bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effect of Sulfate Contaminant on ORR Activity and PEMFC Performanc
Authors: Dinh Huyen N , Bender Guido , Christ Jason M , Zack Jason W. , McGovern Leah , Przywara Jacob , Carey Christian 
Published: February 2020

Lower cost materials for stack hardware and system components help reduce the overall cost of the automotive and stationary fuel cell systems and make these competitive in the market. However, low-cost system component materials need to provide similar function, performance and durability. Intelligently selecting low cost materials for application in polymer electrolyte membrane fuel cell (PEMFC) systems requires understanding the potential adverse effects that system contaminants may have on the fuel cell performance and durability.
There are many prospective balance of plant (BOP) materials that can be used in fuel cell systems. Families of material, based on input from OEMs, fuel cell system manufacturers and other attributes like cost, physical properties, have been studied. These include structural materials, elastomers for seals and (sub)gaskets, and assembly aids (adhesives, lubricants).
The contaminants from the BOP materials were leached out via an accelerated aging procedure. The leachates obtained from these plastics were a mixture of organics, inorganics, and ions. The sulfate anion was one of the anions identified in the leachates and was chosen as the model compound for further studies. Sulfate anions can also come from membrane degradation. Ex-situ electrochemical measurements were carried out to understand the impact of sulfate anion concentration on oxygen reduction reaction (ORR). The ORR scan rate and direction (low to high potential and vice versa) were studied to determine the effect of the initial state of the Pt surface on sulfate contamination. In-situ fuel cell experiments were also carried out. Sulfate anion was introduced to a working fuel cell to determine their effect on fuel cells performance. Our previous work showed that sulfate anion did not result in performance loss when it was infused into the cathode at 0.2 A/cm2. The cathode potential was greater than 0.8 V at this current density. It is postulated that sulfate contamination is potential dependent and that sulfate adsorption only occurs when Pt is in its metallic state. In the current study, the effect of potential on sulfate contamination will be studied by infusing sulfate into the cathode at several constant current densities. Several in-situ diagnostics such as infusion, cyclic voltammetry, electrochemical impedance spectroscopy, and I-V curves were carried out to better characterize the contaminant effects of sulfate anion. The goal is to better understand the contamination mechanisms of specific species so that mitigation strategies can be determined.
The authors would like to acknowledge funding from the U.S. Department of Energy EERE Fuel Cell Technologies Office, under Contract No. AC36-08GO28308 with the National Renewable Energy Laboratory and collaborations with colleagues at GM. Structural plastic materials and leachates were provided by GM for this study.
Evaluation of Acid Accelerators for an Off-Grid PEM Fuel Cell Power Station Utilizing Solid Sodium Borohydride for Hydrogen Storage
Authors: Hsu Lewis , Huang Mindy , Anderson Greg , Rubio Arthur , Kerber Maxwell , Putnam Michael , Phipps Alex 
Published: February 2020

In rural areas, networkable environmental monitoring equipment is often used to provide continuous, real-time information without the need for a dedicated operator for maintenance or monitoring. However, power and energy availability are often controlling factors for operational lifetime when these systems are put on location. In these situations, batteries are often used as the main energy storage medium and require servicing or replacement when exhausted. This can lead high costs related to man-power and logistics to return and maintain the equipment at those locations.
Sodium borohydride hydrolysis was once looked at as a promising way to store hydrogen for use in PEM fuel cells. Concerns regarding hydrogen storage capacity and recyclability of reaction products have prevented its use in larger transportation or energy storage applications. However, the energy density of sodium borohydride still makes the reaction suitable for specific applications where reuse is not needed. As such, present here a system utilizing solid sodium borohydride as a storage medium to meet on demand power needs of these types of systems. The system utilizes a PEM fuel cell integrated with an electro-mechanical system to control chemical metering and power management.
We have previously shown results from our initial testing with solid sodium borohydride using commercial-off-the-shelf tablets for generating hydrogen when added to a reaction vessel containing water. Conceptually, a tablet would be introduced to the reaction vessel whenever additional hydrogen gas would be required. Operating in this manner would require good stability and reproducibility over multiple tablet reaction events.
Initial testing showed good reaction rates when a cobalt catalyst was employed, either pre-doped into the solid tablet mixture or when the catalyst was pre-mixed with the water in the reaction vessel. Analysis of the gas mixture showed high quality hydrogen gas flows could be produced and sent to the PEM fuel cell for power production. However, concerns with the stability, safety, and handling of the catalyst have led to a need to identify a more green chemistry approach.
We present here an alternative approach using common mineral and organic acids as hydrolysis accelerators that could be considered a greener approach to hydrogen generation for remote power applications. These include hydrochloric acid, phosphoric acid, citric acid, and acetic acid. Initial testing shows good reproducibility over multiple hydrogen generation events and reasonable reaction control. A comparison of hydrogen yield and gas composition is also shown. Finally, cost comparison between these accelerators is performed in order to assess their suitability in practical application.
Imaging Phosphoric Acid in HT-PEFC: What Has Been Learnt so Far?
Authors: Büchi Felix N , Eberhardt Sebastian H. , Halter Jonathan , Schmidt Thomas J. 
Published: February 2020

