bluuebunny/crossref_metadata_2025_split huggingface dataset:
Template-Free Electrochemical Synthesis of Selenium Nanowires
Authors: Seyedmahmoudbaraghani Saba , Myung Nosang Vincent 
Published: February 2020

During past years, one-dimensional nanostructures such as nanotubes and nanowires have drown much attention due to the possibility of their application in nanodevices. This is due to their size-dependent physical properties. Selenium is known to be an important elemental semiconductor which has been widely studied because of the exhibition of so many appealing properties such as high photoconductivity and low photomelting temperature, high piezoelectric, thermoelectricity, and non-linear optical responses. There has been extensive research on Selenium nanowires and nanorods among all Se nanostructures. Se nanowires can be fabricated by using solution-phase method, chemical vapor deposition method, and electrodeposition. The electrodeposition technique is more promising due its simplicity, cost-effectiveness, and low growth temperature.
In the present work, we are looking forward to fabricating one-dimensional trigonal Selenium nanowires using electrodeposition. The morphology is controlled as a function of applied potential and pH in the electrolytes. The temperature-dependent annealing will also be performed. The morphology and crystallinity of the Se nanostructures are characterized by Raman spectra, TEM, SEM, and XRD. The electrodeposition of trigonal Selenium nanostructures is demonstrated based on an analysis of linear sweep voltammetry and pH-Eh (pourbaix) diagram.
A New Membrane Electrode Assembly Structure with Novel Flow Fields for Polymer Electrolyte Fuel Cells
Authors: Park Jaehyung , Pasaogullari Ugur , Bonville Leonard J. 
Published: February 2020

A conventional polymer electrolyte fuel cell (PEFC) incorporates a membrane electrode assembly (MEA) which is comprised of the anode catalyst layer-polymer electrolyte -cathode catalyst layer sandwiched between two gas diffusion layers (GDLs), and bipolar plates. Conventional GDL is typically comprised of highly porous carbon paper or cloth to help diffuse the reactant gases onto the electrode, which is coated with a thin micro-porous layer (MPL). At high current densities, mass transport limitations of fuel or oxidizer in the PEFC occur in porous structures of the GDL, particularly at the cathode, which result in a sharp drop in the output voltage. The key to minimizing mass-transport losses is effective water management in the cell. Liquid water in macro-pores of GDL decreases the fuel cell performance at high current density due to the lack of oxygen reaching the catalyst layer.
A new MEA structure is recently introduced, where the carbon paper backing layer is eliminated and the entire gas diffusion layer consists of only the MPL [1]. We have further improved on this concept by directly depositing the MPL onto the CCM, resulting in an improvement in the interfacial contact between the MPL and the catalyst layer, as well as a simplified fabrication and assembly process. Spray deposition method was used for depositing this MPL onto a commercial CCM [2]. This concept was proven to work and perform better than a conventional cell with a micro-channel flow field used to provide the desired pathway for the reactant gases throughout the cell substituting for the macro porous carbon paper and the millimeter sized flow field.
In this work, a porous foam is utilized as the flow field to distribute the reactant gases over the micro-porous layer instead of the micro-channel flow field. Various pore sizes of the foam, i.e. 60-100 PPI, are used to compare with the conventional micro channel flow field. Contact resistance, permeability, electrochemical impedance spectroscopy, and mechanical properties are used to further characterize the new MEA structure incorporating the porous foam flow field. This method can be an effective way of enabling very high power density operation by reducing the mass transport limitations, and provides an improvement in the interfacial contact between the MEA and the flow field as well as improved mechanical properties.
[1] T. Kotaka, Y. Tabuchi, U. Pasaogullari, and C. Y. Wang, Electrochim. Acta, 146, 618 (2014).
[2] J. Park, U. Pasaogullari, L. J. Bonville, ECS Transactions, 69, 1355-1362 (2015).
Electrochemical Characterization of PEMECs Operating at Various Current Densities
Authors: Elsoee Katrine , Madsen Laila G.- , Scherer Guenther G. , Hjelm Johan , Mogensen Mogens Bjerg 
Published: February 2020

