| 1. |
- Hagman, Jens, et al.
(författare)
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Teknisk utveckling och beteende och påverkan på behov av infrastruktur
- 2023
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Denna slutrapport är resultatet av ett direktuppdrag som tilldelades RISE Research Institute of Sweden AB, efter avrop från ramavtal, av Energimyndigheten i maj 2023. Direktuppdraget är en delmängd av regeringsuppdraget ”Handlingsprogram för laddinfrastruktur och tankinfrastruktur för vätgas”. Uppdraget har genomförts av tre forskare från RISE under perioden juni till augusti år 2023 med en total budget på 250 029 kr. Det huvudsakliga syftet har varit att belysa sex teknik- och användartrender inom elektromobilitet som har potential att påverka utbyggnadsbehovet av laddinfrastruktur och tankinfrastruktur för vätgas. De sex teknik- och användartrenderna som identifierats är: Vehicle-to-Everything (V2X), batteribyten, laddhybrider 2.0, batteristorlek, bilpooler och vätgas. Teknik- och användartrenderna har analyserats individuellt genom omvärldsanalys där marknads- och teknikmognad, ledande länder/regioner och företag samt aktuell forskning är huvudsakliga källor. Vidare har varje teknik- och användartrend analyserats utifrån deras möjliga påverkan på utbyggnadsbehovet av laddinfrastruktur eller tankinfrastruktur för vätgas. I rapporten används begreppen DC snabbladdning och AC destinationsladdning. DC snabbladdning utgår ifrån EU:s definition vilket inkluderar DC laddning över 50 kW, i denna rapport innefattas även DC laddning över 150 kW vilket av EU benämns som Ultrasnabbladdning1. AC destinationsladdning syftar i denna rapport på AC laddning på upp till 22 kW, vilket av EU klassificeras som långsam (upp till 7,4 kW) och mediumsnabb AC laddning2. Arbetet bör ses som en övergripande nulägesbild över hur dessa teknik- och användartrender har utvecklats och en preliminär kvalitativ bedömning av dess möjliga påverkan på Sveriges framtida behov av infrastruktur för laddning och vätgas. För huvuddelen av teknik- och användartrenderna råder alltjämt stor osäkerhet kring framtida utveckling och den möjliga påverkan på utbyggnadsbehovet av laddinfrastruktur och tankinfrastruktur för vätgas. Området har hittills fått lite uppmärksamhet i den vetenskapliga litteraturen. Rapporten är uppdelad i sex kapitel, ett kapitel per teknik- och användartrend.
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| 2. |
- Carlson, Annika, et al.
(författare)
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The Hydrogen Electrode Reaction in the Anion Exchange Membrane Fuel Cell
- 2021
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Ingår i: Journal of the Electrochemical Society. - : The Electrochemical Society. - 0013-4651 .- 1945-7111. ; 168:3
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Tidskriftsartikel (refereegranskat)abstract
- The hydrogen electrode in the anion-exchange membrane fuel cell needs further attention to understand the overall cell limitations. In this study, electrochemical impedance spectroscopy and galvanodynamic measurements in combination with a physics-based model are used to determine the kinetic parameters of the hydrogen oxidation reaction and hydrogen evolution reaction on Pt/C porous gas-diffusion electrodes in an AEMFC. Two semicircles are observed in the Nyquist plot of a symmetrical AEM hydrogen cell, indicating a two-step reaction pathway. The fit of the model shows that the Tafel-Volmer pathway describes the kinetics better than the Heyrovsky-Volmer pathway. The reaction rates of the adsorption and charge transfer steps are similar in magnitude implying that both need consideration during modeling and evaluation of the hydrogen electrode. Furthermore, the performance is limited also by the ionic conductivity in the electrode. Comparison of the impedance of the HOR and a hydrogen/oxygen AEMFC indicates that the low-frequency semicircle is mainly associated with the oxygen reduction reaction and the cathode, while the high-frequency semicircle is likely related to a combination of the anode and the cathode. Based on this work, a platform for further studies of losses and total impedance of operating AEMFC has been created.
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| 3. |
- Grimler, Henrik, et al.
(författare)
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Determination of Kinetic Parameters for the Oxygen Reduction Reaction on Platinum in an AEMFC
- 2021
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Ingår i: Journal of the Electrochemical Society. - : The Electrochemical Society. - 0013-4651 .- 1945-7111. ; 168:12, s. 124501-
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Tidskriftsartikel (refereegranskat)abstract
- To promote the development of anion exchange membrane fuel cells (AEMFC), an understanding of the oxygen reduction reaction (ORR) kinetics in porous gas diffusion electrodes is essential. In this work, experimental polarisation curves for electrodes with different platinum catalyst loadings and oxygen partial pressures at the cathode are fitted to a physics-based porous electrode model in the voltage range from open circuit voltage (OCV) to 0.7 V. Polarisation curves measured with different anode catalyst loadings, and hydrogen partial pressures, were used to verify the model. The reactions are described using a two-step Tafel-Volmer pathway at the anode and concentration-dependent Butler-Volmer kinetics at the cathode. A good fit to experimental data in the kinetic region is obtained with an exchange current density of 1.0.10(-8)Acm(-2), a first order dependency on oxygen partial pressure, and a charge transfer coefficient of 0.8 for the ORR. For lower oxygen partial pressure, hydrogen crossover is needed to explain the downward shift of the polarisation curves in the kinetic region. In the experimental data, the polarisation curves show an apparent limiting current density at lower hydrogen partial pressures, explained by the lower rate of the Tafel step at these conditions.
