Thesis--Copenhagen. / Translated by Anna la Cour and Ibbetson James. Bibliography: p. [221]-229.

Carbon monoxide (CO) poisoning represents a global health threat responsible for hundreds of thousands of hospital visits and tens of thousands of deaths annually. Oxygen therapy is the only current approved treatment for CO poisoning. Previous work published in the 1970’s and research conducted in the VCURES lab group has indicated that a reduced form of vitamin B12, hydroxocobalamin (B12r), can potentially serve as an antidote for CO poisoning by converting CO bound to hemoglobin to carbon dioxide (CO2) and mitigating the deleterious neurological effects of CO poisoning. For the first time in documented literature we successfully used a Clark-type polarographic oxygen-sensitive electrode to demonstrate CO-induced decreases in brain tissue oxygen tension in anesthetized rats. Additionally, we demonstrated that B12r is capable of rescuing this CO-induced hypoxia and hypotension within 15 minutes of intraperitoneal administration with no adverse effects on blood chemistry.

Diss. (sammanfattning) Umeå : Univ., 2007. / Härtill 4 uppsatser.

Thesis--Copenhagen University. / Summary in Danish. Bibliography: p. [119]-141.

Thesis--Copenhagen University. / Summary in Danish. Bibliography: p. [119]-141.

Polymer electrolyte membrane (PEM) fuel cells are promising alternative green power source for mobile, portable and stationary applications. However, their cost, durability, and performance are impacted by their sensitivity to impurities in fuel stream. Carbon monoxide (CO), an impurity commonly present in the hydrogen gas produced from hydrocarbon fuels, is known to have a significant degrading effect on PEM fuel cell performance because CO has a strong affinity to the platinum-based catalyst. At present, most studies in literature are limited to either experimental or simplified-dimensional analysis/modeling. In this thesis research, a three-dimensional (3D) multiphase PEM fuel cell model with the CO poisoning and O2 bleeding is developed based on the conservation laws for mass, momentum, energy, and species, and implemented in the commercial software Fluent (6.3.26) through the user-defined functions. Numerical simulations are conducted to simulate a single PEM fuel cell including flow channels, gas diffusion layers, catalyst layers, and PEM. The simulation results are compared with experimental data favorably. The result shows that the reaction rate of hydrogen in the anode catalyst layer is higher near the membrane layer, decreasing towards the gas diffusion layer (GDL) interface, and the reaction rate in general is higher in the inlet region and decreases towards the exit region of the flow channel. It means that the outlet of anode catalyst layer next to the flow channel and GDL has suffered the most significant poisoning effect. The result helps optimize the design of anode catalyst layer by embedding more platinum on the most poisoned area to increase available surface for hydrogen adsorption; similarly, reducing platinum loading on the less poisoned area. The fuel cell performance can be almost fully recovered when switching the anode fuel mixture to pure hydrogen, though it takes a long period of time. The reaction rate of hydrogen decreases significantly along the flow channel when impurity mixture is provided; while there is little change along the channel for pure hydrogen fuel. Adding oxygen into the anode fuel mixture can mitigate CO poisoning, but there is a time delay when the oxygen is introduced into the anode stream and when the performance starts to recover. It is observed that at the beginning of oxygen introduced in the anode stream the recovery rate in the region adjacent to the channel outlet is faster than the rate in the region close to the inlet. This difference in the recovery rate gradually becomes smaller over time. In addition, the influence of CO poisoning and oxygen bleeding on multi-phase water is investigated. The influence on dissolved water is only clearly seen in the anode catalyst layer next to the land area. Finally, response to sudden load changes is simulated by changing cell voltage. It is found that the overshoot and undershoot are more significant at high current densities.

Polymer electrolyte membrane (PEM) fuel cells are promising alternative green power source for mobile, portable and stationary applications. However, their cost, durability, and performance are impacted by their sensitivity to impurities in fuel stream. Carbon monoxide (CO), an impurity commonly present in the hydrogen gas produced from hydrocarbon fuels, is known to have a significant degrading effect on PEM fuel cell performance because CO has a strong affinity to the platinum-based catalyst. At present, most studies in literature are limited to either experimental or simplified-dimensional analysis/modeling. In this thesis research, a three-dimensional (3D) multiphase PEM fuel cell model with the CO poisoning and O2 bleeding is developed based on the conservation laws for mass, momentum, energy, and species, and implemented in the commercial software Fluent (6.3.26) through the user-defined functions. Numerical simulations are conducted to simulate a single PEM fuel cell including flow channels, gas diffusion layers, catalyst layers, and PEM. The simulation results are compared with experimental data favorably. The result shows that the reaction rate of hydrogen in the anode catalyst layer is higher near the membrane layer, decreasing towards the gas diffusion layer (GDL) interface, and the reaction rate in general is higher in the inlet region and decreases towards the exit region of the flow channel. It means that the outlet of anode catalyst layer next to the flow channel and GDL has suffered the most significant poisoning effect. The result helps optimize the design of anode catalyst layer by embedding more platinum on the most poisoned area to increase available surface for hydrogen adsorption; similarly, reducing platinum loading on the less poisoned area. The fuel cell performance can be almost fully recovered when switching the anode fuel mixture to pure hydrogen, though it takes a long period of time. The reaction rate of hydrogen decreases significantly along the flow channel when impurity mixture is provided; while there is little change along the channel for pure hydrogen fuel. Adding oxygen into the anode fuel mixture can mitigate CO poisoning, but there is a time delay when the oxygen is introduced into the anode stream and when the performance starts to recover. It is observed that at the beginning of oxygen introduced in the anode stream the recovery rate in the region adjacent to the channel outlet is faster than the rate in the region close to the inlet. This difference in the recovery rate gradually becomes smaller over time. In addition, the influence of CO poisoning and oxygen bleeding on multi-phase water is investigated. The influence on dissolved water is only clearly seen in the anode catalyst layer next to the land area. Finally, response to sudden load changes is simulated by changing cell voltage. It is found that the overshoot and undershoot are more significant at high current densities.

