bluuebunny/crossref_metadata_2025_split huggingface dataset:
A CFD Simulation for an Air Breathing PEMFC for Power Source Portable Applications
Authors: Carcadea Elena , Varlam Mihai , Stefanescu Ioan , Ingham Derek , Marinoiu Adriana , Patularu Laurentiu , Raceanu Mircea , Schitea Dorin 
Published: February 2020

Air breathing PEM fuel cells are a promising and a potential power source for portable applications. The challenges that air breathing fuel cells has to overcome in order to be used in portable applications and to be cost competitive are related to the ability to use logistic fuels, to the prevention of cathode contamination with impurities from the used air (supplied by active or passive methods), to the reduction of the size and weight.
In this context, the development of a mathematical model for a better understanding of the fundamental processes and characteristics associated with air breathing cathode operation is required. The three-dimensional model developed in this paper based on the ANSYS Multiphysics software was used to analyse the influence of the factors that influence the PEM fuel cell performance (flow field configuration, operating conditions). Regarding the flow field configuration a 3 step-serpentine was used for the anode channel and parallel channels were used in the cathode side for the forced air supply. In this respect, for the cathode side channels, the width, depth and the space between two adjacent channels was varied (1 mm, 1.5 mm, and 2 mm) in order to see their influence on the uniformity of the reactant distribution (particularly water) and on heat management. Regarding the operating parameters that can have a significant influence on the performance, our numerical analysis took into consideration the air flow rate, the humidity and temperature and the results are discussed in the paper. The analysis was intended to identify critical parameters and give an insight into physical mechanisms that can influence this type of air breathing PEM fuel cell.
Impact of Membrane Properties and Membrane Degradation on Cathode Catalyst Layer Degradation
Authors: Dutta Monica , Ghassemzadeh Lida , Lauritzen Mike , Harvey David , Wessel Silvia , Young Alan P , Knights Shanna 
Published: February 2020

Understanding the effect of material properties and the structure of MEA components is critical to understanding MEA performance and degradation. Previous studies have shown that cathode catalyst layer degradation was observed to be influenced by water content within the MEA. Both relative humidity and membrane type were shown to have a substantial effect on the degradation rates1. As the membrane / ionomer plays a key role in the water management within an MEA, affecting water sorption, water crossover and phase changes, an improved understanding of the effects of membrane properties on cathode catalyst degradation is required. This study examines the effect of membrane properties, as well as the effects of membrane degradation on cathode catalyst layer degradation.
In this work, six membranes, including dense membranes Nafion®211 and Nafion®212, experimental reinforced PFSA membranes with low and high equivalent weights (EW), and experimental reinforced partially fluorinated hydrocarbon membranes of high and low equivalent weights, were chosen for investigations of membrane property impacts on beginning of test (BOT) performance and cathode accelerated stress test (AST) durability. These membranes had EW values ranging from ~ 600 to 1100, while the dry thickness ranged from 13 to 50 microns.
Performance variations at BOT for the different membranes may be due to a combination of membrane thickness, resistance, and hydrogen and water cross-over effects. After cathode AST cycling, ECSA loss and performance loss were increased for the thinner, lower EW membranes of each membrane family suggesting that membrane water content was the contributing factor. The effects of membrane degradation on cathode catalyst layer degradation for three down-selected membranes will also be discussed.

Acknowledgements

Funding was provided by Department of Energy EERE Hydrogen and Fuel Cell Technology Program (Project DE-EE0006375).

References

[1] Silvia Wessel, David Harvey, “Development of Micro-Structural Mitigation Strategies for PEM Fuel Cells: Morphological Simulations and Experimental Approaches”, 2013 Annual Merit Review Proceedings: Fuel Cells, 16 May 2013, Project ID# FC049.
FEM Modelling of Diffusional Electrochemical Impedance Spectroscopy at a Channel Electrode
Authors: Holm Thomas , Ingdal Mats , Seland Frode , Harrington David A. 
Published: February 2020