This conference contribution touches upon electrochemical characterization of operating polymer electrolyte membrane electrolysis cells (PEMECs) by the application of electrochemical impedance spectroscopy (EIS). Analysis of differences in impedance spectra (ADIS) (Jensen et al., 2007) can be applied to gain insight into the relative magnitudes of resistance contributions from the two electrodes, the electrolyte and of mass transfer limitations and can help identifying the time scale of the respective processes. The gained knowledge may facilitate further development of the PEMECs.
A state-of-the-art PEMEC obtained from IRD with a 2.9 cm2 active electrode area and loaded with 0.3 mg/cm2 IrO2 on the anode and 0.5 mg/cm2 Pt on the cathode was operated at current densities ranging from 0.07 to 1 A/cm2 while examined with EIS. The cell temperature at operation was 61 ˚C at all current densities, and the cell was conditioned for 20 minutes at each current step prior to EIS measurements. A Solartron 1260 was used for the data acquisition, the frequency range was 100 kHz - 0.01 Hz, the amplitude was 17.3 A/cm2 and 12 points were measured per decade. Nyquist plots of the EIS results are shown in the upper graph in the figure. One arc is evident in the spectrum at 0.07 A/cm2, whereas the spectra at 0.35 and 0.69 A/cm2 include two arcs, and two overlapping arcs are observed at 1 A/cm2. ADIS plots, with the impedance measured at 0.07 A/cm2 subtracted, are shown in the lower graph in the figure. Based on the ADIS plots it can be concluded that the impedance is independent of the current density at frequencies above 100 Hz, whereas two processes observed at approximately 0.4 and 10 Hz are current density dependent, the one increasing and the other decreasing in size with increasing current density.

Acknowledgement

The work is part of the research project e-STORE funded by the Innovation Fund Denmark.

Reference

S. H. Jensen, A. Hauch, P. V. Hendriksen, M. Mogensen, N. Bonanos, T. Jacobsen. (2007). A Method to Separate Process Contributions in Impedance Spectra by Variation of Test Conditions. Journal of The Electrochemical Society, 154 (12), B1325-B1330.

Figure

Nyquist plots (upper graph) and ADIS plots (lower graph) of EIS measured on a PEMEC operating at 0.07, 0.35, 0.69 and 1 A/cm2. The ADIS plots represent the difference between the differentiated real part of the impedance at each current density and the differentiated real part of the impedance collected at 0.07 A/cm2.

Figure 1
(Invited Plenary) Improving the Catalytic Properties of Non-Precious Metal Catalysts - Milestones in the Development of Me-N-C Catalysts
Authors: Kramm Ulrike Ingrid 
Published: February 2020

Me-N-C catalysts are today’s most active non-precious metal catalysts for the oxygen reduction reaction (ORR) in proton exchange membrane fuel cells (PEMFC). The application of these catalysts dates back to 1964 when Jasinski was the first demonstrating ORR activity of different phthalocyanines in alkaline electrolyte. The most important steps in improvement of ORR activity and stability were made by the heat-treatment of MeN4-macrocycles in 1976 and the pyrolysis of independent metal, nitrogen and carbon sources in 1989 as shown by Jahnke et al. respectively Gupta et al..
However, especially during the last decade important progress in the development and fundamental understanding of these catalysts was gained. Based on these findings the ORR activity was boosted significantly. This motivated researchers worldwide to contribute to the development of Me-N-C catalysts and to the controversy of the origin of ORR activity.
In this contribution the most important milestones in the development of Me-N-C catalysts will be summarized. Based on this rational criteria can be defined for the further optimization of these catalysts with respect to a final implementation in the car.
Enduring Anion-Exchange Membrane Fuel Cells
Authors: Holdcroft Steven , Britton Benjamin , Wright Andrew G. , Weissbach Thomas 
Published: February 2020

Alkaline anion exchange membrane fuel cells have become a topic of substantial interest in recent years, opening up a new electrochemical environment for hydrogen fuel cells. Facile kinetics for the oxygen reduction reaction open the promise of non-PGM or even non-metal AEMFCs, and radical stability. The most challenging aspect for the field, as defined by the 2016 DOE AMFC III Workshop, is membrane and ionomer stability in alkaline conditions at elevated operating temperatures. Few papers report endurance data, and best practices for in situ fuel cell conditioning and electrochemical characterization are still being developed by the community.
Here, we report that HMT-PMBI exhibits membrane and ionomer stability in situ as AEMFCs in relevant conditions for device operation. These fuel cells demonstrate re-equilibration from extensive carbonation and complete re-conditioning in a shut-down / start-up cycle. We further report operation in typically challenging conditions, e.g. increased temperature and reduced humidity. Finally, we report on our attempts to define best-practices for electrochemical characterization.
Investigating Catalyst-Electrolyte Interface By Microelectrode, Infrared Reflection Adsorption Spectroscopy and Neutron Reflectometry
Authors: Dumont Joseph H , Hjelm Rex , Watkins Erik , Chung Hoon T , Martinez Ulises , Atanassov Plamen , Kim Yu Seung 
Published: February 2020

