bluuebunny/crossref_metadata_2025_split huggingface dataset:
(Invited) Performance Evaluation of a Hybrid Hydrogen-Vanadium Reversible Fuel Cell
Authors: Nguyen Trung Van , Dowd Regis Paul , Powers Devon , Wycisk Ryszard , Pintauro Peter N 
Published: February 2020

The hybrid hydrogen-vanadium reversible fuel cell consists of a gaseous hydrogen fuel cell electrode and a liquid vanadium flow battery electrode. This hybrid fuel cell system offers a feasible solution for storing electrical energy from the grid or directly from renewable energy sources such as wind and solar. This system is attractive over the all-vanadium system due to the 50% reduction in the amount of vanadium solution required. Furthermore, by replacing the negative vanadium electrode with a hydrogen electrode the effect of self-discharge by the crossover of unwanted ions (vanadium II and III) from the negative electrode to the positive electrode is eliminated. Another benefit of this two-phase hybrid system is the ease of separation of the cross-over species. In this presentation, the effects of operating and design variables such as the vanadium electrolyte flow rate, type of carbon electrodes, and Nafion membranes and electrospun membranes made of perfluorosulfonic acid (PFSA)/ polyvinylidene fluoride (PVDF), which are developed to reduce the crossover rate of vanadium ions, with different thickness will be discussed.

Acknowledgement

The work presented was partially funded by the National Science Foundation under Grant No. EFRI-1038234.

Figure 1
(Invited) Direct Membrane Deposition – A Fast and Simple Technique for Membrane Electrode Assembly Manufacturing
Authors: Klingele Matthias , Vierrath Severin , Breitwieser Matthias , Klose Carolin , Thiele Simon 
Published: February 2020

The membrane is one of the very central polymer electrolyte membrane fuel cell components. At the same time it must conduct protons and inhibit transport of electrons and cross-over of reactant gases. Additionally, degradation effects have to be small to ensure a long lifetime. While traditionally consisting of pure Nafion, up to date membranes contain nanofiber reinforcements and radical scavenger packages to decrease degradation effects. Thus, seminal membranes are multi-layer, multi-component structures.
In the state of the art, membrane electrode assemblies (MEA) are manufactured as catalyst coated membranes (CCMs). To form a CCM, electrodes are deposited either by the decal method, or by another deposition method.
In this talk we present a novel approach for MEA manufacturing. In the so called ‘direct membrane deposition’ (DMD) approach, liquid ionomer is deposited on the catalyst layers of two gas diffusion electrodes which are successively dried and pressed together to form an MEA. Interestingly, this approach enabled power densities more than two times higher than traditional CCM based approaches which are commercially available [1]. Also this approach allows for a simple fabrication of thin multi-layer membranes and improves the water management [2]. DMD applied to low Pt loading electrodes revealed very high power densities per gram Pt of up to 88 kW/g Pt [3]. An analysis of the underlying reasons for the improved performance values revealed a small influence of membrane resistance but mainly an influence in mass transport and charge transfer phenomena [4,5].
In this talk we highlight our latest developments in the field of DMD based manufacturing and give an insight on degradation and durability aspects.
References:
[1] M. Klingele, M. Breitwieser, R. Zengerle, S. Thiele, J. Mater. Chem. A 3 (2015) 11239–11245.
[2] M. Breitwieser, R. Moroni, J. Schock, M. Schulz, B. Schillinger, F. Pfeiffer, R. Zengerle, S. Thiele, Int J Hydrogen Energ 41 (2016) 11412–11417.
[3] M. Breitwieser, M. Klingele, B. Britton, S. Holdcroft, R. Zengerle, S. Thiele, Electrochem. Commun. 60 (2015) 168–171.
[4] M. Klingele, B. Britton, M. Breitwieser, S. Vierrath, R. Zengerle, S. Holdcroft, S. Thiele, Electrochemistry Communications 70 (2016) 65–68.
[5] S. Vierrath, M. Breitwieser, M. Klingele, B. Britton, S. Holdcroft, R. Zengerle, S. Thiele, J. Power Sources 326 (2016) 170–175.170 - 175.
A Thermo-Poro-Viscoelastic Model for the Behavior of Polymeric Porous Separators
Authors: Behrou Reza 
Published: February 2020

