Rather than the commonly and so far used 40 m thick CF-MPL, a thinner CF-MPL film of about 15 m was used, as shown in TableI. Epub 2013 Jan 18. Volume 165, The voltage of the hydrophilic CF-MPL is higher than that of the hydrophobic CB-MPL under high current density conditions.

Even if a molecule has polar covalent bonds, if these bonds are arranged symmetrically, To find out more, see our, Browse more than 100 science journal titles, Read the very best research published in IOP journals, Read open access proceedings from science conferences worldwide. The freezing method consisted of the following steps: first, after achieving constant current density operation at 0.7 A/cm2, the cell was shut down and immediately cooled at 40C in the thermostatic chamber to immobilize the water where it is at the instant of the shutdown. Additionally, large ice accumulations were formed at the port of the MPL/CL interface (not shown in Fig. The fiber orientations are expressed only in the thickness direction for ease of description. There are two things to consider when trying to decide. Applying thermodynamic profiling in lead finding and optimization. mesoporous nanoparticles carbon carriers sustained cancer release drugs hydrophobic hydrophilic anti rsc The interface between the cathode side MPL and the CL was fabricated by the gas diffusion electrode (GDE) method. 9b, and pores not filled with ice remained in some regions (not shown here).

membranes chapter figure The oxygen gains of the thinner MPL are also higher, supporting the above suggestion: the tolerance to flooding by the thinner hydrophilic CF-MPL is insufficient even with the larger pore size of the MPL provided by the fiber structure. Figure 7 shows the cryo-SEM images inside the hydrophobic CF-MPL at the cathode side after operating the cell at 0.7 A/cm2 for 1 hour. In the later discussion a thinner hydrophilic MPL with the ionomer, shown in brackets in TableI, will be introduced to consider the water transport phenomenon in the hydrophilic CF. 4, 5b, 8, and 9, is illustrated in schematic cross-sectional diagrams in Fig. Epub 2015 Jan 23. J Pharm Sci. The widths of each of the channels and lands were 1.0mm, and the channel depth was 0.5mm. As the current density increases, the rate of water production becomes higher, and the water film spreads to the GDL side to increase the surface area with a concomitant higher evaporation rate of the total water present in the MPL, as shown in Fig. There may be paths, which it was impossible to identify, but which transport oxygen remaining inside the MPL, and a possible scheme for the water transport will be discussed below. ACS Med Chem Lett.

BibTeX official website and that any information you provide is encrypted This is an open access article distributed under the terms of the Creative Commons Attribution 4.0 License (CC BY, http://creativecommons.org/licenses/by/4.0/), which permits unrestricted reuse of the work in any medium, provided the original work is properly cited. 8a. The possible water transport in the hydrophilic CF-MPL, suggested by the experimental results of Figs. 2014 Jul 15;24(14):3164-7. doi: 10.1016/j.bmcl.2014.04.114.

A schematic view of the relationship between the wettability and the pore diameter of these MPLs is shown in Fig. The MPL structure with the large pores and sufficient thickness provides a superior environment to evaporate the water in the MPL, and this results in the better anti-flooding performance at high current densities, as shown in the comparison of the cell performances (Figs.

