bluuebunny/crossref_metadata_2025_split huggingface dataset:
On-Board Hydrogen Powered Proton Exchange Membrane Fuel Cells
Authors: Sankir Mehmet , Kara Kenan , Abdullayeva Nazrin , Demirci Sankir Nurdan 
Published: February 2020

One of the main concerns in the commercialization of fuel cell powered electrical vehicles is the on-board storage of hydrogen. Although pressurized vessels used in conventional systems provide higher hydrogen feeding rates, they have disadvantageous due to their extra weight and higher volumes in the systems. In this study, we report direct hydrogen generation from chemical hydrides, which does not require pressurized vessels. Self-dehydrogenation of chemical hydrides is a very slow process. In order to increase hydrogen generation kinetics, highly active and stable catalysts should be used. Although precious catalysts such as platinum and ruthenium meet these demands, their higher cost and recycling problems make them less useful in the fuel cell area.
A novel approach will be presented here for the fast, safe and stable hydrogen generation for fuel cells. This was achieved by circulating the acid and the chemical hydride solutions which were separated by the disulfonated poly(arylene ether sulfone) copolymer membrane. Since the rate of proton transfer is a function of ion exchange capacity (IEC) and scales with the degree of disulfonation of membranes, tailoring the IEC of membranes is crucial during the hydrogen generation. Therefore, membranes with varying sulfonation degrees (25-45 molar %) have been prepared and their hydrogen generation rates have been evaluated. Additionally, it was found that the type of acid and acid concentration influenced the hydrogen generation rates.
The effect of temperature on hydrogen generation performances was also investigated. When temperature exceeded the 80 °C, the hydrogen generation performance of N212 (the state of art membrane, Nafion™) was decreased due to the morphological changes occurred at this temperature. However the performances of our membranes without morphological relaxations continued to increase at higher temperatures. Furthermore, we run a proton exchange membrane fuel cell with our hydrogen generator and demonstrated continuous hydrogen generation more than 400 h. As a result, highly efficient on-board hydrogen generator for electrical vehicles powered by fuel cells presented here completely eliminates the need for separate facilities for producing hydrogen.
Alkaline Stability of Poly(phenylene oxide) Based Anion Exchange Membranes Containing Imidazolium Cations
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 cell (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 group in AEMs is the benzyl trimethylammonium cation. However, it had been shown that quaternary ammonium-based AEMs are sensitive towards Hofmann elimination (1) and direct nucleophilic elimination reactions (2) that result in loss of ion exchange capacity (IEC) and ionic conductivity. To solve the alkaline stability issue inherent to quaternary-ammonium-group-containing AEMs, several alternative cations, including imidazolium, benzimidazolium, guanidinium, phosphonium and metal cations have been proposed and investigated.
Imidazolium-based AEMs have drawn researchers’ interests mainly because of their high hydroxide ion conductivities. In addition to 1-methylimidazole and 1,2-dimethylimidazole, a series of modified imidazole bases, namely 1-heptyl-2-methyl-1H-imidazole and 1-dodecyl-2-methyl-1H-imidazole, were synthesized, wherein these modified bases contained a long alkyl chain at the N-3 position . Anion exchange membranes (AEMs) were prepared with derived imidazolium cations either grafted onto the benzyl position of poly(phenylene oxide)(PPO) or affixed using a hexyl (6-carbon) spacer chain. AEMs with cations affixed to the benzyl position were synthesized by bromination of PPO followed by reaction with the imidazole bases. AEMs with the hexyl spacer were synthesized by Friedel-Crafts acylation of 6-bromo-1-hexanoyl chloride on PPO, followed by reduction of the ketone group and reaction with the imidazole bases. The alkaline stability of the various imidazolium-cation-containing AEMs was evaluated by: 1) measuring the change in IEC after immersion in 1M KOH at 60°C for up to 14 hours; and 2) using 1-D and 2-D NMR spectroscopy to investigate any changes in chemical structure. Both NMR and IEC experiments showed that PPO functionalized with modified imidazolium cations (with long alkyl chain at the N-3 position) did not exhibit better alkaline stability than benchmark AEMs made with 1-methylimidazole. However, the use of a six-carbon spacer did improve AEM alkaline stability when the AEM was prepared directly using 1-methylimidazole and 1,2-dimethylimidazole, but not when the AEM was prepared with the modified imidazolium cations (with a long alkyl chain at the N-3 position).
References
1. C. G. Arges and V. Ramani, Journal of The Electrochemical Society, 160, F1006 (2013).
2. S. Chempath, B. R. Einsla, L. R. Pratt, C. S. Macomber, J. M. Boncella, J. A. Rau and B. S. Pivovar, The Journal of Physical Chemistry C, 112, 3179 (2008).
Bilayer Cathode Structure to Improve Ice Tolerance in PEM Fuel Cells
Authors: Lei Chao , Chuy Carmen , Ngo Tran , Wong Sharon , McDermid Scott 
Published: February 2020

