bluuebunny/crossref_metadata_2025_split huggingface dataset:
Comparing Mitigation Techniques for Effective CO Mitigation in a Polymer Electrolyte Fuel Cell
Authors: Sarma Paran Jyoti , Gardner Chris , Chugh Sachin , Sharma Alok , Kjeang Erik 
Published: February 2020

The presence of carbon monoxide impurities in hydrogen can be a major deterrent to polymer electrolyte fuel cell (PEFC) performance. CO molecules present in hydrogen fuel rapidly get adsorbed on the platinum (Pt) active sites at the anode electrode and deactivate the surface reactions responsible for hydrogen oxidation [1]. On the other hand, obtaining 99.999% hydrogen purity requires major purification processes driving up the cost of hydrogen fuel [2]. To realise an economical hydrogen fuel price for fuel cell applications, reformate hydrogen containing CO can be used along with a suitable mitigation technique to reduce the adsorption of CO on Pt surface by means of oxidation or stripping. Catalyst modifications, air bleeding [3] and pulsed oxidation [4, 5] are commonly used techniques to resolve CO contamination issues in fuel cells. However, a detailed comparison of these techniques to define the efficiency as well as performance improvement in presence of CO contaminated fuel is not available.
In this work, we present a comparison of results and scientific explanation of the use of various mitigation techniques to alleviate the effect of CO on the performance of a PEFC. Experiments were carried out on a single cell fuel cell at 80 ºC having modified anode catalyst (Pt/C and Pt-Ru/C) and a Pt/C cathode catalyst. CO mixed with pure hydrogen was fed to the anode and air was fed to the cathode. The cell potential was monitored when the fuel source was switched from pure hydrogen to CO doped hydrogen at a constant current density to study the impact of poisoning. Anode catalyst modification with ruthenium resulted in 200 mV increase in CO tolerance compared to platinum at a constant current density. Air bleeding in presence of Pt/C and Pt-Ru/C showed similar results in performance which caused a gradual potential loss when operated for extended periods. However, when pulsed oxidation was employed, the cell potential remained close to pure hydrogen potential ranges even for longer testing periods.
Acknowledgement: This work was supported by Indian Oil Corporation (R&D) and Simon Fraser University under the SFU-IOCL joint PhD program in clean energy.
[1] M. Abdollahi, J. Yu, P. K. T. Liu, R. Ciora, M. Sahimi, T. T. Tsotsis, J. Membrane Science, 390-391, 32 (2012)
[2] D. Jansen, J. W. Dijkstra, R. W. van den Brink, T. A. Peters, M. Stange, R. Bredesen, A. Goldbach, H. Y. Xu, A. Gottschalk, A. Doukelis, Energy Procedia 1, 253 (2009)
[3] L-Yu Sung, B-Joe Hwang, K-Lin Hsueh, W-Nien Su, C-Chung Yang, J. Power Sources 242 (2013) 264-272
[4] C.G. Farrell, C.L. Gardner and M. Ternan, J. Power Sources, 117, 282 (2007)
[5] A. H. Thomason, T. R. Lalk, A. J. Appleby, J. Power Sources 135 (2004) 204-211
Improving Reactant and Proton Transport in Catalyst Layers for Direct Alcohol Fuel Cells
Authors: Hauenstein Pascal , Thiele Simon 
Published: February 2020