Phosphoric acid used as the electrolyte in high temperature polymer electrolyte fuel cells (HT-PEFC) is not covalently bound to the membrane polymer. The interaction of phosphoric acid with the nitrogen of the pyridine group of the polybenzimidazole (PBI) polymer backbone [1] is limited to two acid molecules per PBI repeating unit. Consequently, the bulk of phosphoric acid is mobile and the acid concentration and distribution in/and between membrane, catalyst and gas diffusion layers (GDL) is varying, depending on the operating conditions of the fuel cell.
X-ray imaging technology, initially developed for imaging liquid water in the porous structures of LT-PEFC, has been adapted [2] for the imaging of phosphoric acid. Operando tomographic microscopy imaging has shown that acid migration to the anode due to the non-zero transference number of the hydrogen phosphate anion is an important process in acid redistribution [3]. The acid can invade the anode GDL, similar to the injection of water into the cathode GDL of LT-PEFC.
So far, not much has been known about the characteristics of the interaction of phosphoric acid with the porous structure of the gas diffusion layer. Ex-situ acid injection and withdrawal experiments at temperatures up to 160 °C are performed with concurrent tomographic imaging to understand the characteristics, as well as the similarities and differences to the wetting of GDLs with water.
[1] Q. Li, J. O. Jensen, R. F. Savinell, and N. J. Bjerrum, Prog. Polym. Sci., 34, 449–477 (2009)
[2] S.H. Eberhardt, F. Marone, M. Stampanoni, F.N. Büchi, and T.J. Schmidt, J. Synchrotron Radiat., 21, 1319–1326 (2014)
[3] S.H. Eberhardt, M. Toulec, F. Marone, M. Stampanoni, F.N. Büchi, and T.J. Schmidt, J. Electrochem. Soc., 162, F310-F316 (2015)
N-Functionalised Polyketone Ion Exchange Membranes for Aemfcs
Authors: Nawn Graeme , Cavinato Gianni , Pace Giuseppe , Vezzù Keti , Bertasi Federico , Negro Enrico , Bach Delpeuch Antoine , Di Noto Vito 
Published: February 2020

Anion-exchange membrane fuel cells (AEMFCs) provide significant advantages over their proton-exchange membrane counterparts. In the alkaline environment, the oxygen reduction reaction (ORR) is more facile, there is diminished fuel crossover, and a greater flexibility regarding fuel and catalyst choice. The membrane at the heart of AEMFCs not only facilitates the ion exchange but also separates the fuel feedstocks and acts as a support for the membrane-electrode assembly (MEA). However, to date there are still no membrane materials that satisfy all the needs (long-term stability in alkaline environment, high ionic conductivity, low swelling and good structural integrity) for use in AEMFCs and this remains one of the larger obstacles for further AEMFC development.
The amination and subsequent quarternisation of polyketone leads to a new family of ionomers containing N-substituted pyrrole moieties. The degree of amination can be controlled by manipulating reaction conditions, allowing the composition and resulting structural properties of the polymer to be tuned. Membrane fabrication results in thermally stable (TD > 250 oC), structurally robust polymer electrolytes that exhibit ionic conductivity ( > 10-3 S cm-1). These new solid-state ion conducting materials have the potential to be used in a variety of applications including AEMFCs.
Here we present an in-depth study focusing on the structure-property relationships of this new polypyrrole/polyketone polymer. A variety of analytical techniques are used to probe the thermal and structural properties of the polymers, these include high-resolution thermogravimetric analysis, modulated differential scanning calorimetry, dynamic mechanical analysis, vibrational, NMR and UV-Vis spectroscopies. In addition, broadband electrical spectroscopy is used to gauge the interplay between the structural properties and electrical response.

