| 1. |
- Lindberg, Aleksandra, 1990-, et al.
(author)
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Gas phase composition of a NiMH battery during a work cycle
- 2024
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In: RSC Advances. - : Royal Society of Chemistry (RSC). - 2046-2069. ; 14:28, s. 19996-20003
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Journal article (peer-reviewed)abstract
- Side reactions leading to gas evolution are undesirable in batteries and result in reduced coulombic efficiency and shortened lifetime. Quantitative analysis of the gases that evolve is therefore important to improve understanding of the reactions occurring in the battery during cycling and could be used to optimize battery operation. However, the measurements are challenging because batteries are by their nature closed with limited gas space. Nickel metal hydride (NiMH) batteries are widely used due to their good rate capability, reliability, and environmental friendliness. The battery type has been extensively studied in terms of degradation and performance. However, very few studies have been conducted on the gas composition created during a work cycle. In this study, two methods for investigating the internal NiMH battery gas phase composition during different charge/discharge cycles using a mass spectrometer (MS) were developed. In the first method, the battery module was connected by a sampler system. In the second method, the battery was connected directly using a microcapillary, and the gas composition was continuously measured. In addition to the gas composition, the voltage, pressure, and temperature of the battery were recorded. The most abundant component in the measured gas phase was nitrogen, present in the cell from the assembly stage, followed by hydrogen. A clear rising trend of hydrogen pressure as depth of charge (DOC) increased was recorded, while oxygen levels were low except around the end of charge. The methods were found to be a reliable means of investigating NiMH gas composition without negatively affecting the battery and may be adapted to other battery chemistries. In this study, two methods for investigating the internal NiMH battery gas phase composition during different charge/discharge cycles using a mass spectrometer (MS) were developed.
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| 2. |
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| 3. |
- Rossini, Matteo, et al.
(author)
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Rational design of membrane electrode assembly for anion exchange membrane water electrolysis systems
- 2024
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In: Journal of Power Sources. - : Elsevier BV. - 0378-7753 .- 1873-2755. ; 614
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Journal article (peer-reviewed)abstract
- Anion exchange membrane water electrolysis (AEMWE) is a promising and potentially low-cost technology for producing green hydrogen, but a novel manufacturing technique with rational design of the electrodes is essential to improve the performance and stability. In this work, we investigate the effect of electrode structure on activity and the stability of AEMWEs by fabricating membrane electrode assemblies (MEAs). For the first time, the decal transfer method with platinum-group-metal-free (PGM-free) catalyst was successfully used in AEMWEs. With this method, deposition of a compact catalyst layer (CL) on the membrane was achieved without damaging neither the CL nor the membrane. The MEAs were designed for AEMWE using 1 M KOH as the electrolyte and the ionomer content was optimized for both cathode and anode. In the anode, a low ionomer loading improved activity and ionic conductivity, however, a higher ionomer content was beneficial for the cathode. Furthermore, the type of ionomer on the anode side has shown to be the major reason of loss of performance over time. An ionomer with low (1.4–1.7 meq g−1) Ion Exchange Capacity (IEC) and Nafion™ ionomer greatly improved the stability.
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| 4. |
- Bakka, Conrad, 1988-
(author)
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Debunking Debunked? : Challenges, Prospects, and the Threat of Self-Defeat
- 2023
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Doctoral thesis (other academic/artistic)abstract
- Metaethical debunking arguments often conclude that no moral belief is epistemically justified. Early versions of such arguments largely relied on metaphors and analogies and left the epistemology of debunking underspecified. Debunkers have since come to take on substantial and broad-ranging epistemological commitments. The plausibility of metaethical debunking has thereby become entangled in thorny epistemological issues. In this thesis, I provide a critical yet sympathetic evaluation of the prospects and challenges facing such arguments in light of this development. In doing so, I address the following central question: how could genealogical information undermine the epistemic justification of moral beliefs? In Part I, I begin answering the central question by extracting explicit and implicit epistemic principles from three popular debunking arguments. These arguments, due to Gilbert Harman, Richard Joyce, and Sharon Street, generate principles concerning ontological parsimony, explanatory dispensability, epistemic insensitivity, lack of epistemic safety, unexplained reliability, epistemic coincidences, and explanatory constraints on rational belief. Having set out the principles tasked with explaining how genealogical information undermines, Part II of the thesis seeks to evaluate whether debunking arguments built on them succeed. To this end, I consider two types of challenges faced by such arguments. First, there are strategies that attempt to block global moral debunking arguments. I argue that one popular such strategy, the so-called ‘third-factor strategy’, has been misunderstood. When understood correctly, it is of no help in answering debunking arguments. I then flesh out an alternative and more promising strategy for blocking such arguments. I then turn to internal challenges facing debunkers, particularly those who rely on ‘explanationist’ principles. I argue that explanationist debunking arguments, as well as most others, fall prey to one or more of four internal challenges: the implausibility of first-order epistemic principles, the threat of overgeneralization, the threat of self-defeat, and the need for costly metaepistemic commitments.I conclude that current debunking arguments fail to establish that no moral belief is justified. By analyzing why existing arguments fail, I develop two conditions of adequacy that debunkers must satisfy in order to navigate the internal challenges successfully. I end by suggesting future directions that debunkers should pursue to rehabilitate the prospects for global moral debunking arguments.
