Direct measurement of the capillary pressure characteristics of water–air–gas diffusion layer systems for PEM fuel cells

A method and apparatus for measuring the relationship between air–water capillary pressure and water saturation in PEMFC gas diffusion layers is described. Capillary pressure data for water injection and withdrawal from typical GDL materials are obtained, which demonstrate permanent hysteresis between water intrusion and water withdrawal. Capillary pressure, defined as the difference between the water and gas pressures at equilibrium, is positive during water injection and negative during water withdrawal. The results contribute to the understanding of liquid water behavior in GDL materials which is necessary for the development of effective PEMFC water management strategies.     

Water – A key parameter in the stability of anion exchange membrane fuel cells

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Polymeric organic–inorganic proton-exchange membranes for fuel cells produced by the sol–gel method

Approaches to the production of polymeric organic–inorganic hybrid proton-exchange membranes for fuel cells by the sol–gel method are summarized, and a classification is proposed for them. Features of the mechanism of conduction in the proton-conducting membranes are considered. Characteristics of the hybrid membranes and of fuel cells using them are presented. The main directions of research in this field are discussed.     

Physical and morphological characteristics and electrochemical behaviour in PEM fuel cells of PtRu /C catalysts

Platinum-ruthenium catalysts supported on carbon (PtRu/C) have been characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), specific surface area analysis (BET), X-ray photoelectron spectroscopy (XPS) and in proton exchange membrane (PEM) fuel cell tests. The results indicate the presence of strong metal-carbon interactions, which hinder the formation of a single-phase face-centered cubic (fcc) PtRu alloy. The particle size of the PtRu/C catalysts was smaller than both carbon-supported platinum (Pt/C) and ruthenium (Ru/C) catalysts. In the bimetallic electrocatalysts the intercrystallite distance decreased with respect to pure Pt and Ru metals. PEM fuel cell tests in H₂/air operation mode revealed a decrease of performance with increasing carbon content of the catalyst, at a fixed Pt loading. In H₂ + 100 ppm CO/air operation mode the maximum performance of the PEM fuel cell was attained at 0.63 atomic fraction Ru. Received: 2 December 1999 / Accepted: 27 January 2000     

A simple protocol for the synthesis of α-substituted phosphonates

An efficient, easy-to-handle, and mild substitution reaction approach has been developed for the synthesis of phosphonate derivatives, which are very important in the field of industrial, agricultural, and medicinal chemistry. A large number of nucleophiles, including arylamines, alkylamines, heteroarylamines, primary amines and secondary amines, sulfides, and carbides were attempted to react with α-tosyloxyphosphonate 1. The reaction proceeded under catalyst-free and neat conditions and the corresponding phosphonates 2 were afforded in good yields.     

Pt–Ru electrocatalysts for fuel cells: developments in the last decade

Reviewed herein are recent advances in the synthesis and performance of Pt–Ru electrocatalysts, including core–shell-like, for anodes in direct methanol fuel cells (DMFC) and in polymer electrolyte fuel cells (PEMFCs) employing reformate gas. Model systems allowing for a better understanding of composition–property and structure–property relationships, in particular of their CO-tolerance and degradation mechanisms, as well as opportunities for innovative syntheses, support optimization, and durability improvements are discussed. Some other new electrocatalysts for DMFC and PEMFC anodes are compared with Pt–Ru systems.     

A simple algorithm for the calculation of the π ionization energies of substituted benzenes

A simple algorithm, based on HMO approach is used for calculating Π-ionization potentials (Π-IP's) of polysubstituted benzenes. The parameters required for the method are determined from Π-IP's of monosubstituted benzenes. For 50 disubstituted benzenes the first three values of the Π-IPś are obtained with root mean square (rms) error of 0.19 eV. Some examples of application are presented, illustrating the possibility of fast and quite accurate estimation of Π-IP's for polysubstituted benzenes.     

A convenient method for the synthesis of fluorinated α-cyanoacetates via phase-transfer catalysis

A simple and convenient method for the synthesis of fluorinated α-cyanoacetate derivatives has been developed by using electrophilic fluorination of allyl and benzyl substituted α-cyanoacetates with N-fluorobenzensulfonimide (NFSI) as electrophilic fluorinating agent via phase transfer catalysis. The reaction is transition metal free and carried out in aqueous and mild reaction conditions in the presence of readily available tetra-N-butylammonium iodide (TBAI) as phase-transfer catalyst.     

Polyurethane Molecular Stamps for the in situ Synthesis of DNA Microarray

Fabrication of polyurethane molecular stamps (PU stamps) based on polypropylene glycol (PPG) and toluene dissocyanate (TDI), using 3,3′-dichloro-4,4′-methylenedianiline (MOCA) as the crosslinker ,is reported. It was shown from the contact angle measurement that PU stamps surface has good affinity with acetonitrile,guaranteeing the well distribution of DNA monomers on patterned stamps. Laser confocal fluorescence microscopy images of oligonucleotide arrays after hybridization confirmed polyurethane is an excellent material for molecular stamps when ransferring polar chemicals and conducting rections on interfaces by stamping.     