Figure 1
MgO-Templated Mesoporous Carbon As a Catalyst Support for Polymer Electrolyte Fuel Cells
Authors: Kamitaka Yuji , Takeshita Tomohiro , Suzuki Noritomo , Jinnouchi Ryosuke , Murata Hajime , Morimoto Yu 
Published: February 2020

Catalyst poisoning by specific adsorption of the sulfonic acid anion of ionomers has been known as one of the main performance-limiting factors of PEFCs. In a recent study, it was reported that the catalyst poisoning can be suppressed by using a mesoporous carbon (mesoporous carbon nano-dendrites) as a cathode catalyst support [1]. Here, we present that a similar effect can be obtained by using a MgO-templated mesoporous carbon [2] having meso-pores the sizes of which are more-systematically controllable by changing the size of the MgO templates than for conventional carbon supports.
An MgO-templated carbon denoted as CNovel® was purchased from Toyo Tanso Inc. The mean diameter of its mesopores is ca. 5 nm (the template MgO size was 5 nm). The sample was graphitized by a heat treatment at 2,100 °C for improving the chemical stability under electrochemical conditions and was crushed by a bead mill to form secondary particles smaller than hundreds nm in size. The obtained powder was immersed in 1 M HNO3 at 80 °C for 1 h to introduce hydrophilic surface groups for facilitating Pt deposition. After thoroughly washing it with pure water, platinum nanoparticles were deposited in aqueous media by using hexahydroxy-platinate as a platinum source. The ORR activity of the prepared catalyst was evaluated by the thin-film RDE method (without ionomers) in aqueous media (0.1 M HClO4) and in MEAs prepared with a Nafion® ionomer (I/C=1.0). The results were compared those of Pt/Vulcan.
Figures 1a and 1b show that TEM images of the catalysts. Platinum particles of ca. 2 nm are observed on both the carbons. While Pt/Vulcan shows platinum particles only on the outer edge of the carbon particle, Pt/CNovel shows platinum particles not only on the outer edge but also on the mesopores inside the carbon particle. Figure 1c shows the I-V curves of MEAs using Pt/CNovel and Pt/Vulcan. Pt/CNovel exhibits higher cell-voltage than Pt/Vulcan in the low current density region. This result indicates that the former has a higher ORR activity than the latter as specifically indicated in the specific activities at 0.9 V shown in Figure 1d. The trend is, however, opposite in the RDE measurements while the specific activities for both samples by RDE are higher than those measured by the MEAs. These results indicate that the Pt/CNovel suffers less catalyst poisoning by the sulfonic acid anion than Pt/Vulcan in MEAs probably because the anion linked to the ionomer cannot reach the surfaces of the Pt nanoparticles inside the mesopores of CNovel while all Pt nanoparticles on Vulcan® can be reached by the ionomer.

References

[1] M. Hori, et al., 225th ECS Meeting Abstract, #1500 (2013)
[2] T. Morishita, et al., Carbon, 48, 2690 (2010)

Figure 1
Nanofibrous Electrodes with Tunable Electrodeposited Pt Morphologies with High ORR Activity and Durability
Authors: Ercolano Giorgio , Farina Filippo , Cavaliere Sara , Jones Deborah J. , Rozière Jacques 
Published: February 2020

A new approach for the preparation of PEMFC cathode electrocatalysts based on thin layers of platinum deposited on a support instead of conventional Pt nanoparticles supported on carbon black could be achieved adopting various Pt deposition techniques including atomic layer deposition, electrochemical atomic layer epitaxy, self-terminated Pt electrodeposition, thermal dealloying, and galvanostatic displacement of Ni and Cu ions with Pt1,2. This morphology allows for a more effective utilisation of the highly priced noble metal, while increases the durability of the electrodes over time.
The morphology and nature of the support material also plays a crucial role. Nanostructured 1D materials have attracted significant research attention due to the influence of their nanostructure and porosity on performance and durability of the PEMFC3. In this regard, electrospinning is a reliable and scalable technique for the preparation of nanofibers with controlled and uniform diameters and structures. Its versatility allows the production of organic, hybrid and inorganic nanofibres, as well as the possibility of creating different geometries, assemblies and architectures4.
We developed novel nanofibrous electrodes (NFE) based on 3D nanostructured networks of carbon nanofibers covered by Pt nanoislands, merging the advantage of Pt thin layers catalyst and a highly porous robust support. This was achieved by combining electrospinning and high overpotential pulsed Pt electrodeposition.
These catalysts are based on self-standing electrospun carbon nanofibers covered by platinum thin platinum nanoislands. NFEs are highly durable when compared to commercial standards and have a higher degree of platinum exploitation. Electrochemical active specific surface areas as high as 140 m2g-1
Pt with retention in the order of 70 % after accelerated stress testing are measured, making them a suitable alternative to currently available commercial catalyst.
1. S. M. Alia, Y. Yan, and B. Pivovar, Catal. Sci. Technol., 4, 3589–3600 (2014)
2. G. Ercolano, S. Cavaliere, D. Jones, and J. Rozière, ECS Trans., 69, 1237–1242 (2015).
3. S. Cavaliere et al., ChemElectroChem, 2, 1966–1973 (2015).
4. S. Subianto et al., in Electrospinning for Advanced Energy and Environmental Applications, vol. 1, p. 29–60 (2015).
(Invited) Ultra-Low EW Ionomers and Membranes for Fuel Cells
Authors: Yandrasits Michael , Lindell Matthew , Kurkowski Michael , Schaberg Mark S 
Published: February 2020

