bluuebunny/crossref_metadata_2025_split huggingface dataset:
Metal Mesh Gas Diffusion Layers for PEM Fuel Cells
Authors: Fahy Kieran F. , Lapinski Jacek , Kucernak Anthony R. J. 
Published: February 2020

As fuel cells gain increased volumetric power density, there is a need for thinner GDLs that give increased thermal and electrical conductivity, and mechanical stiffness. This has been demonstrated by the introduction of advanced GDL/bipolar plate designs that have been implemented in commercial fuel cells such as that seen in the Toyota Mirai (1).
The use of metal GDLs has been previously examined in ethanol and methanol fuel cells (2,3) but have been largely ignored in PEMFCs due to the corrosive conditions present in PEMFCs which considerably reduce the lifetime of cells with non-passive metals present. Spun carbon fibre GDLs, such as Toray and Avcarb, have previously been the main choice for PEMFC GDLs due to the passivity and gas and water transport properties of these materials. With increased power density in fuel cells however these materials can incur losses due to a lack of thermal and electrical conductivity as well as being relatively thick and brittle.
In this study we have examined a number of metal meshes used in place of carbon paper GDLs in fuel cells. Meshes with different aperture sizes were examined with regard to fuel cell performance as well as flooding of the electrodes and performance under high mass transport conditions. The aperture sizes of these meshes played a significant role in performance in the cell, both in terms of electrical conductivity and water management.
Surface passivation of the meshes by nitriding and using carbon and other passive coatings was also examined in order to increase their durability in the cell. The surface energy properties of these coatings was also examined ex situ via droplet shape analysis in order to achieve the best properties for use in a fuel cell. Adjustment of the hydrophilicity and hydrophobicity of these coatings was also used to improve water management.
The performance of some of these meshes and foams was seen to exceed some of the commercially available carbon papers even without significant optimisation. These materials could soon replace carbon fibre GDLs in PEMFCs leading to much higher volumetric power densities and improved performance.
References

T. Yoshida, K. Kojima, Electrochemical Society Interface, 24 (2015), pp. 45–49.

S. Arisetty, A. K. Prasad, S. G. Advani, Journal of Power Sources, 165, 1, (2007).

W. Yuan, Y. Tang, X. Yang, Z. Wan, Applied Energy, 94 (2012).

Figure 1 (a) Water droplet on metal mesh surface before surface treatment, and (b) after surface treatment. (c) PEM fuel cell performance of a metal mesh GDl compared with two common commercial carbon papers (Toray HGP-H-080 and SGL 24 BC).

Figure 1
Anion Exchange Membrane Separators Based on Polystyrene-Block-Poly(ethylene-ran-butylene)-Block-Polystyrene Triblock Copolymers
Authors: Wang Zhongyang , Parrondo Javier , Ramani Vijay K 
Published: February 2020