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| 5. |
- Berger, Thor, et al.
(author)
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Social Mobility in Sweden before the Welfare State
- 2023
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In: Journal of Economic History. - : Cambridges Institutes Press. - 0022-0507 .- 1471-6372. ; 83:2, s. 431-463
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Journal article (peer-reviewed)abstract
- We use historical census data to show that Sweden exhibited high levels of intergenerational occupational mobility several decades before the rise of the welfare state. Mobility rates were higher than in other nineteenth- and twentieth-century European countries, closer to those observed in the highly mobile nineteenth-century United States. We leverage mobility variation across Swedish municipalities to shed light on potential determinants: economic growth and migration are positively correlated with mobility, consistent with the patterns observed across countries.
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| 6. |
- Boonstra, Wiebren Johannes, Dr. 1976-, et al.
(author)
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Understanding and analysing the complex causality of conflicts over marine environments through process tracing
- 2023
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In: Maritime Studies. - : Springer Nature. - 1872-7859 .- 2212-9790. ; 22:2
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Research review (peer-reviewed)abstract
- As economic activity in marine environments accelerates and expands, conflicts may increase following increased demand over marine resources, unequal distribution of benefits, as well as fluctuating resource availability and quality due to climate change. Anticipation and resolution of these conflicts require understanding of the causal mechanisms through which they originate and persist. Process tracing is a promising social science method that allows producing this knowledge by sequentially ordering events that produce conflict. The aim of this paper is to introduce process tracing as a method for the study of conflicts over marine environments and to assess how the method so far is used in previous studies of conflicts over marine environments. Our review of these studies reveals that scholars of conflicts over marine environments tend to apply process tracing using a deductive approach and a probabilistic understanding of causal mechanisms. The causal mechanisms that are identified to understand the dynamics that drive conflicts over marine environments often include power dynamics between states, institutions, movements or communities. Less articulated is how local social dynamics drives conflicts and how scholars select their cases to represent a wider population of conflicts. We conclude that applying a micro-sociological approach, more attention to case selection, and the interaction between contexts and mechanisms are promising ways forward for further use of process tracing in maritime studies.
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| 7. |
- Butori, Martina, et al.
(author)
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The effect of oxygen partial pressure and humidification in proton exchange membrane fuel cells at intermediate temperature (80-120 degrees C)
- 2023
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In: Journal of Power Sources. - : Elsevier BV. - 0378-7753 .- 1873-2755. ; 563, s. 232803-
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Journal article (peer-reviewed)abstract
- The integration of proton exchange membrane fuel cells (PEMFCs) in heavy-duty vehicles would be facilitated if operating temperatures above 100 degrees C were possible. In this work, the effect of temperature in the intermediate range of 80-120 degrees C is investigated for a commercial membrane electrode assembly (MEA) through polarization curves and electrochemical impedance spectroscopy. The importance of oxygen partial pressure on voltage is systematically studied by decoupling it from humidity and temperature. The results show that adequate oper-ation at intermediate temperature is achievable if the oxygen partial pressure is sufficient. Although the cathode kinetics is faster with rising temperatures, the voltage gain is counteracted by the decreasing equilibrium po-tential. At intermediate temperature, the water transport is enhanced, levelling out the relative humidity dif-ference between anode and cathode. However, ionic conductivity in the polymer can become limiting at high currents, due to a smaller relative humidity increase at these temperatures. To conclude, a higher operating temperature does not inherently cause a decrease in obtained current density. Rather, the difficulty to simul-taneously have sufficient oxygen partial pressure and high relative humidity causes limitations within the cathode that to some extent can be solved by pressurizing the cell.