Direct alcohol fuel cells (DAFC) produce electricity from liquid fuels such as methanol, ethanol etc., where the alcohol is oxidized at the anode and oxygen is reduced on the cathode side of the fuel cell. Operation of alcohol fuel cells is attractive because of the exceptionally high volumetric energy density and easy handling of liquid fuels in comparison to pressurized hydrogen. [1] Especially direct methanol fuel cells (DMFC) have been widely investigated as portable power sources. However, even with these relatively simple fuels, the reaction kinetics of the electro-oxidation are slow in comparison to hydrogen oxidation. Furthermore, DAFC suffer from severe reactant crossover through the membrane, leading to low open circuit voltages and poor overall performance. [2] In order to solve crossover issues, manufacturing of various composite membranes and additional alcohol blocking layers become more and more important in this research field. [3] Nonetheless, also understanding and improving reactant and proton transport in catalyst layers for DAFCs is very important in order to improve current densities and reduce costs, as less expensive platinum group metal catalysts are needed. Commonly, very high loadings on the anode side of DAFC result in thick catalyst layers, which suffer from poor reactant transport and high proton resistances and flooding, especially in the high current density regions.
Our work to be presented is focused on novel architectures of membrane electrode assemblies (MEAs) for applications in direct alcohol fuel cells to target these problems and improve the physical properties of the catalyst layer with a focus on different ionomers, different ionomer contents, and pore size distribution.
[1] R. P. O'Hayre, F. B. Prinz, S.-W. Cha, W. G. Colella, Fuel cell fundamentals, Third edition ed., Wiley, Hoboken, 2016.
[2] C. Xu, A. Faghri, X. Li, T. Ward, International Journal of Hydrogen Energy
2010, 35, 1769–1777.
[3] P. Prapainainar, N. Pattanapisutkun, C. Prapainainar, P. Kongkachuichay, International Journal of Hydrogen Energy
2019, 44, 362–378.
(Invited) Poly(norbornene) Hydroxide Conductive Polymers: Stable, High Conductivity Hydroxide Conducting Block Copolymer Membranes and Their Applications
Authors: Kohl Paul A , Mandal Mrinmay , Huang Garrett 
Published: February 2020

Block copolymer, anion-exchange membranes (AEM) were synthesized using the vinyl-addition polymerization and ring-opening metathesis polymerization of norbornene monomers. The intended use is for use electrochemical devices operating at high pH including fuel cells, electrolyzers, and flow batteries. The focus of this talk is on the impact very high conductivity AEM with low water uptake on device performance. The low molecular weight of the norbornene monomers enabled the design of very high ion exchange capacity (IEC) membranes, up to 4.73 meq/g. A wide variety of norbornene monomers are available allowing for the synthesis of membranes with optimized properties. The norbornene backbone is an all-hydrocarbon structure giving the polymers excellent chemical stability in 1 M NaOH at 80°C. The monomers were synthesized into a multi-block copolymer with hydrophilic and hydrophobic blocks. AEM membranes were solvent cast with and without a supporting polymer reinforcement. The hydrophobic, ion-conducting block of the copolymers formed a lamellar phase during casting.
Tetrablock copolymers synthesized by vinyl-addition reaction had an IEC of 1.88 meq/g and conductivity of 123 mS/cm at 80°C. Light cross-linking was found to provide a critical control of water uptake allowing the incorporation of very high IEC without unwanted water uptake. Without light cross-linking, unwanted water uptake would cause swelling and softening of the membrane at high IEC values, as with other AEMs. Thus, the path to achieving exceptionally high ionic conductivity includes high mobility ion channels (achieved here through the use of block copolymers), and light crosslinking to permit the use of high IEC values (e.g. approaching 4 meq/g). The best performing membrane had an ionic conductivity of 212 mS/cm at 80°C. There was little or no drop in ionic conductivity over 1,000 h of aging in 1 M NaOH at 80°C. This is the highest reported hydroxide conductivity at 80°C to date for a chemically stable AEM. The number of bound and free water molecules per ion pair were measured in order to analyze the role of water. The membranes are suitable for electrochemical devices and were used in AEM fuel cells and electrolyzers.
Development of ACLS Electrodes for a Water Electrolysis Cell
Authors: Yoshinaga Norihiro , Kanai Yuta , Fukazawa Taishi , Nakano Yoshihiko , Mei Wu 
Published: February 2020

1.Introduction

Water electrolyzers are important devices for power-to-gas systems. Compared with other types of water electrolyzers, polymer electrolyte membrane (PEM) electrolyzers have the advantages of quick response, small footprint, ability to generate high gas pressure than other types of electrolyzers, and high durability against ON/OFF cycling1. The anode of PEM electrolyzers is conventionally an iridium oxide electrocatalyst powder combined with a platinum coating layer on a porous titanium layer (PTL)2,3. However, these noble metal catalysts are scarce and expensive, and reducing their use is essential for PEM electrolyzers. At Toshiba, we have developed an alternating catalyst layer structure (ACLS) catalytic electrode composed of multiple iridium oxide sheets and air gap layers without a platinum coating layer and fabricated by a sputtering process, and we are studying its application in PEM electrolyzers. In this presentation, we report the results of comparisons between powder and ACLS electrocatalysts used in PEM electrolyzers.

