bluuebunny/crossref_metadata_2025_split huggingface dataset:
Anion Exchange Membrane Electrolyzers Showing 1 A/cm2 at Less Than 2 V
Authors: Masel Richard I , Liu Zengcai , Sajjad Syed 
Published: February 2020

This paper will describe the performance of alkaline water electrolyzers using newly developed Sustainion™-X5 membranes.
Sustainion™ membranes have a styrene base, and mixtures of other components to produce a high conductivity in alkaline systems. The membranes are stable when soaked in 1 M KOH at room temperature for months. A CO2electrolyzer has run for over 4000 hours with no loss in performance. Initial tests also show stability in 1 M KOH at 60°C, See Figure 1, although no long term tests have yet been completed.
The work here considers the performance of the membranes in model alkaline membrane electrolyzers. We manufactured a small MEA using platinum coated carbon paper as a cathode and a IrO2 coated carbon paper as an anode and a Sustainion™-X5 membrane. The MEA was mounted into Fuel Cell Technologies 5 cm² cell hardware with carbon flowfields. The cell was heated to 60 °C and 1 M KOH was fed into the anode and cathode.
Figure 2 shows how the cell voltage varied with time at a fixed current of 0.8 A/cm² and 1 A/cm². The data were taken on a single cell, at a fixed current of 1 A/cm² during the day and 0.8 A/cm² at night. Initially the cell produced 0.8 A/cm² at 1.74 V and 1 A/cm² at 1.81 V, but the voltage rose to nearly 2V after 150 hours of operation. Disassembly of the cell showed that the carbon paper on the anode was corroding leading to a loss of anode catalyst.
We have also started work on nickel catalysts. The initial results were modest, but additional results will be presented at the meeting.

Acknowledgement

Parts of this work were supported by ARPA-E under contract DE-AR0000684 and by 3M. The opinions here are those of the authors and may not reflect the opinions of ARPA-E or 3M.

Figure 1
Manganese Oxide/Poly(3,4-ethylenedioxythiophene) Hybrid Electrocatalysts for the Oxygen Reduction Reaction in Alkaline Fuel Cells
Authors: Lambert Timothy N. , Vigil Julian A. 
Published: February 2020

Manganese oxide/poly(3,4-ethylenedioxythiophene) (MnOx/PEDOT) nanostructured hybrid thin films are readily prepared using a simple anodic electrodeposition process from aqueous solution. Using this approach, MnOx/PEDOT films with thicknesses and mass loadings up to 100 nm and 40 μg cm-2 were prepared, then tested for oxygen reduction reaction (ORR) activity in alkaline electrolyte using rotating disk electrode and rotating ring disk electrode methods. MnOx/PEDOT provided improvements over MnOx-only and PEDOT-only control films, with > 0.2 V decrease in onset and half-wave overpotentials and > 1.5 times increase in current density. The MnOx/PEDOT film exhibited only a slightly lower reaction order (n = 3.86-3.92) than the 20% Pt/C benchmark electrocatalyst (n = 3.98) across all potentials. MnOx/PEDOT also displayed a more positive half-wave potential and superior electrocatalytic selectivity for the ORR upon methanol exposure than 20% Pt/C. The high activity and synergism of MnOx/PEDOT towards the ORR is attributed to effective intermixing/dispersion of the two materials, intimate substrate contact and the improved charge transfer processes attained by co-electrodepositing MnOx with PEDOT. PEDOT has previously been demonstrated in fuel cells to limit methanol crossover. PEDOT has also been used as a catalyst support in fuel cells. These facts, combined with the substantially lower cost of Mn versus Pt (Mn is ~ 17,000 times cheaper), augurs for further development and testing of MnOx/PEDOT hybrid materials as ORR electrocatalysts with application in alkaline fuel cells.
This work was supported by the Laboratory Directed Research and Development program at Sandia National Laboratories, a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.
Iridium-Platinum Core-Shell Nanoparticles As Catalysts for the Oxygen Reduction Reaction
Authors: Strickler Alaina Leigh , Jackson Ariel , Jaramillo Thomas F 
Published: February 2020