Perfluorosulfonic acid (PFSA) ionomers have long been used to fabricate membranes for proton exchange membrane fuel cells (PEMFC). When used in combination with mechanical reinforcements and peroxide scavenging additives, this class of ionomers has demonstrated excellent durability and performance in both accelerated lab testing and in end-use applications.
Automotive traction applications, among others, have very demanding performance targets at relatively high temperature and low humidity, driven by the need to reduce overall system cost. In order to meet these targets, ionomers with increased proton conductivity are required. Under dry conditions, conductivities of commercial ionomers are insufficient to achieve several of the targets, as they are limited to equivalent weights (EWs) of about 700 g/mol. Not only are low EW PFSA ionomers difficult to polymerize, they also tend to become water soluble as the amount of the tetrafluoroethylene (TFE) co-monomer is reduced.
One strategy for achieving lower equivalent weight, while maintaining suitable TFE content, is a multi-acid side chain (MASC) approach. We have developed a synthetic process to use the 3M precursor polymer to prepare a new ionomer containing both bis(sulfonyl)imide and sulfonic acid groups in each sidechain, to form the perfluoro-imide acid (PFIA) ionomer. Both functional groups are strong acids, and their combination results in EWs in the range of 620-650 g/mol, with increased conductivity under all conditions, including low humidity. This approach has been extended to include multiple bis(sulfonyl)imide groups per side chain to form materials classified as perfluoro-ionene chain extended (PFICE) ionomers, with EWs as low as 440 g/mol.
Characterization of these new ionomers for conductivity, solubility, and performance will be presented, along with a discussion of the practical limits of the MASC approach. Like PFSA ionomers, the PFIA and PFICE ionomers require both mechanical reinforcement and stabilizing additives in order to fabricate a viable PEMFC membrane. Development of membrane design considerations will be presented.
Water Balance in Non-Humidified PEM Fuel Cell with Different Membrane Thicknesses
Authors: Pivac Ivan , Penga Zeljko , Barbir Frano 
Published: February 2020

It is possible to design and operate a fuel cell with non-humidified reactant gases, by relying on water produced by electrochemical reaction inside the fuel cell. However, in order to do so there must be adequate water and heat management applied. For example, temperature distribution along the cathode channel must be such that relative humidity is maintained close to 100%. As water is produced on the cathode side there is a water concentration gradient across the mebrane, and in order to humidify hydrogen on the other side there must be back-diffusion flux greater than or at least equal to the electroosmotic drag. Membrane thickness, thus, plays an important role in realization of this concept.
A segmented fuel cell is designed such that each segment can be maintained at different pre-determined temperature. The temperatures of the segments along the cathode channel are selected by the help of Molliere h-x diagram such that relative humidity is maintained close to 100%. Operating conditions are selected such that the product water is sufficient to saturate the cathode exhaust without appearance of liquid water. Humidity measurements are taken between each segment on both anode and cathode sides. The anode and cathode exhaust streams are condensed so that water balance may be established.
The entire setup is modeled with FLUENT CFD package, and the experiments are conducted with two different mebrane thickness. Good agreement is achieved between the modeling and experimental results.
The results indicate that it is possible to establish the required temperature profile along the cathode channel and keep the cathode stream relatively well humidified without external humidification. Performance of such variable temperature fuel cell is better than the uniform temperature fuel cell. The thinner membrane results in better humidification of the hydrogen side, which is important especially at higher current densities, i.e., at higher electro-osmotic drags.