Porous separator membranes play an important role in the long-term performance of lithium battery cells. They provide a barrier between two electrodes and enable migration of lithium ions through the pores, where lithium ions migrate through the electrolyte via diffusion-migration and reach the electrode materials. During the discharge process, the intercalation of Li ions into active materials in the electrode leads to swelling of active particles, expansion of the electrode, mechanical stresses, and compression of the separator membrane. Moreover, the extreme thermal condition lessens the performance of the separator by closing the pores through a melting process. To assess the performance of the separator under mechanical and thermal conditions, we present a thermo-poro-viscoelastic model for polymeric porous separators. We study the thermo-mechanical behavior of fully saturated porous separators through the thermo-poromechanics formulations. Two-phase mixture with solid and fluid phases is considered. Governing and balance equations are presented for the solid-fluid mixture, where the displacement of the solid skeleton, temperature and fluid pore pressure are considered as unknowns with a quasi-static loading condition. The stress-strain behavior of the polymeric separator membrane is described by a viscoelastic constitutive law in the form of convolution integral, where the thermal effects are considered through the thermal strain. The flow of the fluid through the porous medium is described by the Darcy’s law. The constitutive equation for the Darcy fluid velocity is described by the permeability of the fluid. To present more realistic physical phenomena, the hydraulic conductivity is described as a function of the porosity in the solid phase. Numerical simulations are performed to study the performance of the separator in a saturated porous medium.
Structure-Activity-Durability Relationships of (CM+PANI)-Me-C PGM-Free Catalysts
Authors: Martinez Ulises , Komini Babu Siddharth , Holby Edward F. , Artyushkova Kateryna , Lin Ling , Chung Hoon T , Purdy Geraldine M , Zelenay Piotr 
Published: February 2020

The development of durable and highly active platinum group metal-free (PGM-free) electrocatalysts is key to overcoming the greatest barrier in the commercialization of fuel cell electric vehicles: the high cost and limited availability of PGM catalysts utilized in polymer electrolyte fuel cells. While the majority of research on PGM-free catalysts has focused on developing active and selective materials for the sluggish oxygen reduction reaction (ORR), minimal work has been devoted to the understanding of the physical and chemical structure of active PGM-free catalysts and its relationship with the long-term stability of these novel materials. This understanding is imperative for the further development of next-generation PGM-free catalysts with improved activity and durability that could ultimately replace PGM-based ORR catalysts in fuel cells.
PGM-free catalysts with high volumetric activity, four-electron selectivity (i.e., low hydrogen peroxide yield), and long-term stability in highly acidic and strongly oxidizing environment of the fuel cell cathode are desired as replacements for PGM-based ORR catalysts. For this presentation, state-of-the-art PGM-free ORR catalysts, developed by our group [1, 2], which are obtained via high-temperature treatment of dual nitrogen precursors, cyanamide (CM) and polyaniline (PANI), different transition metal precursors (Fe, Co, Mn), and with or without carbon support are used as model PGM-free catalyst systems. Depending on the transition metal used, catalysts with different physical and electrochemical characteristic properties are obtained. Specifically, Fe-based catalysts are generally known for their high activity and low peroxide yield generation. However, Co- and Mn-based catalysts generate highly graphitic structures which could improve catalyst long-term stability. In this work, structure-activity-durability relationships are developed based on comprehensive physical, chemical, and electrochemical characterization of highly active (CM+PANI)-Me-C catalysts (Me = Fe, Co, Mn), correlating properties such as carbon structure, elemental speciation, and CO2 generation.

Acknowledgement

Financial support for this research by DOE-EERE through Fuel Cell Technologies Office is gratefully acknowledged.
[1] Chung, H.T., Holby, E.F., Purdy, G.M., Babu, S.K., Litster, S., Cullen, D.A. More, K.L., Zelenay, P. (2015). “Combining Nitrogen Precursors in Synthesis of Non-Precious Metal ORR Catalysts with Improved Fuel Cell Performance.” ECS Meeting Abstracts, MA2015-02 (37), 1278.
[2] Martinez, U., Holby, E.F., Dumont, J.H., Chung, H.T., Zelenay, P. (2016) “Non-PGM ORR Catalysts Based on Transition Metals Alternative to Iron.” ECS Meeting Abstracts, MA2016-01, 1719.
(Invited) Porous Hollow PtNi/C Nanoparticles and Their Many Facets
Authors: Asset Tristan , Chattot Raphaël , Le Bacq Olivier , Pasturel Alain , Drnec Jakub , Bordet Pierre , Nelayah Jaysen , Dubau Laetitia , Maillard Frederic 
Published: February 2020