2.Experimental

First, iridium together with pore-forming metal was sputtered onto a commercially available PTL substrate and then only pore-forming metal was sputtered, and this process was repeated to deposit multiple layers (Figure 1). Then, the pore-forming metal was removed to prepare the ACLS anode. The loading of iridium metal was adjusted by the number of iridium layers. Next, an MEA was made by hot pressing of the ACLS anode, Nafion115®, and the Pt/C cathode. A conventional sprayed iridium oxide powder layer on Nafion115 and a platinum-coated PTL substrate was prepared for reference. Water electrolysis performance of the MEAs was measured in a single-cell configuration by supplying water to the anode side at 80℃ and applying current to the cell under atmospheric pressure.

3
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Results and discussion

Figure 2 shows the water electrolysis cell voltage at 2 A/cm2 for each type of anode with various iridium loadings. At a low iridium loading (0.1 mg-Ir/cm2), the voltage of the ACLS electrocatalyst (1.8 V) was lower than that of the powder catalyst (2.0 V). From Tafel plot analysis, this result is attributed to the low diffusional overpotential of the ACLS anode. We assume that its optimal porous structure increases the diffusivity of water and oxygen gas in the catalyst layer. Moreover, the ACLS anode showed almost no voltage rise up to 7000 h of operation without platinum coating on the PTL. The ACLS is effective for reducing the amount of noble metals used in PEM electrolyzers.
(1) K. E. Ayers et al., ECS Transactions, 41,15 (2012).
(2) C. Rakousky et al., J. Power Sources, 326, 120 (2016).
(3) C. Rozain et al., Appl. Catal. B Environ., 182,153 (2016

Figure 1
(Invited) Advanced in Situ Characterization of Energy Conversion Electrocatalysts
Authors: Shviro Meital , Gocyla Martin , Park Seongeun , Carmo Marcelo , Dunin-Borkowski Rafal E. , Stolten Detlef 
Published: February 2020

Sluggish reaction kinetics to split water into hydrogen and oxygen are hindering the market penetration of water electrolyzers for renewable energy storage.1 It is therefore of paramount importance to design the next generation of electrocatalysts, which offer enhanced performance and maximize catalyst utilization, while guaranteeing a durability of approximately 50.000 hours. However, current synthesis and characterization methods for electrocatalysts are not satisfactory. In particular, innovative and transformative characterization methods are required to provide a detailed experimental understanding of physical-chemical/electrochemical relations between the atomic structures of electrocatalysts and their activity, stability and degradation.2

Here, we show how in situ transmission electron microscopy (TEM) and identical-location TEM can be used to follow dynamic changes in electrocatalyst morphology, faceting and elemental segregation under real electrochemical working conditions. We study the relationship between nanoparticle morphology, composition and activity and demonstrate the ability to tune the structure-stability relationships of bimetallic nanoparticles for use as electrocatalysts.

References

(1) Carmo, M.; Fritz, D. L.; Mergel, J.; Stolten, D. A Comprehensive Review on PEM Water Electrolysis. Int. J. Hydrogen Energy
2013, 38 (12), 4901–4934.
(2) Shviro, M.; Gocyla, M.; Schierholz, R.; Tempel, H.; Kungl, H.; Eichel, R. A.; Dunin-Borkowski, R. E. Transformation of Carbon-Supported Pt-Ni Octahedral Electrocatalysts into Cubes: Toward Stable Electrocatalysis. Nanoscale
2018, 10 (45), 21353–21362.
Development of Membrane Electrode Assemblies for State-of-the-Art Anion Exchange and Proton Exchange Membrane Electrolysis
Authors: Motz Andrew R , Capuano Christopher B , Ayers Katherine E. 
Published: February 2020

