bluuebunny/crossref_metadata_2025_split huggingface dataset:
Development of Free-Metal Electrocatalyst from Inexpensive Sources of Carbon: A Novel Electrode Material for Cathode Reaction in PEM Fuel Cells
Authors: Alonso-Lemus Ivonne Liliana , Lardizabal Daniel , de la Torre Saenz Luis , Sanchez-Castro Maria Esther , Rodríguez-Varela F.J. 
Published: February 2020

The development of alternative energy sources is of great interest in the scientific community in last decades. Fuel cells are a clean and sustainable alternative for power generation. However, the development of the polymer exchange membrane fuel cells (PEMFC) has been limited due that this systems use platinum as catalyst. Platinum is expensive and scarce, which limited the production of the PEMFC at industrial scale. Moreover, oxygen reduction reaction (ORR) is the reaction in the cathode of the PEMFC. This reaction has the slower kinetic, so limiting the kinetics of the entire cell.
Recently, free noble metal electrocatalysts have been obtained, which are capable of carrying out the ORR with comparable performance to Pt. These novel electrocatalysts are doped nanostructured carbon (ej. nitrogen doped carbon nanotubes N-NTC and nitrogen doped reduced graphene, N-rG). Nowadays, the synthesis of these nanostructured materials has several technological challenges, because it production is still expensive and has a significant environmental impact. In this work, we have obtained novel metal-free electrocatalysts from two different inexpensive carbon source: i) an organic waste and ii) mineral coal from Sabinas region in Coahuila Mexico. These electrocatalysts have a significantly lower cost than conventional platinum based electrocatalysts and the recently synthetized nanostructure free-metal catalyst.
The organic waste were pyrolyzed in a nitrogen atmosphere, and then an activation process with chemical agents was carried out. Moreover, in order to increase their surface area and modify the C-N chemical bond, a thermochemical process was carried out for mineral coal.
The features and electrochemical performance of both electrocatalyst were compared. The electrocatalysts obtained have surface areas until of 2000 m2/g. The morphology and structural features were observed by Scanning Electron Microscopy (SEM), X-ray diffraction (XRD) and Raman Spectroscopy. The electrocatalytic activity for these novel electrocatalysts was evaluated for the oxygen reduction reaction (ORR) by rotary disk electrode technique. The results show that these electrocatalysts are an inexpensive and promising alternative for use as cathodes in PEMFC.
Application of Modified-ACLS Electrodes on Low-platinum PEFCs
Authors: Mei Wu , Fukazawa Taishi , Yang Tianyi , Yoshinaga Norihiro , Kanai Yuta 
Published: February 2020

The commercialization of PEFCs is necessary for enabling a sustainable hydrogen-based economy. To reduce platinum (Pt) loading in PEFCs, we have proposed a novel catalyst structure, Alternating Catalyst Layer Structure (ACLS), via depositing different materials alternately on conventional substrate such as carbon papers [1, 2]. The ACLS can be characterized as a unique cabbage-like structure, where Pt “leaves” are partly separated by pore layers (gap layers). Its other features are: support-free and ionomer-free structure, high porosity and continuous Pt surfaces mainly consisting of contracted (111) crystalline planes. In this report, modification of the ACLS in these years and its potential as a powerful candidate for PEFC electrodes will be presented, including the enhancement of ORR activity and load cycle durability. The single cell performance of modified-ACLS electrodes (M electrodes) and its application on PEFC anode will be also introduced.
1) W. Mei, J. Tamura, M. Yamazaki, T. Nakano, Japan Patent P4861445, US Patent 8128986
2) W. Mei, T. Fukazawa, Y. Nakano, Y. Akasaka, K. Naito,ECS Trans. 50(2) (2013) 1377

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Pt "Monolayer" Electrocatalysts Revisited: Structure, Lattice Geometry Effects, and Ethanol Oxidation Activity of Pt on Au
Authors: Loukrakpam Rameshwori , Brankovic Stanko R , Strasser Peter 
Published: February 2020

