ETA-Florence Renewable Energies

In the framework of a private research program the development of a compact proton exchange membrane (PEM) electrolyzer system with a capacity of 300 Nl/h was developed. In this paper, the electrochemical properties of electrolyzer stack (10 cells of 100 cm2 geometrical area) were investigated at different temperatures. Overall stack efficiencies of 73% and 85%, at 60 A and 70 °C, with respect to the low and high heating value of hydrogen, respectively, were obtained. These results confirmed the successful scale-up of a previous lab-scale device.

In this paper we report on the application of statistical information obtained from 2D micrographs of catalyst layers (CL) of proton exchange membrane fuel cell (PEMFC), to derive stochastic replicas of their 3D pore networks at two scales. The main focus is on assessing the scaling strategy to determine effective transport coefficients and the analysis of the experimental results. The continuity equation for charge transport is solved directly on the 3D reconstructed CL to determine effective electrical conductivities at "internal-scale" and to simulate the electrical global performance at "macro-scale". The electrical performance is experimentally determined. The applied image processing method makes use of two immediate scales to improve the image resolution. Pore size distribution of the reconstructed scales is used to avoid the superposition of equal pore sizes. The relative porosities were determined by the statistical analysis of SEM micrographs and verified by mercury intrusion porosimetry.

The structural and morphologic properties of different carbonaceous materials were studied by X-ray diffraction (XRD), Brunauer–Emmet–Teller (BET) porosimetry and transmission electron microscopy (TEM) analyses. The electrochemical behaviour of these powders used as counter electrode in dye-sensitized solar cells (DSSCs) was investigated by polarization experiments and electron impedance spectroscopy. Results were compared with DSSC using Pt as counter electrode. All DSSCs based on the carbonaceous materials showed conversion efficiencies higher than those equipped with Pt. Among the various carbon materials investigated, Acetylene Black in conjunction with graphite showed the best performance. This was interpreted from the physico-chemical analysis as due to a compromise between pores accessibility for the I3− reactant presents in electrolyte and appropriate surface graphiticity index of this carbonaceous material. A high degree of graphitization for the carbon black was found to enhance electron conduction and charge transfer properties.