scholarly journals Modelling Carbon Corrosion during a PEMFC Startup: Simulation of Mitigation Strategies

Energies ◽  
2020 ◽  
Vol 13 (9) ◽  
pp. 2338 ◽  
Author(s):  
Bolahaga Randrianarizafy ◽  
Pascal Schott ◽  
Mathias Gerard ◽  
Yann Bultel
Keyword(s):  
3D Model ◽  
Carbon Dioxide Concentration ◽  
Carbon Support ◽  
Mitigation Strategies ◽  
Carbon Corrosion ◽  
Sem Images ◽  
Local Conditions ◽  
Cathode Electrode ◽  
Cathode Degradation ◽  
A Current

This paper presents a study of the carbon support corrosion and mitigation strategies through the use of a pseudo-3D model. This model consists in coupling a 2D model along the channel with another model perpendicular to the flow at the rib/channel scale. Simulations offer a deeper understanding of the corrosion through the analysis of the local conditions. Rib/channel heterogeneities show the higher degradation in the zones facing the anodic rib. These results are validated qualitatively on literature data by analysis of SEM images and carbon dioxide concentration at the cathode outlet. Three mitigation strategies are studied using the model. The first one consists in speeding up the hydrogen filling of the cell. The second strategy involves an external electrical resistance to create a current leak during the startup. Third, a design study of the rib/channel is performed to minimize the cathode degradation. Whatever the mitigation strategy, it consists in reducing either the duration or the magnitude of the high cathode electrode potential.

scholarly journals Effects of Environmental Conditions on Cathode Degradation of Polymer Electrolyte Fuel Cell during Potential Cycle

2019 ◽  
Vol 10 (2) ◽  
pp. 24
Author(s):  
Yoshiyuki Hashimasa ◽  
Hiroshi Daitoku ◽  
Tomoaki Numata
Keyword(s):  
Fuel Cell ◽  
Active Surface ◽  
Carbon Support ◽  
Load Cycle ◽  
Polymer Electrolyte Fuel Cell ◽  
Active Surface Area ◽  
Test Protocol ◽  
Carbon Corrosion ◽  
Durability Test ◽  
Cathode Degradation

We investigated the effects of cell temperature and the humidity of gas supplied to the cell during the load cycle durability test protocol recommended by The Fuel Cell Commercialization Conference of Japan (FCCJ). Changes in the electrochemically active surface area (ECA) and in the amount of carbon support corrosion were examined by using the JARI standard single cell. The ECA declined more quickly when the gas humidity was raised, and the carbon corrosion was at the same level. These results suggest that the agglomeration of platinum was accelerated by the same agglomeration mechanism, i.e., by raising the humidity of the gas supplied to the cell.

scholarly journals Single-Cell Tests to Explore the Reliability of Sofc Installations Operating Offshore

Energies ◽  
2020 ◽  
Vol 13 (7) ◽  
pp. 1624
Author(s):  
Nelson Thambiraj ◽  
Ivar Waernhus ◽  
Crina Suciu ◽  
Arild Vik ◽  
Alex C. Hoffmann
Keyword(s):  
Cell Structure ◽  
Oxygen Depletion ◽  
X Ray Diffraction ◽  
Short Term ◽  
Sem Images ◽  
Cathode Degradation ◽  
Air Supply ◽  
Different Temperatures ◽  
Effect Of Oxygen

This paper studies the robustness of off-shore solid oxide fuel cell (SOFC) installations and the nature and causes of possible cell degradation in marine environments. Two important, cathode-related, impediments to ensuring SOFC reliability in off-shore installations are: cathode degradation due to salt contamination and oxygen depletion in the air supply. Short-term and long-term tests show the effect of salt contamination in the cathode feed on cell performance, and reveal the underlying cause of the degradation seen. SEM/X-ray Diffraction/(XRD) analyses made it possible to identify salt taken up in the cathode microstructure after the short-term testing while the macroscopic cell structure remained intact after the short-term tests. The long-term degradation was found to be more severe, and SEM images showed delamination at the cathode/electrolyte interface with salt present, something that was not seen after long-term testing without salt. The effect of oxygen depletion on the performance was also determined at three different temperatures using I-V curves.

scholarly journals Application of various strategies and methodologies for landslide susceptibility maps on a basin scale: the case study of Val Tartano, Italy

2020 ◽  
Author(s):  
Vasil Yordanov ◽  
Maria Antonia Brovelli
Keyword(s):  
Random Forest ◽  
Landslide Susceptibility ◽  
Risk Mitigation ◽  
Model Performance ◽  
Initial Step ◽  
Mitigation Strategies ◽  
Landslide Susceptibility Mapping ◽  
Statistical Index ◽  
Local Conditions ◽  
Basin Scale