Proton exchange membrane (PEM) electrolysis and anion exchange membrane (AEM) electrolysis are both able to directly produce high purity hydrogen from electricity and water. Key benefits of electrolysis using polymer membrane separators include a quick response rate, enabling load following, and ability to operate with high differential pressure. Operation under differential pressure allows for simultaneous electrolysis and electrochemical compression, simplifying overall system design. The development and stack integration of new, high performance electrolysis materials must include consideration of operating range and durability under differential pressure to maintain the technologic benefits.
PEM electrolyzers are commercially available on the megawatt scale and produce hydrogen fuel that is increasingly cost competitive with fossil fuel in select parts of the world. Better utilization of low cost electricity from renewable energy (wind and solar) is one route to additional hydrogen cost reductions, for which a wide current operating range is beneficial. Thinner membranes, more active catalysts, and better electrode design enable high currents at acceptable cell efficiencies. Performance and durability data will be presented on state-of-the-art PEM electrolyzer materials operating under differential pressure.
AEM electrolyzers are not currently commercially available, but promise membrane, catalyst, and balance of stack cost reductions. To begin to compete with PEM technology, performance and durability need to be improved. This work focuses on membrane stability under differential cell pressure and material integration into high performance AEM electrolyzers.
Microstructured Cathodes for Enhanced Transport in Unitized Reversible Fuel Cells
Authors: Komini Babu Siddharth , Brounstein Zachary Ryan , Uddin Md. Aman , Spendelow Jacob S 
Published: February 2020

Large scale energy storage challenges are increasing with increasing energy demand. Unitized reversible fuel cells (URFCs) coupled with intermittent renewable power sources could be instrumental in enabling the transition away from non-renewable sources. URFCs operate as a fuel cell (FC) and electrolyzer (E) in a single cell/stack (1, 2). However, several technical barriers must be overcome to make URFCs competitive with other energy storage technologies. For low-temperature membrane-based systems, the optimal operation in E mode requires high liquid water saturation, while FC mode requires just enough water to maintain ionic conductivity. The conflicting saturation requirements prevent transport optimization for either mode, while also causing inefficiencies when switching between the operating modes.
In this work, we present a novel binary array structure that could lead to improved operation in both E and FC mode while avoiding any need for gas purging when switching between operating modes. This is achieved by patterning the electrodes and diffusion media to induce localized hydrophilic and hydrophobic domains. The hydrophobic domain enables improved gas transport during switching between the different operating modes. However, electrodes with only hydrophobic domains can provide an improvement in FC mode, but E mode performance suffers due to poor water transport as seen in Figure 1. Binary array electrode enhances water management and thereby increases performance in both the operating modes.

Acknowledgments

This research is supported by DOE Fuel Cell Technologies Office; Technology manager: Nancy Garland.

References

B. Paul and J. Andrews, Renewable and Sustainable Energy Reviews, 79, 585 (2017).

Y. Wang, D. Y. C. Leung, J. Xuan and H. Wang, Renewable and Sustainable Energy Reviews, 65, 961 (2016).

Figure 1
On the Role of the Porous Transport Layer Structure in Polymer Electrolyte Water Electrolysis
Authors: Schuler Tobias , Schmidt Thomas J. , Büchi Felix N. 
Published: February 2020

In polymer electrolyte water electrolysis, the mass transport losses are the least understood overvoltage contribution. Underlying origin as well as correlation parameters with the structure of the porous transport layer (PTL) are not identified, because in the past the focus was set on the PTL bulk1,2and not on the PTL surface properties. The application of X-ray tomographic analysis of the interface3 (an example shown in Figure 1), in combination with electrochemical characterization leads to the identification of governing parameters. PTL interface properties (interfacial contact area, membrane deformation) seem to be key properties, as they correlate with cell performance. Based on these findings, novel two layer PTL materials were designed and characterized. Increased performance and reduced mechanical deformation were obtained in comparison to conventional PTL materials, also enabling the employment of ultra-thin membranes.
1. M. Suermann, K. Takanohashi, A. Lamibrac, T. J. Schmidt and F. N. Büchi, Journal of The Electrochemical Society, 2017, 164, F973-F980.
2. S. A. Grigoriev, P. Millet, S. A. Volobuev and V. N. Fateev, International Journal of Hydrogen Energy, 2009, 34, 4968-4973.
3. T. Schuler, R. De Bruycker, T. J. Schmidt and F. N. Büchi, Journal of The Electrochemical Society, 2019, 166, F270-F281.