During the last two years, the electricity prices in Sweden have risen due to unstable weather conditions, recovery from the COVID-19 pandemic and limited access to electricity. This has led to people finding alternative ways of heating up their residences, e.g., fireplace. The Swedish Medical Products Agency found an increase in carbon monoxide poisoning related to residential heating during 2022, which gave the topic a boost in the news and media. The aim for the study was to investigate the knowledge about carbon monoxide poisoning among Swedish house owners, and to see if there was a correlation between electricity prices and number of cases carbon monoxide poisoning in Sweden during the period 2008-2021. A paper- and web survey was conducted and sent out to 480 Swedish houseowners, selected by Postnord. Electricity prices and cases of carbon monoxide poisoning was received from the internet via Statistics Sweden and the Swedish National Board of Health and Welfare. Regarding the questions covered in this study, house owners' knowledge varied. Recognition of the symptoms and prevalence of carbon monoxide poisoning was known by most of the respondents, whilst course of action in case of intoxication was not as well known. A weak positive correlation was shown between electricity prices and number of cases carbon monoxide poisoning. The increase in electricity prices and the number of cases carbon monoxide poisoning during the 2020s, would make it interesting to do further investigation.

Οι κυψέλες καυσίμου είναι ηλεκτροχημικές διατάξεις οι οποίες επιτρέπουν την απευθείας μετατροπή της ελεύθερης χημικής ενέργειας ενός καυσίμου σε ηλεκτρική. Οι κυψέλες καυσίμου πολυμερικής μεμβράνης (ΡΕΜ) αποτελούν μία υποσχόμενη τεχνολογία που βρίσκεται κοντά στο στάδιο της εμπορευματοποίησης. Το κυριότερο καύσιμο που χρησιμοποιείται στις κυψέλες καυσίμου είναι το υδρογόνο, το οποίο παράγεται συνήθως από αναμόρφωση υδρογονανθράκων ή αλκοολών. Το μονοξείδιο του άνθρακα που παράγεται επίσης κατά την διαδικασία της αναμόρφωσης αποτελεί ένα σημαντικό άλυτο πρόβλημα στις κυψέλες ΡΕΜ, καθώς η ρόφησή του στην άνοδο της κυψέλης προκαλεί την υποβάθμιση της λειτουργίας της. Το φαινόμενο της ηλεκτροχημικής ενίσχυσης συνίσταται στην μη-φαρανταϊκή τροποποίηση της ενεργότητας ενός καταλύτη που βρίσκεται σε επαφή με έναν στερεό ηλεκτρολύτη, ως αποτέλεσμα της μετακίνησης προωθητικών ειδών από τον ηλεκτρολύτη προς την καταλυτική διεπιφάνεια μετάλλου/αερίου, που προκαλείται από την επιβολή ρεύματος ή δυναμικού μεταξύ του καταλύτη και ενός ηλεκτροδίου αναφοράς. Στην παρούσα διατριβή μελετήθηκε η ηλεκτροχημική ενίσχυση της οξείδωσης μίγματος αναμόρφωσης μεθανόλης από ανόδους πλατίνας και χρυσού μίας κυψέλης ΡΕΜ. Αποδείχθηκε πως η ηλεκτροχημική ενίσχυση επηρεάζεται σημαντικά από το διαχεόμενο διαμέσου της πολυμερικής μεμβράνης οξυγόνο, όπως επίσης και από τις συνθήκες λειτουργίας της κυψέλης καυσίμου. Επίσης μελετήθηκε η ηλεκτρική απόδοση ανόδων πλατίνας και χρυσού παρουσία CO. Προσδιορίστηκαν οι τιμές της ενθαλπίας ρόφησης του CO στα ηλεκτρόδια πλατίνας και χρυσού, καθώς και οι τιμές της ενέργειας ενεργοποίησης της απομάκρυνσης του CO από το κάθε ηλεκτρόδιο. Επίσης μελετήθηκε η επίδραση της θερμοκρασίας στο φαινόμενο της πολλαπλότητας μονίμων καταστάσεων κατά την λειτουργία κυψελών ΡΕΜ. Παρατηρήθηκε εξασθένηση του φαινομένου με την αύξηση της θερμοκρασίας, σε συμφωνία με τις προβλέψεις του μοντέλου γ. / Fuel cells are electrochemical devices which convert chemical energy of a fuel directly to electricity. Polymer electrolyte membrane (PEM) fuel cells are close to commercialization. The most common fuel used is hydrogen, which is usually produced via hydrocarbons or alcohol reforming. However, during this process, carbon monoxide is formed as well, adsorbs strongly on the anode of the cell and thus impairs significantly its performance. The electrochemical promotion effect is a phenomenon where application of constant current or potential between a catalyst supported on a solid electrolyte and a reference electrode, leads to non-Faradaic changes in catalytic activity. In this thesis, it was studied the electrochemical promotion of oxidation of a methanol reformate mixture on platinum and gold anodes of a PEM fuel cell. It was found that electrochemical promotion is influenced by oxygen crossover through the polymer membrane and also by the cell operating conditions. Moreover, the electrical efficiency of platinum and gold anodes in presence of CO was studied and the values of the heat of CO adsorption on each anode and the activation energies of CO removal were estimated. Finally, the effect of temperature on the phenomenon of steady-state multiplicities was studied. It was found that increasing the temperature, the phenomenon of multiplicities is suppressed in agreement with the gama model.