Proton transport for fuel cells

No abstract

Selective Hydrogenation of Furfural in a Proton Exchange Membrane Reactor Using Hybrid Pd/Pd Black on Alumina

Invited for this month’s cover picture are the groups of Dr. Peter Pintauro (Vanderbilt University, Tennessee, USA), Dr. Levi Thompson (University of Delaware, Delaware, USA), and Dr. William Tarpeh (Stanford University, California, USA). The cover picture shows the controlled variation of furfural hydrogenation product speciation based on varying cathode formulations of hybrid Pd black and Pd on alumina support. Read the full text of the article at 10.1002/celc.201901314.“The performance of different cathode compositions is evaluated at different current densities (which varies with hydrogen production) in terms of production rate, faradaic efficiency, and selectivity. To isolate the influences of the electrocatalyst in the hybrid catalyst, the performance of electrocatalyst Pd black is evaluated separately. These four variations of the hybrid cathode are investigated to test the hypothesis that the addition of the metal loaded on metal oxide to the electrocatalyst enhances the production rate for hydrogenated products compared to electrodes with only an electrocatalyst…“ Learn more about the story behind the research featured on the front cover in this issue’s Cover Profile. Read the corresponding Article at 10.1002/celc.201901314.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/152714/1/celc201901737.pd

A Comprehensive Study of an Acid-Based Reversible H2-Br2 Fuel Cell System

The regenerative H2-Br2 fuel cell has been a subject of notable interest and is considered as one of the suitable candidates for large scale electrical energy storage. In this study, the preliminary performance of a H2-Br2 fuel cell using both conventional as well as novel materials (Nafion and electrospun composite membranes along with Pt and RhxSy electrocatalysts) is discussed. The performance of the H2-Br2 fuel cell obtained with a conventional Nafion membrane and Pt electrocatalyst was enhanced upon employing a double-layer Br2 electrode while raising the cell temperature to 45°C. The active area and wetting characteristics of Br2 electrodes were improved upon by either pre-treating with HBr or boiling them in de-ionized water. On the other hand, similar or better performances were obtained using dual fiber electrospun composite membranes (PFSA/PPSU) versus using Nafion membranes. The RhxSy electrocatalyst proved to be more stable in the presence of HBr/Br2 than pure Pt. However, the H2 oxidation activity on RhxSy is quite low compared to that of Pt. In conclusion, a stable H2 electrocatalyst that can match the hydrogen oxidation activity obtained with Pt and a membrane with low Br2/Br− permeability are essential to prolong the lifetime of a H2-Br2 fuel cell

Dehydroalanine and Lysinoalanine in Thermolyzed Casein do not Promote Colon Cancer in the Rat

Thermolysis of proteins produces xenobiotic amino-acids such as the potentially toxic lysinoalanine, and the alkylating agent, dehydro¬alanine, which have been considered possible health hazards. We observed that thermolysed casein promoted aberrant crypt foci (ACF) and colon cancer growth in rats initiated with azoxymethane and speculated that promotion might be due to the formation of these compounds. To test this notion we first measured the concentration of the modified amino acids as a function of thermolysis time. The concentration of dehydroalanine in the casein paralleled the degree of promotion, that of lysinoalanine did not. We then tested diets containing foods with high levels of dehydroalanine (thermolysed sodium-caseinate, cooked Swiss cheese) for their effect on ACF promotion. They decreased the number and/or size of ACF significantly, indicating that dehydroalanine did not promote, but protected rats against colon carcinogenesis. These results do not support the notion that lysinoalanine or dehydroalanine are a hazard with respect to colon carcinogenicity

Selective Hydrogenation of Furfural in a Proton Exchange Membrane Reactor Using Hybrid Pd/Pd Black on Alumina

