Andrew Herring

Fabricated ionomer films based on HPAs with high • loadings that have proton conductivities >0.1 S cm at >80oC and <50% RH. The results were verified independently by 3M and Scribner and Associates. Showed that proton conductivity was strongly • correlated with chemistry, best performance was from films containing only HPA as the protogenic group. Also showed that process conditions strongly • influenced morphology that affected all film properties. Ultraviolet (UV)-cured films were brittle, but had proton conductivities that made all targets shown above, whereas thermally cured films were much stronger but had poor proton conductivity.

There is increasing interest in the alkaline exchange membrane (AEM) fuel cells as this device, if realized, could allow the use of inexpensive metal catalysts and the oxidation of a variety of convenient liquid fuels. While there have been some dramatic early achievements, there is still a need for a fundamental study of anion transport, cation stability and the formation of robust thin films in this area. We have undertaken a comprehensive study of AEMs where theory is linked to well-defined model systems, both in solution and in the solid state, which are characterized using very careful environmental control such that the models can be validated and used predictively. We are also fabricating a number of random copolymer AEMs that can be produced readily in large quantities, allowing us to understand film formation coupled with transport and stability. Those based on perfluorinated backbones invite interesting comparisons with the analogous proton exchange membranes.

We report the design, synthesis and photoelectrochemical characterization of cobalt phosphate (Co-Pi) oxygen evolution catalyst modified heterojunction photoelectrodes consisting of one-dimensional WO3 nanorods (1D-WO3) and highly porous BiVO4 layers. The 1D-WO3 nanorods were prepared by the decomposition of the tetrabutylammonium decatungstate precursor in the presence of poly(ethylene glycol) as a binding agent. The porous BiVO4 layers were spray deposited using a surfactant assisted metal-organic decomposition method. The Co-Pi oxygen evolution catalyst was deposited onto the BiVO4/1D-WO3/FTO heterojunction electrode using a photoassisted electrodeposition method. The Co-Pi catalyst modified heterojunction electrodes exhibited a sustained enhancement in the photocurrent compared to the unmodified BiVO4/1D-WO3/FTO heterojunction electrodes. The improved photoelectrochemical properties profited from the enhanced charge carrier separation achieved through the integration of highly porous BiVO4 layers on top of 1D-WO3 nanorods and from the superior kinetics due to the presence of the Co-Pi oxygen evolution catalyst on top of BiVO4/1D-WO3/FTO heterojunction electrodes.

Results A polarization curve with a Pt/C MEA control and an HWV4-Pt/C modified MEA can be seen in Figure 1. The HWV4 modified electrode shows an improvement in performance when compared to the Pt/C control MEA. A similar performance increase was seen for the other HPAs tested.

Results A polarization curve with a Pt/C MEA control and an HV2-Pt/C modified MEA can be seen in Figure 1. The HV2 modified electrode shows an improvement in performance when compared to the Pt/C control MEA. Even though the performance seen in Figure 1 is still below that of Pt-Ru catalysts, it is still noteworthy that the addition of the HPA causes an increased performance. Anodic polarizations were also performed, by feeding N2 to the cathode. In this type of experiment the produced protons and electrons recombine at the ...

Proton exchange membrane (PEM) fuel cells hold enormous promise for automotive applications. For the PEM fuel cell to be reduced to practice in automobiles the fuel cell needs to be less expensive, more durable and operate at temperatures above 100ºC with no inlet humidification of reactant gases. Currently the PEM is fabricated from a perfluorosulfonic acid (PFSA) polymer such as Nafion®. Unfortunately PFSA ionomers must be fully hydrated to achieve practical levels of hydration. This necessitates humidifying the ...

Proton exchange membrane (PEM) fuel cells represent a promising renewable energy conversion device for stationary applications, automobiles and portable devices.[1] There is direct correlation between proton conduction of the PEM membrane and actual fuel cell performance. Optimum conductivity in PEM membranes at their standard operating temperature is only achieved under full hydration. Conductivity decreases dramatically as humidity drops below 100% in Nafion® membranes. A strong association between ...

Fuel cells have the potential to replace batteries in small electronics and internal combustion engines in cars because they can generate electricity like a battery but can be refueled instead of recharged. The cost of expensive platinum catalysts and their intolerance to carbon monoxide levels in hydrogen fuels made by reforming hydrocarbons are two reasons that fuel cells are not commonly used today. A potential replacement for Pt catalysts is a group of inorganic materials called heteropolyacids (HPAs). The fact that HPAs are good ...

Alkaline ion exchange membranes are the key component of fuel cells. Such membranes involve grafting of ion exchange cationic moieties to the polymer matrix. The grafting moieties involved are tetraalkyl ammonium, tetraalkyl phosphonium cations, etc. which make the membranes conductive. So the measurement of conductivity of these cation moieties in aqueous solution plays a crucial role in determining the grafting cation type. Our current research work involves measuring conductivity of these moieties in aqueous medium at various concentrations ...