Understanding of the catalyst-ionomer interfacial behavior is critically important for fuel cell research. In fact, alkaline membrane fuel cells (AMFCs) have shown limited performance compared to proton exchange membrane fuel cells due to relatively poor hydrogen oxidation reaction (HOR) kinetics [1]. Previous work has shown that cationic adsorption at the surface of the catalyst was closely related to the HOR activity [2, 3]. Here, we present the results of a study of the benzyltrimethyl ammonium electrolyte-Pt interface in hydrogen oxidation reaction (HOR). More specifically, we will discuss the adsorption of the cationic group that may inhibit the HOR activity of Pt electrocatalysts. Microelectrode, Infrared Reflection Adsorption Spectroscopy (IRRAS) and Neutron Reflectometry are complementary tools to investigate the catalyst-ionomer interface.

Acknowledgement

US department of Energy Fuel Cell Technologies Program (Program Manager: Nancy Garland) supports this research through Fuel Cell Incubator Project. We also wish to acknowledge Oak Ridge National Laboratory Spallation Neutron Source, the NIST Center for Neutron Research and the Los Alamos Neutron Science Center.

References

[1] W.C. Sheng, H.A. Gasteiger, Y. Shao-Horn, “Hydrogen Oxidation and Evolution Reaction Kinetics on Platinum: Acid vs Alkaline Electrolytes,” J. Electrochem. Soc., 157, B1529 (2010).
[2] H. T. Chung, U. Martinez, J. Chlistunoff, Y. S. Kim, Y. K. Choe, and I. Matanovic, “Impact of Organic Cation Adsorption on the Hydrogen Oxidation Reaction of Pt in Alkaline Fuel Cells”, 2015, ECS Meeting Abstracts, 1510-1510
[3] Sung-Dae Yim, Hoon T. Chung, Jerzy Chlistunoff, Dae-Sik Kim, Cy Fujimoto, Tae-Hyun Yang, Yu Seung Kim, “A Microelectrode Study of Interfacial Reactions at the Platinum-Alkaline Polymer Interface,” J. Electrochem. Soc., 162, F499 (2015).
Impact on Diffusion Parameters Computation in Gas Diffusion Layers, Considering the Land/Channel Region, Using the Lattice Boltzmann Method
Authors: Espinoza Mayken , Sundén Bengt , Andersson Martin 
Published: February 2020

A deep understanding of the behavior of microstructural parameters in proton exchange fuel cells (PEFCs) will help to reduce the material cost and to predict the performance of the device at cell scale. Changes in morphological configuration, i.e., fiber diameter and fiber orientation, of the gas diffusion layers (GDLs) result in variations of fluid behavior throughout the layer, and therefore; the microstructural parameters are affected. The aim of this study is to analyze, for three selected fiber diameters and different percentages presence of inclined fibers, the behavior of the different microstructural parameters of the GDLs.
This study is carried out over digitally created two-dimensional GDL models in which the fluid behavior is obtained by means of the Lattice Boltzmann method (LBM). Once the fluid behavior is determined, the microstructural parameters, i.e., the porosity, gas-phase tortuosity, obstruction factor, through-plane permeability, and inertial coefficient, are computed. Several relationships are found to predict the behavior of such parameters as function of the fiber diameter, presence of inclined rods or porosity. The results presented in this work are compared and validated by previous theoretical and experimental studies found in the literature.
Structural Characterization and Transport Modeling of Pt and Pt Alloy Polymer Electrolyte Fuel Cell Cathode Catalyst Layers
Authors: Cetinbas Firat , Ahluwalia Rajesh , Kariuki Nancy , More Karren L. , Cullen David A. , Sneed Brian , Winarski Robert P. , Ilavsky Jan , De Andrade Vincent , Myers Deborah J 
Published: February 2020