Porous hollow PtM/C electrocatalysts (where M is a 3d transition metal element) have proven to enhance remarkably the oxygen reduction reaction (ORR) kinetics in proton exchange membrane fuel cells. However, their mechanism of formation, the nature of adequate alloying elements and carbon supports as well as the rationale for their interesting electrocatalytic properties remain open questions.
Herein, we describe the mechanism of formation and growth of porous hollow PtNi/C NPs using operando wide angle X-ray scattering, scanning transmission electron microscopy and X-ray energy dispersive spectroscopy 1. The results show that Ni-rich NPs covered by a NixByOz shell form first before acting as a sacrificial template for the deposition of Pt2+ ions via galvanic replacement (Figure 1). Finally, the solid Ni-rich core@Pt-rich shell NPs are transformed into alloy hollow PtNi/C NPs via the nanoscale Kirkendall effect (a vacancy mediated interdiffusion mechanism). Density Functional Theory (DFT) calculations were then used to gain insights on the impact of atomic vacancies on the surface structure and the reactivity of the porous hollow PtNi/C nanoparticles 2. The DFT and experimental results show that porous hollow PtM/C nanoparticles feature unique catalytic advantages (i) open percolated structure exposing two catalytic surfaces (inner and outer), and (ii) structural defects that distort the metal lattice and produce catalytic sites that are highly active for both electrooxidation (COadsmonolayer electrooxidation, methanol and ethanol electrooxidation) and electroreduction (ORR) reactions.
1. R. Chattot, T. Asset, J. Drnec, P. Bordet, J. Nelayah, L. Dubau, F. Maillard, Nano Lett. (2017). DOI: 10.1021/acs.nanolett.7b00119
2. O. Le Bacq, A. Pasturel, R. Chattot, B. Previdello, J. Nelayah, T. Asset, L. Dubau, F. Maillard, ChemCatChem. (2017). DOI: 10.1002/cctc.201601672

Figure 1.Conventional and scanning transmission electron microscopy images and elemental maps of the different intermediate nanostructures forming during the synthesis of hollow PtNi/C nanoparticles.

Figure 1
Rotating Disk Electrode Study of Carbon Supported Pt-Nanoparticles Synthesized Using Microwave-Assisted Method
Authors: Vaarmets Kersti , Valk Peeter , Nerut Jaak , Tallo Indrek , Aruväli Jaan , Sepp Silver , Lust Enn 
Published: February 2020

Carbon supported platinum catalysts are widely used in PEMFC applications. The catalytic activity of the catalyst is strongly dependent on size and size distribution of the Pt nanoparticles deposited onto porous carbon support. In this study, the microwave-assisted synthesis method was used to study the effect of the Pt particle size and content (mass%) on the electrochemical activity of oxygen reduction reaction1,2.
The Pt nanoparticles were deposited onto the carbon support using the microwave-assisted method3–6. H2PtCl6×6H2O (99.9%, Alfa Aesar) was dissolved in ethylene glycol (Riedel-de Haën), the carbon powder (commercial Vulcan XC72) was added and pH was regulated using NaOH. The synthesis mixture was heated in a commercial microwave oven until boiling two times. The product was filtered and thereafter washed with MilliQ+ water. Varying the pH level of the reaction media affected the Pt nanoparticle size and Pt content in the catalysts.
The X-ray diffraction and low temperature nitrogen sorption methods were used to characterize the catalysts materials.
The materials were electrochemically characterised using the rotating disk electrode technique as described by S. Kocha et. al 7,8 in 0.1 M HClO4 solution. The highest electrochemical surface area 93.8±13.3 m2g−1 with mass activity of 436 mA mg−1 and specific activity of 449 µA cm−2 have been achieved.
The content of platinum in the catalyst was determined before and after the experiments using the electrochemical dissolution of platinum from the electrode in 6 M HCl solution. The average weight percentage of Pt in different catalyst materials was 17.3±4.1.
References
1. B. C. H. Steele and A. Heinzel, Nature, 414, 345–352 (2001) .
2. H. A. Gasteiger, S. S. Kocha, B. Sompalli, and F. T. Wagner, Appl. Catal. B Environ., 56, 9–35 (2005).
3. W. X. Chen, J. Y. Lee, and Z. Liu, Chem. Commun., 2588–2589 (2002).
4. X. Li, W.-X. Chen, J. Zhao, W. Xing, and Z.-D. Xu, Carbon, 43, 2168–2174 (2005).
5. Z. Liu, J. Y. Lee, W. Chen, M. Han, and L. M. Gan, Langmuir, 20, 181–187 (2004).
6. S. Horikoshi and N. Serpone, Eds., Microwaves in nanoparticle Synthesis: Fundamentals and Applications, WILEY-VCH Verlag GmbH & Co KGaA, (2013).
7. K. Shinozaki, J. W. Zack, R. M. Richards, B. S. Pivovar, and S. S. Kocha, J. Electrochem. Soc., 162, F1144–F1158 (2015).
8. K. Shinozaki, J. W. Zack, S. Pylypenko, B. S. Pivovar, and S. S. Kocha, J. Electrochem. Soc., 162, F1384–F1396 (2015).
Acknowledgements This work was supported by Estonian target research project IUT20-13, Personal Research Grant PUT55, Estonian Centre of Excellence Projects No. 2014-2020.4.01.15-0011 and 3.20101.11-0030.
Uniformity of Carbon Supported Pt Nanocatalysts Produced By Arc Plasma Deposition
Authors: Saito Toshifumi 
Published: February 2020