In polymer electrolyte fuel cells, the freezing of product water deteriorates fuel cell performance at sub-zero temperatures. When ice forms in the membrane electrode assembly (MEA), catalyst sites are blocked from oxygen resulting in large portions of the MEA to become inactive during Freeze Start- up (FSU).
Improving the ice tolerance of the CCM is important to increase the robustness of the MEA to Freeze-Start up failure mechanisms. It is believed that the cathode catalyst layer is one of the key sub-components for ice tolerance, which is the ability of the MEA to accumulate ice before the MEA becomes inoperable. Isothermal Constant Current (ICC) measurements in units of (C/cm2) are commonly used to indicate this capability.
ICC data shows a clear correlation of ice tolerance with thickness of the catalyst layer. However, many of the control factors which can be used to improve ice tolerance in MEAs by increasing the thickness of the catalyst layer are limited by design constraints related to material cost and performance trade-offs. It would be difficult to achieve catalyst layer thickness >20um without seriously impacting performance under hot conditions or mass transport at high current densities.
Using a carbon/ionomer layer adjacent to the cathode catalyst layer allows to tune-in cathode attributes related to water management and ice distribution under freezing conditions, such as: thickness, porosity, hydrophilicity, interfaces and electric resistance. By changing attributes of the carbon bilayers separately from the cathode catalyst layer, the impact to the ORR reaction under normal or hot/dry operating conditions and mass transport region can be minimized.
Toughened Membrane/Catalyst Layer Interface with Mechanical Nano-Fastener for Hydrocarbon Membrane Based Polymer Electrolyte Membrane Fuel Cell
Authors: Kim Hee-Tak , Yuk Seongmin 
Published: February 2020

Polymer electrolyte fuel cells (PEMFCs) have been spotlighted as one of the promising eco-friendly energy technologies for stationary and automotive applications owing to zero CO2 emission, high energy density and moderate operation conditions. In this technology sector, polymer electrolyte membrane, one of the key components of PEMFC, has been intensely studied for several decades. Conventionally,perfluorinated sulfonic acid (PFSA) membranes like Nafion are used due to their high proton conductivity and mechanical stability. However, their high cost has been pointed out as a significant drawback interrupting mass commercialization of fuel cell electric vehicle. In this regard, hydrocarbon (HC) membranes, as cheaper alternatives, have been intensively studied in replacing PFSA membrane.
However, until now, the challenge in adopting cost-effective HC membrane for PEMFCs has been the poor interfacial adhesion between catalyst layers (CLs) and HC membrane, which causes the membrane to delaminate easily, losing efficiency with use. Here, we present scalable mechanical nano-faster featured by three-dimensional interlocked interfacial structure between HC membrane and PFSA-based CL as a novel strategy to tackle the interfacial issue. It is realized by forming nano-porous skins on the both side of HC membrane and successively fiiling the pores with PFSA ionomer with scalable wet coating methods. The interlocking interface tightly binds the HC membrane and CL owing to its highly-interlocked ball and socket joint structure. The interfacial adhesion is dramatically enhanced by 37-fold with the nano-fastener. The membrane electrode assembly (MEA) with the three-dimensional interlocking interface exhibits 17 times higher durability than that with flat interface, paving a way to realize highly robust and cost-effective HC membrane-based PEMFCs for automotive use.
External Reinforcement of Hydrocarbon Membrane By Combining Toughened Catalyst Layers and Interlocking Interfaces for High Mechanical Robustness of PEMFC
Authors: Yuk Seongmin , Lee Dong Hyun , Choi Sungyu , Doo Gisu , Kim Hee-Tak 
Published: February 2020