Conventional thermocatalytic hydrogenation employs high temperatures and pressures and often exhibits low selectivity toward desired products. Electrochemical hydrogenation can reduce energy input by operating at ambient conditions and improving process control and selectivity; however, electrocatalysts face stability and conductivity limitations. To overcome these obstacles, we physically mixed a traditional electrocatalyst (Pd black) with a hydrogenation‐active metal (Pd) supported on a conventional metal oxide support (alumina, Al2O3) and investigated electrochemical hydrogenation of furfural, a model biomass compound. Experiments were conducted in a proton exchange membrane (PEM) reactor, in which synthesized electrocatalysts were used as cathodes. Catalysts with Pd black and varying loadings of Pd on Al2O3 were used to determine the impact of hydrogen spillover on electrocatalytic hydrogenation mechanisms, selectivity, and rates. Observed hydrogenation rates and selectivities were linked to structural and compositional properties of the catalyst mixtures. Of the Pd black cathodes tested, 5 wt % Pd/Al2O3 exhibited production rates as high as pure Pd black and higher selectivity towards completely hydrogenated products. Improved selectivity and rates were attributed to a synergistic interaction between Pd black and 5 wt % Pd/Al2O3 in which Pd/Al2O3 increased the number of active sites, while Pd black provided stable conductivity.Breaking away from convention: The performance of hybrid cathodes, consisting of a traditional electrocatalyst (Pd black) with a hydrogenation‐active metal (Pd) supported on a conventional metal oxide support (Al2O3), is investigated using electrochemical hydrogenation of furfural in a proton exchange membrane reactor. Varying loadings of Pd on Al2O3 within the hybrid cathode elucidates the impact of structural and compositional properties of the catalyst mixtures on hydrogenation rates and selectivities.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/152702/1/celc201901314-sup-0001-misc_information.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/152702/2/celc201901314.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/152702/3/celc201901314_am.pd

Macroscopic Modeling of Polymer-Electrolyte Membranes

In this chapter, the various approaches for the macroscopic modeling of transport phenomena in polymer-electrolyte membranes are discussed. This includes general background and modeling methodologies, as well as exploration of the governing equations and some membrane-related topic of interest

New Membrane Nano-Morphologies for Improved Fuel Cell Operation

Presented on February 4, 2009, from 4-5 pm in room G011 of the Molecular Science and Engineering Building on the Georgia Tech Campus.Runtime: 60:08 minutesPolymeric membranes play a crucial role during the generation of electricity in hydrogen/air and direct methanol proton-exchange membrane (PEM) fuel cells. The membrane in such devices has three functions: (1) to physically separate the positive and negative electrodes (so there is no electrical short circuit), (2) to prevent mixing of the fuel and oxidant, and (3) to provide a conduit for proton transport between the electrodes. For hydrogen fuel cells, the membrane must exhibit low gas permeability and high proton conductivity. For a direct liquid methanol PEM fuel cell, the ion-exchange membrane must conduct protons and be a good methanol barrier. For any fuel cell, the membrane must have good mechanical properties in the wet and dry states and be chemically stable under fuel cell operating conditions. DuPont’s Nafion® (a perfluorosulfonic acid polymer) has many attractive properties and has been widely studied in PEM fuel cells, but it does not meet all performance criteria. In a hydrogen/air fuel cell, Nafion loses water and the conductivity drops at temperatures 80oC, unless the water activity in the feed gases is near unity. Nafion has also been used in direct methanol fuel cells, but high methanol crossover (permeation) leads to low power output due to cathode depolarization. Polymer nano-morphology manipulation/control is a promising strategy to improve the performance of fuel cell membranes. Two examples of this approach will be discussed: (i) pre-stretched recast Nafion for direct methanol fuel cells and (ii) composite membranes based on proton conducting ionomeric nanofibers. Membrane fabrication methods and the results of membrane characterization tests will be described. Physical property data relevant to PEM fuel cell applications will be related to the membrane’s nanostructure and fuel cell performance data will be presented

Aluminum: Its Toxicity and Use in Modern Medicine

This thesis is being archived as a Digitized Shelf Copy for campus access to current students and staff only. We currently cannot provide this open access without the author's permission. If you are the author of this work and desire to provide it open access or wish access removed, please contact the Wahlstrom Library to discuss permission.This paper examines the relationship of aluminum toxicity and modern medicine through a review of the current literature using PubMed and Cochrane Library databases. This review describes the effects of both acute and chronic aluminum toxicity in addition to the general pharmacokinetics of aluminum. The question of Alzheimer’s disease, autism spectrum disorder and neurodegenerative conditions and their relation to aluminum is explored as well as the implication of aluminum toxicity on the future of medicine