Fuel cells are a promising source of renewable, clean energy. Widespread commercialization of fuel cell technology, however, has been hampered by technological and economic hurdles due to inadequate device efficiencies and expensive Pt electrocatalysts. To address these challenges, considerable research has focused on enhancing the kinetics of the oxygen reduction reaction (ORR) at the cathode which is the dominant source of voltage loss in state-of-the-art fuel cells.1 Recent work has sought to increase intrinsic catalyst activity and reduce Pt loading via core-shell nanoparticles where a Pt shell surrounds the core of a different metal or alloy. These nanostructures provide the ability to increase Pt mass activity through a larger Pt surface area to volume ratio as well as enhance the Pt intrinsic activity by altering its electronic structure though stain and ligand effects. These electronic changes dictate the binding energies of reaction intermediates to the catalyst surface and thus reactivity for the ORR. To identify a core material capable of improving ORR activity, we utilized a systematic approach for catalyst design developed in a previous study. This study found that activity can be improved by selecting a core material that is theoretically predicted to over-weaken the oxygen binding energy when covered with a Pt monolayer.2 The oxygen binding energy can then be strengthened towards its optimum by increasing the Pt shell thickness and through nanoscale effects where undercoordinated sites demonstrate stronger binding to adsorbates. Through this method, iridium was identified as a promising core material. Therefore, this work focuses on the synthesis, characterization, activity, and stability of Ir-Pt core-shell nanoparticles. Ir-Pt nanoparticles with three different compositions were synthesized using a highly scalable, inexpensive polyol method. TEM, STEM-EDS, and XPS were used to characterize particle size and composition. ORR activities of the Ir-Pt catalysts were compared to synthesized Ir-only and Pt-only nanoparticles as well as to the state-of-the-art commercial standard Pt catalyst, TKK. Electrochemical analysis demonstrates the high activity of the Ir-Pt catalyst with a specific activity of approximately 2 times that of TKK. This catalyst also demonstrates high stability after 10,000 stability cycles showing improvements in both mass and specific activity upon cycling with the latter increasing to 2.6 times that of TKK.
1. Stephens, I.E.L., et al., Energy & Environ. Sci.
5
, 6744-6762, (2012).
2. A. Jackson et al., ChemElectroChem 1, 67-71 (2014).
Engineered Carbon Supports for Low Precious-Metal-Content Catalysts
Authors: Stephenson Thomas , Lubers Alia , McCool Geoff , Romero Henry , McKinney Samuel , Halevi Barr 
Published: February 2020

In the development of PEMFC fuel cells much attention and development is devoted to the "active" portion of the catalysts system, the precious metal nano-particles. While this approach has led to great improvement in specific activity, existing catalysts are still not meeting the combination of performance and cost necessary for the commercialization of PEMFC.
A key limitation to catalysts today arises from reliance on carbon black(CB) supports that serve to disperse and stabilize the precious metal catalyst nanoparticles, but which corrode under certain operating conditions. Carbon support modifications that rely on "top-down" graphitization of CB's have so far improved resistance to carbon corrosion, but at the cost of reduced stabilization of precious metal dissolution.
Pajarito Powder developed a "bottom-up" approach where Engineered Carbon Support are made from organic precursors that yield a highly tailorable carbon support with great corrosion resistance. This method which is based on technologies licensed from the University of New Mexico, Northeastern University, and Los Alamos National Laboratory allows manufacture of highly graphic carbonaceous powders with excellent control of pore sizes and particle roughness.
Pt/C catalysts made using these Engineered Carbon Supports maintain performance under carbon corrosion test protocols and thus demonstrate their utility in achieving the performance/price balance needed for commercializing PEMFCs. The catalyst characteristics and performance, as well as economics of this approach will be presented and discussed.