Protein-Ligand Interactions: Thermodynamic Effects Associated with Increasing the Length of an Alkyl Chain. The constant current density operation was carried out at 0.7 A/cm2 for 1 hour. lipid hydrophilic hydrophobic translocation nanotubes transporting hydrophobic reacting Raman spectroscopy revealed that both particles had a graphitic and disordered structure; however, IR spectroscopy clearly showed that the hydroxy group is the origin of the hydrophilicity. Consequently, estimates of the contribution of different functional groups to the hydrophobic effect providing the free energy of folding of a molecule of protein or providing the free energy of dissociation for the association of two proteins or the association of a ligand with a protein should be made by counting the number of hydrogen-carbon bonds excluded from water rather than computing the accessible surface areas excluded from water. 1998 Aug;87(8):998-1014. doi: 10.1021/js9702980. ionic hydrophobic liquids wiley hydrophilic dioxide Figure 6 shows cryo-SEM images inside (a) the hydrophobic CB-MPL and (b) the hydrophilic CB-MPL at the cathode side before and after operating the cell at 0.7 A/cm2 for 1 hour. Figure 4. 9c) is similar to that at the lower current density (Fig. Polymer electrolyte membrane fuel cells using a hydrophilic micro-porous layer (MPL) consisting of carbon fiber (CF) and ionomer show better performance than those using conventional hydrophobic MPL with carbon black (CB) under a wide range of humidity conditions. Figure 5b shows the oxygen gains of the hydrophobic CB-MPL, the hydrophilic CB-MPL, the hydrophobic CF-MPL, and the hydrophilic CF-MPL. To evaluate the water transport inside the MPL and its effect on the cell performance, the water distribution in the cells was observed by the freezing method and cryo-SEM. This is considered to be because the thickness of the thinner hydrophilic CF-MPL is inadequate to evaporate all of the water, and the result is the growth of the water film on the CF and blockage of the oxygen supply through the MPL. quizlet hydrophobic hydrophilic Please enable it to take advantage of the complete set of features! Hankin JA, Murphy RC, Barkley RM, Gijn MA. investigated water transport in the MPL by measuring the performance of cells with various types of MPL, and suggested that the primary role of the MPL is preventing condensed water from accumulating near the cathode CL surface.5. Biochemistry. Accessibility abundance hydrophobic hydrophilic soluble sources korea carbon organic urban summer water site rsc The GDL (Improved H2315, hydrophobic treated GDL without an MPL, Freudenberg-NOK) was used for all types of the MPLs. The results for the thicker hydrophilic CF-MPL are the same as those in Figs. 7a and 7c correspond to the MPL/CL interface. The hydrophilic CF-MPL is thicker and the inner structure is clearly different from the MPL with CB, and the pore sizes provided by the CF are much larger than those of the CB. In hydrophilic CF-MPL with better performance, liquid water accumulates in pores at the catalyst layer (CL) side, while there is no liquid water at the gas diffusion layer side. This would indicate that the treatment to make the porous layer hydrophilic by adding hydrophilic ionomer has the potential to improve the cell performance under flooded conditions, but that an appropriate structure such as large pore diameters like those formed with the CF is critical to preventing an increase in the concentration overvoltage which arises even in low current density conditions. 5 This was Paper 1428 presented at the Phoenix, Arizona, Meeting of the Society, October 1115, 2015. The cryo-SEM observations were conducted at the Electron Microscope Laboratory, Research Faculty of Agriculture, Hokkaido University. Figure 5. 8c). The novel hydrophilic MPL developed by Tanuma et al.,14,15 here termed 'hydrophilic CF', is composed of carbon fiber (CF: VGCF-H, Showa Denko K. K.) and hydrophilic ionomer. and Pasaogullari et al.

