Serena Gagliardi

Nanomaterials-Based PEM Electrodes by Combining Chemical and Physical Depositions

The real market penetration of polymer electrolyte fuel cells is hindered by the high cost of this technology mainly due to the expensive platinum catalyst. Two approaches are followed to reduce the cost: one way is to increase the Pt utilization efficiency reducing at the same time the total load and the other way is to increase the catalytic activity of the catalyst/support assembly. In this work, the increase of utilization efficiency is addressed by optimizing the catalyst distribution on the uppermost layer of the electrode via electrodeposition and sputter deposition, while the improvement of the catalyst activity is pursued by nanostructuring the catalysts and the carbon-based supports. A very low Pt loading 0.006 mg cm 2 was obtained by sputter deposition on electrodes that exhibited a mass specific activity for methanol oxidation reaction better than a commercial product. Carbon nanofibers used as catalyst support of electrodeposited platinum nanoparticles resulted in improved mass specific activity and long term stability compared to conventional carbon-based supports. Finally, PtAu alloys developed by sputter deposition were found more efficient than commercial PtRu catalyst for the methanol oxidation reaction. In conclusion, polymer electrolyte membrane fuel cell electrode based on nanomaterials, developed by combining physical and chemical deposition processes, showed outstanding electrochemical performance. DOI: 10.1115/1.4003629

Laser-Assisted Fabrication of Biomolecular Sensing Microarrays

With the aim of obtaining high density biosensing arrays we use pulsed laser deposition to immobilize functional biomolecules on useful surfaces, and micro- and nanopatterning techniques for fabrication of prototype immunosensing bioarrays. We report biological activity tests demonstrating the functional properties of the immobilized proteins and atomic force microscopy characterization of films of nanometric dimensions. Laser-fabricated immunofluorescent arrays are analyzed to check that the intensity and contrast of the sensing sites allow efficient device fabrication. We have also developed an elementary array of heterogeneous reaction sites and tested its performance by simultaneous incubation with the different specific antigens.

Experimental determination of the light-trapping-induced absorption enhancement factor in DSSC photoanodes

Summary For dye-sensitized solar cells (DSSC), the fundamental process that determines the maximum short-circuit current is the absorption of light. In such devices, this is produced by the concurrent phenomena of light absorption by dye molecules and light trapping in the mesoporous, titania photoanode structure. The decoupling of these two phenomena is important for device characterization and the design of novel photoelectrode geometries with increased optical performance. In this paper, this task is addressed by introducing a spectral absorption enhancement factor as a parameter to quantify the light trapping effect. The experimental value of this parameter was obtained by comparing the experimentally determined fraction of absorbed light by a dye-sensitized photoanode with the light absorbed by the dye without the mesoporous titania structure. In order to gain more insight from this result, the fraction of light absorbed in the photoanode (on the basis of the dye loading capacity of the titania nanospheres) was also calculated by an optical model for the two extreme cases of the absence of light trapping and maximum light trapping. Accordingly, the photocurrent was calculated under the assumption of solar irradiation, which defined two useful boundaries. Using the experimentally derived values of the spectral absorption enhancement factor in the photoanode optical model, the DSSC short-circuit current can be calculated with good agreement with the value measured in practical devices based on the same photoanode structures. Therefore, our approach provides a realistic description of a practical device and can be exploited as an useful tool to assess the optical functionality of novel photoanode structures.

Laser techniques for the fabrication of nanobiodevices

Laser ablation and ionization is investigated as a technique suitable to the fabrication of nanowire interconnects and of biological and organic molecule monolayer immbilization. The technique can be exploited both as an unconventional source of material in conventional top-down lithographic approaches and in bottom up approaches based on the use of scanning probe instruments. Recent results demonstrating maintenance of integrity of thin layers of immobilized aromatic molecules and functionality of nanopatterned biomolecular monolayers are shown. Also, ultrathin and uniform metallic layers suitable for the fabrication of nanowire interconnects are obtained. Finally, first results on the bottom up fabrication of nanoscopic metallic features are shown.

Nanofabrication Tools and Techniques for Bio-inorganic Interfaces

This paper describes some progresses in the development of technical and biomimetic machineries for nanobiofabrication. Together with nanotechnological methods, both ready made natural nanostructures and the assembling properties of proteins and nucleic acids are exploited to obtain mesoscale structural scaffolds, stencils, position-specific addressable architectures, and eventually nanoscale devices.

Pt Alloys on Carbon Nanostructures as Electrocatalysts for Direct Methanol Fuel Cell

Extensive efforts are focused on the development of Direct Methanol Fuel Cells, due to the intrinsic advantages of this type of devices for mobile power supply system. One of the major drawback of the DMFC resides in the easy poisoning of the anode electrocatalyst (platinum) by COlike reaction intermediates, which implies the need of high platinum load in order to obtain reasonable performances. The development of platinum alloys is considered one of the promising routes for overcoming this problem: the second metal in fact acts as inhibitor of the Pt poisoning. In this work we have combined the use of unconventional methods to deposit the electrocatalyst nanoparticles with unconventional carbon supports. PtAu alloys have been deposited by sputter deposition process on carbon nanofibers with platelet morphology grown by plasma enhanced chemical vapour deposition on carbon paper. Cyclic voltammetry in H2SO4 was used to determine the electrochemical active surface and the electrocatalytic performance for methanol oxidation reaction. Even at lower Pt load, respect to the ones prepared with commercial catalysts supported on carbon black, the innovative electrodes showed higher performance and stability.