There is a growing interest in using anion exchange membranes (AEMs) as separators in alkaline membrane fuel cells (AMFCs) and in other energy conversion and storage systems such as redox flow batteries (RFBs), alkaline water electrolyzers (AWEs) and reverse electrodialysis (RED) cells. The most commonly used cation in AEMs is the benzyl trimethylammonium cation. It is easy to synthesize due to the basicity of the trimethylamine, results in relatively large ion exchange capacities (IECs), and the resulting AEMs have good ionic conductivities. AEMs based on the benzyl trimethylammonium cation are good candidates for separators in redox flow batteries. However, it had been shown that the quaternary-ammonium-based AEMs are sensitive towards Hofmann elimination and direct nucleophilic elimination reactions under alkaline conditions, which impedes their use in AMFCs and AWEs. To solve the alkaline stability problem encountered by quaternary ammonium cations, researchers have investigated cations without alpha hydrogens to avoid degradation through ylide formation. Gu and Yan (1) first synthesized a polysulfone based ionomer containing the benzyl tris-(2,4,6-trimethoxyphenyl) phosphonium (TTMP+) cation and they found it had an outstanding stability under alkaline conditions. In our lab, we attempted to attach TTMP to polyphenylene oxide (PPO) and other polymer backbones to make alkaline stable AEMs, but the resultant AEMs were extremely brittle. Therefore, we have devoted attention to studying more robust backbones.
Polystyrene-block-poly-(ethylene-ran-butylene)-block-polystyrene (SEBS) is a chemically stable and elastomeric triblock copolymer, which deforms elastically to accommodate bulky cations (TTMP+) without becoming too brittle. There have been several attempts to make SEBS-based AEM by chloromethylation, however, the degree of functionalization (DF) obtained were relatively low due to gelation during the reaction (2, 3). In our work, we have optimized the chloromethylation conditions by selecting the appropriate solvent, temperature and reaction time. The resulting polymers have DFs up to 0.3 (mol of chloromethyl groups per polymer repeat unit). We have been able to synthesize highly robust SEBS-based AEMs containing benzyl trimethyl ammonium (TMA+) and benzyl tris- (2,4,6-trimethoxyphenyl) phosphonium (TTMP+) cations. 1H-NMR spectroscopy, ion exchange capacity and tensile tests were employed to characterize the AEMs. We will report the results obtained.
References
1. S. Gu, R. Cai, T. Luo, Z. Chen, M. Sun, Y. Liu, G. He and Y. Yan, Angewandte Chemie International Edition, 48, 6499 (2009).
2. R. Vinodh, A. Ilakkiya, S. Elamathi and D. Sangeetha, Materials Science and Engineering: B, 167, 43 (2010).
3. L. Sun, J. Guo, J. Zhou, Q. Xu, D. Chu and R. Chen, Journal of Power Sources, 202, 70 (2012).
Effect of Chemical Structure on Properties of Multiblock Copolymers for Alkaline Membrane Fuel Cell
Authors: Shin Dongwon , Lee Sojeong , Kim Eunyoung , Bae Byungchan 
Published: February 2020

Alkaline membrane fuel cells (AMFCs), which use anion exchange membrane (AEM) as a solid electrolyte, continue to receive increased attention because of their advantages of fast oxygen reduction reaction in alkaline media, efficient water management, and the ability to use non-precious metal catalysts (e.g., nickel, cobalt, silver, iron, and etc.). Hydrocarbon-based aromatic polymers have been widely used as AEMs due to their good thermal and mechanical stabilities and easiness of synthesis and functionalization. However, poor chemical stabilities under strong alkaline environment and low ionic conductivity of AEMs should be improved for commercialization of AMFCs. Hydrophilic and hydrophobic phase separation is helpful for improvement in chemical stability and ionic conductivity. Well-developed hydrophilic domains form effective ion transport pathways resulting in enhanced ionic conductivity, while hydrophobic domains maintain mechanical and chemical stabilities because most nucleophilic sources, which can attack polymer backbone and cationic groups, are in hydrophilic domains. It is well known that block copolymers are the most promising chemical architecture for developing hydrophilic and hydrophobic phase separation.
Based on these backgrounds, we synthesized poly(arylene ether sulfone) based block copolymers to investigate the effect of chemical structure on AEM properties. These block copolymers were functionalized with cations after selective chloromethylation of hydrophilic blocks. The degree of chloromethylation was controlled to optimize ion exchange capacity values of block copolymers. The molecular weight of each oligomer was controlled by changing the feed ratio of monomers and confirmed by nuclear magnetic resonance (NMR) and gel permeation chromatography (GPC). All block copolymers showed well-developed morphology and outstanding AMFC performances. More detailed results will be discussed.
Investigation of a Correlation Between Structures of Mesoporous Carbon an Gas Adsorption Characteristics
Authors: Katagami Masataka , Akiba Etsuo , Hayashi Akari 
Published: February 2020

Introduction

PEFCs are paid much more attention since the commercialization of FCVs and are deeply related to carbon materials, which are components of PEFCs themselves and also related systems. In our group, we have been studying mesoporous carbon (MC), which has meso-channel structures with about 10 nm diameter, as a catalyst support and have successfully improved durability of PEFCs, so far. In order to further improve performance and durability of PEFCs and related systems, it is important to understand the fundamentals of adsorption properties of fuels involving hydrogen gas, oxygen gas, and water vapor. In this research, a correlation between structures of mesoporous carbon and gas adsorption characteristics is investigated.