Abstract Landslide susceptibility mapping is a crucial initial step in risk mitigation strategies. Landslide hazards are widely spread all over the world and, as such, mapping the relevant susceptibility levels is in constant research and development. As a result, numerous modelling techniques and approaches have been adopted by scholars, implementing these models at different scales and with different terrains, in search of the best-performing strategy. Nevertheless, a direct comparison is not possible unless the strategies are implemented under the same environmental conditions and scenarios. The aim of this work is to implement three statistical-based models (Statistical Index, Logistic Regression, and Random Forest) at the basin scale, using various scenarios for the input datasets (terrain variables), training samples and ratios, and validation metrics. A reassessment of the original input data was carried out to improve the model performance. In total, 79 maps were obtained using different combinations with some highly satisfactory outcomes and others that are barely acceptable. Random Forest achieved the highest scores in most of the cases, proving to be a reliable modelling approach. While Statistical Index passes the evaluation tests, most of the resulting maps were considered unreliable. This research highlighted the importance of a complete and up-to-date landslide inventory, the knowledge of local conditions, as well as the pre- and post-analysis evaluation of the input and output combinations.

Using a Stack Shunt to Mitigate Catalyst Support Carbon Corrosion in Polymer Electrolyte Membrane Fuel Cell Stacks During Start-Stop Cycling

2013 ◽  
Vol 11 (1) ◽  
Author(s):  
Denis Bona ◽  
Dennis E. Curtin ◽  
Francesco Pedrazzo ◽  
Elena Maria Tresso
Keyword(s):  
Fuel Cell ◽  
Corrosion Rate ◽  
Degradation Rate ◽  
Catalyst Support ◽  
Catalyst Layer ◽  
Carbon Support ◽  
Ex Situ ◽  
Carbon Oxidation ◽  
Carbon Corrosion ◽  
Voltage Degradation

Carbon black based electrodes are generally recognized as state of the art for PEM fuel cell technology due to the high performance achieved with a relatively low Pt content. However, the catalyst carbon support is prone to carbon oxidation. This leads to a loss of the catalyst area and overall performance, along with a higher mass transport loss due to an increased flooding tendency. This phenomenon is particularly severe when the fuel cell experiences repetitive start-stop cycles. Therefore, specific countermeasures against catalyst layer carbon oxidation are required, especially for automotive and backup power applications, where the startup/shutdown rate is considerably high. The authors evaluated a basic design that uses a stack shunt. A properly modified control protocol, which includes the stack shunt, is able to avoid high cathode potential peaks, which are known to accelerate catalyst carbon support corrosion and its negative effects. During two separate durability tests, one adopting the shunt design and another using nonprotected shutdown, a 24-cell stack was subjected to continuous starts and stops for several months and its performance constantly monitored. The results show that when the shunt is used, there is a 37% reduction in the voltage degradation rate for each startup/shutdown cycle and a two-fold increase in the number of startup/shutdown cycles before an individual cell reached the specified “end of life” voltage criteria. Furthermore, ex situ FE-SEM analysis revealed cathode catalyst layer thinning, which is an indication that the emerging degradation mechanism is the catalyst support carbon corrosion, as expected. This provides further support that the constant voltage degradation rate typically experienced in PEMFCs can be primarily attributed to the catalyst support carbon corrosion rate. The proposed shunt protocol is very cost effective and does not require any substantial changes in the system. For this reason, its adoption is recommended as a viable method to decrease the catalyst support carbon corrosion rate and extend the operating life of the PEMFC stack.

Electrochemical catalytic behavior for platinum functionalized TiO2 nanotube arrays in PEM fuel cells

2013 ◽  
Vol 1497 ◽  
Author(s):  
Anurag Y Kawde ◽  
Alexander W O'Toole ◽  
Xiaoli He ◽  
Richard Phillips ◽  
Adam Lemke ◽  
...  
Keyword(s):  
Fuel Cells ◽  
Electrochemical Performance ◽  
Proton Exchange Membrane ◽  
Specific Area ◽  
Carbon Support ◽  
Pem Fuel Cells ◽  
Aqueous Salt Solution ◽  
Proton Exchange ◽  
Nanotube Arrays ◽  
Carbon Corrosion

ABSTRACTConventional carbon electrode supports for platinum used in proton exchange membrane (PEM) fuel cell assemblies have issues related to carbon corrosion at typical cell operating and transient conditions. This corrosion gives rise to the evolution of greenhouse gases such as CO2, eventually degrading the carbon support and causing a loss of the catalyst specific area necessary to achieve the desired electrochemical performance. In this study, preliminary results are presented for Pt-functionalized TiO2 nanotube arrays as cathode catalyst supports for PEM fuel cells. The electrochemically synthesized TiO2 nanotube arrays were functionalized by different weight % of Pt via a solution-based approach using a dilute aqueous salt solution of hexachloroplatanic acid. Electron-beam based characterization techniques were used to study the structural and morphological features of the as-synthesized TiO2 nanotube arrays and functionalized Pt/TiO2 nanotube arrays. The electrochemical performance of the functionalized TiO2 nanotube arrays was studied by using cyclic voltammetry.