Effective utilization of the high energy density of ethanol as a fuel for polymer electrolyte fuel cells is contingent upon complete oxidation of ethanol to carbon dioxide. Major problems associated with the development of electrocatalysts for ethanol oxidation are the high content of Pt and partial oxidation of ethanol to acetaldehyde and acetic acid instead of complete oxidation to carbon dioxide via the 12 electron process. Monolayers of Pt on Au have been proposed and reported1 to be beneficial for EtOH oxidation and possibly for C-C bond splitting. We address this issue with atomic scale microscopy and spectroscopy.
In this report, Pt atomic layers supported on both well-defined, extended Au(111) and Au NPs were studied as electrocatalysts for ethanol oxidation reaction (EOR)2. The catalyst were prepared using galvanic displacement methods using Pt(II) and Pt(IV) precursors. Electrochemical testing of these electrocatalysts showed that Au@Pt(II) had substantially higher activity towards EOR than Au@Pt(IV). The atomic scale structure of the resulting Pt layers on Au will be studied using HAADF-STEM-EDX elemental mapping as well as depth resolved XPS. Evidence is provided that the so-called Pt “monolayer” catalysts actually consist of 2-4 atom layers of Pt, often aggregated in small clusters. The effect of Pt cluster sizes on the Au surface and the tensile strain on Pt due to the underlying Au and their effect on EOR will be discussed. Using in-situ FTIR we also studied the catalytic EtOH activity of the catalysts and their ability to perform C-C bond splitting.
1. Li, M.; Liu, P.; Adzic, R. R., Platinum Monolayer Electrocatalysts for Anodic Oxidation of Alcohols. J. Phys. Chem. Lett. 2012, 3, 3480-3485.
2. Loukrakpam, R.; Yuan, Q. Y.; Petkov, V.; Gan, L.; Rudi, S.; Yang, R. Z.; Huang, Y. H.; Brankovic, S. R.; Strasser, P., Efficient C-C bond splitting on Pt monolayer and sub-monolayer catalysts during ethanol electro-oxidation: Pt layer strain and morphology effects. Phys. Chem. Chem. Phys. 2014, 16, 18866-18876.
Microgravity Effect on Ammonia Oxidation at Platinum Nanoparticles Modified Mesoporous Carbon Supports
Authors: Poventud Carlos , Acevedo Raul , Morales Camila , Betancourt Luis E , Diaz-Cartagena Diana C , Rodriguez Manuel A , Larios Eduardo , Jose-Yacaman Miguel , Nicolau Eduardo , Flynn Michael , Cabrera Carlos R 
Published: February 2020

Microgravity effect on the electrochemical oxidation of ammonia at platinum nanoparticles modified mesoporous carbon (MPC) substrates, with three different pore diameters, e.g. 64, 100, and 137 Å, have been studied in a parabolic flight between 24,000 and 32,000 ft. Microgravity effects on the chronoamperometric ammonia oxidation current density was a function of the mesoporous carbon support used. This support may be described as graphitic multilayer hollow globules, even though the carbon globules do not present a specific shape as seen in the HRTEM images. Platinum nanoparticles were successfully chemically deposited, with a high dispersion, throughout the support’s topography. An onboard accelerometer was the trigger in order to start each chronoamperomtric ammonia oxidation experiments when the microgravity condition of less than 0.02g (i.e. gravitational force) was achieved. Pt/MPC64 sustained the current density between terrestrial and microgravity conditions by a slight margin over Pt/MPC100. However, Pt/MPC137 resulted with the smallest current density decrease under microgravity conditions versus ground based experiments. Pt/MPC137 has the largest pore diameter and shows a better capacity to sustain the oxidation current, which involves N2 formation. This effect can be ascribed to an easier diffusional process obtained by the larger pore diameter, which improves the access for the mobility of the ammonia molecules towards the electroactive sites and the corresponding detachment of the gaseous N2molecules (bubbles) from the MPC cavities. Pt/MPC137 catalyst resulted with the smallest current density decrease under microgravity conditions versus ground based experiments. This MPC support has the largest average pore diameter (137 Å) and shows a better capacity to sustain the oxidation current. This effect can be ascribed to an easier diffusional process facilitated by the larger pore diameter, which improves the access for the mobility of the ammonia molecules towards the electroactive sites and the corresponding detachment of the gaseous N2 molecules (bubbles) away from them. In conclusion, it was demonstrated that under microgravity environment a porous infrastructure for a catalyst support has an impact on the mass transfer process of electroactive species, and a current density decreasing factor of ca. 50 - 67% must be taken into account. The lowest being the MCP average pore diameter 137 Å. In order to improve the current densities for ammonia oxidation, (100) faceted Pt nanoparticles need to be achieved.
Study of Polyphenylene Oxide Membranes Containing Long and Short Alkyl Side Chains
Authors: Amel Alina , Ein Eli Yair 
Published: February 2020

