<p>This thesis deals with modeling of two types of fuel cells:the polymer electrolyte fuel cell (PEFC) and the directmethanol fuel cell (DMFC), for which we address four majorissues: a) mass transport limitations; b) water management(PEFC); c) gas management (DMFC); d) thermal management.</p><p>Four models have been derived and studied for the PEFC,focusing on the cathode. The first exploits the slenderness ofthe cathode for a two-dimensional geometry, leading to areduced model, where several nondimensional parameters capturethe behavior of the cathode. The model was extended to threedimensions, where four di.erent flow distributors were studiedfor the cathode. A quantitative comparison shows that theinterdigitated channels can sustain the highest currentdensities. These two models, comprising isothermal gasphaseflow, limit the studies to (a). Returning to a two-dimensionalgeometry of the PEFC, the liquid phase was introduced via aseparate flow model approach for the cathode. In addition toconservation of mass, momentum and species, the model wasextended to consider simultaneous charge and heat transfer forthe whole cell. Di.erent thermal, flow fields, and hydrodynamicconditions were studied, addressing (a), (b) and (d). A scaleanalysis allowed for predictions of the cell performance priorto any computations. Good agreement between experiments with asegmented cell and the model was obtained.</p><p>A liquid-phase model, comprising conservation of mass,momentum and species, was derived and analyzed for the anode ofthe DMFC. The impact of hydrodynamic, electrochemical andgeometrical features on the fuel cell performance were studied,mainly focusing on (a). The slenderness of the anode allows theuse of a narrow-gap approximation, leading to a reduced model,with benefits such as reduced computational cost andunderstanding of the physical trends prior to any numericalcomputations. Adding the gas-phase via a multiphase mixtureapproach, the gas management (c) could also be studied.Experiments with a cell, equipped with a transparent end plate,allowed for visualization of the flow in the anode, as well asvalidation of the two-phase model. Good agreement betweenexperiments and the model was achieved.</p><p><b>Keywords:</b>Fuel cell; DMFC; PEFC; one-phase; two-phase;model; visual cell; segmented cell; scale analysis; asymptoticanalysis.</p>

Developing highly active and durable oxygen reduction reaction (ORR) catalysts is crucial to reduce the cost of polymer electrolyte fuel cells (PEFCs). To meet those requirements, unsupported Pt-Cu alloy nanochains (aerogels) were synthesized by a simple co-reduction route in aqueous solution and their structure was characterized by X-ray absorption spectroscopy and STEM-EDX. These catalysts exceeded the ORR activity of commercial Pt/C catalysts by more than 100 % in RDE experiments and met the US DOE targets, thereby qualifying as very promising materials. The behavior of Pt-Cu aerogels under PEFC operation conditions was mimicked by acid washing experiments which showed that the Cu content in the alloy phase and ORR activity decrease through this step. Comparing composition, structure and ORR activity for various specimens, the Cu content in the alloy phase was identified as the main descriptor of ORR activity. An almost linear correlation was found between those two parameters and complemented by supporting data from the literature.