For decades, in polymer electrolyte membrane fuel cell (PEMFC) field, hydrocarbon (HC) membranes have been constantly studied to replace perfluorinated sulfonic acid membranes owing to their low cost and high fuel efficiency. However, adopting HC membranes to practical PEMFCs has been not successful due to their poor mechanical stability which causes a mechanical failure with generating pin-hole under repeated volume expansion/shrinkage during cell operation. Conventionally, the problem has been addressed by inserting a porous mechanical supporter in HC membrane which is denoted as ‘internal reinforcement’. However, the introduction of the inert support decreases proton conduction and increases membrane cost.
Here we present an external reinforcement of HC membrane as a new strategy to enhance mechanical durability of HC membrane. It features the incorporation of mechanically tough porous fibrous network into catalyst layers and the strong connection of HC membrane and the toughened catalyst layers with introducing an interlocking interface. The mechanically toughened catalyst layers and interfaces can effectively mitigate the volume change of HC membrane, lowing the membrane failure. Under an accelerated humidity cycling test, the externally reinforced HC membrane exhibits an enhanced durability compared to un-reinforced counterpart. Furthermore, contrary to the internal reinforcement, the external reinforcement strategy does not cause any loss of proton conductivity of HC membrane. Therefore, the external reinforcement coupled with toughed catalyst layers and interfaces can provide an effective way to enhance durability with preserving the proton conductivity of pristine HC membrane.
High-Performance Polymer Electrolyte Membrane Fuel Cells Based on Fe/N/C ORR Catalyst
Authors: Wang Yu-Cheng , Lai Yu-Jiao , Zhou Zhi-You , Sun Shi-Gang 
Published: February 2020

One of the barriers hindering the commercialization of polymer electrolyte membrane fuel cell (PEMFC) is the high cost, in large part due to the expensive Pt-based catalyst for both the cathodic oxygen reduction reaction (ORR) and anodic hydrogen oxidation. The ORR requires more Pt catalyst than anodic hydrogen oxidation because of the sluggish kinetics. Therefore, ternary Fe/N/C material, as a non-Pt catalyst for ORR, is being studied intensively as one of the most promising alternatives for expensive Pt-based catalysts. However, the catalytic activity of Fe/N/C materials is considerably inferior to that of Pt-based catalyst in acidic medium. What’s more, the stability of Fe/N/C is poor and the decay mechanism remains unclear.
Here, we found that iron salts can also greatly influence the ORR activity of Fe/N/C, and the use of Fe(SCN)3 instead of FeCl3 can nearly double the ORR activity. The improvement may be correlated with S doping and high surface area. The Pmax of PEMFC using this improved catalyst reached 0.94 and 1.03 Wcm-2 at 1 and 2 bar back-pressure, respectively. Moreover, we find that oxidized environment in PEMFC, mainly caused by oxygen, high voltage and hydrogen peroxide, can deteriorate Fe/N/C catalyst.

Figure 1
Preparation of Iridium-SnO2/VGCF Electrocatalysts for Water Electrolysis
Authors: Anai Hiroki , Matsuda Junko , Noda Zyiyun , Tachikawa Yuya , Hayashi Akari , Ito Kohei , Sasaki Kazunari 
Published: February 2020

Introduction
Hydrogen energy has been paid more attention since the commercialization of FCVs. In order to further distribute FCVs, efficient production of hydrogen fuel becomes important. Water electrolysis is one possible method to produce hydrogen without emitting any carbon dioxide. Moreover, water electrolysis is the best technology to successfully use excess renewable energy, which is often hard to use due to the strong energy fluctuation. With this method, renewable energy can be converted into hydrogen, which can be stored for a long time and used anytime in any places.
Among various water electrolysis systems, the system based the polymer electrolyte has many advantages. Easy and rapid starting/stopping of the system is possible. Also, there exist many similar points to the PEFC system, and the technologies developed for PEFC can be shared. On the other hand, anode catalysts must be newly developed for the electrolysis cell since the carbon support dispersing Pt nanoparticles in PEFC cannot be used under high potential like nearly 2.0 V. Therefore, in this study, novel iridium-based SnO2/VGCF electrocatalysts were developed. Since SnO2, mostly working as a support material for iridium-based catalysts, is highly durable even under such high potential, iridium-based SnO2/VGCF is most likely a good candidate for anode catalysts. Therefore, the aim of this study is development and electrochemical evaluation of iridium-based SnO2/VGCF electrocatalysts.
Experimental
Sn0.98Nb0.02O2/VGCF was synthesized through an ammonia co-precipitation method, using SnCl2・2H2O and NbCl5. Then, IrO2(Ir) nanoparticles were decorated on Sn0.98Nb0.02O2/VGCF via the method that the aqueous solution mixture containing Sn0.98Nb0.02O2/VGCF and H2IrCl6・nH2O was completely evaporated while stirring, followed by the heat treatment at 440 oC in air. Actual amounts of Sn0.98Nb0.02O2 and IrO2were determined based on weight loss by VGCF obtained from TG-DTA. Electrocatalysts were further analyzed by STEM and XPS
Results and discussion
The composition of IrO2/Sn0.98Nb0.02O2/VGCF was determined to be 23 wt.% of IrO2, 58 wt.% of Sn0.98Nb0.02O2, and 19 wt.% of VGCF. From STEM observation, IrO2 (or Ir) particles were successfully observed on the surface of SnO2. Furthermore, in order to clarify either IrO2 or Ir, Ir 4f binding energy was analyzed by XPS and is shown in Figs. 2 and 3. When the electrocatalyst was synthesized in air, iridium-based catalysts most likely exist as IrO2 according to the previous report[1] as seen in Fig. 2. On the other hand, when it was made under 5% H2-N2, the catalysts mostly stay as Ir metal particles as shown in Fig. 3. Electocatalytic activity on water electrolysis is further discussed with these newly prepared electrocatalysts.
References
[1] D.Xu, P.Diao, T.Jin, Q.Wu, X.Liu, X.Guo, H.Gong, F.Li, M.Xiang, Y.Ronghai, ASC Apple. Mater. Interfaces 7, 16746 (2015).