Figure 1
Numerical Simulation of PEFC Stack System for Design of Configuration and Control of Anode Systems
Authors: Takayama Tsutomu , Yoshimura Hideto , Motegi Haruki , Tsukamoto Takayuki , Takayama Ryo , Yoneda Masakazu 
Published: February 2020

Overview
Performances of cell stacks are simulated, focusing on driving state of anode system. This simulation technique takes overall transport phenomena in PEFC fuel cell systems, such as transport of gas species and liquid water in both anode and cathode channels and across MEA, thermal balance, electrochemical reactions and current distributions. Injector and exhaust systems are modeled by boundary conditions, mimicking actual driving conditions. Relation between cell performances and driving state of anode system, for example, consumption of hydrogen, build-up of liquid water and cross-over nitrogen and purging by control of injector and/or ejector can be discussed based on simulated results. Over-all performance of anode system is one of crucial issue for durability and cost-reduction of fuel cell systems. These results show good applicability of this kind of simulations on design of PEFC stack system.
Numerical Modeling and Results
Simulation is performed by our own simulation software for PEFCs, which is capable of simulating full-stack fuel cell system for fuel cell vehicles (up to 400 cells) under transient operating conditions. An important feature of this software is that macroscopic models are applied for microscopic phenomena in the MEA such as electrochemical reactions and proton/water transport. Heat transfer and fluid of liquid-gas two phase fluid with phase changing are also taken into account. These models are coupled with multi-dimensional heat and mass transport equations, including effective parameters for gas diffusivity and permeability in the GDL and equivalent hydraulic diameter in the flow channel. This software can also simulate cathodic degradation by carbon corrosion reactions.
Performances of up to 400 cells stacks are simulated. A numerical model of anode system is constructed by adding transient boundary conditions for an injector and an exhaust system with an ejector. These transient boundary conditions represent open / close timings of injector and ejector under actual driving conditions. Distributions and consumptions of hydrogen, build-up of cross-leak nitrogen and condensate liquid water can be shown under constant (up to 30A) loading.
Simulated results show difference of cell potential between of stacked cells, and relation between performance distributions and balances of transport phenomena in stack systems. Effects of configuration of stack systems are also shown. Based on these results, design of stack systems and control schemes of anode system can be discussed. Those discussion can provide useful information for improving durability of stacked cells by avoiding depletion of hydrogen, and / or examination of control schemes which can efficiently utilize hydrogen fuel.
(Invited) Fuel Cell Stack Technology of Toyota
Authors: Suzuki Toshiyuki 
Published: February 2020

Toyota Motor Corporation launched the Prius, the world’s first mass-production hybrid vehicle (HV), in 1997. The global popularization of the Prius and other HVs has helped to counteract the negative effects of vehicles on the environment. As emerging markets continue to develop economically and the world’s population grows, vehicles are likely to have an even greater impact on the environment. Therefore, if vehicles are to remain of benefit and interest to society in the next one-hundred years, it will be even more important to find answers to issues related to energy and the ideal form of mobility in the future. Through the development of hybrid, plug-in hybrid, and battery electric vehicles, Toyota is already acting proactively to encourage the use of electricity. In addition, Toyota has also taken the step of developing fuel cell vehicles (FCVs) to help promote the use of hydrogen for contribution to environment.
A fuel cell (FC) generates power by electrochemical reactions through an electrocatalyst using hydrogen and oxygen in the air. Since these reactions generate only water as a by-product, FCs are regarded as an extremely clean and efficient means of generating power, with the potential to help resolve energy and environmental issues in the future. Greatly enhancing the performance and reducing the size and cost of the FC stack is an important part of measures aimed to facilitate the widespread adoption of FCVs.
A FC stack consists of a wide range of materials, including various types of mechanical elements and electronic parts. In particular, cells inside the FC use many materials that are not found in conventional vehicle parts. In contrast to the research phase, which prioritized efforts to enhance the functional performance of the FC stack, the new mass-production MIRAI FCV was developed as a normal industrial product with an emphasis on both performance and the applicability of manufacturing methods. This article describes several examples of manufacturing methods adopted to ensure high quality and productivity while reducing cost.
Differential Electrochemical Mass Spectroscopy Study of CO2 Concerned Anode Reaction in Polymer Electrolyte Fuel Cell
Authors: Tamura Shigehisa , Jia Siyuan , Sato Kazutaka , Shironita Sayoko , Umeda Minoru 
Published: February 2020