Investigation on the subject of structure and chemical stability was carried out on two anion exchange membranes that have a great potential for being candidates in alkaline fuel cells. Both of the membranes contain poly(2,6-dimethylphenylene oxide) (PPO) backbone, one has benzyltrimethyl ammonium cation (BTMA) while the other has long (10 carbons) alkyl side chain pendant to the nitrogen-centered cation (C10) as can be seen in Scheme. Membrane with the long alkyl side chain contributes to better hydrophilic–hydrophobic separation which significantly influence on the ionic channels of the membranes.Membrane morphology and in particular hydrophilic-hydrophobic separation was investigated using tapping-mode AFM. Both of the membranes exhibit phase-separated morphology and connectivity among the hydrophilic domains. AFM measurements show that long alkyl side chain contributed to better phase separation in the C10 membrane, where the hydrophilic domain size was ∼8 nm compared to ∼5 nm in BTMA. In addition, chemical stabilities of the membranes were evaluated under accelerated-aging conditions. Degradation process was determined by measuring FTIR, Elemental analysis and EDS during the aging. It was found that long side chain contributes to its chemical stability under basic and high temperature conditions.

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Resistance Measurements for Multilayer Supported Membranes
Authors: Peppin Daniel M. , Yandrasits Mike , Fochs Austin S 
Published: February 2020

In cell, through plane resistance is an important quantity for proper characterization of multilayer supported composite membranes. Through plane resistance of a supported composite membrane is impacted by the addition of a non-conductive supporting material, effectively decreasing the density of acid sites in the composite layer. Additionally, there could be other impacts on through plane resistance due to phenomena such as changes in water transport resulting in localized lambda variation as well as possible tortuosity effects due to the support.
It is possible to characterize, separately, the through plane resistance of the neat ionomer skin layers as well as the ionomer filled support composite layer by measuring the through plane resistance for a series of supported membranes varying only in ionomer skin thickness. The conductivity of the composite layer can then be compared to the conductivity of the neat ionomer, allowing for the determination of a "conductivity restriction" factor. This conductivity restriction factor can then be compared to the volume fraction of nonconductive support material in the composite layer to determine whether the impact on conductivity is due solely to acid site dilution or if there are additional losses. This analysis can be used to compare various support materials for their impact on through plane resistance. The results of this work will help guide the choice of support materials to optimize mechanical properties while minimizing the impact on through plane resistance.
Current Density Distribution in the Lateral Direction of Conventional and Interdigitated Flow Field
Authors: Shrivastava Udit N , Tajiri Kazuya 
Published: February 2020

In proton exchange membrane fuel cells, diffusion is a primary mechanism to transport gaseous species (oxygen and water vapor) between the flow channel and the catalyst layer in conventional flow field, whereas in an interdigitated flow field convection and diffusion both play vital role. Similarly, in a conventional flow field capillary effect is dominant in removal of liquid water, while in an interdigitated flow field both capillarity and the pressure difference between inlet and outlet channels contribute to the liquid water removal. Many computational studies available in literature have proven that this fundamental difference in transport mechanisms results in the differences in the overall cell performance and in the current density distribution in the land-channel direction between PEMFCs with interdigitated flow field and conventional flow field such as [1-2]. However, to best of our knowledge there is no study present in literature to experimentally show the current distribution in land-channel direction.
Our objective is to measure current density distribution in the land-channel direction and compare current density distribution profile for interdigitated and conventional flow field. A segmented cell is developed to measure current density distribution in the land-channel direction at sub-millimeter resolution of 350 μm. This technique is then applied to study current density distribution in land-channel direction of PEM fuel cell with interdigitated flow field and conventional flow field (see Figure 1a and b).
Figure 1. Current density distribution in the land-channel direction at 0.2 V, 60 oC and 90% RH a) conventional b) interdigitated flow field