We propose a new approach for the preparation of Pt/C catalysts by arc plasma deposition (APD), in which Pt nanoparticles are deposited on carbon in a vacuum; this method has been applied in a number of fields other than fuel cell catalysts. The solid cathode material is transformed into a completely ionized plasma that leaves the cathode with a velocity of 1-2 x 104 m/s(this number is the same for all cathode materials). This velocity corresponds to an ion kinetic energy of 20 eV (light ions such ascarbon) to 300eV (heavy ions such as platinum). Thus, the cathode material is eroded and forms anenergetic plasma jet.
When carbon powder is irradiated with a platinum-based plasma, the Pt+ ions collide with the carbon and become atoms, which then migrate and interact with other Pt atoms to form nanoparticles (NPs) with dimensions of 2 to 3 nm on the carbon surface. Figure 1 shows a scanning electron microscopy (SEM) image of Pt NPs on Ketjen black. Although the surface of the Ketjen black is extremely rough, the NPs are seen to be uniformly distributed. We compared the electrochemical properties of Pt/C catalysts prepared by APD with those of the commercially available catalyst TEC10E50E. Although the electrochemical surface area (ECSA) was almost the same, the specific activity for Pt/C(APD) was about 2 times higher than that for TEC10E50E, which led to an approximately 2 times higher mass activity. However, one remaining problem with Pt/C(APD) is that NPs are not deposited in some regions. Figure 2 shows an SEM image of Ketjen black containing regions where no Pt NPs are present. To address this issue, we made improvements to the stirring vessel, and optimized deposition parameters such as the plasma pulse interval and the powder surface conditions. We will describe the effects of these optimizations on the electrochemical properties of Pt/C(APD).

Figure 1
Tuning the Alloy Behavior and Particle Size of Ptm (M=Ni, Co) Nanoparticles By Using in Situ High-Temperature X-Ray Diffraction
Authors: Werheid Matthias , Weber Daniel Jochen , Weber Philipp , Oezaslan Mehtap 
Published: February 2020