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| 8. |
- Dribe, Martin, et al.
(author)
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From Sweden to America: Migrant Selection in the Transatlantic Migration, 1890-1910
- 2023
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In: European Review of Economic History. - : Oxford University Press (OUP). - 1474-0044 .- 1361-4916. ; 27:1, s. 24-44
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Journal article (peer-reviewed)abstract
- We examine selection by class origin and gender in the emigration from Sweden to the United States during the age of mass migration. We use full-count census data linked to emigration lists to create a panel of over one million men and women. Class selection was similar for men and women, with children from medium-skilled backgrounds being most likely to leave. Selection on class origin was most pronounced in poorer and less industrialized regions, but similar in rural and urban areas. These patterns suggest that not only returns to skill determined migrant selection but also class-specific costs of migration.
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| 9. |
- Marra, Eva, et al.
(author)
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ORR activity and stability of carbon supported Pt3Y thin films in PEMFCs
- 2023
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In: Electrochimica Acta. - : Elsevier BV. - 0013-4686 .- 1873-3859. ; 472
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Journal article (peer-reviewed)abstract
- In order to investigate stability of oxygen reduction reaction (ORR) on a Pt3Y thin film under relevant fuel cell conditions, we performed an accelerated stress test (AST) consisting of 3600 potential cycles between 0.4 and 1.4 V at 1 V s−1 in a single proton exchange membrane fuel cell (PEMFC). The ORR activities were evaluated via polarization curves before and after the AST. Electrochemical active surface area (ECSA) was obtained by CO-stripping voltammetry whereas the morphological changes were monitored by means of scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Variations in surface composition and electronic structures were evaluated by energy-dispersive X-ray spectroscopy (EDX) and X-ray photoelectron spectroscopy (XPS). After AST, the polarization curves show loss of ORR activity in all voltages for both Pt and Pt3Y. Except at very high voltages (E > 0.85 VRHE), the ORR activity of Pt3Y after AST is very close to that of Pt before AST. This correlates well with the results from the deconvolution of Pt-4f XPS spectra where the binding energy of metallic Pt in Pt3Y is comparable to pure Pt (71.22 eV). SEM and TEM images demonstrate that the morphologies of the aged Pt3Y and as-sputtered Pt are similar, whereas EDX results confirm a steady bulk composition of Pt3Y thin films throughout the entire electrochemical test. By correlating all these results, we conclude that the loss of ORR activity for Pt3Y is due to an increase in the thickness of the Pt overlayer which induces a relaxation of the Pt overlayer decreasing the compressive strain effect. For pure Pt, the loss of ORR activity is associated with a growth of the Pt domains associated with Ostwald ripening process.
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| 10. |
- Novalin, Timon, et al.
(author)
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Demonstrating the absence of metal ion contamination in operando PEM fuel cells utilizing unmodified stainless steel bipolar plates
- 2023
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In: Applied Energy. - : Elsevier BV. - 0306-2619 .- 1872-9118. ; 349
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Journal article (peer-reviewed)abstract
- Using stainless steel as material for bipolar plates (BPPs) in proton exchange membrane fuel cells (PEMFCs) carries a perceived risk of corrosion and subsequent metal ion contamination of the membrane electrode as-sembly (MEA). However, assessments in literature on this hazard to PEMFC systems have been based on ex-situ corrosion studies, where general assumptions made on the BPP environment might not be a correct simulation of real on-site conditions. In this contribution, uncoated BPPs from stainless steel grades 304 L, 316 L and 904 L were subjected to in-situ hybrid endurance/stress testing to simulate realistic conditions in operating fuel cell systems and re-evaluate the need of additional corrosion protection. A post analysis of the plates showed no signs of surface dissolution on any of the tested samples and the concentration of iron in the MEA averaged 7 to 10 ppm for uncoated samples and 7 to 11 ppm for coated and graphitic reference tests, displaying a negligible amount of trace metals compared to critical thresholds found in literature. Contact resistance values were stable for all samples and observable changes in cell performance and voltage degradation was confirmed to be un-related to the presence of uncoated bipolar plates. The combined effects of decoupling of bipolar plate surface potentials from electrode potentials and operational control of stable gas flow compositions to sustain stainless steel surface passivation, were identified as explanation for the experimentally observed corrosion resistance of uncoated stainless steel plates in PEMFCs.
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