In recent years, numerous Pt-based nanoparticle catalysts with very high oxygen reduction reaction activity have been developed, most of these based on transition metal alloys of Pt with or without post-synthesis de-alloying. As intrinsic electrocatalytic activities have been improved, the performance limitation of the cathode catalyst layers has shifted from activity to facile transport of reactants to catalytic sites. Electrode structure has thus become increasingly important in defining electrode performance. Effective transport of reactants through the thickness of the electrode (~10 µm) is highly dependent on the agglomerate structure and spatial distribution of the conducting phases and the pores. Ultra-small angle scattering and TEM analyses have shown that the agglomerate structure of electrodes based on representative high activity Pt alloy catalysts is different than that of Pt catalyst-based electrodes. In this presentation, we will compare the structure of Pt alloy-based electrodes and Pt electrodes, characterized by a variety of techniques, including ultra-small-angle X-ray scattering, TEM, and X-ray tomography. The information obtained from these techniques has been used as input to an electrode structural model. The model has been probed to analyze the transport processes of protons, electrons, oxygen, and water. The results from alloy and Pt-based electrodes fabricated from inks with different ionomer to carbon ratio, solvent, and ionomer equivalent weight have been examined to establish the empirical relationship between the microstructure and ink composition and the ultimate performance of the electrode layer.
1,2,3-Triazole-Functionalized Polysulfone Synthesis and Application in Proton Exchange Membranes for Low and High Temperature PEMFC
Authors: Sood Rakhi , Donnadio Anna , Giancola Stefano , Kreisz Aurélien , Jones Deborah J. , Rozière Jacques , Cavaliere Sara 
Published: February 2020

The 1,2,3-triazole functionality demonstrates high chemical stability towards severe hydrolytic, oxidizing, and reducing conditions, even at elevated temperatures. Furthermore together with aromatic character and ability to form hydrogen bonds, it is reported to possess anti-oxidant properties1. All these features make polymers functionalized with 1,2,3-triazole of interest in proton exchange membranes as reinforcement or matrix for application in low and high temperature fuel cells.
We will describe a fast and high-yielding synthesis of 1,2,3-triazole functionalized polysulfone through microwave-assisted copper-catalyzed azide-alkyne cycloaddition (CuAAC) click chemistry. Polymers with various degrees of substitution of the side-chain functionality of 1,4-substituted 1,2,3-triazole with alkyl and aryl pendant structures were prepared and characterized to assess the completeness of the reaction. The thermal and thermo-chemical properties of the modified polymers were also characterized.
In one approach, cast membranes of 1,2,3-triazole functionalized polysulfone were doped with phosphoric acid for application in HT-PEMFC and their properties compared with conventional polybenzimidazole based systems. These novel membranes presented promising performance with high proton conductivity in anhydrous conditions and satisfactorily high elastic modulus2.
In another strategy with targeted low temperature PEMFC applications, nanocomposite membranes were prepared based on functionalized polysulfone and a perfluorosulfonic acid ionomer. As already evidenced for PBI-PFSA composites3, the specific interaction between the basic triazole functionalized polymer and the acidic ionomer lead to electrolytes with improved mechanical properties and without significant loss in proton conductivity.
1. J. Totobenazara and A. J. Burke, Tetrahedron Lett., 56, 2853–2859 (2015).
2. R. Sood, A. Donnadio, S. Giancola, A. Kreisz, D.J. Jones, S. Cavaliere, ACS Appl. Mater. Interf., in press.
Sulfonated and Partially Fluorinated Poly(aryl) Multiblock-Co-Ionomers for Fuel Cells
Authors: Bender Johannes , Kerres Jochen A. 
Published: February 2020

In this paper, proton exchange membranes are presented on the basis of multiblock co-ionomers. The multiblock-co-ionomers are prepared from hydrophobic, partially fluorinated polymer [1] and hydrophilic, sulfonated ionomer blocks [2]. The synthesis of the individual polymer blocks is done by nucleophilic aromatic step-growth polycondensation. The multiblock-co-ionomer membranes are cast and dried according to standard procedure. The interest in multiblock-co-ionomer membranes for use in PEMFCs is that they form microphase- or nanophase-separated regions [3]. The areas with hydrophobic character ensure the stability of the membrane and the areas with hydrophilic character of the proton conduction. In case of longer hydrophilic blocks it is necessary to blend the multiblock-co-ionomers with basic polybenzimidazoles like PBI-OO or F6-PBI for mechanical stability.
In this contribution the first results in terms of characterization by means of NMR spectroscopy, molecular weight distribution, thermal stability and proton conductivity will be presented.
Literature:
1: Kerres. J. A.; Xing, D.; Schöneberger, F. J.Polym. Sci.
PART B: Polym. Phys.
2006, 44, 2311-2326
2: Kerres. J. A.; Schöneberger, F. J.Polym. Sci.
PART A: Polym. Chem.
2007, 45, 5237-5255
3: Kerres, J. A. Polymer Reviews
2015, 55, 273-306
Relating the Influence of Surface Characteristics of Carbon Electrocatalyst Support to the Performance and Durability of a PEMFC through Calorimetric, Adsorption, Spectroscopic and Electrochemical Measurements
Authors: Jimenez Morales Ignacio , Dupont Marc , Cavaliere Sara , Jones Deborah J. , Rozière Jacques , Zajac Jerzy , Larsen Mikkel Juul , Odgaard Madeleine , Mornaghini Flavio , Rodlert Marlene 
Published: February 2020

