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Details of experimental procedure Electrode preparationA Pt single crystal disk surfaced with a certain facet (hkl) (99.99%, 0.196 cm 2 , MaTecK) was annealed using electromagnetic inductive heating for 10 minutes at 1400 -1650 K in the flow of a mixture of H 2 and Ar (3 % H 2 , Taiyo Nippon Sanso, the purity of each gas: H 2 : 99.99999%, Ar: 99.999%). The annealed specimen was cooled slowly to room temperature in the flow of the same gas mixture and then, the (hkl) surface was covered with a droplet of ultrapure water (Milli-Q, 18.2 MΩ). The prepared Pt (hkl) surface was immersed into 10 µM HAuBr 4 . After 1 minute, it was moved to 0.1 M HClO 4 saturated with Ar while the electrode potential was preset at 0.07 V vs. the reversible hydrogen electrode (RHE) in the configuration of hanging meniscus rotating disk electrode (HM-RDE). The Au-modification treatment may be repeated until a desired amount of Au is deposited on the electrode surface. Electrochemical proceduresThe electrode potential was cycled between 0.07 -0.87 V at a scan rate of 50mV•s -1 until the cyclic

In this study the dielectric properties are reported for human skin tissues over the frequency range 1-450 MHz at 36 degrees C. Healthy volunteers, collagen disease patients and dialysis patients are studied in order to investigate, primarily, the variability among (1) different regions of one individual, (2) the same region among different individuals and (3) skin conditions due to diseases. Considerable differences exist among the skin dielectric properties obtained from different regions of one individual body. Although region dependence is observed, larger variability is found even in the same skin region among individuals.

The objective of this work is to clarify the location and magnitude of flooding in polymer electrolyte fuel cells with a conventional flow field experimentally and by a numerical calculation. In the experiment, a newly developed cell with a conventional, interdigitated-switchable gas-flow field was used and the pressure drop between the inlet and outlet of the cathode was measured with the interdigitated flow field after the cell was operated with the conventional flow field. Significant pressure drop was observed after high current densities were flown; the pressure drop indicates the flooding level in a gas diffusion layer ͑GDL͒ during the conventional flow field operation. The cell performance and the flooding behavior depended significantly on wetting properties of catalyst layers and GDLs. In the simulation, liquid water distribution in the cathode GDL was predicted using a two-phase model, and validated by comparing the pressure drop measured and calculated using a gas-flow model. The simulation results agreed well with experimental data at high humidity condition and showed that a large amount of liquid water exists in the cathode GDL at high current densities.Polymer electrolyte fuel cells ͑PEFCs͒ are considered a promising power source for stationary and automotive applications. For the automotive application, however, the performance needs to be improved, especially at high current densities. The concentration loss at high current densities is generally agreed to be mainly due to flooding in cell components: a catalyst layer ͑CL͒, a gas diffusion layer ͑GDL͒, or a flow channel. The phenomenon of flooding in PEFCs, however, has not been well understood because flooding in the cell is not easily observable.Some experimental studies on flooding of PEFCs have been conducted. Barbir et al. 1 investigated flooding of PEFCs by monitoring the pressure drop in the flow channel. Tuber et al. 2 and Yang et al. 3 studied flooding by a visualization technique with a transparent fuel cell. These studies addressed flooding in the flow channel.The flooding in the CL and the GDL, however, likely occurs prior to that in the flow channel because water is produced in the CL by the electrochemical reaction and is expelled from the CL through the GDL to the flow channel. Satija et al. 4 and Chuang and Mench 5 visualized flooding and calculated the liquid water content in the cell using a neutron imaging technique; it is difficult, however, to separate water in the anode from water in the cathode with this method. He et al. 6 proposed a novel diagnostic method to monitor electrode flooding by measuring the pressure drop across a cell with an interdigitated flow field. This simple method can provide direct information on the flooding level in the GDL during its operation. The interdigitated flow field design is, however, not widely used and, therefore, the flooding measurement for the cell with the widely used conventional flow field design has been needed.Modeling studies also have been conducted on flooding for PEFCs. He et...

Accelerated durability tests (ADTs) were carried out for a carbon-supported platinum catalyst using a rotating disk electrode at various rotation rates for various catalyst loadings. The electrochemical surface area (ECSA) of platinum, TEM-observed relative particle size distribution, and Pt ion concentration in the electrolyte were analyzed. Their results were combined to provide the absolute change in the particle size distribution. The loss of the normalized ECSA increased with increasing the rotation rate and/or decreasing the catalyst loading. The detailed analysis showed that the reciprocal of the normalized ECSA loss rate linearly increased with the increases in ω −1/2 (ω: angular frequency of rotation) and the catalyst loading; these results suggests that ECSA loss in ADTs is significantly affected by Pt ion diffusion in the electrolyte. By extrapolating these linear relations to zero, the ECSA loss rate at the hypothetical conditions, in which all the dissolved platinum ions would flow out to the electrolyte without re-deposition, was obtained.