For a power generation of a polymer electrolyte fuel cell (PEFC), reformed hydrogen gas is fueled to the anode. The reformed hydrogen gas contains a small amount of carbon monoxide and 10-30% carbon dioxide [1]. The carbon dioxide is reported to be reduced at Pt electrode [2, 3]. In this study, CO2 reduction is performed at various potential of Pt/C-based membrane electrode assembly(MEA). The product of CO2reduction was analyzed by a mass spectrometer.
Electrocatalyst of Pt/C (Pt: 45.7 wt%) was sprayed on a gas diffusion layer. The electrolyte membrane was sandwiched by two pieces of the gas diffusion layers which were coated electrocatalyst layers (metal amount: 1.0 mg cm-2), and then, it was hot-pressed to obtain on MEA. Geometric electrode area of the MEA was 3×3 cm2. The prepared MEA was installed in a single cell having a dynamic hydrogen electrode (DHE) as a reference electrode. The temperature of the single cell was controlled at 80°C. Humidified carbon dioxide gas (purity: 99.995%) and humidified hydrogen gas (purity: 99.999%) were supplied to the working electrode and counter electrode, respectively, at a flow rate of 50 cm3 min-1. Cyclic voltammograms were measured at a potential scan rate of 10 mV s-1and the potential scan range was between 0.00-1.38 V vs. DHE. The exhaust gas was introduced directly into the mass spectrometer (JEOL, JMS-Q1050GC Ultra Quad GC/MS ).
Figure 1 shows a result of differential electrochemical mass spectroscopy measured at 0-1.38 V vs. DHE. In Fig. 1 (a), cyclic voltammograms at the Pt/C-based MEA were obtained under CO2 and Ar atmospheres. Under the CO2 atmosphere, a typical anodic current at around 0.5 V vs. DHE is observed. This is due to the re-oxidation of the CO2 reductant which was generated at < 0.1 V vs. DHE by the CO2 reduction. Mass spectra of m/z = 2, 16, 45 versus electrode potential under CO2 atmosphere shown in bottom of Figure 1 (b)-(d). The m/z = 2, 16, 45 were originaled from hydrogen, methane and formic acid. Generation of m/z = 16 is seen at < 0.2 V vs. DHE, and m/z = 2, m/z = 45 are seen at < 0.1 V vs. DHE. It was found that there is a potential dependency for CO2reduction at Pt/C-based MEA. Consequently, adsorbed CO2reductant on the Pt remains in the potential range of 0-1.38 V vs. DHE which influences the hydrogen oxidation reaction.
[1] K. Kortsdottir, C. D. Fernandez, R. W. Lindstrom, ECS Electrochem. Lett.,
2, F41-F43 (2013).
[2] N. Hoshi, S Kawatani, M. Kudo, Y. Hori, J. Electroanal. Chem., 467, 67–73 (1999).
[3] S. Shironita, K. Karasuda, K. Sato, M. Umeda, J. Power
Sources, 240, 404-410 (2013).

Figure 1
Synthesis and Properties of Partially Fluorinated Anion Exchange Membranes Containing Ammonium-Functionalized Fluorenyl Groups
Authors: Ozawa Mizuki , Miyake Junpei , Miyatake Kenji 
Published: February 2020