Perfluorinated sulfonic acid (PFSA) polymer membranes have received enormous interest in recent years because of their application in fuel cells as proton conducting solid electrolytes. All the currently used PFSA ionomers are composed of carbon-fluorine backbones and perfluorinated ether side chains containing sulfonic acid groups. The fluorinated backbone is responsible for the outstanding mechanical flexibility and chemical durability, and the sulfonated side chains provide hydrophilicity and proton conductivity for the material. ...

Anion-exchange membranes (AEMs) consisting of poly(vinyl benzyl trimethylammonium)-b-poly(methylbutylene) of three different ion exchange capacities (IECs), 1.14, 1.64, and 2.03 mequiv g, are studied by High-Resolution Thermogravimetry, Modulated Differential Scanning Calorimetry, Dynamic Mechanical Analysis, and Broadband Electrical Spectroscopy in their OH form. The thermal stability and transitions are elucidated, showing a low temperature T and a higher temperature transition assigned to a disorder-order transition, T, which depends on the IEC of the material. The electric response is analyzed in detail, allowing the identification of three polarizations (only two of which contribute significantly to the overall conductivity, σ and σ) and two dielectric relaxation events (β and β), one associated with the tolyl side groups (β) and one with the cationic side chains (β). The obtained results are integrated in a coherent picture and a conductivity mechanism is proposed, involving t...

ABSTRACT Understanding the role of water in anion exchange membrane (AEM) used in fuel cells is essential for commercial application.1 Many literatures published have emphasized the important of water to optimize membrane properties such as ionic conductivity, ion transport, and mechanical and chemical stability.1-3 Recently, the idea of using thin layers of catalyst and solubilized ionomer is very common and demands the greater understanding of hydration behavior of AEMs.4 Several techniques have been used to understand the diffusion of water in membranes. Elabd et al5 have summarized the diffusion coefficient values from different methods and mentioned the in-consistency among different methods. A time resolved Fourier transform infrared- attenuated total reflectance (FTIR-ATR) spectroscopy is a less common method to measure the water diffusion through AEMs although this method has been recently used in other materials.6, 7 FTIR-ATR spectra were collected using Nexus 4700 (Thermo-fisher) with an ATR accessory (Specac, Inc). A liquid nitrogen cooled mercury cadmium telluride (MCT) detector was used to collect a spectrum with 128 scans every 25 seconds with a resolution of 4 cm-1. A custom built design was used to control RH of the membrane sample during experiments. In order to verify the experimental setup, the diffusion coefficient of water through Nafion 117® membrane was observed at the same order of magnitude (1.63±0.27 x 10-7 cm2/s vs 3.71x 10-7 cm2/s observed by Elabd et al7) when the relative humidity of the sample was changed from 0 to 100 %RH. Water diffusion coefficient was then measured for AEMs as a function of temperature and RH. The Fickian water diffusion coefficient for AEMs was observed to be lower than proton exchange membranes by one order of magnitude. Figure 1 shows the comparison of water diffusion kinetics between one of the anion exchange membranes and Nafion 117® at 30 oC. In this work, water behavior of different AEMs as a function of temperature and RH will be presented, the energy barrier for the water diffusion through these membrane will be discussed and the science behind a slow water diffusion through AEMs will be explored. Figure 1. Time-resolved normalized absorbance for O-H stretching vibration collected using FTIR-ATR at 30oC when RH was increased from 0 to 100%. Acknowledgement The authors would like to thank the US Army Research Office for the funding under the MURI #W911NF-10-1-0520and the purchase of FTIR microscope from ARO DURIP #W911NFNF-0462 References * Merle, G.; Wessling, M.; Nijmeijer, K., Anion exchange membranes for alkaline fuel cells: A review. Journal of Membrane Science 2011, 377, 1-35. * Duan, Q. J.; Ge, S. H.; Wang, C. Y., Water uptake, ionic conductivity and swelling properties of anion-exchange membrane. Journal of Power Sources 2013, 243, 773-778. * Myles, T. D.; Kiss, A. M.; Grew, K. N.; Peracchio, A. A.; Nelson, G. J.; Chiu, W. K. S., Calculation of Water Diffusion Coefficients in an Anion Exchange Membrane Using a Water Permeation Technique. Journal of the Electrochemical Society 2011, 158, B790-B796. * Mehta, V.; Cooper, J. S., Review and analysis of PEM fuel cell design and manufacturing. Journal of Power Sources 2003, 114, 32-53. * Hallinan, D. T.; Elabd, Y. A., Diffusion of Water in Nafion Using Time-Resolved Fourier Transform Infrared−Attenuated Total Reflectance Spectroscopy. The Journal of Physical Chemistry B 2009, 113, 4257-4266. * Sundfors, F.; Lindfors, T.; Hofler, L.; Bereczki, R.; Gyurcsanyi, R. E., FTIR-ATR Study of Water Uptake and Diffusion through Ion-Selective Membranes Based on Poly(acrylates) and Silicone Rubber. Analytical Chemistry 2009, 81, 5925-5934. * Hallinan, D. T.; Elabd, Y. A., Diffusion and Sorption of Methanol and Water in Nafion Using Time-Resolved Fourier Transform Infrared−Attenuated Total Reflectance Spectroscopy. The Journal of Physical Chemistry B 2007, 111, 13221-13230.