ATP responsive idrogel based on alginate and gold nanoparticles

reservedGli idrogel sono sistemi colloidali in forma semisolida caratterizzati da un network polimerico 3D capace di adsorbire grandi quantità di acqua. Gli idrogel sono utilizzati in moltissimi ambiti per le loro proprietà, tra cui l’ambito medico, chimico, farmaceutico e alimentare. La caratteristica principale di alcuni idrogel è l’essere sensibili a stimoli esterni. Lo scopo del mio progetto di tesi è lo sviluppo e lo studio delle proprietà di uno “stimuli responsive” idrogel basato su alginato reticolato con nanoparticelle d’oro passivate da tioli equipaggiati con un complesso 1,4,7-triazaciclonano·Zn2+ (NPs-TACN·Zn2+). L’ipotesi di questo progetto è che l’idrogel così formato mantenga le proprietà tipiche delle sue componenti, quali l'elevata affinità per l'ATP e la selettività nei confronti di GMP mostrata dalle NPs-TACN·Zn2+. Ciò permetterebbe di spiazzare l’iterazione con l’alginato in favore di quella nucleotidefosfato-nanoparticelle, causando quindi lo scioglimento del gel e il rilascio del carico inglobato. Dopo aver ottimizzato le condizioni di formazione dell’idrogel, abbiamo studiato le proprietà di incapsulamento e di risposta a stimoli esterni, quali ATP e analoghi. Nella preparazione delle NPs si è potuto constatare che piccole molecole rimanevano incapsulate nell’idrogel solo se capaci di interagire almeno con le nanoparticelle. La capacità di inglobare proteine è stata testata usando la Creatina Fosfochinasi, ma dovrà essere ulteriormente esplorata utilizzando altri enzimi compatibili con l’alginato. Gli esperimenti effettuati hanno mostrato come l’idrogel di alginato-NPs-TACN·Zn2+ sia più selettivo per i gruppi fosfati rispetto ai carbossilati. In particolare, l’ATP si è mostrato in grado di spiazzare l’alginato, andando a rompere i nodi del reticolo e causando quindi lo scioglimento del gel. L’affinità dell’idrogel per ADP e AMP è progressivamente minore. Inoltre, abbiamo visto che con nucleotidi monofosfato l’idrogel ha avuto una risposta selettiva per il GMP rispetto al TMP.Hydrogels are semisolid colloidal systems with a 3D polymeric network capable of adsorbing large quantities of water. Thanks to their properties, hydrogels are used in different areas such as medical, chemical and pharmaceutic. The main characteristic of hydrogels is to be stimuli responsive. The aim of my thesis project is to develop and study of the properties of a stimuli responsive hydrogel, based on alginate crosslinked with gold nanoparticles functionalised with 1,4,7-triazacicleonane·Zn2+ groups (NPs-TACN·Zn2+). The hypothesis of my project is that such hydrogel would maintain some important features typical of his components, such the high affinity for ATP and the selectivity towards GMP shown by NPs-TACN·Zn2+. This would cause the hydrogel melting, that can be exploited to release the cargo in the presence of specific external stimuli. We initially optimised the conditions of hydrogel preparation. Then we studied the encapsulating properties of the gel, and we observed that small molecules were efficiently encapsulated only if interacting with the nanoparticles. The ability to encapsulate proteins was tested using Creatine Phosphokinase, but further experiments are required. The stimuli responsive properties of the hydrogel were studied in the presence of ATP or similar. We observed that ATP is able to displace the alginate, breaking the crosslinking knots and causing the melting of the gel and consequent cargo release. The affinity of the hydrogel to ADP and AMP is progressively lower. Finally, we proved that the hydrogel has a selective response to GMP over TMP