Adaptation and mitigation strategies for dairy cattle: Myths and realities in Indian condition -A review

2015 ◽  
Vol 36 (4) ◽  
Author(s):  
Sumit Mahajan ◽  
Janailin S. Papang ◽  
Shivraj Singh ◽  
K. K. Datta
Keyword(s):  
Climate Change ◽  
Smallholder Farmers ◽  
Mitigation Strategies ◽  
Farm Households ◽  
Local Conditions ◽  
Climate Conditions ◽  
Change Impact ◽  
Vector Borne ◽  
The Impact ◽  
Adaptation And Mitigation

The anticipated climate change will adversely affect the productivity of livestock directly due to increased heat stress, indirectly it will affect the livestock by causing feed and fodder shortages, reducing biodiversity, water availability and increasing the incidences of vector-borne livestock diseases. On the other hand, the livestock keeping farm households mainly small farm households will be affected directly as they rear livestock for their livelihood. Interestingly, over the years, the livestock keeping households have increased at a tremendous rate for the small and marginal, medium and semimedium farm household categories as they reduce the risk arising from extreme climate conditions. So, it becomes imperative to adopt adaptation and mitigation strategies to reduce the impact of climate change on livestock given their importance in smallholder farmers’ livelihood in India. Some of researchers in past have recommended certain adaptation and mitigation strategies for reducing the climate change impact on livestock. But, are these adaptation and mitigation strategies applicable or viable in the context of smallholder farmers in India? This remains an unsolved puzzle. This paper tries to demystify certain myths associated with these strategies as well as explore the ground realities. The present policy of indiscriminate crossbreeding of local cattle with exotic cattle should be reviewed and reoriented for smallholder dairy farmer especially, in dry and rainfed regions where there is scarcity of fodder and water which are required heavily by crossbred cattle. The study clearly reflects that the adaptation research should be country specific as the strategies suitable for one country may not be viable for the others as there is considerable difference in local conditions of different countries.

Targeted urban heat mitigation strategies using urban morphology databases and micro-climate modelling to examine the urban heat profile

2020 ◽  
Author(s):  
Kerry Nice ◽  
Ashley Broadbent
Keyword(s):  
Thermal Comfort ◽  
Urban Morphology ◽  
Mitigation Strategies ◽  
Local Context ◽  
Climate Modelling ◽  
Local Conditions ◽  
Local Climate ◽  
Human Thermal Comfort ◽  
Local Climate Zones ◽  
Urban Heat

<p>Strategies for urban heat mitigation often make broad and non-specific recommendations (i.e. plant more trees) without accounting for local context. As a result, resources might be allocated to areas of lesser need over those where more urgent interventions are needed. Also, these interventions might return less than optimal results if local conditions are not considered. This project aims to assist with these interventions by providing a method to examine the urban heat profile of a city through an automated systematic approach. Using urban morphology information from databases such as WUDAPT, areas of cities are clustered into representative local climate zones (LCZs) and modelled at a micro-scale using localised features and properties. This bottom up modelling approach, using the VTUF-3D, UMEP, and TARGET models, allows these areas to be assessed in detail for their human thermal comfort performance and provide a city-wide heat map of thermal comfort. It also allows mitigation scenarios to be tested and targeted for each cluster type. A case study performed using this method for Melbourne is presented.</p>

scholarly journals The Use of Diamond for Energy Conversion System Applications: A Review

2012 ◽  
Vol 2012 ◽  
pp. 1-20 ◽  
Author(s):  
K. I. B. Eguiluz ◽  
J. M. Peralta-Hernández ◽  
A. Hernández-Ramírez ◽  
J. L. Guzmán-Mar ◽  
L. Hinojosa-Reyes ◽  
...  
Keyword(s):  
Supported Catalysts ◽  
Morphological Changes ◽  
Polymer Electrolyte Membrane ◽  
Pyrolytic Graphite ◽  
Lithium Ion ◽  
Catalytic Efficiency ◽  
Carbon Support ◽  
High Energy ◽  
Boron Doped Diamond ◽  
Carbon Corrosion

