Sébastien Garbarino

3D RuO₂ Microsupercapacitors with Remarkable Areal Energy.

Large areal capacitance electrodes made of ruthenium oxide on highly porous gold current collectors are realized by an attractive approach. The hybrid structure exhibits a capacitance in excess of 3 F cm(-2) and an areal energy density for all-solid-state microsupercapacitors that is comparable to those of microbatteries.

Electrodeposition of Arrays of Ru, Pt, and PtRu Alloy 1D Metallic Nanostructures

Arrays of Ru, Pt, and PtRu one dimensional 1D nanowires NWs and nanotubes NTs were prepared by electrodeposition through the porous structure of an anodic aluminum oxide AAO membrane. In each case, micrometer-long NW and NT were formed with an outer diameter of ca. 200 nm, close to the interior diameter of the porous AAO membrane. Arrays of NW and NT can be formed by varying the metallic salt concentration, the applied potential, and the conductivity of the electrolyte. The Ru and Pt deposition rates were measured in the various deposition conditions, using an electrochemical quartz crystal microbalance. The mechanisms responsible for the formation of Ru and Pt NW and NT are discussed based on the observed deposition rates and models found in the literature. Finally, it is shown that arrays of PtRu alloy NT and NW can be readily prepared and their compositions can be varied over the whole compositional range by changing the metallic salt concentration of the electrodeposition bath.

Oxygen Reduction Kinetics on Pt x Ni100 − x Thin Films Prepared by Pulsed Laser Deposition

Mixed Pt–Ni thin films were prepared by crossed beam pulsed laser deposition. The depositions were performed at high kinetic energy conditions in the presence of 0.1 Torr He. X-ray diffraction patterns and X-ray reflectometry measurements showed that all films are made of a single face-centered cubic phase compound whose lattice parameter and density vary linearly with the bulk Pt composition. Likewise, X-ray photoelectron spectroscopy revealed that the Pt surface composition of PtxNi100�x thin films closely follows the bulk Pt concentration. The electrochemical active surface area EASA was evaluated by estimating QHupd ,t he hydrogen desorption charge in the potential region of ca. 0.05–0.35 V where UPD stands for underpotential deposited. QHupd is almost constant for PtxNi100�x with x 60 but increases steadily for lower values of x. This is thought to reflect the fact that dissolution of Ni atoms occurs, leading to an increase in the EASA and Pt enrichment at the surface of the films, as determined by XPS measurements. A positive potential shift 60 mV of the half-wave current potential for oxygen reduction is observed as the Pt content is reduced from x = 100 to x = 27. This effect is mostly related to an increase in the EASA as the intrinsic ORR activity of PtxNi100�x thin films, as determined from normalized kinetic current density values, is constant and does not vary with the bulk Pt content of the film.

Synthesis and characterization of well aligned Ru nanowires and nanotubes

Arrays of well aligned Ru nanowires and nanotubes were prepared by electrodeposition through porous anodic aluminum oxide membranes. It is shown that Ru nanowires are formed at low cathodic deposition overpotential, while nanotubes are prepared at higher cathodic overpotential. The inner diameter of the nanotube can be controlled by the deposition potential, and it varies from 0 to 70% of the outer diameter as the deposition potential is changed from -0.30 to -0.45 V vs SCE.

Potentialities of micro-supercapacitors as energy storage buffers in embedded micro-systems

Thanks to their unique properties and potential applications in various smart electronic devices, micro-supercapacitors have been increasingly investigated for on-chip energy storage. In this presentation, we describe our most recent attempts to increase the areal capacitance and energy of micro-supercapacitors. We deposited hydrated ruthenium oxide onto a highly porous gold current collector to realize a 3D electrode with unprecedented performances, fully compatible with current micro-fabrication and silicon-based device technology. The resulting electrode exhibits a capacitance per surface area in excess of 3 F.cm-2, and - for the first time - an all-solid-state micro-supercapacitor with a specific energy per surface area comparable to that of lithium-ion micro-batteries has been achieved, but with superior power and cycling stability.