A graphene-based microporous layer for proton exchange membrane fuel cells: Characterization and performance comparison

The final publication is available at Elsevier via http://dx.doi.org/10.1016/j.renene.2018.03.065 © 2018. This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/Water management is a critical issue for proton exchange membrane (PEM) fuel cells, and the use of a microporous layer (MPL) substantially improves the PEM fuel cell performance, reliability and durability through improved water management. In this study, graphene, technically a yet-to-be-developed category of material, is investigated as a potential MPL material, due to its high electrical and thermal conductivity. MPLs made of graphene (G-MPL) have been fabricated and assessed through morphological, microstructural, physical, and electrochemical characterizations and performance testing in a single scaled-up cell. Comparison is also made with MPLs made of a conventional material, Vulcan (V-MPL). The results show that the G-MPL has a unique morphology composed of horizontally packaged graphene flakes that improves water management, in-plane electrical conductivity (up to 2 times), catalyst activity, and platinum (Pt) utilization (up to 10%). The cell with the G-MPL has a better performance than the cell with the V-MPL under both fully (100% RH) and partially (40% RH) humidified conditions, with the peak power densities of 0.98 W cm−2 and 0.60 W cm−2, respectively – these peak power densities are about 7% and 43% higher than those obtained for the cell with the V-MPL at 100% and 40% RH, respectively.Ontario-China Research and Innovation Fund (OCRIF Round 3) Natural Sciences and Engineering Research Council of Canada (NSERC) via a Discovery Gran

A novel membrane electrode assembly design for proton exchange membrane fuel cells: Characterization and performance evaluation

The final publication is available at Elsevier via https://doi.org/10.1016/j.electacta.2019.01.064 © 2019. This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/Conventional membrane-electrode assembly (MEA), a key component in proton exchange membrane fuel cells, only operates reasonably within a narrow range of operating conditions. In this study, a scaled-up MEA that can perform adequately under a wide range of humidification and flow conditions is developed. It consists of a microporous layer (MPL) composed of graphene for the cathode electrode, catalyst layers (CLs) prepared with a short-side-chain (SSC) ionomer, and a SSC electrolyte membrane. The results show that the graphene-based MPL employed on the cathode provides an excellent platform for the CL (hence promotes catalyst activity and catalyst utilization) and improves water retention, due to its unique microstructure and morphology. The proposed MEA provides stable and highly promising performance independent of flow conditions under the relative humidities (RHs) of 70% and 100%. Interestingly, the MEA also demonstrates relatively better cell performance under low-humidity conditions (40% RH), such that it performs noticeably better, as the reactants are supplied to the cell under low-flow condition, rather than moderate- and high-flow conditions.Ontario-China Research and Innovation FundNatural Sciences and Engineering Research Council of CanadaCatalysis Research for Polymer Electrolyte Fuel CellsAutomotive Partnership Canada [APCPJ 417858-11

Effect of Pt loading and catalyst type on the pore structure of porous electrodes in polymer electrolyte membrane (PEM) fuel cells

The final publication is available at Elsevier via http://dx.doi.org/10.1016/j.energy.2018.02.134 © 2018. This manuscript version is made available under the CC-BY-NC-ND 4.0 license https://creativecommons.org/licenses/by-nc-nd/4.0/Catalyst layer (CL) has a significant impact on the overall pore structure of the entire electrodes, thereby impacting the transport processes and the performance of polymer electrolyte membrane (PEM) fuel cells. In this study, the contribution of the CL to the entire electrode structure is experimentally investigated. The electrodes are prepared by using two types of catalysts with different platinum/carbon (Pt/C) ratios and Pt loadings and characterized by the method of standard porosimetry (MSP). The results show that for the same type of catalysts, as the Pt loading is increased, both the porosity and mean pore size of the electrode decrease, whereas the pore surface area increases. For a constant Pt loading, a lower Pt/C ratio results in a thicker electrode with a smaller porosity, smaller pore size, and larger pore surface area. The fractal dimension is found to be a good representative of the complexity of the pore structure of the electrode; a larger fractal dimension is detected for a higher Pt loading and a smaller Pt/C ratio.Ontario-China Research and Innovation Fund (OCRIF Round 3)Natural Sciences and Engineering Research Council of Canada (NSERC) via a Discovery GrantAutomotive Partnership Canada (APC), Natural Sciences and Engineering Research Council of Canada [Grant No. APCPJ 417858 - 11

Monitoring of particle motions in gas-solid fluidized beds by electrostatic sensors