The role played by the surface properties of carbon blacks used as electrocatalyst supports in fuel cell electrodes is crucial in determining the performance and durability characteristics of the final membrane electrode assembly. These key surface properties include the polar character arising from the presence of heteroatoms, and the proportion of the surface area that corresponds to graphitic carbon sites.
We have used flow calorimetry to characterise the surface properties of a family of carbon blacks having the same BET surface area (400±10 m2/g), but different pore size characteristics and different properties in terms of polar and graphitic surface sites. The preferential heat of adsorption of n-dotriacontane and n-butanol for basal plane sites and polar sites respectively has been determined for the carbon sites immersed in n-heptane1. The overall hydrophobic character of the carbon surface was evaluated by measuring the heat of adsorption of n-butanol from its aqueous solution2.
Platinum nanoparticles prepared by a microwave-assisted polyol method2 were deposited on each of the carbons, and the electrochemical surface area, the mass and specific activity of the Pt/C samples were determined. Membrane-electrode assemblies were prepared using the electrocatalysts at the cathode and they were tested in fuel cell over a range of temperatures and relative humidities, when the observed performance could be related to the relative hydrophobic/hydrophilic properties of the carbons. Further, the stability of the carbons to electrochemical corrosion was assessed by submitting them to high voltage (1.4 V/RHE) and determining the corrosion current and the corresponding mass loss, and the results related to the graphitic character of the carbons determined from flow microcalorimetry and Raman spectroscopy.
This understanding will be beneficial in the tuned design of PEMFC electrocatalyst supports for the targeted operation conditions. This work demonstrates the importance of calorimetric methods in characterising carbons for electrochemical applications.

References

1. J. Zajac, A. J. Groszek, Carbon 35 (1997) 1053-1060.
2. L. Kaluža et al., Electrocatalysis, (2016) http://dx.doi.org/10.1007/s12678-016-0312-3.
Nanofibrous Electrode Design By CNT-Winded Pt/TiO2 for Superior PEMFC Performance and Durability at High Temperature
Authors: Ji Yunseong , Cho Yongil , Jeon Yukwon , Hwang Ho Jeong , Lee Jin Goo , Park Myeonggeun , Lee Gicheon , Jang Jeongseok , Jeon Oksung , Kwon Oh Chan , Hwang Jusoon , Shul Yong Gun 
Published: February 2020

Fuel cell is one of the most promising electrochemical energy conversion devices that has many advantages such as high efficiency, high power density, CO2 free, noise free, rapid start up, etc. Especially, polymer electrolyte membrane fuel cell (PEMFC) has been shown a lot of attention due to its high power density and relatively good portability. Generally, Pt supported on carbon black is used as an electrocatalyst in PEMFC. However, carbon corrosion is one of the main problem for electrode structure collapse and catalyst activity loss, which can be further accelerated at high temperature. Therefore, we need to find an alternative catalyst support material that is electrochemically stable and interacts strongly with the catalyst active sites.
Recently, metal oxide supports have been reported as promising materials due to their excellent mechanical resistance and inherently higher stability. Among many candidates, titanium dioxide (TiO2) support has an extraordinary stability under severe acidic atmosphere, which provides the possibility to directly use as a support material. However, the low electrical conductivity, catalytic activity and surface area of TiO2hinder the direct apply to the PEMFC electrode.
In order to solve these problems, we prepared TiO2 nanofibers by electrospinning method and platinum nanoparticles are deposited by microwave-assisted polyol method to synthesize an effective electrode catalyst. Then, CNT was winded around the catalyst surface to boost up the electrical conductivity. Furthermore, we found a modified Pt electronic structure that takes advantage of the strong synergetic interactions of TiO2 nanofibers, Pt nanoparticles and winded-CNT. This structure influences on a decrease of the d-band vacancy of Pt due to electron transfer from the support, resulting in an improved oxygen reduction reaction. Therefore, the cathode with the CNT modified Pt/TiO2 nanofiber composite shows higher catalytic activity due to the elimination of the drawback associated with conductivity and enhanced electronic active structure. As from various PEMFC tests, our CNT-Pt/TiO2 catalyst shows superior performance and durability, which is definitely distinguishable at high temperature condition of 120 oC and RH 40% compare to the commercial Pt/C.