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| 4. |
- Carlson, Annika, et al.
(författare)
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Fuel cell evaluation of anion exchange membranes based on poly(phenylene oxide) with different cationic group placement
- 2020
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Ingår i: Sustainable Energy & Fuels. - : Royal Society of Chemistry. - 2398-4902. ; 4:5, s. 2274-2283
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Tidskriftsartikel (refereegranskat)abstract
- Four novel poly(phenylene oxide)-based anion exchange membranes were investigated for electrochemical performance, ionic conductivity and water transport properties in an operating anion exchange membrane fuel cell (AEMFC), using Pt/C gas diffusion electrodes with Tokuyama ionomer. The poly(phenylene oxide)-membranes have a 1- or 5-carbon alkyl spacer between the backbone and a trimethylalkylammonium (TMA) or piperidinium (Pip) cationic group, and ion-exchange capacities (IECs) between 1.5 and 1.9 mequiv g(-1). The polymer with a 5-carbon alkyl spacer, a TMA cationic group, and a higher IEC showed the highest ion conductivity and performance in the AEMFC. The results also show that introducing a 5-carbon alkyl spacer does not improve performance unless the IEC is increased and that exchanging the TMA with a Pip cationic group results in lower fuel cell performance despite a higher IEC. A discrepancy in ion conductivity between fuel cell and ex situ test was observed for the 5-carbon spacer polymers and is attributed to a higher sensitivity for dehydration. Similar water flux under load, from the anode to the cathode with increased water content at both electrodes, was observed for all membranes and only varied with membrane thickness. The deviation in fuel cell performance observed between the membranes could not be explained by differences in water flux or ionic conduction, suggesting that the electrode-membrane interaction plays a major role. Nevertheless, the study emphasizes that high membrane conductivity (for the lambda-range in a fuel cell) and efficient water transport (obtained by lower membrane thickness) promote higher electrochemical performance.
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| 5. |
- Carlson, Annika, et al.
(författare)
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Fuel cell evaluation of anion exchange membranes based on poly(phenylene oxide) with different cationic group placement
- 2020
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Ingår i: Sustainable Energy & Fuels. - 2398-4902. ; 4:5, s. 2274-2283
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Tidskriftsartikel (refereegranskat)abstract
- Four novel poly(phenylene oxide)-based anion exchange membranes were investigated for electrochemical performance, ionic conductivity and water transport properties in an operating anion exchange membrane fuel cell (AEMFC) , using Pt/C gas diffusion electrodes with Tokuyama ionomer. The poly(phenylene oxide)-membranes have a 1- or 5-carbon alkyl spacer between the backbone and a trimethylalkylammonium (TMA) or piperidinium (Pip) cationic group, and ion-exchange capacities (IECs) between 1.5 and 1.9 mequiv g-1. The polymer with a 5-carbon alkyl spacer, a TMA cationic group, and a higher IEC showed the highest ion conductivity and performance in the AEMFC. The results also show that introducing a 5-carbon alkyl spacer does not improve performance unless the IEC is increased and that exchanging the TMA with a Pip cationic group results in lower fuel cell performance despite a higher IEC. A discrepancy in ion conductivity between fuel cell and ex-situ test was observed for the 5-carbon spacer polymers and is attributed to a higher sensitivity for dehydration. Similar water flux under load, from the anode to the cathode with increased water content at both electrodes, was observed for all membranes and only varied with membrane thickness. The deviation in fuel cell performance observed between the membranes could not be explained by differences in water flux or ionic conduction, suggesting that the electrodes – membrane interaction plays a major role. Nevertheless, the study emphasizes that high membrane conductivity (for the λ-range in a fuel cell) and an efficient water transport (obtained by lower membrane thickness) promote higher electrochemical performance.
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| 6. |
- Carlson, Annika
(författare)
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Electrochemical properties of alternative polymer electrolytes in fuel cells
- 2019
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Fuel cells, using hydrogen as energy carrier, allow chemically‑stored energy to be utilized for many applications, including balancing the electrical grid and the propulsion of vehicles. To make the fuel cell technology more accessible and promote a sustainable energy society, this thesis focuses on alternative polymer electrolytes, as they can potentially lead to a lower cost and a more environmentally‑friendly fuel cell. The main subject is anion exchange membrane fuel cells (AEMFCs), for which the importance of gas diffusion electrode morphology and platinum electrode reactions are investigated. Properties of the membrane such as water flux during operation are evaluated. Furthermore, novel polymer electrolytes are studied: variations of poly(phenylene oxide)‑based membranes in AEMFCs; and cellulose‑based membranes in a proton exchange membrane fuel cell (PEMFC). The AEMFC results show that the performance is dependent on the electrode morphology. Electrochemical experiments in a hydrogen/hydrogen cell combined with modelling show that the hydrogen oxidation reaction proceeds through the Tafel‑Volmer reaction pathway on platinum. Application of the model in a hydrogen/oxygen cell shows that the cathode has the slowest reaction rate. During operation, the water flux through the membrane is directed from the anode where water is produced to the cathode where it is consumed. This leads to an increase in water content at both electrodes, which implies that electrode flooding is more likely than dry‑out during operation. The effect of membrane thickness on water flux is shown to be larger than the effect of polymer structure for several different types of poly(phenylene oxide)‑based membranes. The comparison of these polymers also indicates that a high conductivity, for the relative humidity achieved in a fuel cell, promotes increased performance. Finally, the study of cellulose-based membranes in a PEMFC shows that cellulose as a renewable, natural polymer has promising properties, such as stable conductivity for relative humidities above 65 % and a low gas permeability.