Indiana University-Purdue University Indianapolis (IUPUI) / There are three parts in this work centered on the catalyst layer of Polymer Electrolyte Fuel Cell (PEFC) in this thesis. The first part is for making best MEA structure. One of the major aims of this investigation is to understand the micro-structural organization of ionomer particles and Pt/C aggregates dispersed in a catalyst ink. The dispersion of Nafion® ionomer particles and Pt/C catalyst aggregates in liquid media was studied using ultra small angle x-ray scattering (USAXS) and cryogenic TEM technologies. A systematic approach was taken to study the dispersion of each component (i.e. ionomer particles and Pt/C aggregates) first, then the combination, last the catalyst ink. A multiple curve fitting was used to extract the particle size, size distribution and geometry from scattering data. The results suggests that the particle size, size distribution and geometry of each system are not uniform, rather, vary significantly. The results also indicate that interaction among components (i.e. ionomer particles and Pt/C aggregates) exists. The cryogenic TEM, by which the size and geometry of particles in a liquid can be directly observed, was used to validate the scattering results, which shows the excellent agreement. Based on this study, a methodology of analyzing dispersion of Pt/C particles, Nafion® particles in a catalyst ink has been developed and can serve as a powerful tool for making a desired catalyst ink which is a critical step for making rational designed MEA. The carbon corrosion process is the second part of the thesis. The carbon corrosion process of low–surface-area Pt/XC72 and high-surface-area Pt/BP2000 was investigated xi using an developed accelerated durability testing (ADT) method under simulated fuel cell conditions (a Rotating Disk Electrode (RDE) approach). Compared with the complex MEA system, this innovated approach using RDE can simply focus on carbon corrosion process and avoid the use of MEA in which many degradation/corrosion processes simultaneously occur. It was observed that different carbon corrosion processes resulted in different performance (electrochemical active surface area, mass activity and double layer capacity) decay of catalysts. The corrosion process was studied using TEM. It was found that in the case of Pt/XC72, major corrosion occurred at the center of the Pt/XC72 particle, with some minor corrosion on the surface of the carbon particle removing some amorphous carbon black filaments, while in the case of Pt/BP2000, the corrosion started on the surface. The understanding of carbon corrosion process provides the guidance for making high corrosion resistance catalysts to increase the durability performance of PEFC. Based on the second work, XC72 carbon blacks were etched using steam under different time and used as a new high corrosion resistance catalysts support for the oxygen reduction reaction. TEM results show that the center part of the XC72 particle was more easily etched away. XRD results show that the 002 and 10 peaks of the XC72 based samples are initially sharp, but then broaden during the corrosion process. TEM results of Pt particles show that the steam etching can improve dispersion uniformity of Pt nanoparticles on the surface of carbon support and reduce the Pt particles size. Electrochemical characterization results show that the mass activity of etched carbon black for 1 hour was 1.3 and 34 times greater than that of the carbon blacks etched for 3h and that of carbon blacks non-ecthed. ECSA of the carbon blacks was also significantly increased after etching. MEA test showed after 45 hours testing, the performance MEA with steam etching 1 hour XC72 based catalyst decreases much less than the MEA with commercial catalyst. Clearly, steam etching is a simple and efficient method to increase the performance and durability of the fuel cells catalysts.

Miljöcertifieringssystemen PEFC och FSC ställer krav på uppföljning och revision för att säkerställa att kraven och kvalitén uppnås. Studiens syfte var att belysa de skogliga maskinentreprenörerna och förvaltarnas/virkesinköparnas erfarenheter av arbete med uppföljning inom miljöcertifierat skogsbruk. Materialet insamlades genom telefonintervjuer och analyserades med kvalitativ innehållsanalys, vilket ledde fram till resultatet. Uppföljningen och traktdirektivet har en viktig roll för att nå miljöcertifieringarnas krav. Dialog och delaktighet mellan de olika yrkesgrupperna var viktig, enligt respondenterna, för att miljöcertifieringen ska nå en hög kvalité och för att skapa engagemang och vilja att förbättra arbetet. / The environmental certification systems PEFC and FSC require follow-up and auditing to ensure that the requirements are followed and that quality is achieved. The purpose of this study was to illuminate the experience of machine entrepreneurs, forestry managers and timber buyers of work with evaluation of environmental certified forestry. Data was gathered through telephone interviews and was analysed using qualitative content analysis. Evaluation and contract directives have an important role in achieving environmental certification requirements. Dialogue and co-operation between the different groups is important, according to respondents, for environmental certifications to achieve high quality and to create commitment and desire to improve the work.