Calculation of the electrochemical impedance spectroscopy for a diffusional process at a channel electrode with laminar flow necessitates the solution of the diffusion-convection equation with appropriate boundary conditions.
Although the full equation has not been solved analytically, two sets of assumptions have been used previously, and the resulting equations were solved analytically:
i) The axial diffusion is neglected and the Poiseuille flow is simplified as a Lévêque flow1,2.
ii) Convection is neglected and it is solved as a simple diffusion process3.
However, although the assumptions intuitively allow for solving the problem in a large parameter space, parameters for which these approximations are valid have not been determined.
We demonstrate by using FEM software (Comsol Multiphysics™), that the full problem can be solved numerically. The solution obtained by FEM software is compared to experimental results and the two analytical solutions. The method shows good correspondence with the experimental results and a large flexibility, making it possible to solve more complex problems such as different diffusion coefficients4 and unconventional geometries. An example of a comparison between experimental results, numerical results using FEM software, and an analytical solution is shown in Fig. 1. The parameter space of the analytical solutions is investigated using two non-dimensional parameters, A and B, and a validity area is found where the analytical solutions are well-suited. The parameter A is a version of the Péclet number, A = 6vavh/D, and B is the ratio of electrode width and channel height, B = w/h.
References:
[1] B. A. Coles, R. G. Compton, J. Electroanal. Chem.
127,37 (1981).
[2] R. G. Compton, G. R. Sealy, J. Electroanal. Chem.
145,35 (1983).
[3] R. G. Compton, J. Winkler, J. Phys. Chem.
99,5029 (1995).
[4] Y. Wang, J. G. Limon-Petersen, R. G. Compton J. Electroanal. Chem.
652,13 (2011).

Fig 1: Nyquist plot of impedance spectroscopy at a channel electrode showing experimental values (blue boxes), values modelled in Comsol (blue line), values calculated analytically by neglecting axial diffusion and simplifying the flow (upward pointing black triangles), and values calculated by neglecting convection (downward pointing black triangles). Impedance values are dimensionless.

Figure 1
Thin TiO2 Overlayers As Catalysts for Oxygen Reduction and Evolution Reactions
Authors: Tavassol Hadi , Haile Sossina M 
Published: February 2020

We report on the electrochemical activity of thin TiO2 overlayers on titanium micro-particles toward oxygen reduction and evolution reactions in a CsH2PO4 solid acid electrochemical system. The electrocatalysis at the interface of the super-protonic (at 245 °C) CsH2PO4 solid acid with the electrodes occurs at active sites which are also accessible to the humidified gases. Pt remains the best catalyst for the O2 reduction reaction in the cathodes of the solid acid fuel cells. Because of the strong O=O bond, oxygen reduction is a slow reaction even on a Pt surface at 245 °C, requiring high loadings of the precious Pt catalyst. Solid state TiO2 catalysts are an attractive alternative. TiO2 catalysts show a range of activity depending on the relative ratio of the rutile to anatase polymorphs. Rutile phase exhibits a lower overpotential for the ORR. TiO2 films are grown on Ti metal micro-particles under slightly oxidizing environment at elevated temperature (600-900 °C). The thickness and relative ratio of the rutile to anatase phase is controlled by the growth temperature and holding time. X-ray diffraction analysis of the films reveals that the amount of the oxide increases with increasing the growth temperature. At higher growth temperatures, the oxide layer formed is mostly rutile. The activity of the TiO2 films is controlled by both the phase and thickness of the films. Between 700-900 °C, the activity of the TiO2 overlayers for oxygen reduction reaction increases with increasing the growth temperature. Interestingly, thin oxide overlayers with mostly rutile phase grown at 600 °C show higher activity. We will discuss the origin of the improved activities of thin TiO2 overlayers.
Mediator-Less Direct Electron Transfer and Oxygen Reduction By Bilirubin Oxidase Adsorbed on to a Bucky Paper Electrode
Authors: Walgama Charuksha , Pathirana Anuruddha , Means Nick , Goff Alan Le , Cosnier Serge , Krishnan Sadagopan 
Published: February 2020