Current trends in the development of A. M. Butlerov’s theory of chemical structure

The chemical structure concept developed by A. M. Butlerov supplemented by the views on spatial (J. H. van’t-Hoff and J. A. Le Bel) and electronic (G. Lewis) configurations of molecules constitute the basis of the classical theory of chemical structure. The advent of quantum mechanics and development of the computer chemistry extended and enhanced the conceptual basis of theoretical chemistry, which nevertheless retains its independent value and cannot be reduced to direct physical definitions. The review deals with the evolution of the key concepts of the classical theory of chemical structure and introduction of new notions and approaches to analysis of the structure and reactivity problems, which is associated with the advent of the quantum mechanics and quantum chemistry views and methods.     

Analysis of soluble intermediates in the lithium–sulfur battery by a simple in situ electrochemical probe

This paper describes a simple setup using a thin, insulated platinum wire as an in situ electrochemical probe for analysis of the soluble polysulfide intermediates formed and consumed during the course of the discharge process of a lithium–sulfur cell. The probe, sharing common reference and counter electrodes with the cell, can be used to follow the changes in concentration of polysulfides in the electrolyte. The results herein both support and complement more advanced techniques studied elsewhere for understanding the dominant processes occurring in the cell.     

A simple approach for the synthesis of new pyrimidinyl α-amino acids

A simple synthetic method for the preparation of optically active pyrimidinyl α-amino acids is presented. A nucleophilic ipso-substitution reaction between 2-(benzylsulfonyl)-4-isopropoxypyrimidines and a nucleophilic side chain of several protected natural α-amino acids is investigated to obtain new pyrimidin-2-yl α-amino acids. A detailed optimisation study of this reaction is discussed. Moreover, the selective O-alkylation of 2-(benzylsulfanyl)-4(3H)pyrimidinones with a hydroxylic side chain of some natural α-amino acids under Mitsunobu conditions is studied as a method to prepare new pyrimidin-4-yl α-aminoesters.     

A simple strategy for the synthesis of Zn-IL-SBA-15 by sol–gel and the application in desulfurization

Journal of Sol-Gel Science and Technology - SBA-15 functionalized with both zinc ions and ionic liquids was simply synthesized by sol–gel method. The characterization results of Fourier...     

In situ solid-state NMR spectroscopy of protein in heterogeneous membranes: the baseplate antenna complex of Chlorobaculum tepidum

A clever combination: an in situ solid-state NMR analysis of CsmA proteins in the heterogeneous environment of the photoreceptor of Chlorobaculum tepidum is reported. Using different combinations of 2D and 3D solid-state NMR spectra, 90?% of the CsmA resonances are assigned and provide on the basis of chemical shift data information about the structure and conformation of CsmA in the CsmA-bacteriochlorophyll a complex.     

Oxidative degradation of polyglycols by the Ruff’s system in the aqueous solutions

We have studied oxidative degradation of polypropylene glycol and polyethylene glycols of varied molecular mass induced by hydrogen peroxide in the presence of iron(III) ions. At pH 3, the process is accompanied by aggregation of iron hydroxides and occurs in the microheterogeneous system. In the cases of high-molecular substrates, the oxidation is accompanied by decrease in the polymer globulas size due to the degradation of the polymer chain.     

Reduction in the operating temperature of solid oxide fuel cells—potential use in transport applications

The development of solid oxide fuel cells (SOFC) offers new perspectives, in particular as auxiliary power units for vehicle applications. The elaboration of thin electrolyte layers is the main challenge in order to reduce their operating temperature. A brief review of the deposition techniques and of the potential electrolytes is presented. A relatively new technique, Atomic Layer Deposition (ALD), allows to produce thin, dense and homogeneous layers, i.e. zirconia or zirconia-based thin layers can be deposited on different substrates. The interest of elaborating bi- or multi-layer electrolytes is outlined.     

Recent progress in fluorinated electrolytes for improving the performance of Li–S batteries

Lithium–sulfur(Li–S) batteries represent a "beyond Li-ion" technology with low cost and high theoretical energy density and should fulfill the ever-growing requirements of electric vehicles and stationary energy storage systems. However, the sulfur-based conversion reaction in conventional liquid electrolytes results in issues like the so-called shuttle effect of polysulfides and lithium dendrite growth, which deteriorate the electrochemical performance and safety of Li–S batteries. Optimization of conventional organic solvents(including ether and carbonate) by fluorination to form fluorinated electrolytes is a promising strategy for the practical application of Li–S batteries. The fluorinated electrolytes, owing to the high electronegativity of fluorine, possesses attractive physicochemical properties, including low melting point,high flash point, and low solubility of lithium polysulfide, and can form a compact and stable solid electrolyte interphase(SEI) with the lithium metal anode. Herein, we review recent advancements in the development of fluorinated electrolytes for use in Li–S batteries. The effect of solvent molecular structure on the performance of Li–S batteries and the formation mechanism of SEI on the cathode and anode sides are analyzed and discussed in detail. The remaining challenges and future perspectives of fluorinated electrolytes for Li–S batteries are also presented.