This thesis is concerned with the study of morphology and properties of sub-micron thin Nafion® films. The motivation of the work arises from the need to characterize the 4 -10 nm thin ionomer films in the catalyst layer of polymer electrolyte fuel cell (PEFC). A protocol for the fabrication of self-assembled ultra-thin Nafion® films on planar substrates was successfully developed. Films of thickness ranging 4 nm-300 nm, determined by three different techniques - variable angle spectroscopy ellipsometry (VASE), atomic force microscope (AFM) and x-ray photo-electron spectroscopy (XPS), could be reproducibly generated on SiO2/Si wafer. The 4 nm thin film is one of the thinnest, continuous film of Nafion® ever reported. This is the first time that the structure/properties of such thin Nafion® film have been investigated. An interesting finding is the thickness-dependent structure and property of these films. Films with thickness <55 nm exhibited hydrophilic-free surface but thicker films (>55 nm) had hydrophobic surface. Similarly, sub-55 nm films had a lower and thickness-independent protonic conductivity compared to thicker films that exhibited thickness-dependent conductivity. Anomalously high water uptake (by quartz crystal microbalance) and swelling (by ellipsometry) of sub-55nm films indicate that low conductivity is not due to low water content However, differences in surface morphology were observed by the AFM phase contrast analysis. The lack of ionic domain was also observed in the thinner films (4-30 nm) from the grazing incidence small x-ray scattering (GISAXS) experiments. Thermal annealing over a range of temperature (110-160 oC) revealed a dramatic switching of the film surface from hydrophilic to hydrophobic was observed for sub-55 nm films with lower thickness film requiring higher annealing temperature. Bulk proton conductivity was significantly reduced after annealing for all films. An interesting finding was the regeneration of conductivity after to prolonged liquid water exposure and a corresponding switching back of the surface to hydrophilic. The thickness-dependent structure/property of ultra-thin Nafion® films is attributed to substrate induced confinement effect. Self-assembly of Nafion® on various substrates (SiO2, carbon, Pt and Au) was studied. The ionomer/substrate interaction and resulting film morphology followed a trend with respect to substrate surface energies and Nafion® dispersion compositions. / Thesis (Ph.D, Chemical Engineering) -- Queen's University, 2013-09-29 12:36:19.05

Denna rapports mål är att få en geografisk överblick över vilka församlingar Derome Skog AB gör många respektive få råvaruinköp i. Hur mycket den verkliga volymen skiljer sig från den uppskattade, samt hur stor andel av antalet inköp som är PEFC – certifierade. Information om virkesåren 2005-2007 hämtades och studerades från företagets affärssystem och kartprogram. Resultatet visade att antalet inköp var som störst virkesår 2005. Geografiskt sett hade företaget som flest råvaruinköp i församlingarna i nära anslutning till koncernens egna sågverk. Den verkliga volymen var något större än den uppskattade för alla studerade virkesår. Andelen certifierade inköp låg runt 50 procent, de studerade virkesåren. Geografiskt sett var andelen PEFC - certifierade inköp större i de södra samt mellersta delarna av företagets inköpsområde än i de norra. Följande slutsatser har gjorts: - Företaget är geografiskt sett starkast i de församlingar närmast koncernens sågverk - Företaget måste satsa mer energi på att skaffa nya kontakter i de församlingar där få eller inga inköp görs - Andelen PEFC - certifierade inköp är större i södra och mellersta delarna av företagets inköpsområde - Inköparna måste bli bättre på att certifiera markägare / This report aims to get a geographic overview in which parish Derome Skog AB make many respective few purchase. How much different there is between the real and estimated volume and how big share of the purchase that are certified. Information about the wood year 2005-2007 collected and study’s from the company’s businessystem and mapprogramme. The result shows that the company has as most number of purchases the wood year 2005. Geographical has the company as most purchase in the parish nearest the groups own sawmills. The real volume was a little more than the estimated in all the year that have been study. The share of purchases that are PEFC - certified lie around 50 percent under the three study wood year. Geographical was the share of PEFC - certified purchases bigger in the south and middle of the company’s sphere of activities than in the north. Following conclusion has taken: - The company are geographical strongest in the parish close to the groups own sawmills - The company must put more energy to get new contacts in the parish there are week in - The share PEFC - certified purchase was higher in the southern and middle of the company’s sphere of activies - The inpurchaser have to get better in PEFC - certify the landowner