Figure 1
Modeling PGM-Free Active Site Structures: Activity and Durability
Authors: Holby Edward F. , Martinez Ulises , Chung Hoon T , Zelenay Piotr 
Published: February 2020

Two of the largest hurdles facing platinum group metal-free (PGM-free) oxygen reduction reaction (ORR) electrocatalysts for polymer electrolyte fuel cell (PEFC) cathodes are the need for improved activity and increased durability. Quantum chemical modeling (in particular, density functional theory, DFT, coupled with thermochemical models) can be utilized to better understand both activity and durability of these materials at the atomic scale. In this work, we apply quantum chemical modeling approaches to study the activity of N-coordinated Mn, Fe, Co, and Ni containing zig-zag edge sites. Both Metal-N4 as well as Metal2-N5edge structures are considered. Spontaneous *OH ligand modification in which the *OH intermediate is persistently bound to metal centers above a relatively low potential is found to be applicable to both structures but only for certain metal species. Experimentally determined trends in activity as a function of metal species fit well with theoretical predictions based on the spontaneous *OH ligand modification hypothesis. In addition, strain-modification of structures and resultant shifts in activity are explored. It is found that, due to anisotropic changes in binding energies with strain, this approach can lead to minor improvements of the computationally obtained ORR activity descriptor.
With regards to the durability hurdle of PGM-free electrocatalysts, a structurally sensitive and computationally accessible descriptor is explored. First-principles molecular dynamics derived knock-on displacement threshold energy may serve as a high-throughput, corrosion-mechanism-agnostic descriptor of active site structure durability that does take into account the kinetics of local bond breaking. Further comparisons between computational predictions and experimental findings are required to ascertain the applicability of this simplified durability descriptor for non-PGM active site structures. Current progress and future directions will be discussed.
(Invited) Core-Shell Nanosheet Catalysts: Enhanced Activity and Durability for Oxygen Reduction and Hydrogen Oxidation Reactions
Authors: Sugimoto Wataru , Takimoto Daisuke , Ohnishi Tomohiro , Nutariya Jeerapat , Shen Zhongrong , Ayato Yusuke , Mochizuki Dai , Boulineau Adrien , Demortiere Arnaud 
Published: February 2020