Catalytic layers of polymer electrolyte membrane fuel cell (PEMFC) electrodes are usually composed of platinum nanoparticles dispersed on an electron conductive carbon support, which can undergo several degradation processes like dissolution of Pt and carbon corrosion under PEMFC working conditions. In this context, the major advantage of conductive boron-doped diamond (BDD) surfaces is their mechanical and chemical stability. BDD is also considered as a good substrate for studying the intrinsic properties of deposited catalysts, avoiding some problems encountered with other substrates, that is, surface corrosion, oxide formation, or electronic interactions with the deposit. Thus, the first part of this review summarized the surface modification of BDD materials, with emphasis in different techniques, to improve the catalytic efficiency of supported catalysts for PEMFCs. In addition, it is known that graphite carbon or lithium metal alloys used in advanced lithium-ion high-energy batteries suffer morphological changes during the charge-discharge cycling, which in turn results in a very poor cycle life. Thus, the use of diamond materials in these applications was also reviewed, since they have very stable surfaces and exhibits excellent electrochemical properties when compared with other carbon forms like glassy carbon and highly oriented pyrolytic graphite.

scholarly journals Droplet and Aerosol Generation With Endonasal Surgery: Methods to Mitigate Risk During the COVID-19 Pandemic

2020 ◽  
pp. 019459982094980
Author(s):  
Harish Dharmarajan ◽  
Monika E. Freiser ◽  
Edward Sim ◽  
Devi Sai Sri Kavya Boorgu ◽  
Timothy E. Corcoran ◽  
...  
Keyword(s):  
Nasal Cavity ◽  
3D Model ◽  
Cascade Impactor ◽  
Mitigation Strategies ◽  
Mitigation Measures ◽  
Endonasal Surgery ◽  
Fluorescent Tracer ◽  
3 Dimensional ◽  
Aerosol Generation ◽  
3D Printed

Objective To define the aerosol and droplet risks associated with endonasal drilling and to identify mitigation strategies. Study Design Simulation series with fluorescent 3-dimensional (3D) printed sinonasal models and deidentified cadaveric heads. Settings Dedicated surgical laboratory. Subjects and Methods Cadaveric specimens irrigated with fluorescent tracer and fluorescent 3D-printed models were drilled. A cascade impactor was used to collect aerosols and small droplets of various aerodynamic diameters under 15 µm. Large droplet generation was measured by evaluating the field for fluorescent debris. Aerosol plumes through the nares were generated via nebulizer, and mitigation measures, including suction and SPIWay devices, nasal sheaths, were evaluated regarding reduction of aerosol escape from the nose. Results The drilling of cadaveric specimens without flexible suction generated aerosols ≤3.30 µm, and drilling of 3D sinonasal models consistently produced aerosols ≤14.1 µm. Mitigation with SPIWay or diameter-restricted SPIWay produced same results. There was minimal field contamination in the cadaveric models, 0% to 2.77% field tarp area, regardless of drill burr type or drilling location; cutting burr drilling without suction in the 3D model yielded the worst contamination field (36.1%), followed by coarse diamond drilling without suction (19.4%). The simple placement of a flexible suction instrument in the nasal cavity or nasopharynx led to complete elimination of all aerosols ≤14.1 µm, as evaluated by a cascade impactor positioned immediately at the nares. Conclusion Given the findings regarding aerosol risk reduction, we strongly recommend that physicians use a suction instrument in the nasal cavity or nasopharynx during endonasal surgery in the COVID-19 era.

scholarly journals A Concept for Three-Dimensional Particle Metrology Based on Scanning Electron Microscopy and Structure-from-Motion Photogrammetry

2020 ◽  
Vol 125 ◽  
Author(s):  
Vipin N. Tondare
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Structure From Motion ◽  
3D Model ◽  
Three Dimensional ◽  
Sem Images ◽  
Shape Information ◽  
Size And Shape ◽  
Future Work ◽  
Scanning Electron

Scanning electron microscopy (SEM) has been frequently used for size and shape measurements of particles. SEM images offer two-dimensional (2D) information about a particle’s lateral dimensions. Unfortunately, information about the particle’s three-dimensional (3D) size and shape remains unavailable. To resolve this issue, I propose a new concept in SEM: 3D particle metrology obtained by applying structure-from-motion (SfM) algorithms to multiple rotational SEM images of particles deposited onto a cylindrical substrate to generate a 3D model from which size and shape information can be extracted. Particles can have any size that is suitable for SEM imaging. SEM images of the sample can be acquired from 0° to 360° using a rotational-tip SEM substage. Here, I will discuss the concept and, for clarity, illustrate it with aquarium gravel particles that are glued onto a craft roll and imaged optically before generating the 3D model of that handmade craft. Future work will include the experimental SEM realization, as well as further development of the SfM algorithms. In my view, this proposed concept may become an integral part of SEM-based particle metrology.

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