Figure 1
Investigation on the Improvement of PEM Fuel Cell Performance through Two Novel Flow Field Designs
Authors: Shen Shuiyun , Wang Chao , Zhang Qinglei , Zhang Junliang 
Published: February 2020

To further improve the cell performance of a proton exchange membrane fuel cell (PEMFC), thus meeting the high requirement for its automotive and stationary application, great efforts have been made on the optimization of the flow field pattern[1,2]. In this work, two novel flow field patterns are proposed and the influences on the cell performance are investigated. Both two novel flow field designs lead to superior cell performance than the conventional flow field patterns do, and this can be attributed to their superiority in removing water at high current densities while increasing the flow velocity near the outlet. The velocity magnitude in flow fields is examined and compared through the computational fluid dynamics modeling.

Acknowledgements

This work was supported in part by National Natural Science Foundation of China (Grant No. 21373135 and 21533005) and Science Foundation of Ministry of Education of China ( Grant No. 413064).

References

[1] Soler, J., E. Hontanon, and L. Daza, Electrode permeability and flow-field configuration: influence on the performance of a PEMFC. Journal of Power Sources, 2003. 118(1): p. 172-178.
[2] Lee, B., K. Park, and H.-M. Kim, Numerical Optimization of Flow Field Pattern by Mass Transfer and Electrochemical Reaction Characteristics in Proton Exchange Membrane Fuel Cells. Int. J. Electrochem. Sci, 2013. 8: p. 219-234.
Development of Highly Active and Stable Compressive Pt Cathode Catalyst for Pemfcs
Authors: Kim Taekeun , Popov Branko N 
Published: February 2020

Cathode durability, cost, and performance are some of the key issues preventing the commercialization of polymer electrolyte membrane fuel cells (PEMFCs) for automotive applications. The support degradation during start-up/ shut-down and the catalyst degradation during driving potential cycling limit overall cathode catalyst lifetime. The ultra-low Pt cathode catalyst development project at the University of South Carolina (USC) has developed highly-stable activated carbon composite supports (ACCS) as well as highly-active and stable compressive Pt lattice cathode catalysts, Pt*/ACCS (Pt* = Compressive Pt lattice catalyst) that retain their activity after accelerated stress tests (AST) to simulate start-up/shut-down and driving potential cycling [1-7].
The novel USC technology is based on a two-step patented process. In the first step, the following major constraint was addressed: the support should be chemically and electrochemically stable at high potentials, low pH, and high temperature. To accomplish these requirements, ACCS was synthesized with optimization of: (i) BET surface area, porosity, pore-size and distribution, (ii) hydrophilic/ hydrophobic ratio, (iii) structural properties (amorphous/ crystalline ratio), and (iv) Pt-support interaction through inclusion of active surface functional groups.
In the second step, compressive Pt lattice catalyst (Pt*) was synthesized through a USC-developed annealing procedure that controls the particle size during annealing and forms several monolayers of Pt* by diffusing Co atoms into Pt which is deposited on ACCS support. The Pt*/ACCS shows high rated power density (0.174 gPt kW−1), excellent support stability (8 mV loss at 1.5 A cm−2), and enhanced catalyst durability (24 mV loss at 0.8 A cm−2) under AST conditions.
References
[1] T. Kim, B. N. Popov, Int. J. Hydrogen Energ., 41 (2016) 1828-1836.
[2] T. Kim, T. Xie, W. Jung, F. Gadala-Maria, P. Ganesan, B.N. Popov, J. Power Sources, 273 (2015) 761-774.
[3] W. Jung, T. Xie, T. Kim, P. Ganesan, B.N. Popov, Electrochim. Acta, 167 (2015) 1-12.
[4] T. Xie, W. Jung, T. Kim, P. Ganesan, B.N. Popov, J. Electrochem. Soc., 161 (2014) F1489-F1501.
[5] Á. Kriston, T. Xie, B. N. Popov, Electrochim. Acta, 121 (2014) 116-127.
[6] Á. Kriston, T. Xie, D. Gamliel, P. Ganesan, B. N. Popov, J. Power Sources, 243 (2013) 958-963.
[7] Á. Kriston, T. Xie, P. Ganesan, B. N. Popov, J. Electrochem. Soc., 160 (2013) F406-F412.

Figure 1