A. Kazim, H.T. Liu, P. Forges. Journal of Applied Electrochemistry, 29, 1409 (1999).

L. Chen, H. B. Luan, Y.L. He, W. Q. Tao. International Journal of Thermal Sciences, 51 132 (2012).

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Studies of MEA Durability in Proton Exchange Membrane Water Electrolysis
Authors: Xu Hui , Rasimick Brian , More Karren L. , Alia Shaun M , Pivovar Bryan S 
Published: February 2020

Hydrogen production from proton exchange membrane (PEM) water electrolysis is attractive due to its simple and clean nature. Membrane and electrode assemblies (MEAs) of PEM electrolyzers typically use iridium (Ir) as an anode catalyst and Pt as a cathode catalyst. The durability of MEAs plays an essential role for the electrolyzers’ lifetime and cost. However, unlike the well-established MEA durability protocols of PEM fuel cells, there have been a lack of effective procedures for PEM electrolyzer MEA durability evaluation.
The objective of this work is to establish a series of test protocols that can help to rapidly evaluate PEM electrolyzer MEA durability. Three testing approaches have been used in this work, which include high-voltage hold (>1.8 V), voltage cycling (1.4 to 1.8 V or 2.0 V), and constant low-current operations. The electrochemical surface area (ECSA) and polarization curves of the MEAs will be obtained after each test.
Two categories of anode catalysts have been evaluated using the above durability test protocols: one is the commercial Ir black and the other is Ir supported on tungsten-doped titanium oxide (Ir/WxTi1-xO2) developed at Giner. The supported Ir/WxTi1-xO2 catalyst proves to possess 8-10 x higher mass activity than the Ir black. The MEAs made of these two anode catalysts have been evaluated at a variety of loading, low (0.1 mg/cm2), medium (0.4 mg/cm2) and high (1.0 mg/cm2). Figure 1 shows the durability of these two catalysts after voltage cycling from 1.4 V to 1.8 V: (a) 2 mg/cm2 Ir from Ir black; (b) 0.4 mg/cm2 Ir from Ir/WxTi1-xO2. It can be seen that at medium to high Ir loadings, these two catalysts demonstrates minimal performance decay after voltage cycling.
The morphology and structure of MEAs after durability tests will be characterized to correlate to their performance and to elucidate their degradation mechanisms.

Acknowledgement: The financial support is from the Department of Energy under the Contract Grant DE-SC0007471.

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In-Situ Analysis of Gas Crossover in PEM Water Electrolysis - the Effect of Membrane Variation
Authors: Lüke Wiebke , Carmo Marcelo , Schalenbach Maximilian , Stolten Detlef 
Published: February 2020