Development of Pt-based catalysts with higher activity and durability is essential for implementation of cost-competitive polymer electrolyte membrane fuel cells. Nanoparticle catalysts with core-shell, skeleton, or skin-type structures have shown to outperform Pt nanoparticles. However, complications arise when such catalysts are exposed to harsh operation conditions of the fuel cell where Pt and the alloying metal undergoes consecutive oxidation/reduction and dissolution, de-activating the catalyst. Compared to nanoparticles, extended surfaces (bulk electrodes and nanostructured thin films) are more stable, but suffers from low surface area.
In this study, we describe the concept of “nanosheet catalysts” with surface area, activity, and durability that are higher than conventional core-shell nanoparticles for the oxygen reduction reaction as well as the hydrogen oxidation of reformate fuel. Our approach utilizes metallic Ru nanosheets [1] with atomic-scale thickness prepared via thermal reduction of exfoliated RuO2nanosheets [2,3]. The metallic Ru nanosheet is used as a core for the synthesis of two-dimensional Ru-core@Pt-shell catalysts.
Sub to a few monolayer Pt shell was successively formed on metallic Ru nanosheets with monoatomic thickness via galvanic displacement reaction between Cu and Pt2+. The electrochemically active Pt surface area of Ru-core@Pt-shell nanosheets with 1.5-4.5 monolayer Pt-shell was 112-151 m2 (g-Pt)‒
1. This corresponds to Pt nanoparticles with 1-1.5 nm of diameter. A carbon supported core-shell nanosheet catalyst with a 3.5 monolayer Pt-shell (Ru@Pt-3.5ML(ns)/C) showed 4.5 times higher activity than the benchmark Pt/C catalyst for the oxygen reduction reaction with a slower degradation rate even at high potentials. For the anode reactions, Ru@Pt-1.5ML(ns)/C had 2 times higher hydrogen oxidation activity in pure H2 as well as 300 ppm CO containing H2, and better stability against potential cycling. The developed nanosheet catalysts should provide the high utilization of Pt towards catalytic reactions and concurrently the stability of extended surfaces, offering a practical solution to the trade-off issue.
This work was supported in part by the “Polymer Electrolyte Fuel Cell Program” from the New Energy and Industrial Technology Development Organization (NEDO), Japan.
[1] K. Fukuda and K. Kumagai, e-Journal Surf. Sci. Nanotechnol., 12, 97 (2014).
[2] W. Sugimoto, H. Iwata, Y. Yasunaga, Y. Murakami and Y. Takasu, Angew. Chem. Int. Ed., 42, 4092 (2003).
[3] K. Fukuda, H. Kato, J. Sato, W. Sugimoto and Y. Takasu, J. Solid State Chem., 182, 2997 (2009).

Figure 1
High-Temperature Synthesized PGM-Free Oxygen Reduction Reaction Catalyst
Authors: Chung Hoon T , Cullen David A. , Sneed Brian , Lin Ling , Yin Xi , Martinez Ulises , Purdy Geraldine M , More Karren L. , Zelenay Piotr 
Published: February 2020

Platinum group metal-free (PGM-free) oxygen reduction reaction (ORR) electrocatalysts have demonstrated substantial improvements in electrochemical cell and fuel cell performance in the last decade. However, the durability of these catalysts is still insufficient for the implementation of these catalysts in polymer electrolyte fuel cells (PEFCs), particularly in automotive power systems. Recently, carbon oxidation has been reported as a main cause for the destruction of ORR active sites in heat-treated metal-nitrogen-carbon (M-N-C) PGM-free catalysts (1). This result suggests that in order to improve their durability, M-N-C catalysts should be synthesized at as high a temperature as possible to maximize the graphitic content thereby making the catalyst more oxidation resistant. An optimum heat-treatment temperature for the best ORR activity of M-N-C catalysts depends on many factors, including the synthesis approach, type of precursors used, and the precursor ratio. One more factor to account for, based on the reasoning above, is the need to maximize the heat-treatment temperature without sacrificing catalyst activity.
In this work we have found that for the high-temperature synthesis of active M-N-C catalysts, the most important factors are the selection of the nitrogen precursor, adjustment of the precursor ratio, and the choice of the synthesis route. Without fine-tuning of the synthesis conditions, the ORR activity of the PGM-free catalysts usually decreases when heat-treated above 900° C. By selecting an appropriate synthesis route and catalyst precursors we have been able to perform synthesis at 1100° C and obtain catalysts that show high RDE activity (E½
of 0.81 V vs. RHE, Figure 1). In this presentation, we will summarize the electrochemical and fuel cell performance of these catalysts, with particular emphasis on their durability.

Acknowledgement

Financial support of this research by DOE-EERE through Fuel Cell Technologies Office is gratefully acknowledged. Microscopy research was supported through a user project at ORNL’s Center for Nanophase Materials Sciences, which is an Office of Science User Facility.

Reference

Choi Chang Hyuck, Claudio Baldizzone, Jan-Philipp Grote, Anna K. Schuppert, Frédéric Jaouen, and Karl J. J. Mayrhofer, Stability of Fe-N-C Catalysts in Acidic Medium Studied by Operando Spectroscopy. Angew. Chem. Int. Ed.
54, 1 (2015).

Figure 1