Direct immobilization of enzyme films on nanostructured electrodes has the advantage of enhancing electrocatalytic currents. Bilirubin oxidase (BOD), a blue multi-copper enzyme, extracted from Myrothecium verrucaria has been recognized as a highly efficient oxygen reduction catalyst at near neutral pH with a minimal overpotential requirement. BOD contains four redox active Cu centers, which are classified based on their spectroscopic characteristics as T1 (one), T2 (one), and T3 (two). T1 Cu-center of BOD has been proposed to be the electron-receiving center from electrode and the catalytic oxygen reduction was suggested to occur at the tri-nuclear Cu clusters of T2/T3.1 Direct electron transfer between BOD and the electrode has been shown in slightly acidic and anaerobic conditions without mediators (E°´
T1 = ~0.5 V, E°′
T2/T3 = ~0.16 V vs Ag/AgCl).2
,3a Reported studies showed that the oxygen reduction by BOD is highly effective with electrodes modified with a redox polymer hydrogel,3b a poly-lysine composite film,4 gold nanoparticles,5 carbon nanotube-pyrene units,6 and functionalized multiwalled nanotubes (MWNT).7
,
8
Here we will present our findings on the direct electron transfer and electrocatalytic oxygen reduction currents by a BOD film directly adsorbed on to bucky paper electrodes prepared from MWNT. Our preliminary work also suggests the role of bucky paper thickness in controlling the extent of catalytic currents and direct electrochemistry. BOD integrated bucky papers have immense usability in highly efficient biological fuel cells and we envision employing these BOD electrodes as cathodes for enzymatic fuel cell applications.6,9

Acknowledgements. Financial support by the Oklahoma State University is greatly acknowledged.
(1) dos Santos, L.; Climent, V.; Blanford, C. F.; Armstrong, F. A. Physical Chemistry Chemical Physics
2010, 12, 13962.
(2) Ivnitski, D.; Artyushkova, K.; Atanassov, P. Bioelectrochemistry
2008, 74, 101.
(3) (a) Ramírez, P.; Mano, N.; Andreu, R.; Ruzgas, T.; Heller, A.; Gorton, L.; Shleev, S. Biochimica et Biophysica Acta - Bioenergetics
2008, 1777, 1364; (b) Mano, N.; Fernandez, J. L.; Kim, Y.; Shin, W.; Bard, A. J.; Heller, A. Journal of the American Chemical Society
2003, 125, 15290.
(4) Tsujimura, S.; Kano, K.; Ikeda, T. Journal of Electroanalytical Chemistry
2005, 576, 113.
(5) Murata, K.; Kajiya, K.; Nakamura, N.; Ohno, H. Energy & Environmental Science
2009, 2, 1280.
(6) Krishnan, S.; Armstrong, F. A. Chemical Science
2012, 3, 1015.
(7) Lopez, R. J.; Babanova, S.; Ulyanova, Y.; Singhal, S.; Atanassov, P. ChemElectroChem
2014, 1, 241.
(8) Milton, R. D.; Giroud, F.; Thumser, A. E.; Minteer, S. D.; Slade, R. C. T. Chemical Communications
2014, 50, 94.
(9) Bourourou, M.; Elouarzaki, K.; Holzinger, M.; Agnes, C.; Le Goff, A.; Reverdy-Bruas, N.; Chaussy, D.; Party, M.; Maaref, A.; Cosnier, S. Chemical Science
2014, 5, 2885.
Electrochemical Characterisation of Cobalt-Oxide Catalysts with Different Cobalt Loading for Oxygen Reduction Reaction in Alkaline Media
Authors: Uhlig Lisa Maria , Dyck Alexander , Sievers Gustav Wilhelm , Brüser Volker , Wittstock Gunther 
Published: February 2020

