Gas diffusion layer for proton exchange membrane fuel cells-A review

[[abstract]]Gas diffusion layer (GDL) is one of the critical components acting both as the functional as well as the support structure for membrane-electrode assembly in the proton exchange membrane fuel cell (PEMFC). The role of the GDL is very significant in the H-2/air PEM fuel cell to make it commercially viable. A bibliometric analysis of the publications on the GDLs since 1992 shows a total of 400+ publications (>140 papers in the journal of Power Sources alone) and reveals an exponential growth due to reasons that PEMFC promises a lot of potential as the future energy source for varied applications and hence its vital component GDL requires due innovative analysis and research. This paper is an attempt to pool together the published work on the GDLs and also to review the essential properties of the GDLs, the method of achieving each one of them, their characterization and the current status and future directions. The optimization of the functional properties of the GDLs is possible only by understanding the role of its key parameters such as structure. porosity, hydrophobicity, hydrophilicity, gas permeability, transport properties, water management and the surface morphology. This paper discusses them in detail to provide an insight into the structural parts that make the GDLs and also the processes that occur in the GDLs under service conditions and the characteristic properties. The required balance in the properties of the GDLs to facilitate the counter current flow of the gas and water is highlighted through its characteristics. (C) 2009 Elsevier B.V. All rights reserved

Gas diffusion layer for proton exchange membrane fuel cells-A review

[[abstract]]Gas diffusion layer (GDL) is one of the critical components acting both as the functional as well as the support structure for membrane-electrode assembly in the proton exchange membrane fuel cell (PEMFC). The role of the GDL is very significant in the H2/air PEM fuel cell to make it commercially viable. A bibliometric analysis of the publications on the GDLs since 1992 shows a total of 400+ publications (>140 papers in the Journal of Power Sources alone) and reveals an exponential growth due to reasons that PEMFC promises a lot of potential as the future energy source for varied applications and hence its vital component GDL requires due innovative analysis and research. This paper is an attempt to pool together the published work on the GDLs and also to review the essential properties of the GDLs, the method of achieving each one of them, their characterization and the current status and future directions. The optimization of the functional properties of the GDLs is possible only by understanding the role of its key parameters such as structure, porosity, hydrophobicity, hydrophilicity, gas permeability, transport properties, water management and the surface morphology. This paper discusses them in detail to provide an insight into the structural parts that make the GDLs and also the processes that occur in the GDLs under service conditions and the characteristic properties. The required balance in the properties of the GDLs to facilitate the counter current flow of the gas and water is highlighted through its characteristics. © 2009 Elsevier B.V. All rights reserved

Non-Platinum metal oxide nano particles and nano clusters as oxygen reduction catalysts in fuel cells.

An attempt has been made in this study to prepare the oxygen electrodes containing low-scale particles of copper, nickel, cobalt and iron oxides and evaluate their catalytic activity for the oxygen reduction. 1:1 stoichiometric oxides (Copper and Nickel) and higher stoichimetric oxides (Cobalt and Iron) have been synthesized and their catalytic properties have been analyzed by electrochemical methods. The conductivity of the fabricated electrodes showed steady values even with change in temperature from the ambient (30 ± 20 C) to 700 C

Pore-scale modeling of fluid flow through gas diffusion and catalyst layers for high temperature proton exchange membrane (HT-PEM) fuel cells

This work represents a step towards reliable algorithms for reconstructing the micromorphology of electrode materials of high temperature proton exchange membrane fuel cells and for performing pore-scale simulations of fluid flow (including rarefaction effects). In particular, we developed a deterministic model for a woven gas diffusion layer (GDL) and a stochastic model for the catalyst layer (CL) based on clusterization of carbon particles. We verified that both of the models developed accurately recover the experimental values of the permeability, without any special ad hoc tuning. Moreover, we investigated the effect of catalyst particle distributions inside the CL on the degree of clusterization and on the microscopic fluid flow, which is relevant for the modeling of degradation (e.g. loss of phosphoric acid). The three-dimensional pore-scale simulations of the fluid flow for the direct numerical calculation of the permeability were performed by the lattice Boltzmann method (LBM

Gas diffusion layer for proton exchange membrane fuel cells—A review

[[abstract]]Gas diffusion layer (GDL) is one of the critical components acting both as the functional as well as the support structure formembrane–electrode assembly in the proton exchangemembrane fuel cell (PEMFC). The role of the GDL is very significant in the H2/air PEM fuel cell to make it commercially viable. A bibliometric analysis of the publications on the GDLs since 1992 shows a total of 400+ publications (>140 papers in the Journal of Power Sources alone) and reveals an exponential growth due to reasons that PEMFC promises a lot of potential as the future energy source for varied applications and hence its vital component GDL requires due innovative analysis and research. This paper is an attempt to pool together the published work on the GDLs and also to review the essential properties of the GDLs, the method of achieving each one of them, their characterization and the current status and future directions. The optimization of the functional properties of the GDLs is possible only by understanding the role of its key parameters such as structure, porosity, hydrophobicity, hydrophilicity, gas permeability, transport properties,water management and the surface morphology. This paper discusses them in detail to provide an insight into the structural parts that make the GDLs and also the processes that occur in the GDLs under service conditions and the characteristic properties. The required balance in the properties of the GDLs to facilitate the counter current flow of the gas and water is highlighted through its characteristics