<p>Denna rapports mål är att få en geografisk överblick över vilka församlingar Derome Skog AB gör många respektive få råvaruinköp i. Hur mycket den verkliga volymen skiljer sig från den uppskattade, samt hur stor andel av antalet inköp som är PEFC – certifierade.</p><p>Information om virkesåren 2005-2007 hämtades och studerades från företagets affärssystem och kartprogram. Resultatet visade att antalet inköp var som störst virkesår 2005. Geografiskt sett hade företaget som flest råvaruinköp i församlingarna i nära anslutning till koncernens egna sågverk. Den verkliga volymen var något större än den uppskattade för alla studerade virkesår. Andelen certifierade inköp låg runt 50 procent, de studerade virkesåren. Geografiskt sett var andelen PEFC - certifierade inköp större i de södra samt mellersta delarna av företagets inköpsområde än i de norra.</p><p>Följande slutsatser har gjorts:</p><p>- Företaget är geografiskt sett starkast i de församlingar närmast koncernens sågverk</p><p>- Företaget måste satsa mer energi på att skaffa nya kontakter i de församlingar där få eller inga inköp görs</p><p>- Andelen PEFC - certifierade inköp är större i södra och mellersta delarna av företagets inköpsområde</p><p>- Inköparna måste bli bättre på att certifiera markägare</p> / <p>This report aims to get a geographic overview in which parish Derome Skog AB make many respective few purchase. How much different there is between the real and estimated volume and how big share of the purchase that are certified.</p><p>Information about the wood year 2005-2007 collected and study’s from the company’s businessystem and mapprogramme. The result shows that the company has as most number of purchases the wood year 2005. Geographical has the company as most purchase in the parish nearest the groups own sawmills. The real volume was a little more than the estimated in all the year that have been study. The share of purchases that are PEFC - certified lie around 50 percent under the three study wood year. Geographical was the share of PEFC - certified purchases bigger in the south and middle of the company’s sphere of activities than in the north.</p><p>Following conclusion has taken:</p><p>- The company are geographical strongest in the parish close to the groups own sawmills</p><p>- The company must put more energy to get new contacts in the parish there are week in</p><p>- The share PEFC - certified purchase was higher in the southern and middle of the company’s sphere of activies</p><p>- The inpurchaser have to get better in PEFC - certify the landowner</p>

The objectives of this doctoral thesis are to give a basisincluding methods for the development of stationary polymerelectrolyte fuel cell (PEFC) systems for combined heat andpower production. Moreover, the objectives include identifyingprerequisites, requirements and possibilities for PEFC systemsproducing heat and power for buildings in Sweden. The PEFCsystem is still in a pre-commercial state, but low emissionlevels, fast dynamics and high efficiencies are promisingcharacteristics. A thermodynamic model to simulate stationary PEFC systemshas been constructed and pinch technology and exergy analysesare utilised to design and evaluate the system. The finalsystem configuration implies a high total efficiency ofapproximately 98 % (LHV). A flexible test facility was built in connection with theresearch project to experimentally evaluate small-scalestationary PEFC systems at KTH. The research PEFC system hasextensive measurement equipment, a rigorous control system andallows fuel cell systems from approximately 0.2 to 4 kWel insize to be tested. The simulation models of the fuel processorand the fuel cell stack are verified with experimental datataken from the test facility. The initial evaluation andsimulation of the first residential installation of a PEFCsystem in Sweden is also reported. This PEFC system, fuelled bybiogas and hydrogen, is installed in an energy system alsoincluding a photovoltaic array, an electrolyser and hydrogenstorage. Technical aspects of designing a fuel cell system-basedenergy system, including storages and grid connections, whichprovides heat and power to a building are presented in thisthesis. As a basis for the technical and economic evaluations,exemplifying energy systems are constructed and simulated. Fuelcell system installations are predicted to be economicallyunviable for probable near-term conditions in Sweden. The mainfactor in the economic evaluations is the fuel price. However,fuel cell system installations are shown to have a higher fuelutilisation than the conventional method of energy supply. The methods presented in this thesis serve as a collectedbasis for continued research and development in the area. Keywords:Small-scale, stationary, fuel cell system,polymer electrolyte fuel cell, PEFC system, reformer,thermodynamic modelling, pinch technology, exergy analyses,system configuration, test facility, experiments, application,simulation, installation, energy system, energy storage, heatand power demand.

