Stéphane Cuynet

One-step synthesis and chemical characterization of Pt-C nanowire composites by plasma sputtering.

Plasma increases activity: A one-step synthesis of Pt-C nanowire composites using a plasma co-deposition method is reported. Electrodes with a very low Pt loading can be obtained. Pt particles with sizes ranging from 1 to 2 nm are decorating the columnar carbon nanostructures because of strong interactions. The composite microstructure is responsible for a very high metal utilization rate as exemplified by reactions occurring in fuel cell electrodes.

PdPt catalyst synthesized using a gas aggregation source and magnetron sputtering for fuel cell electrodes

, +33 (0)2 3849 4352 KEYWORDS. gas aggregation source, magnetron sputtering, platinum, nanoclusters, catalyst. Abstract. PdPt catalysts with different morphologies and atomic ratios have been synthesized on native SiO2/Si and on proton exchange membrane. The combination of the gas-aggregation source and of the magnetron sputtering techniques allows the formation of quasi core-shell Pd0.97Pt0.03@Pt nanoclusters. Transmission electron microscopy and grazing incidence wide angle X-ray scattering measurements on Pd-rich core reveal a mean diameter of 4 nm and a fcc structure. The Pt shell around the half of the Pd-rich core is formed by magnetron sputtering which leads to the increase of nanocluster diameter (up to 10 nm) and of the overall Pt content (up to 85%). The membranes coated by PdPt core catalyst and PdPt@Pt catalyst (resulting in the formation of catalyst coated membrane) are incorporated into fuel cells and their electrical characteristics are measured. The association of the two deposition techniques resulting in the formation of quasi core-shell PdPt@Pt nanoclusters improves the startup step of the fuel cell.

An efficient way to evidence and to measure the metal ions fraction in high power impulse magnetron sputtering (HiPIMS) post- discharge with Pt, Au, Pd and mixed targets

The proportion of metal ions in a High Power Impulse Magnetron Sputtering discharge is a key information for the potential development of new materials and new layer architectures deposited by this technique. This paper aims to measure this proportion by using a homemade system consisting of a quartz crystal microbalance and a grid energy analyzer assembly. Such a system yields relevant results on the composition of the post-discharge depending on the nature of the gas (Ar, Kr, Xe) and the target materials (Pt, Pd, Au, Pt50Au50 and Pt5Pd95). In our conditions, the highest proportions of metal ions in the post-discharge are obtained by using Ar gas and reaches 10 %, 12 %, 50 %, 19 % and 88 % for respective Pt, Au, Pd, Pt50Au50 and Pt5Pd95 target, respectively.

Influence of the High-Power Impulse Magnetron Sputtering Voltage on the Time-Resolved Platinum Ions Energy Distributions

High-power impulse magnetron sputtering (HiPIMS) is a common way to create a high- and dense-ionized metallic vapor without the use of an alternative ionizing device, like radio frequency loops. HiPIMS has been used to perform the deposition of platinum thin films to control their morphology. This feature, known to depend on the energy of the Pt species incoming onto the substrate during the deposition, has to be carefully studied. Therefore, it is necessary to study the ions energy distribution during the sputtering pulse and to follow its evolution with the HiPIMS regime. Pictures of this evolution are presented.