Structural and Electrochemical Characterization of Metastable PtAu Bulk and Surface Alloys Prepared by Crossed-Beam Pulsed Laser Deposition

Abstract

Crossed-beam pulsed laser deposition in a moderate He background gas pressure was used to prepare PtAu thin films. The Pt bulk content was determined by neutron activation analysis, whereas X-ray diffraction and X-ray photoelectron spectroscopy were used to assess the bulk and the surface structure of the films, respectively. It is shown that metastable PtAu alloys with a unique fcc structure are formed over the whole composition range. The surface composition of the films closely follows the bulk content, and X-ray photoelectron spectroscopy reveals that the surface of the films is also made of a PtAu alloy. These films are stable under ambient conditions. The electrochemical properties of these films were determined by cyclic voltammetry in H 2 SO 4 electrolyte, and their reactivity toward the electrooxidation of CO and the electroreduction of O 2 was assessed. The CO stripping peak potential value increases with the Au content, indicating an increased binding energy in comparison with polycrystalline Pt. Similarly, there is a cathodic shift of the Pt oxide reduction peak for the Au-rich alloy that indicates stronger Pt-O binding energies as compared with Pt-rich alloy electrodes. At the surface, the presence of Au in close proximity to Pt atoms induces a shift of the d-band center of the Pt atoms that translates into stronger bonds with CO-and O-containing species at the surface of the samples. As far as we can tell, the surface composition and structure of the deposits are not modified following the electrochemical measurements.

The Beneficial Role of the Cometals Pd and Au in the Carbon-Supported PtPdAu Catalyst Toward Promoting Ethanol Oxidation Kinetics in Alkaline Fuel Cells: Temperature Effect and Reaction Mechanism

“…Seemingly, the gold catalyst exhibited the lowest 2θ value, being significantly different from that of the other catalysts. 19 The lattice parameters of these catalysts were obtained from the XRD patterns displayed in Table 1. It was found that the addition of Pd and Au to the Pt matrix barely makes any effect on the crystalline structure of Pt/ C because Pt, Pd, and Au have almost the same fcc crystalline Low-resolution TEM images of Pt 30 Pd 38 Au 32 /C catalysts and the corresponding particle size distribution histograms are shown in Figure 2a,b, respectively, and the data from TEM analysis are listed in Table 1.…”

Highly Active PtAu Nanowire Networks for Formic Acid Oxidation

“…For Pt 1 Au 1 NWNs, the binding energies of Pt 4f 7/2 and 4f 5/2 peaks were almost invariable compared with that for monometallic Pt. [11] The atomic ratios of Pt/Au on surface calculated from the XPS spectra are 0.98:1, 1:3.07, and 1:6.11 for Pt 1 Au 1 , Pt 1 Au 3 , and Pt 1 Au 6 NWNs, respectively. [11] The atomic ratios of Pt/Au on surface calculated from the XPS spectra are 0.98:1, 1:3.07, and 1:6.11 for Pt 1 Au 1 , Pt 1 Au 3 , and Pt 1 Au 6 NWNs, respectively.…”

“…[11] The atomic ratios of Pt/Au on surface calculated from the XPS spectra are 0.98:1, 1:3.07, and 1:6.11 for Pt 1 Au 1 , Pt 1 Au 3 , and Pt 1 Au 6 NWNs, respectively. [11] It can be seen that a larger Au fraction in the feeding solution will result in a higher Au content on the surface of the PtAu NWNs. The atomic ratios of Pt/Au were also estimated on the basis of ICP analysis to be 1.01:1, 1:3.09 ,and 5.85:1 for Pt 1 Au 1 , Pt 1 Au 3 , and Pt 1 Au 6 NWNs, respectively, and these values are very close to the XPS analysis.…”

Characterization of Metallic Nanoparticles Based on the Abundant Usages of X-ray Techniques

“…This strongly indicates the formation of an alloy structure. To more fully support the conclusion of alloy formation, the fcc lattice parameter was plotted versus the platinum feeding ratio ([Pt] feeding ) and shows a nearly linear relationship which follows Vegard's law for binary metallic alloys [17]. It also suggests that the platinum content in alloy nanoparticles is indeed close to the platinum feeding content which shows the tuning ability of the Pt/Au alloy composition using this method.…”