The proton exchange membrane fuel cell (PEMFC) is a potential electrochemicalpower device for vehicles, auxiliary power units and small-scale power plants. In themembrane electrode assembly (MEA), which is the core of the PEMFC single cell,oxygen in air and hydrogen electrochemically react on separate sides of a membraneand electrical energy is generated. The main challenges of the technology are associatedwith cost and lifetime. To meet these demands, firstly, the component expensesought to be reduced. Secondly, enabling system operation at elevated temperatures,i.e. up to 120 °C, would decrease the complexity of the system and subsequentlyresult in decreased system cost. These aspects and the demand for sufficientlifetime are the strong motives for development of new materials in the field.In this thesis, MEAs based on alternative materials are investigatedwith focus on hydrocarbon proton-conducting polymers, i.e. ionomers, and newcatalyst supports. The materials are evaluated by electrochemical methods, such ascyclic voltammetry, polarisation and impedance measurements; morphological studiesare also undertaken. The choice of ionomers, used in the porous electrodes andmembrane, is crucial in the development of high-performing stable MEAs for dynamicoperating conditions. The MEAs are optimised in terms of electrode compositionand preparation, as these parameters influence the electrode structure andthus the MEA performance. The successfully developed MEAs, based on the hydrocarbonionomer sulfonated polysulfone (sPSU), show promising fuel cell performancein a wide temperature range. Yet, these membranes induce mass-transportlimitations in the electrodes, resulting in deteriorated MEA performance. Further,the structure of the hydrated membranes is examined by nuclear magnetic resonancecryoporometry, revealing a relation between water domain size distributionand mechanical stability of the sPSU membranes. The sPSU electrodes possessproperties similar to those of the Nafion electrode, resulting in high fuel cell performancewhen combined with a high-performing membrane. Also, new catalystsupports are investigated; composite electrodes, in which deposition of platinum(Pt) onto titanium dioxide reduces the direct contact between Pt and carbon, showpromising performance and ex-situ stability. Use of graphitised carbon as catalystsupport improves the electrode stability as revealed by a fuel cell degradation study.The thesis reveals the importance of a precise MEA developmentstrategy, involving a broad methodology for investigating new materials both as integratedMEAs and as separate components. As the MEA components and processesinteract, a holistic approach is required to enable successful design of newMEAs and ultimately development of high-performing low-cost PEMFC systems. / QC 20100922

<p>The objectives of this doctoral thesis are to give a basisincluding methods for the development of stationary polymerelectrolyte fuel cell (PEFC) systems for combined heat andpower production. Moreover, the objectives include identifyingprerequisites, requirements and possibilities for PEFC systemsproducing heat and power for buildings in Sweden. The PEFCsystem is still in a pre-commercial state, but low emissionlevels, fast dynamics and high efficiencies are promisingcharacteristics.</p><p>A thermodynamic model to simulate stationary PEFC systemshas been constructed and pinch technology and exergy analysesare utilised to design and evaluate the system. The finalsystem configuration implies a high total efficiency ofapproximately 98 % (LHV).</p><p>A flexible test facility was built in connection with theresearch project to experimentally evaluate small-scalestationary PEFC systems at KTH. The research PEFC system hasextensive measurement equipment, a rigorous control system andallows fuel cell systems from approximately 0.2 to 4 kWel insize to be tested. The simulation models of the fuel processorand the fuel cell stack are verified with experimental datataken from the test facility. The initial evaluation andsimulation of the first residential installation of a PEFCsystem in Sweden is also reported. This PEFC system, fuelled bybiogas and hydrogen, is installed in an energy system alsoincluding a photovoltaic array, an electrolyser and hydrogenstorage.</p><p>Technical aspects of designing a fuel cell system-basedenergy system, including storages and grid connections, whichprovides heat and power to a building are presented in thisthesis. As a basis for the technical and economic evaluations,exemplifying energy systems are constructed and simulated. Fuelcell system installations are predicted to be economicallyunviable for probable near-term conditions in Sweden. The mainfactor in the economic evaluations is the fuel price. However,fuel cell system installations are shown to have a higher fuelutilisation than the conventional method of energy supply.</p><p>The methods presented in this thesis serve as a collectedbasis for continued research and development in the area.</p><p><b>Keywords:</b>Small-scale, stationary, fuel cell system,polymer electrolyte fuel cell, PEFC system, reformer,thermodynamic modelling, pinch technology, exergy analyses,system configuration, test facility, experiments, application,simulation, installation, energy system, energy storage, heatand power demand.</p>