Anion exchange membrane fuel cells (AEMFCs) are one of the promising energy conversion devices because of their high efficiency and possible use of non-precious metal catalysts. However, the existing anion exchange membranes, main component of AEMFCs, do not show sufficient ion conductivity and stability. In this study, we report a novel series of AEMs composed of perfluoroalyl chains and ammonium-functionalized fluorenyl groups (Fig. 1). The perfluoroalkyl groups are expected to provide chemical stability as well as flexible membrane forming capability, while the ammonium-functionalized fluorenyl groups contain high ionic density for high ion conductivity. We have investigated in details synthetic procedure, structure, and properties of the title AEMs.
The hydrophobic monomer containing perfluroaklyl groups was synthesized by Cu-catalyzed Ullmann coupling reaction, and fluorenyl-containing monomers were synthesized by Sandmeyer reaction. Precursor polymers were synthesized by Ni-mediated Ullman coupling reaction. Then, chloromethyl groups were introduced onto the precursor polymers by Friedel-Crafts reaction. The chloromethyl groups were quarternized with trimethyl amine by Menshutkin reaction.
It is known that the chloromethylation reaction often accompanies with unfavorable side reactions such as cross-linking. By carefully optimizing the Friedel-Crafts reaction conditions, we have successfully controlled the degree of chloromethylation. In fact, the number and the position of chloromethyl groups substituted on fluorenyl groups were controllable.
The chloromethylated precursors were soluble in organic solvent and the solutions were cast to thin films. The ion exchange capacities obtained by titration were lower than calculate from DC. The difference of IEC value was increased with increase of DC. It is suggest that when ionic group density becomes higher, there is an ammonium group which is not functioning as ionic groups by their steric hindrance. The quaternized polymer membranes exhibited high hydroxide ion conductivity and the maximum conductivity was 29 mS/cm in water at 80 °C for the membrane with IEC = 1.6 meq/g. It was found that meta-linked polymers in the hydrophilic component showed slightly higher ion conductivity than that of para-linked polymers. Other properties such as morphologies and stabilities will also be reported.
Acknowledgement
This work was partly supported by Japanese Science and Technology Agency (JST), CREST.

References
1) Manai Shimada, Shigefumi Shimada, Junpei Miyake, Makoto Uchida, Kenji Miyatake, J. Polym. Sci., A: Polym. Chem.,
2015, 7,935-944.
2) Hideaki Ono, Junpei Miyake, Shigehumi Shimada, Makoto Uchida and Kenji Miyatake, J. Mater. Chem. A, 2015, 3, 21779–21788.

Figure 1
Thermal Behaviour of Nafion Thin Films
Authors: Zhang Chi , Ozhukil Kollath Vinayraj , Karan Kunal 
Published: February 2020

Sub-micron Nafion films are relevant to several electrochemical devices including polymer electrolyte fuel cells, sensors and actuators. Such thin films are invariably fabricated from dispersion of the ionomer in suitable solvent, e.g. by drop-casting, spin-coating or self-assembly. Often a thermal treatment or annealing step is applied to improve the mechanical properties of the film and relax the polymers. Thus, understanding the response of the ionomer thin film subjected to thermal changes is important. Furthermore, thermal characteristics of the ionomer such as glass transition temperature and thermal expansion coefficient can provide fundamental insight into structure and the nature of the interaction with the substrate.
We have initiated an in-situ thermal ellipsometry and thermal FTIR study to probe the response of 20-650 nm thick Nafion thin films supported on SiO2 substrate. Ellipsometry experiments yield the thickness change as a function of temperature. This set of data yields thermal expansion coefficient of the Nafion films. The change in slope of the thickness change with temperature provides information on the nature of phase transition – glassy to rubbery or disorder-to-order. The thermal FTIR is being used as a complimentary technique to probe whether the phase change phenomenon manifests as a dramatic change in response in one of the characteristic peaks.
The results obtained so far indicate that the thermal expansion coefficient of Nafion films 60 nm and lower thickness is changes with thickness but those of the films above 60 nm thickness converges to that of the bulk material. No distinct transition in slope of thickness change is observed. That is, no glass transition like behavior is observed. No thickness-dependent response in FTIR peak is observed. A sharp change in the 638-626 cm-1 doublet region is observed at temperature corresponding to the so-called a transition for Nafion.
To the best of our knowledge, there have been no prior studies on in-situ thermal ellipsometry or in-situ thermal FTIR of Nafion thin films.