Figure 1
(Invited) The Processing Science and Engineering Research Portfolio for Advanced Vehicle Batteries at the U.S. Department of Energy
Authors: Faguy Peter W. 
Published: February 2020

The widespread adoption of electric vehicles using advanced battery technologies and the development of their manufacturing base in the United States are critically important for the US economy and therefor a major focus of research and development sponsored by DOE’s Office of Energy Efficiency and Renewable Energy. Materials development is often touted as the most important enabling activity, however in a rank of major cost items, manufacturing costs ranks just below the cathode components. In addition to the need to reduce costs, US R&D should also focus on new, yet-to-be-scaled processing technologies that, when developed and implemented in the US provide both a strong component of US energy security and US-based employment in the production of electric vehicle batteries. This presents a major economic opportunity to the USA, as the global electric vehicle market is expected to grow to over $100 billion in the next ten years. Advances in battery processing science and technology could lead directly to the displacement of the established non-US-based manufacturing base via creative destruction--new innovative technologies lead to new manufacturing facilities, facilities that could be built and run in the USA.
Processing science and engineering has traditionally been underrepresented in federally funded electrochemical energy storage R&D. Over the last nine years, the Vehicle Technologies Office (VTO) has been building an advanced processing R&D portfolio. This includes competitively funded research at universities, small businesses, and large corporations as well as programs supported across the national laboratory complex. Processing science and technology projects organize into two general activities: scaling-up materials production and developing innovative electrode fabrication approaches. This presentation will provide an overview of the sub-program’s history and several example successes. Future research directions and scenarios for possible funding opportunities will also be discussed.
Elevated Mixing and Coating Temperatures Yield Beneficial Processing Properties of Organic Solvent-Based Lithium-Ion Battery Cathode Slurries
Authors: Hawley William Blake , Li Jianlin 
Published: February 2020

In traditional lithium-ion battery cathode manufacturing, the slurry mixing and coating stages bear tremendous influence on downstream processing steps and, consequently, the viability of the end product. Two avenues for improving these two stages include increasing the coating throughput to meet rising consumer demands and to make coatings with more consistent, homogeneous distributions of slurry components in order to create higher-performing devices. In state-of-the-art slot die coating operations, coating speed is maximized and imperfections (i.e. air bubbles and thickness variations) are minimized by reducing the viscosity of the material being coated. The active materials, which routinely form agglomerates with diameters on the order of 10 μm, must be prevented from settling under gravity to form a homogeneous active layer. In this work, heating the slurry during the mixing and coating stages is proposed as a scalable and effective solution to achieve faster and more reliable coating operations.
This study demonstrates that increasing the mixing and coating temperature from 25°C to 60°C can reduce the slurry viscosity by 21 percent at practical industrial coating speeds. At low shear rates, slurries mixed at 60°C are also 10 percent more viscous, providing the additional benefit of sharper edge contours and, thus, less cut-off waste during processing. Oscillatory shear probing revealed that the gel strength of heated slurries is also greater, meaning there is greater sedimentation resistance due to increased polymer bridging. The discharge capacity of the cathode mixed and coated at 60°C was about 4% greater than that of the cathode mixed and coated at 25°C for all C-rates between C/10 and 5C, which could be indicative of an improved distribution of components. The results indicate that mild heating of the slurry (1) does not irreversibly gel the slurry such that it is unable to be processed, (2) provides rheological properties that correlate to quicker and more consistent coating operations, and (3) yields slightly higher-performing cathodes at C-rates of practical interest. Heating the slurry also provides the manufacturer with the option to increase the solid loading to reduce drying times and solvent recovery.
Understanding the Silicon/Binder Interaction and Influence on Anode Properties
Authors: Burdette Mary Kathyrn , Rogers Alexander M , Armstrong Beth , Veith Gabriel M. 
Published: February 2020

Polymeric binder interactions with silicon were investigated as a function of electrode processing and electrochemical behavior. Using ultra-small angle neutron scattering, the evolution of the dynamics between a poly(acrylic acid) and silicon slurry showed that, under shear conditions, the slurry aggregated heavily when compared to the no shear condition. This behavior is undesirable as silicon anode slurries must de-agglomerate under shear conditions for a uniform electrode cast, which facilitates even lithiation across the anode. Electrodes made from these slurries show the connection between the binder/silicon interaction and electrochemical behavior. Additionally, the role of the silicon surface chemistry on the rheology of the electrode slurry was elucidated and connected to electrode processing and electrochemical performance. Based on these results, the binder for the silicon anode materials may need to be re-evaluated in order to improve the viability of silicon anodes.
Acknowledgement: This work was supported by the US Department of Energy’s Office of Energy Efficiency and Renewable Energy through the Vehicle Technology Office (Brian Cunningham Program Manager).