Ion-exchanged and salt hydrates-encapsulated zeolites for solar refrigeration

Solar refrigeration is the best method of utilization of solar energy due to the in-phase relationship between the availability of the solar radiation and the refrigeration requirements. Zeolites with their water content and ion-exchange capability can be used as the material for solar refrigeration. This study aims at further enhancement in the adsorption refrigeration capacity of zeolite by salt hydrate encapsulation. Ion-exchanged and salt hydrate encapsulated zeolites are prepared and characterized for their application as potential candidates in solar refrigeration. A sorption machine has been constructed with the salt-encapsulated zeolite and the results highlight the enhanced suitability of the salt-encapsulated zeolites for solar refrigeration

ETHNOPHARMACOLOGICAL IMPORTANCE OF MORINDA CITRIFOLIA L.

Morinda citrifolia L. (commonly known as Noni) has been used in folk remedies over the years and has a broad range of therapeutic effects, including antibacterial, antiviral, antifungal, antitumor, analgesic, hypotensive, anti-inflammatory, and immune enhancing effects. The effect of oral administration of the bioactive principles isolated from Morinda citrifolia. L was studied in streptozotocin induced diabetic nephropathy rats to assess the anti-diabetic nephropathy activity in terms of glucose, protein, urea, uric acid, creatinine in serum, potassium, sodium, alkaline phosphatase and urinary craetinine. Streptozotocin induced animals showed high level of protein compared to control group. The increased serum protein level is due to increased renal failure with progressive atrophy of the nephrons. Treatment of diabetic nephropathy rats with Morinda citrifolia fruit extract has been found to decrease the damage of kidney and has restored the level of glucose, protein, urea, uric acid, creatinine, potassium, sodium and kidney alkaline phosphatase to that of normal level. Noni is rich in proxeronine, which combines with enzymes in the body to form an essential substance known as xeronine. It activates the immune system at cellular level thereby repairing and protecting kidney from damage. The extract of noni is found to possess nephroprotective effects as revealed by the histopathological studies. The fruit extract of the plant has anti-diabetic nephropathy effects, and possesses both high antioxidant properties and immunomodulatory properties. Morinda is believed to fortify and maintain cell structures. This can be accomplished by acting as an adaptogen that can aid ”sick” cells in repairing themselves

Novel Nanofluids Based on Magnetite Nanoclusters and Investigation on Their Cluster Size-Dependent Thermal Conductivity

To probe the effect of particle size on thermal conductivity (<i>k</i>) enhancement in nanofluids, especially in a very large particle size range, we study the cluster size-dependent <i>k</i> in novel nanofluids containing magnetite (Fe₃O₄) nanoclusters. The Fe₃O₄ nanoclusters in the size range of 115 to 530 nm were synthesized by a facile and cost-effective solvothermal approach. The structural, surface, and magnetic characteristics of Fe₃O₄ nanoclusters were investigated by powder X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), and vibrating sample magnetometer (VSM). Thermal conductivity studies in diethylene glycol (DEG)-based Fe₃O₄ cluster nanofluids showed an enhancement in <i>k</i> with an increase in nanocluster size. With a fixed volume fraction (ϕ) = 0.0193, the <i>k</i> enhancement was about 5.3% and 12.6%, respectively, for nanofluids having cluster size of 115 and 530 nm. The observed increase in nanofluid <i>k</i> with increase in cluster size being contrary to the microconvection hypothesis confirms the less prominent role of Brownian motion-induced microconvection on the <i>k</i> enhancements of nanofluids. The increase in nanofluid <i>k</i> with increase in cluster size is attributed to the growth of clusters into fractal-like aggregates in the suspensions which was confirmed by optical microscopy, dynamic light scattering (DLS), and atomic force microscopy (AFM) studies. Furthermore, the experimental <i>k</i> data fall within the upper and lower Maxwell bounds for homogeneous systems, confirming the classical nature of thermal conduction in nanofluids. The nanofluids developed in the present study are promising candidates for heat transfer applications because of their improved thermal conductivity and long-term stability. The present study can provide new insights for engineering efficient nanofluids containing nanoclusters with superior thermal conductivity for heat transfer applications