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| 7. |
- Carlson, Annika, et al.
(författare)
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Kinetic parameters in anion-exchange membrane fuel cells
- 2019
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Ingår i: ECS Transactions. - : Electrochemical Society Inc.. - 1938-6737 .- 1938-5862. - 9781607685395 ; , s. 649-659
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Konferensbidrag (refereegranskat)abstract
- Understanding limitations in an operating AEMFC is essential to .enhance the technology. Here the electrode processes are studied experimentally as well as by two physics-based models taking the porosity of the electrodes into account. The aim is to use the models to determine kinetic parameters specific for in-situ operation. The models can also be used to explain the experimental .behavior. From the impedance model of a symmetric H2/H2 cell it is shown that the hydrogen oxidation reaction (HOR) proceeds through the Tafel-Volmer reaction pathway, with the hydrogen adsorption as the slower reaction step. Based on the HOR model a •steady-state model of an O2/H2 cell is used to evaluate data from 14 experimental I-V curves, obtained for different gas partial pressures and catalyst loadings, in order to study the effects of the oxygen reduction reaction and overall cell limitations. The results show that the oxygen reduction reaction kinetics limit the cell performance for low current densities. However, at higher currents the uneven current distribution and locally low hydrogen adsorption at the anode increasingly affect the overall performance. Uneven current distribution is also observed at the cathode and likely caused by insufficient effective ionomer conductivity.
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| 8. |
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| 9. |
- Eriksson, Björn, et al.
(författare)
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Quantifying water transport in anion exchange membrane fuel cells
- 2019
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Ingår i: International journal of hydrogen energy. - : Elsevier. - 0360-3199 .- 1879-3487. ; 44:10, s. 4930-4939
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Tidskriftsartikel (refereegranskat)abstract
- Sufficient water transport through the membrane is necessary for a well-performing anion exchange membrane fuel cell (AEMFC). In this study, the water flux through a membrane electrode assembly (MEA), using a Tokuyama A201 membrane, is quantified using humidity sensors at the in- and outlet on both sides of the MEA. Experiments performed in humidified inert gas at both sides of the MEA or with liquid water at one side shows that the aggregation state of water has a large impact on the transport properties. The water fluxes are shown to be approximately three times larger for a membrane in contact with liquid water compared to vaporous. Further, the flux during fuel cell operation is investigated and shows that the transport rate of water in the membrane is affected by an applied current. The water vapor content increases on both the anode and cathode side of the AEMFC for all investigated current densities. Through modeling, an apparent water drag coefficient is determined to −0.64, indicating that the current-induced transport of water occurs in the opposite direction to the transport of hydroxide ions. These results implicate that flooding, on one or both electrodes, is a larger concern than dry-out in an AEMFC.
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| 10. |
- Guccini, Valentina, et al.
(författare)
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Highly proton conductive membranes based on carboxylated cellulose nanofibres and their performance in proton exchange membrane fuel cells
- 2019
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Ingår i: Journal of Materials Chemistry A. - : Royal Society of Chemistry. - 2050-7488 .- 2050-7496. ; 7:43, s. 25032-25039
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Tidskriftsartikel (refereegranskat)abstract
- The performance of thin carboxylated cellulose nanofiber-based (CNF) membranes as proton exchange membranes in fuel cells has been measured in situ as a function of CNF surface charge density (600 and 1550 μmol g−1), counterion (H+ or Na+), membrane thickness and fuel cell relative humidity (RH 55 to 95%). The structural evolution of the membranes as a function of RH, as measured by Small Angle X-ray Scattering, shows that water channels are formed only above 75% RH. The amount of absorbed water was shown to depend on the membrane surface charge and counter ions (H+ or Na+). The high affinity of CNF for water and the high aspect ratio of the nanofibers, together with a well-defined and homogenous membrane structure, ensures a proton conductivity exceeding 1 mS cm−1 at 30 °C between 65 and 95% RH. This is two orders of magnitude larger than previously reported values for cellulose materials and only one order of magnitude lower than Nafion 212. Moreover, the CNF membranes are characterized by a lower hydrogen crossover than Nafion, despite being ≈30% thinner. Thanks to their environmental compatibility and promising fuel cell performance the CNF membranes should be considered for new generation proton exchange membrane fuel cells.
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