Experimental

General MC was synthesized by mixing Pluronic® F127, resorcinol, formaldehyde, and trimethyl orthacetate and heated under nitrogen atmosphere. Other MC materials1 were also made by slightly different conditions as shown in Table 1. Then, gas adsorption properties of each sample were evaluated after the ball milling and heat treating at 900 oC.

Results & discussion

Hydrogen adsorption dependence on the pore size of MC is discussed here. If MC#1 and MC#2 in Table 1are compared, MC#2 has larger pores based on the pore distribution obtained from nitrogen adsorption measurements. The values of BET specific surface area of the MC#1 and the MC#2 results in not very much different, 615 m2/g and 650 m2/g, respectively. The maximum hydrogen absorption content (wt%) at 7 MPa has resulted in 0.6 % for MC#1 and 0.35 % for MC#2. Considering Chahine rule2 for carbon materials, revealing that linear relationship between the hydrogen absorption content and the specific surface area, our results are against that rule. Therefore, hydrogen adsorption properties can be explained by other than the specific surface area in our materials. The possible mechanism of hydrogen adsorption is further discussed through the analyses of several MC materials.
(1) Y. Sonoda, A. Hayashi, Y. Minamida, E. Akiba, Chemistry Letters, 44, 503-505 (2015).
(2) R. Chahine, T.K. Bose, 11th WHEC, 1996; Pergamon Press: Oxford, U.K., 1259 (1996).

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Electrocatalysts for Direct Alcohol Oxidation Fuel Cells Prepared Using Ion Beam Assisted Deposition Technique
Authors: Poplavsky Vasily 
Published: February 2020

Active layers of the electrocatalysts for oxidation of methanol and ethanol were prepared by ion beam assisted deposition (IBAD) of platinum and activating rare earths metals (Ce, Yb) onto carbon (AVCarb® Carbon Fiber Paper Р50 and Toray Carbon Fiber Paper TGP-H-060 Т) supports. The deposition method is characterized by the use of deposited-metal ions as assisting ions. Metal deposition and mixing between the precipitable layer and surface of the substrate by accelerated ions of the same metal were carried out on the experimental unit from a neutral vapor fraction and the vacuum-arc discharge plasma of a pulsed electric arc ion source, respectively. Ion accelerating voltage is 10 kV; vacuum – 10–
2 Pa.
Investigation of the composition and microstructure of layers was carried out by RBS, SEM, EPMA and XRF methods. It has been established that the obtained catalytic layers contain atoms of the deposited metals and substrate material, as well as impurity oxygen atoms; their thickness reaches ~30–100 nm. Content of platinum atoms in the layers is ~2×1016 cm–2, concentration of deposited metals atoms in the maximum of distribution equals about a few at.%.
According to investigations with use of cyclic voltammetry the electrocatalysts with prepared layers exhibited high catalytic activity in the reactions of electrochemical oxidation of methanol and ethanol, which form the basis for the principle of operation of low temperature fuel cells (DMFC and DEFC) (Figure 1).
Figure 1. Cyclic voltammograms in the ethanol comprising solution of electrocatalyst prepared using ion beam deposition of ytterbium and platinum onto Toray Carbon Fiber Paper TGP-H-060 Т
In comparison with the traditional multistage chemical methods of preparation of the deposited catalysts, the proposed IBAD method appears to be promising and often more preferable. It allows of the introduction of micro amounts of a doping impurity in the near-surface of a substrate under non equilibrium conditions and of the formation of cohesive catalytic layers at ultra-low platinum consumption.