Alloying process has emerged as a promising strategy to tailor the chemical, physical and catalytic properties of metals. According to the phase diagram, the physical and chemical properties and behaviors of macroscopic alloys are well known. On the atomic and nano-scale, the formation mechanisms of nano-alloys are, yet, poorly understood since nanostructured alloys possess different segregation tendency and reaction enthalpies compared to those of bulk materials. In the last 20 years, bimetallic alloy nanoparticles have attracted great attention in different fields such as catalysis, seniors, medicine due to their unique optical, electronic, magnetic, morphological and catalytic properties. Partial substitution of Platinum by less noble metals like Nickel or Cobalt enables to decrease the material costs in combination with improved electrocatalytic activity for the oxygen reduction reaction (ORR) in polymer electrolyte membrane fuel cells (PEMFC).[1,2,3] However, the alloyed state and the homogeneity of bimetallic PtM (M=Ni, Co) nanoparticle electrocatalysts are crucial for the manufacturing. A simple and facile synthetic route to prepare Pt-based alloy nanoparticles is the wet impregnation approach followed by thermal annealing. The challenge is to control the alloy formation and particle growth of these bimetallic nanoparticles. Therefore, the implementation of in situ high-temperature X-ray diffraction (HT-XRD) is a powerful tool to simultaneously probe the changes in crystallographic phases and crystallite size of these nano-alloys during the thermal treatment.[4,5]
We analyzed the formation dynamics and particle growth of carbon supported PtM (M = Co, Ni) alloy nanoparticles by using in situ HT-XRD. We developed a tool box how annealing control parameters such as heating rate, temperature and time influence the crystallographic phase structure, composition and crystallite size of the bimetallic nanoparticles. Afterwards, the alloy nanoparticles are tested for the ORR to correlate their structure, composition and particle size with the resulting catalytic properties.
The HT-XRD studies on Pt-based alloy nanoparticles enable to improve the preparation of nano-alloys with desired composition, crystalline phase and particle size for PEMFC applications.
References:
[1] F. Hasché, M. Oezaslan, P. Strasser, Journal of The Electrochemical Society, 2012, 159, B25-B34.
[2] J. Zhang (Ed.), PEM Fuel Cell Electrocatalysts and Catalyst Layers: Fundamentals and Applications, Springer-Verlag, London, 2008.
[3] Oezaslan, M.; Strasser, P., Journal of Power Sources, 2011, 196, 5240-5249.
[4] F. Hasché, M. Oezaslan, P. Strasser, PhysChemPhys,
2012, 13, 828-834.
[5] M. Oezaslan, F. Hasché, P. Strasser, Chemistry of Materials, 2011, 23, 2159-2165.
Electrochemical Characterization of MEAs with Different Pt-Loading for the Efficient Use of Pt
Authors: Uda Keisuke , Noda Zhiyun , Sasaki Kazunari , Hayashi Akari 
Published: February 2020

Introduction The reduction of Pt-loading particularly in PEFC cathode layers is essential for cutting the cost of PEFCs and further spreading PEFC technology. Nowadays, several approaches of reducing Pt-loading have been reported, and then the importance of optimizing the microstructure of cathode layers including carbon supports has been confirmed.1-2 Therefore, the objective of our research is to develop low Pt-loading PEFCs with high efficiency by optimizing the mount of both Pt and carbon. As a first step, MEAs with varied Pt-loading in cathode layers were prepared with a standard catalyst, TEC10E50E, and a common spray-printing method. Then, the minimum amount of Pt, which is necessary for cathode layers, was evaluated though the detailed electrochemical characterization.

Experimental MEAs with varied Pt-loading in cathode layers, such as 0.05, 0.10, 0.15, 0.20, 0.30, and 0.40 mg/cm2, were prepared, while the amount of Pt in anode layers were kept to 0.30 mg/cm2. Then, their performances were evaluated by measuring the IV response, impedance, and Hupd electric charge. Also, the cross-sections of cathode layers were observed by FIB-SEM.

Results and discussion From IR-corrected IV curves, activation overvoltage was separately analyzed. Activation overvoltage was clearly proportional to Pt-loading in the region of 0.05 - 0.15 (0.20) mg Pt/cm2, but did not change much in 0.15 (0.20) - 0.40 mg Pt/cm2. Therefore, further with ECSA analyses, the minimum amount of Pt needed for the cathode layer was determined to 0.15 - 0.20 mg Pt/cm2 in this experimental condition. Interestingly, concentration overvoltage increased with decrease in the amount of Pt. In this case, since the amount of carbon decreased, the thickness of cathode layers resulted in decreasing. Possible reasons for this phenomenon can be explained in Figure 1. Although the shorter pathway for fuel diffusion is expected to reduce concentration overvoltage, the blockage of the pathway by water produced during the fuel cell reaction should also be considered. If the same amount of water is produced in catalyst layers with the different thickness, the path is more easily blocked in the thinner layer, leading to higher concentration overvoltage. Therefore, optimization of the cathode layer thickness is also an important factor to design better PEFCs. Accordingly, we will report the approach to develop highly efficient MEAs using the minimum amount of Pt and also reducing concentration overvoltage through controlling the amount of carbon.
References
(1) M. Lee, M. Uchida, D. A. Tryk, H. Uchida, M. Watanabe, Electrochim, Acta, 56 4783 (2011).
(2) K. Takahashi, K. Kakinuma, M. Uchida, J. Electrochem. Soc. 163.(10) F1182 (2016)

Figure 1