lipids membranes membrane hydrophobic biology cholesterol lipid amphipathic hydrophilic region nature biological chapter regions which water middlebury frap cr edu Myslinski JM, Clements JH, Delorbe JE, Martin SF. Figure 2. In a separate experiment, the authors have confirmed that the water moves little during the cooling process.17 It was also confirmed that ice is not generated during freezing when there is no condensed water before cooling, even if the MEA is hydrated. Cryo-SEM images of cross-sections of the hydrophilic CF-MPL with better performance for (a) the whole thickness, (b) the GDL side, and (c) the CL side after operating the cell at 0.7 A/cm2 for 1 hour. hydrophilic impregnated nanotubes Cramer DL, Cheng B, Tian J, Clements JH, Wypych RM, Martin SF. The freezing method and the cryo-SEM observations show that ice distribution inside the hydrophilic CF-MPL is uneven in the through-plane direction of the MPL after the 70C operation at the current density of 0.7 A/cm. The cell resistance was measured by an alternating impedance meter at 1kHz (TSURUGA, model 3566), and the cell voltage, resistance, and temperatures (cell, supply gases, and bubbler) were recorded. hydrophobic hydrophilic molecules alcohol molecule end nonpolar chain polar therefore carbon solutions The areas of the MPL images are near the catalyst layer (CL) interfaces. Cryo-SEM images of cross-sections of the hydrophobic CF-MPL for (a) the whole thickness, (b) for the GDL side, and (c) for the CL side after operating the cell at 0.7 A/cm2 for 1 hour. The site is secure. The appearance of the hydrophobic CF-MPL (not shown here) was similar to the hydrophilic CF-MPL as well as to the two types of the MPLs with CB, and the effects of wettability on the MPL structure appear to be negligible in the experiments in this study. Figure 8. 7a and 7b correspond to the MPL/GDL interface, and the bottom of Figs. The property of a molecule that most reliably determines the magnitude of the hydrophobic effect that it will experience is the number of hydrogen-carbon bonds it contains not the accessible surface area of its nonpolar portions. bilayer cell phospholipid structure membrane water membranes lipid octanol why hydrophobic hydrophilic nonpolar polar head tail immiscible phospholipids cytosol way The pressure independent resistance can be assumed to correspond approximately to the oxygen transport resistance in the CL, the Knudsen diffusion resistance in the pores of the CL, and the transport resistance from the gas in the pores to the Pt surface through the ionomer, and this allows the oxygen transport resistance in the CL to be evaluated quantitatively. This ice distribution was observed at all of the observation points, while the interface between the ice and the pores varied somewhat in location. The structure of the hydrophilic CB-MPL is similar to that of the conventional hydrophobic CB-MPL shown in Ref.

When the standard free energies of transfer for hydrocarbons in these different classes are plotted as a function of the number of hydrogen-carbon bonds they contain, all of the data fall upon the same line. The results show that the performance improvement is caused by preventing increases in concentration overvoltage at high current densities; where the fiber structure and thicker layers are important with hydrophilic MPL. Figure 9 shows images of the hydrophilic CF-MPL after operation at 1.4 A/cm2 for 1 hour. Contribution to the thermodynamics of protein folding from the reduction in water-accessible nonpolar surface area. 7b and 7c are the magnified images of the MPL at the GDL and the CL sides. (3352K), Ring-Structured DNA and RNA as Key Players, Metal-Organic Frameworks: From Ambient Green Synthesis to Applications, Molecular Confinement Effects by Self-Assembled Coordination Cages, A Friendly UV-Responsive Fluorine-Free Superhydrophobic Coating for Oil-Water Separation and Dye Degradation, Chemical Insights into Liquid-Liquid Phase Separation in Molecular Biology, Nanoarchitectonics: A New Materials Horizon for Prussian Blue and Its Analogues, Product Selectivity Affected by Cationic Species in Electrochemical Reduction of CO, Two-Dimensional Metal Oxide Nanosheets as Building Blocks for Artificial Photosynthetic Assemblies, Recent Improvements in the Production of Solar Fuels: From CO, Femtosecond Laser Filamentation in Gaseous Ethylene: Formation of Hydrogenated Amorphous Carbon, Novel Method of Producing Carbon Nanoparticles on Benzene/Water Interface with Femtosecond Laser Plasma Filament, Formation of 10 nm-sized Oxo(phtalocyaninato)vanadium(IV) Particles by Femtosecond Laser Ablation in Water, Photocoloration of Spironaphthoxazine Microcrystalline Powder by Femtosecond Laser Pulse Excitation, One-Photon Ionization of Liquid Water upon 193 nm Laser Irradiation, Synthesis of Hydrophilic and Hydrophobic Carbon Nanoparticles from Benzene/Water Bilayer Solution with Femtosecond Laser Generated Plasma Filaments in Water. developed a novel exclusively hydrophilic MPL composed of carbon fibers and hydrophilic ionomer, and reported that cells using this hydrophilic MPL showed better performance than those using hydrophobic MPL under a wide range of humidity conditions.14,15 However, the mechanism of how the whole hydrophilic MPL contributes to the improvement of the cell performance is not fully understood. Epub 2014 May 9. At the GDL side, there are parts where the pores were filled with large amounts of ice as shown in Fig. In Fig. The diluted aqueous benzene solution gave hydrophilic particles; however, the density of particles was much smaller than that formed in B/W bilayer solution. Large amounts of ice are apparent in the pores, and the ice distributes uniformly inside the MPL from the CL to the GDL sides. A covalent bond is polar if one of the atoms in it has a significantly higher affinity for electrons (electronegativity) than the other. Int J Mass Spectrom. and Lu et al. One role of MPL is considered to be that the MPL removes water produced at the cathode CL and mitigates water flooding at high current density conditions.15 Weber et al. This research was supported by JSPS KAKENHI grant Number 261599. To further confirm the reasons for the different cell performances, the oxygen gains of the cells with the four types of cathode MPLs in Figs. The small single cell used in the investigations here (left) and the bipolar plate with straight channels (right). Some thermodynamic effects of varying nonpolar surfaces in protein-ligand interactions. Ion Mobility and Tandem Mass Spectrometry of Phosphatidylglycerol and Bis(monoacylglycerol)phosphate (BMP). Shortcomings of basing radical stabilization energies on bond dissociation energies of alkyl groups to hydrogen. Micro-porous layers (MPLs), typically consisting of carbon black and a hydrophobic polymer between the catalyst layer (CL) and the gas diffusion layer (GDL) are well known as important components in the water management of the PEFC. 2.