Novel carbon nanostructures are attracting increasing interest and the combination of graphitic substrates with grafted biodegradable polymers may ultimately be of interest in a variety of biomedical and sensing applications. Here, a novel graphitic nanosubstrate, carbon nanospheres derived from cellulose, is functionalized with polylactides (PLA) using an established thionyl chloride intermediate scheme; the resulting supramolecular bionanocomposite is 97% from renewable resources. In addition, a direct ‘grafting from’ approach is utilized to grow polylactide chains on multi-walled carbon nanotubes (MWCNT). In the latter case, unlike previous approaches, the ring-opening polymerization is initiated directly from a hydroxyl bearing surface. Verification of the covalent attachment and characterization of the grafted layer are accomplished via a variety of techniques and methods. Even after repeated washing, thermal gravimetric analysis clearly shows the presence of a grafted layer, which decomposes at approximately 300°C, a value characteristic of PLA; it is found that 20 mg m–2 of PLA is grafted to the MWCNT and 3.9 mg m–2 of PLA is grafted to the carbon nanospheres. Solubility tests clearly show the graphitic structures have been fundamentally altered in their physiochemical properties; they become highly soluble in chloroform after the grafting reaction is complete. Transmission electron microscopy provides evidence of a 2–3 nm thick polymer layer. Finally, Fourier transform infrared spectroscopy shows several characteristic peaks of PLA including the ester group at 1760 cm–1.

Biodiesel is an oxygenated diesel fuel made from vegetable oils and animal fats by conversion of the triglyceride fats to esters via transesterification. In this study we examined biodiesels produced from a variety of real-world feedstocks as well as pure (technical grade) fatty acid methyl and ethyl esters for emissions performance in a heavy-duty truck engine. The objective was to understand the impact of biodiesel chemical structure, specifically fatty acid chain length and number of double bonds, on emissions of NOx and particulate matter (PM). A group of seven biodiesels produced from real-world feedstocks and 14 produced from pure fatty acids were tested in a heavy-duty truck engine using the U.S. heavy-duty federal test procedure (transient test). It was found that the molecular structure of biodiesel can have a substantial impact on emissions. The properties of density, cetane number, and iodine number were found to be highly correlated with one another. For neat biodiesels, PM emissions were essentially constant at about 0.07 g/bhp-h for all biodiesels as long as density was less than 0.89 g/cm3 or cetane number was greater than about 45. NOx emissions increased with increasing fuel density or decreasing fuel cetane number. Increasing the number of double bonds, quantified as iodine number, correlated with increasing emissions of NOx. Thus the increased NOx observed for some fuels cannot be explained by the NOx/PM tradeoff and is therefore not driven by thermal NO formation. For fully saturated fatty acid chains the NOx emission increased with decreasing chain length for tests using 18, 16, and 12 carbon chain molecules. Additionally, there was no significant difference in NOx or PM emissions for the methyl and ethyl esters of identical fatty acids.

Abstract: Water-soluble organic compounds are selectively oxidized by aqueous solutions of chloroplatinum (II) and chloroplatinum (IV) salts. p-Toluenesulfonic acid undergoes stepwise hydroxylation to the corresponding alcohol and aldehyde, with no further oxidation to the carboxylic acid: p-ethylbenzenesulfonic acid is functionalized at both benzylic and methyl positions. Ethanol is converted to a spectrum Of C2 (chloro) oxygenates, including ethylene glycol and 2-chloroethanol, products resulting from methyl functionalization. n-Propanol is ...

The present invention encompasses methods and apparatus for creating metal nanoparticles embedded in a carbonaceous char, the conversion of an carbonaceous char with embedded metallic nanoparticles to graphite-encased nano-sized metal particles surrounded by char, the separation of the graphite encased metal particles from the char matrix, and the related preparation and isolation of carbon nanosphere materials with or without the enclosed metal nanoparticles, and the uses of such carbon nanospheres and ...

Composite membranes consisting primarily of a polymer and an inorganic proton conducting particle or a proton conducting polymer containing inorganic particles for use as proton exchange membranes in low and intermediate temperature fuel cells are reviewed. The chemistry of major inorganic additives that have been used is described in terms of their structure and intrinsic ability to conduct protons. Composites are classified in terms of four main classes: inorganic proton conductors suspended in inert polymers; inorganic ...