In order to understand the origin of the enhanced activity of these alloys, we have investigated thin films of these alloys on bulk Pt(111) crystals, i.e. Y/Pt(111) and Gd/Pt(111). These surfaces exhibit a 4-fold improvement over Pt(111). We observe the formation of a thick Pt overlayer after the electrochemical measurements, both on Y/Pt(111) and Gd/Pt(111). Using surface sensitive X-ray diffraction we revealed that crystalline closely packed Pt overlayers were formed. The diffraction experiments showed that the strain and crystallinity of the overlayers are strongly dependent on the electrochemical treatment, and in general show lateral compression. [ABSTRACT FROM AUTHOR]

Alloys of platinum and lanthanides present a remarkable activity for the oxygen reduction reaction—both in the form of extended surfaces and nanoparticulate catalysts. Co-sputter-deposited thin film catalysts based on platinum and gadolinium show great oxygen reduction activity improvement over pure Pt. The sputter-deposition technique represents a viable and versatile approach for investigating model catalyst systems with different compositions. In this work, co-sputtered Pt5Gd and Pt7.5Gd thin films were investigated using X-ray absorption spectroscopy as well as standardized electrochemical techniques. These investigations revealed the importance of forming alloys with specific stoichiometry, supporting the need of forming compressively strained Pt overlayers in order to achieve optimum catalytic performances. [ABSTRACT FROM AUTHOR]