Polymer electrolyte membrane (PEM) water electrolysis is well identified today as a sustainable solution for the production of hydrogen, and of paramount importance when coupled to renewable but intermittent power sources such as wind and solar.
PEM water electrolysis is based on a solid polymer electrolyte concept first realized by Grubb in 1960s, where a thin solid sulfonated polystyrene membrane is used as an electrolyte. The polymer electrolyte membrane is responsible for providing high proton conductivity, compact system design, and low gas crossover. However, depending on the power load range, operating temperature, pressure range, membrane thickness, and a number of other parameters diffusion processes of the product gases through the membrane occur. The diffusion of hydrogen into the oxygen compartment for example reduces the efficiency of the electrolyzer, and allows the extensive mixing of gases that must be avoided in order to preserve efficiency and safety. This is particularly severe at a low power load – important when coupling to intermittent power sources – where the oxygen production rate decreases, thus drastically increasing the hydrogen concentration to unwanted and dangerous levels (lower explosion limit > 4 mol-% H2).
Nevertheless, PEM water electrolysis can operate at high current densities, capable of achieving values above 4 Acm-2, provided by very low ohmic losses. Though, very high current densities (over 6 Acm-2) can only be achieved if thin membranes (20 – 50 µm) are used which lead to lower cell resistances. In this case unfortunately, the crossover of gases across the membrane is drastically enlarged, if compared to the use of thicker membranes (100 – 200 µm).
In any case, PEM electrolysis is recognized for practically covering a wide power density range. However, the practical power operation range of PEM water electrolysis has not been consistently evaluated yet, especially when considering the variation of perfluorosulfonic acid (PFSA) membrane, thickness, and operation pressure.
In this study, the in-situ crossover aspect of a series of PFSA Nafion membranes at different operation conditions will be evaluated and compared to a simulation study of the gas permeation pathways. The main message is to clearly define the power load and pressure range for the PEM water electrolysis technology when using different membrane alternatives, providing a road map in order to aid scientists with regards to the R&D of PFSA membranes for PEM water electrolysis.
New Polymer Structures for Anion Exchange Membranes
Authors: Zhu Liang , Pan Jing , Hickner Michael 
Published: February 2020

New membranes for alkaline fuel cells and other ion transport applications continue to generate a lot of interest in the electrochemical community. Over the last 10 years there has been great progress in determining the key attributes of anion exchange membranes that lead to high fuel cell performance and moderate lifetime devices. A current limitation of the field is the lack of readily available membranes and ionomer solutions. Scalable, inexpensive materials are needed to promote more studies of electrode fabrication, device operation, and optimization, particularly in the area of longevity.
Our group has demonstrated a number of new polymer structures based on commercially-available polymers and inexpensive modification reagents. We have focused on poly(phenylene oxide) as a backbone platform and employed ammonium cations that have relatively good stability in light of their low cost and reasonable performance. In previous work, we employed alkyl chains to cause phase separation in random copolymers. This phase separation increased the conductivity and decreased the water uptake of the materials. We have since continued to investigate crosslinking and interpenetrating networks as further methods to optimize the properties of anion exchange membranes. Many of these polymers have shown reasonable performance in anion exchange membrane devices, but more work is required to extend the lifetimes of the cells beyond 1000 hours.
This talk will highlight our recent work on new polymer structures and demonstrate how stability and conductivity can be increased by iterating on quaternary ammonium poly(phenylene oxide)-based materials.
Understanding Liquid-Water Management in PEFCs Using X-Ray Computed Tomography and Modeling
Authors: Zenyuk Iryna V , Weber Adam Z 
Published: February 2020

Optimal liquid-water management is essential for commercializing polymer-electrolyte fuel cells (PEFCs), especially those with next-generation material sets. At low operating temperatures there is a need to remove liquid water from the cathode electrode where it can impede reactant transport. Optimization of water transport and removal requires a careful design consideration for the porous carbon components, specifically the gas-diffusion layers (GDLs). These heterogeneous materials serve a multifunctional purpose of conducting electrons and heat in the solid phase, providing structural support to the membrane and electrodes, and delivering reactants to the electrode and removing product water. Two-phase transport inside the GDLs, especially during operation, is complex and requires detailed knowledge of a given GDLs’ morphology and transport properties. In this talk, we will elucidate the GDL’s morphological properties using synchrotron-based X-ray micro computed tomography (XCT) and study in-situ water-distributions for different materials. Conditions studied include varying liquid pressure, gas-channel flow-rate, and land-channel compression. The XCT studies are complemented with two-dimensional modeling studies to gain an understanding of liquid-water transport under in-operando conditions.
Acknowledgement
This work was funded by Assistant Secretary for Energy Efficiency and Renewable Energy, Fuel Cell Technologies Office, of the U. S. Department of Energy under contract number DE-AC02-05CH11231, program manager Donna Ho. This work made use of facilities at the Advanced Light Source (ALS), supported by the Office of Science, Office of Basic Energy Sciences, of the U.S. Department of Energy.