Alkaline fuel cells are very promising because of their high efficiencies (1). In fuel cells the reduction of oxygen on cathode side is the performance-limiting step (2, 3). Catalysts, e.g. platinum, are used to enhance the oxygen reduction reaction (ORR) rate and also the performance. Due to the high costs of the fuel cell components, especially for the platinum catalyst (4), the fuel cell is not common for various applications up to now. The alkaline media enables the use of non-precious metals, e.g. cobalt or manganese oxides (5-8), to enhance the kinetic on the cathode side.
The electroactivities of different non-precious metal catalysts like cobalt oxide are promising to achieve a similarly high activity as platinum. A cobalt acetate precursor is plasma-treated and resulting cobalt oxide catalysts with different cobalt loading were investigated in different alkaline media and at temperatures between 25 and 75 °C using a rotating ring disk electrode (RRDE) analysis. The advantage of plasma treatment is the better distribution of particles, they are less agglomerated compared due to the common heat treatment (9-11). This leads to a higher activity of the catalyst material (9). Different characterisation methods are used to identify the catalyst material like XRD, TEM and SEM. A custom-built Teflon cell is used for the RRDE analysis to avoid glass corrosion in alkaline media. Glass corrosion affects the electrochemical measurements (12), therefore it is necessary to replace glass components for the experiments.
References:
1. E. Gülzow, Fuel Cells, 4, 251 (2004).
2. K. Kordesch, V. Hacker, J. Gsellmann, M. Cifrain, G. Faleschini, P. Enzinger, M. Ortner, M. Muhr and R. R. Aronson, Jounal of Power Sources, 5 (1999).
3. B. Viswanathan, C. V. Rao and U. V. Varadaraju, in Photo/Electrochemistry & Photobiology in the Environment, Energy and Fuel, p. 43 (2006).
4. G. Wu, K. L. More, C. M. Johnston and P. Zelenay, Science, 332, 443 (2011).
5. S. Lu, J. Pan, A. Huang, L. Zhuang and J. Lu, Proc. Natl. Acad. Sci. U. S. A., 105, 20611 (2008).
6. H. Meng and P. K. Shen, Electrochem. Commun., 8, 588 (2006).
7. F. Cheng, J. Shen, W. Ji, Z. tao and J. Chen, Applied Materials & Interfaces, 1, 460 (2009).
8. M. Mamlouk, S. M. S. Kumar, P. Gouerec and K. Scott, J. Power Sources, 196, 7594 (2011).
9. V. Brüser, N. Savastenko, A. Schmuhl, H. Junge, I. Herrmann, P. Bogdanoff and K. Schröder, Plasma. Process. Polym., 4, S94 (2007).
10. N. A. Savastenko, K. Anklam, A. Quade, M. Brüser, A. Schmuhl and V. Brüser, Energy Environ. Sci., 4, 3461 (2011).
11. I. Herrmann, U. I. Kramm, S. Fiechter, V. Brüser, H. Kersten and P. Bogdanoff, Plasma.
Process. Polym., 7, 515 (2010).
12. K. J. J. Mayrhofer, G. K. H. Wiberg and M. Arenz, J. Electrochem. Soc., 155, P1 (2007).
Electroreduction of Oxygen on Carbon Supported Palladium Nanocubes
Authors: Erikson Heiki , Sarapuu Ave , Tammeveski Kaido , Solla-Gullón José , Feliu Juan 
Published: February 2020

In recent years palladium has proven to be a good alternative to platinum in low-temperature fuel cell cathode catalysts.1 The electrocatalytic activity of Pd catalysts toward the oxygen reduction reaction (ORR) can be improved by preparing shape-controlled nanoparticles.2

The aim of this study was to investigate the electrocatalytic activity of carbon-supported Pd nanocubes of different size and varied metal loading toward the ORR. CTAB or PVP were used as capping agents to prepare the Pd nanocubes of different sizes.
The morphology of Pd/C catalyst was evaluated using transmission electron microscopy, which showed that the particles are cube shaped and their size depends on the synthesis method. The thermogravimetric method was used to determine the Pd loading on carbon. The nominal Pd contents of the prepared catalysts were 5, 20 and 50 wt% and the measured content deviated only slightly.
Electrochemical experiments were carried out in acid and alkaline solutions. The catalysts were electrochemically characterized by cyclic voltammetry and by oxidation of pre-adsorbed CO. Both electrochemical methods showed characteristics that can be attributed to Pd(100) facets that are predominant on cubic Pd nanoparticles. From cyclic voltammograms the electrochemically active surface area was found, expectedly it increased with increasing Pd content in the catalyst and also with decreasing the particle size.
The ORR studies in 0.5 M H2SO4 showed that the half-wave potentials increase with palladium content and with decreasing the particle size, following the changes in the electrochemical surface area. The mass-activity of the catalysts did not depend on the Pd loading, but increased with decreasing the particle size. From the rotating disk electrode studies the number of electrons transferred per O2molecule was found to be near 3.5, showing that some hydrogen peroxide is formed. The Tafel analysis revealed that the ORR mechanism on carbon-supported Pd nanocubes was the same as on bulk Pd.
In alkaline media the half-wave potentials were in the same order as in acid solution, but more subtle differences were evident. The Koutecky-Levich analysis of the RDE data showed that the number of electrons transferred per oxygen molecule was 4 in the whole range of potentials studied. The Tafel analysis showed that the rate limiting step is the sluggish transfer of first electron to O2molecule.
References
1. E. Antolini, Energy Environ. Sci., 2, 915 (2009).
2. H. Erikson, A. Sarapuu, N. Alexeyeva, K. Tammeveski, J. Solla-Gullon, and J. M. Feliu, Electrochim. Acta, 59, 329 (2012).