Figure 1
A PEFC Parametric Study: CO Tolerance As a Function of Operating Conditions
Authors: Williams Stefan , Rockward Tommy , Mukundan Rangachary 
Published: February 2020

Abstract:
One of the current barriers listed in the Safety Codes and Standards section of the Fuel Cell Technologies Office Multiyear Research, Development, and Demonstration Plan is: ‘insufficient technical data to revise standards’ [1]. More specifically, SAE J2719 and ISO-14687-2 are two recently developed standards for gaseous hydrogen fuel specifications whose revisions are being planned [2,3]. Both standards are applicable for fuel cell vehicles and each governs contaminants and their maximum allowable concentration in H2. Of the contaminants listed in these fuel specifications, we focus our efforts on carbon monoxide (CO), whose allowable level is 200 parts per billion (ppb). In our Polymer Electrolyte Fuel Cell (PEFC) parametric study, we utilized 25cm2 Membrane Electrode Assemblies (MEAs) with 2015 DOE target loadings for platinum (0.15mg Pt/cm2). While it is virtually impossible to test the impact of CO using all of the possible testing conditions, we have systematically formed a set of experiments (Table 1) that encompasses a broad spectrum of Fuel Cell (FC) operating parameters. For each experiment, we fixed the cell temperature at 80oC and operated the FC at 1 A/cm2 with H2 and air stoichiometric flows equivalent to 83% and 50% utilization, respectively. The table reflects the parameters we vowed such as: relative humidity (32, 50, and 100% RH), back pressure (ambient, 150kPa, and 275kPa) and CO concentration (0.2, 0.5, 1.0ppm). The CO dosage remained constant throughout the experiments conducted in this study. In this presentation we will provide data to modelers for enhancing their predictive capabilities in order to help the FC community deduce the CO impact at other operating condition.

References:

http://energy.gov/sites/prod/files/2015/06/f23/fcto_myrdd_safety_codes.pdf

SAE J2719: Hydrogen Fuel Quality for Fuel Cell Vehicles, www.sae.org

ISO 14687-2, Hydrogen Fuel – Product Specification, Part 2: PEM fuel cell applications for road vehicles, http://www.iso.org/iso/catalogue_detail.htm?csnumber=55083

Acknowledgements:

The authors gratefully acknowledge the financial support of the DOE Fuel Cell Technologies Office and the support of Technology Development Manager, Charles (Will) James, Jr

Figure 1
Liquid Cooled PEMFC Bipolar Plates Development for Stationary Applications
Authors: Patularu Laurentiu G , Schitea Dorin , Varlam Mihai , Carcadea Elena , Stefanescu Ioan 
Published: February 2020

High power density along with low gravimetric and volumetric characteristics for Proton Exchange Membrane Fuel Cell stacks are desired in order to be successfully implemented in the stationary applications market.
Liquid cooling is currently the most widely used cooling strategy used in PEMFC stacks construction, especially for those who incorporate a large active area and high number of cells, since the heat transfer coefficients with liquid flow are much higher than airflow for the same pumping power.
This paper presents the manufacturing steps for an in house production of graphite type PEMFC bipolar plates with internal liquid cooling circuit and investigation results for a short stack construction based on 92cm2 active area.
Probing the Electrochemical Characteristics of Carbon-Supported Platinum Catalysts
Authors: Rockward Tommy , Spears Andre , Dumont Joseph H , Sansiñena José-María , Chlistunoff Jerzy 
Published: February 2020

Platinum (Pt) is the state-of-the-art catalyst for both anodic and cathodic reactions that occur in polymer electrolyte fuel cells (PEFCs). However, the cost of platinum has severely hindered the commercialization and distribution of PEFCs. One of the challenges for the next generation of fuel cells is to significantly reduce the Pt content of both electrodes while maintaining excellent activity and high durability. By anchoring platinum to carbon substrates, the amount of platinum can be substantially reduced without compromising its activity. While this approach may address the cost concerns; it may also induce durability issues depending on the operating conditions. In this work, we have investigated the effects of aging on different carbon supported, low Pt loading catalysts, using accelerated stress tests (AST). These tests consist of series of voltammetric cycles conducted in solution to accelerate the rate of degradation of the carbon support. Structural, chemical, and morphological information will be presented via X-ray techniques (XRD and XRF) along with electron microscopy (SEM,TEM). Electrochemically active surface area (EASA) will be measured via H2 adsorption and desorption along with CO stripping techniques. The electrochemical activity of the catalysts versus the number of cycles will be shown using RRDE as well as some complementary fuel cell data. Preliminary results show a decrease the EASA with time; however, the rate and extent of decay varied depending on the type of carbon support.
Promotion Effect of Adding Cr/Al/Fe to Cu/ZnO on the Stability of Hydrogen Produciton Catalyst for Dimethyl Ether Steam Reforming
Authors: Xie Jing , Ding Kaijie , Li Ranjia , Yu Changchun , Ban Shuai , Zhou Hongjun 
Published: February 2020