Gas-solid fluidized beds are widely applied in numerous industrial processes. Particle motions significantly affect the performance of fluidized bed reactors and the characterization of particle movements is therefore important for fluidization quality monitoring and scale-up of reactors. Electrostatic charge signals in the fluidized bed contain much dynamic information on particle motions, which are poorly understood and explored. In this work, correlation velocities of Geldart B and D particles were measured, analyzed and compared by induced electrostatic sensors combined with cross-correlation method in the fluidized bed. The results indicated that the average correlation velocity of particle clouds increased and the normalized probability density distributions of correlation velocities broadened when the superficial gas velocity increased in the dense-phase region. Both upward and downward correlation velocities could be acquired in the dynamic bed level region. Under the same excess gas velocity, the average correlation velocity of Geldart D particles was significantly smaller than that of Geldart B particles, which was caused by the smaller bubble sizes caused by the dominant bubble split over coalescence and less volume of gas forming bubbles for Geldart D particles. The experimental results verified the reliability and repeatability of particle correlation velocity measurement by induced electrostatic sensors in the gas-solid fluidized bed, which provides definite potential in monitoring of particle motions

NOx Reduction in Fluidized Bed Combustors

A fundamental research program has been undertaken to improve combustion efficiency and emission levels in a coal water slurry fuelled fluidized bed combustor. The effect of freeboard hydrodynamics on particulate emissions, i.e. elutriation; and gaseous emissions, such as carbon monoxide, sulphur oxides and nitrogen oxides, is being investigated. Previous studies indicated that due to the bubbling nature of fluidized bed combustors, gas-gas mixing in the freeboard region is limited by the action of large scale eddies in the form of isolated gas pockets. It has also been shown that in the combustion of coal or char additional NOx reduction reactions are possible provided that a reducing zone is available. Thus, to improve the mixing in the freeboard and create a reducing environment, a secondary air injector was installed in the freeboard. The injection of swirling secondary air introduces a tangential component to the velocity vector, thus develops a shear flow between the isolated air pockets and the surrounding air flow. It also creates a cyclonic air motion along with char particles. The net result is increased turbulence, increased solids residence time distribution and reduction in NOx emissions due to additional reactions of NOx with char particles and unburnt volatiles. The work is carried out in two separate phases; cold hydrodynamics study and actual hot experiments. The results from both studies are presented

Measurement of Local Particle Velocities in the Freeboard of a Wood-Fueled Fluidized Bed by Laser Doppler Velocimetry

Historically the major drawbacks to the utilization of wood as a fuel for swirl stabilized burners have been its high moisture content and its fibrous nature which makes pulverization difficult. Data from a variety of experiments are presented here which show that the other physical, chemical, and therefore combustion properties of wood fuels are substantially superior to those for the higher rank bituminous coals, thus reducing the requirement for drying and size reduction. These data bfiuw that wood has a very high reactivity due to its 90+ percent volatile matter content under high heating rate conditions. The ignition times for wood can be as small as one-tenth those for higher rank fuels. Rapid devolatilization and char combustion also result in significantly shorter burnout times. These fuel properties impact the optimum design of a swirl stabilized burner for wood. To demonstrate this, a mathematical model has been developed of the flow and mixing patterns for a swirl burner. This model couples the fuel properties with the mixing rates of the primary, secondary, and recirculation flows in order to predict the ignition and stability limits for a variety of fuels including wood and bituminous coal. It is shown that the unique properties of wood allow it to be burned stably at higher moisture content levels and with coarser size distribution than for bituminous coals. A mixing map has been developed from this model of the ignition time as a function of the rate of mixing of both the recirculation gas and secondary air with the primary air/fuel stream. This map shows that rapid mixing with the recirculation gas along with slower mixing with the secondary air yields optimum conditions for ignition of pulverized wood fuels

Mechanisms Contributing to Suicidal Ideation: The Relationships Between Borderline Personality Disorder Symptoms, Gender, and Emotion Dysregulation

This study examined the relationships between gender, borderline personality disorder (BPD) symptoms, emotion dysregulation, and suicidal ideation. Emotion dysregulation was examined as a potential mediator in the relationship between BPD symptoms and suicidal ideation. The moderating role of gender in these relationships was also explored. Participants were a community sample of 101 adults experiencing BPD symptomatology. Assessments were completed at baseline, 6-months, and 12-months, and included diagnostic interviews as well as questionnaires on symptomatology and suicidality. Emotion dysregulation did not mediate the BPD symptom-suicidal ideation relationship when examining the full sample. The nonacceptance of emotional responses and lack of emotional clarity dimensions of emotion dysregulation emerged as significant mediators among females only. Impulsiveness was a significant mediator among males only. The results of this study provide insight into gender differences in mechanisms contributing to suicidal ideation among individuals with BPD symptoms and highlights potential gender-specific treatment targets.M.A

Developing Fuel Map to Predict the Effect of Fuel Composition on the Maximum Efficiency of Solid Oxide Fuel Cells