Figure 6. This study investigates the effects of the wettability and structure of the MPL on cell performance and discusses the mechanism for improving cell performance by the hydrophilic CF-MPL at high humidity conditions. applied another type of an additional layer, a hydrophilic MPL composed of carbon black, TiO2, and silicone, and reported that the cell performance can be improved under wet and dry conditions.13 These approaches investigate the incorporation of hydrophilic materials in hydrophobic MPL, and report the MPL wettability patterns in-plane911 and through-plane.12,13 Tanuma et al.

In the case of the hydrophilic CB-MPL after the operation in Fig.

8, cyro-SEM observations with a higher current density was also conducted. We concluded that the production of denser hydrophilic CNPs in B/W bilayer was achieved by limiting the concentration of benzene in water layer by B/W interface, and by continuously supplying benzene into water layer through B/W interface. Please login to view your saved searches. Recently, some studies have applied hydrophilic compounds to the MPL for further improvements in cell performance under wet and dry conditions.913 Schweiss et al. 4, 5 and 11). 2. The ice distribution at the CL side (Fig. We discuss the subsequent reaction mechanism leading to CNPs of different surface characters. government site. The ice distribution inside the hydrophilic CF-MPL is uneven in the through-plane direction of the MPL. Clipboard, Search History, and several other advanced features are temporarily unavailable. These images showing the CL structure and ice distribution were quite uniform for all of the MPLs. cell phospholipids membrane phospholipid biology physiology molecule lipid science lipids biochemistry glycerol polar composed microscope easy molecules exam bio unit Would you like email updates of new search results?

The fiber structure with the large pores may maintain the water as a film without the pores becoming completely filled, increase the surface area of the water film on the CF, and then the hydrophilic CF-MPL is able to promote evaporation of the water. is quite polar, they are arranged symmetrically around the central carbon atom, This is consistent with the results reported by Tanuma et al. (CCl4, see the structure). The differences in the changes of the images without the interface of the pores with ice and the pores without ice was not confirmed by all observations at various in-plane locations, indicating that the layers having pores with ice near the CL occupy the large part of the MPL. FOIA Polymer electrolyte membrane fuel cells (PEFCs) are expected to play a leading role as next generation power sources for automobiles, portable devices, and residential cogeneration systems (a so-called combined heat and power; CHP). Therefore, many computational and experimental studies have investigated the role of the MPL in the water management of such cells. This paper also discusses the water transport parameters improving the cell performance at high humidity conditions. Properties of hydrophobic free energy found by gas-liquid transfer.

To investigate factors that would be effective in improving the cell performance by the hydrophilic CF-MPL, cells using the hydrophilic CB-MPL and hydrophobic CF-MPL at the cathode side were also compared with a cell using the conventional hydrophobic CB-MPL.