Figure 1
Extensive Studies of the Electrochemical Behavior of Pt Ni/MWCNT Catalysts in Alkaline Media
Authors: Valenzuela-Muñiz Ana Maria , Rosado Gabriel , Verde Gomez Ysmael 
Published: February 2020

Multi-walled carbon nanotubes (MWCNT) enclose properties and characteristics that are interesting and suitable for electrochemical applications. In this way, the deposition of metallic particle in the surface of MWCNT has been a topic of intense study. It is well know that bimetallic systems of Pt with other metal are of great interest due to the possibility of reduce the costs by decreasing the metal loading, and at the same time increase the properties of the electrocatalyst. In specific, PtNi/MCNT systems have proven to have high activity in different electrochemical reactions in acid media, along with good tolerance to CO poisoning. However, the main drawback is the poor stability in acidic environments. Thus, the electrochemical evaluation of these materials in alkaline media becomes an interesting field of study. Previous investigations of the research group performed in alkaline media showed that the system PtNi/MWCNT exhibited activity towards the hydrogen oxidation reaction as well as the oxidation of methanol. As a continuation, in this work a more detailed study was performed including the evaluation of different materials PtNi/MWCNT in the oxygen reduction reaction. The experimental matrix was designed to evaluate the influence of PtNi structure on the electrochemical behavior, interesting results were found. The materials were characterized by microscopy as well as x-ray diffraction. The electrochemical tests were done in a conventional three electrodes cell, using a glassy carbon rod as working electrode, a Pt wire as counter electrode, a Ag/AgCl (KCl Sat) electrode as reference, and 1M NaOH solution as electrolyte. The results as well as the discussion will be presented at the conference.
Authors acknowledge the support to CONACyT under grant No. 213373
Field-Dipole Interactions at p-GaAs (100) Electrode in Sodium Dodecyl Sulfate Acid Solution
Authors: Lazarescu Valentina , Enache Mirela , Dobrescu Gianina , Anastasescu Mihai , Negrila Catalin , Lazarescu Mihail Florin 
Published: February 2020

Electrochemical impedance spectroscopy (EIS), X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM) have been used to investigate the effects of the sodium dodecyl sulfate (SDS) at the electrified p-GaAs(100) / H2SO4 interface. The analysis of the EIS data revealed that the surfactant adsorption brings about a pronounced decrease of the capacitive contributions of the semiconductor surface state (Fig. 1 B) accompanied by a shift to more positive potentials of the Mott-Schottky plot (Fig. 1 A). According to the XPS (Fig 1 C) and AFM data, SDS forms a well-ordered protective overlayer on p-GaAs(100) which prevents the surface oxidation in air. However, the field-dipole interactions acting under the applied potential control become preponderant at the electrified GaAs / solution interface yielding distinct effects at the end of the direct and forward potential scans as seen in Fig 1 C. These results suggest that SDS interaction with GaAs substrate might be an efficient tool to improve both the electronic properties of the semiconductor and its protection against the surface oxidation in air.
Acknowledgements
This work was supported by a grant of the Romanian National Authority for Scientific Research, CNCS – UEFISCDI, project number PN-II-ID-PCE-2011-3-0304

Figure 1
The Importance of Testing and Designing Lithium-Ion Batteries in the Relevant Environment
Authors: Jeevarajan Judith A 
Published: February 2020

Lithium-ion batteries have the highest energy density and cycle life of the rechargeable battery chemistries in the commercial battery market today. However, associated with that high energy density is its tendency to go into thermal runaway when the battery is not designed or used appropriately. Although the size of the lithium-ion batteries in various applications are growing in energy and power, the nature of tests carried out to characterize their safety has not grown to adequately understand the hazards associated with the battery designs. Typical hazards associated with these batteries are overcharge, external and internal short circuites and high temperatures. Thermal runaway can occur in these batteries in many ways including the failure of internal cell protective devices. One needs to characterize not only a cell design but also the appropriate module and battery design especially if the cell level controls are used as one of the first two levels of control. The thermal dissipation characteristics and the propensity of any cell going into thermal runaway to propagate to other cells should also be considered for faults that are not fully understood at the battery level for the environment it is to be used in. Stringent certification and qualification tests of the battery design in the relevant environment with post-test destructive and non-destructive analysis will help in defining the safety as well as provide insight on the robustness of the safety controls. This paper will discuss the various aspects of the li-ion battery design that needs to be characterized and provide some insight into recommended design solutions.