At any given cell operating condition, a fuel map can be developed to predict the effect of a fuel containing carbon, hydrogen, oxygen and inert gas atoms on the maximum cell efficiency (MCE) of solid oxide fuel cells (SOFCs). To create a fuel map, a thermodynamic model is developed to obtain the fuels that would yield identical MCE for SOFCs. These fuels make a continuous curve in the ternary coordinate system. A fuel map is established by developing continuous fuel curves for different MCEs at the same operating condition of a cell and representing them in the carbon–hydrogen–oxygen (C–H–O) ternary diagram. The graphical representation of fuel maps can be applied to predict the effect of the fuel composition and fuel processor on the MCE of SOFCs. As a general result, among the fuels that can be directly utilized in SOFCs, at the same temperature and pressure, the one located at the intersection of the H–C axis and the carbon deposition boundary (CDB) curve in the C–H–O ternary diagram provides the highest MCE. For any fuel that can be indirectly utilized in SOFCs, the steam reforming fuel processor always yields a higher MCE than auto-thermal reforming or partial oxidation fuel processors at the same anode inlet fuel temperature

Understanding opiate dependence: The influence of personality disorders during detoxification

Background: Dependence on opiates is a major health issue in North America. The recent increases in both prescription and illicit opiate abuse have exacted enormous tolls in terms of health care, mental illness, quality of life, unemployment, and crime, while the difficulty in treating opioid dependent patients with standard abstinence-based therapies is not well understood. Objectives: The objective of this study was to provide a novel approach to understanding the poor outcomes of opiate dependent patients. Addiction severity, medical, and psychiatric comorbidity among opiate-dependent patients was compared with a sedative-hypnotic control group. In addition, craving, mood, objective and subjective withdrawal symptoms, subjective experiences of pain, and objective measures of hyperalgesia were prospectively monitored during inpatient detoxification. Lastly treatment completion, entry into aftercare, and substance use at three and six months follow-up was examined. Methods: This study was conducted at the Addictions Unit of the McGill University Health Center in Montreal. A total of 106 patients were prospectively monitored during inpatient detoxification for opiate dependence or sedative-hypnotic dependence in terms of craving, mood, withdrawal symptoms, vital signs, subjective experiences of pain, and objective measures of hyperalgesia and allodynia. Patient psychiatric comorbidity (Axis I and Axis II disorders), chronic medical conditions (pain syndromes), and severity of substance dependence were also considered. Results: Opiate patients reported more subjective pain and hyperalgesia during inpatient detoxification. 76.7% reported chronic pain compared to 2.3% of sedative-hypnotic patients, and 39.5% of opiate-dependent patients had both chronic pain and a personality disorder. Cluster B personality disorders were particularly prevalent among both opiate (20.93%) and sedative-hypnotic(16.28%) patients. During treatment patients with cluster B personality disorders reported more negative mood symptoms (anger, anxiety, fatigue, confusion), craving and greater scores on objective measures of withdrawal. Completion rates of detoxification were high (83.5%), although at three months follow-up 51% of patients had slipped or relapsed.Conclusions: Together these findings suggest that hyperalgesic, highly sensitive opiate-dependent patients with cluster B personality disorders and chronic pain experience substantial difficulty tolerating both the physical and emotion symptoms of withdrawal. These particularly sensitive patients may benefit from the development of targeted interventions focusing on pain management and concurrent treatment of personality disorders.2. 1. RésuméContexte : La dépendance aux opiacés est un problème de santé majeur en Amérique du Nord. Les récentes augmentations de cas d'abus d'opiacés prescrits ou illicites ont eu des impacts dramatiques au chapitre des soins de santé, de la santé mentale, de la qualité de vie, du chômage et de la criminalité. Par ailleurs, la difficulté de traiter les patients dépendants aux opiacés avec les thérapies standards à base d'abstinence n'est pas bien comprise.Objectifs : L'objectif de cette étude était de développer une nouvelle approche pour comprendre les piètres résultats de patients dépendants aux opiacés. La gravité de la toxicomanie et la comorbidité médicale et psychiatrique chez les patients dépendants aux opiacés ont été comparées à celles d'un groupe témoin de patients dépendants aux sédatifs hypnotiques. De plus, l'état de besoin, l'humeur, les symptômes objectifs et subjectifs de sevrage, les expériences subjectives de la douleur, et les mesures objectives de l'hyperalgésie ont fait l'objet d'un suivi prospectif pendant la désintoxication en milieu hospitalier. Enfin, la conclusion du traitement, l'entrée en postcure, et la consommation de substances constatée lors des suivis de trois et six mois ont été examinés.Méthodes : Cette étude a été menée à l'Unité d'alcoologie et de toxicomanie du Centre universitaire de santé McGill à Montréal. Un total de 106 patients a fait l'objet d'un suivi prospectif pendant leur désintoxication en milieu hospitalier pour une dépendance aux opiacés ou une dépendance aux sédatifs hypnotiques. Ce suivi portait sur l'état de besoin, l'humeur, les symptômes de sevrage, les signes vitaux, les expériences subjectives de la douleur et les mesures objectives de l'hyperalgie. La comorbidité psychiatrique des patients (troubles de l'Axe I et de l'Axe II), les problèmes de santé chroniques (syndromes de la douleur), et la gravité de la dépendance aux substances ont aussi été pris en considération