Steam reforming (SR) of dimethyl ether (DME) is one of the promising ways to produce hydrogen for fuel cells (FCs) [1]. DME is harmless with a high H/C ratio, handling DME is easy because it is liquefied under ca. 6 atm and conventional facilities providing LPG can be used due to the similarity of DME to LPG.Coppper based materials were considered as good catalyst for DME SR [2]. However the durability of copper based catalysts is not good because of the copper sintering as reaction running. There are two ways to improve the durability of copper based catalysts, one is to enhance the dispersion of copper or to improve the thermal stability of copper by forming a spinel oxide or alloy [3].
γ-Al2O3 was used as support. The Cu/ZnO/γ-Al2O3, Cu/ZnO/Cr2O3/γ-Al2O3 and Cu/ZnO/Fe2O3/γ-Al2O3 catalysts were prepared by impregnation method. The nitrates were impregnated into support for 6 h, then dried at 323 K for 12 h, calcined at 823 K for 4h. The DME SR was carried out with a fixed bed flow reactor under atmospheric pressure using 1 g of catalyst at 773 K. After the catalyst was reduced by 12 v% H2/Ar at 503 K for 3 h, the mixed gas of DME and N2 (20 v%) were fed into the reactor with GHSV=500 ml/(g·h), the water was pumped into the reactor though a 473 K heater. The H/C ratio was 3. The catalysts were characterized by means of XRD, TPR, SEM, and BET.
Steam reforming of DME was carried out at 773 K over Cu/ZnO/γ-Al2O3, Cu/ZnO/Cr2O3/γ-Al2O3 and Cu/ZnO/Fe2O3/γ-Al2O3 catalysts. The conversion of DME and the hydrogen yield reached 100% and 87% respectively for Cu/ZnO/γ-Al2O3 at the initial stage. The durability of this catalyst exhibted degradation. After running for 97 h, the hydrogen yield decreased to less than 60%. The reason for this degradation was supposed to be the sintering of copper, therefore, a metal oxide with better thermal stability was added into the catalyst to prevent the sintering of copper. The time-on-stream results indicate that the addtion of Cr2O3 or Fe2O3 can improve the durability of the catalyst for DME SR significantly. After running for 100 h, the hydrogen yield was kept at 84% and 85%, respectively. Figure 1 is the time-on-stream result of DME conversion over Cu/ZnO/ Cr2O3. Figure 1 is the time-on-stream result of DME conversion over Cu/ZnO/ Fe2O3. The mechanism of the improvement of the durability of catalysts were further investigated by XRD, SEM, BET and TPR.

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A Study on Performance By Oxygen Concentration According to Driving Environmental of Fuel Cell Vehicle
Authors: Goo Youngmo , Kim Myong-Hwan , Yoo Seung Eul 
Published: February 2020

Partial pressure of oxygen is a significant factor for determining performance of fuel cell. As is well known, the oxygen concentration in air is generally 21%, but it is about 20% at urban area which has numerous vehicles and is reduced by 18% at underground parking lot with stuffy ventilation facilities. Also, the oxygen concentration in air is 21% at a high altitude, but efficiency of fuel cell vehicle can be decreased by low oxygen partial pressure.
In this study, change of fuel cell performance was analyzed by applying empirical equation about I-V curves using experimental results according to oxygen concentration.
The performance of fuel cell in oxygen concentration of 18%~23% and altitude of 0~4km was prospected by a deducted empirical equation. In case of stoichiometric ratio(SR) 2.0, performance of fuel cell in oxygen concentration of 18% was decreased over 10% in comparison with concentration of 21%, the results was revealed as reduction in performance of 22%. Also, the performance of fuel cell at 4km altitude appeared decrease of 25% owing to low partial pressure.