bluuebunny/crossref_metadata_2025_split huggingface dataset:
Testing of Large Format Lower Temperature SOFCs and Stacks with Hydrocarbon Fuels
Authors: Blackburn Bryan M. , Yoon Hee Sung , Gore Colin M. , Wachsman Eric D. 
Published: February 2020

Redox Power Systems and the University of Maryland Energy Research Center have been developing lower temperature solid oxide fuel cell (SOFC) stacks and systems for a variety of applications.
In this work, results will be presented from single cell and short stack testing using reformate mixtures consisting of CH4, H2, CO, CO2, and steam. Tests utilized large format (approximately 10 cm by 10 cm) cells based on GDC electrolytes with an active area of ~80 cm2. Current-voltage characteristics and impedance spectroscopy data were collected at various currents using electronic load and potentiostat/FRA equipment. Additionally, gas compositions in the fuel exhaust stream were determined using gas chromatography.
Initial results at 650 °C showed a single cell power of ~53 W running on hydrogen and ~51 W running on 100% reformate slip (~21% CH4). Long term test results using a constant applied load of 18 A for a 2 cell short stack showed no evidence of coking even when run on 50% CH4/50% H2O for ~50 hours and 97% CH4/3% H2O for ~150 hours. Additional long term test results will be presented along with a study on degradation.
Impact of Leakage Current on Performance of Solid Oxide Fuel Cell Stacks with Gadolinia-Doped Ceria Electrolytes
Authors: Wang Lei , Jackson Gregory S. , Blackburn Bryan M. 
Published: February 2020

Gadolinia-doped ceria (GDC) has been studied as an electrolyte material for solid oxide fuel cells (SOFCs) at intermediate temperatures (500–650°C) due to its high oxide-ion conductivity and better compatibility with high-activity lanthanum strontium cobalt ferrite (LSCF) cathodes. Recent studies have shown high surface activity for fuel oxidation and suppression of carbon deposition in GDC-based SOFC anodes due to mixed ionic and electronic conductivity (MIEC) at the reducing environments1, 2. On the other hand, the MIEC behavior results in deleterious leakage (electronic) current, which reduces the open circuit voltage (OCV) and SOFC stack efficiency during operation3. The electronic current depends strongly on electrolyte thickness and external current load. In this study, a 3-D model has been developed in COMSOL which calculates the leakage current through GDC-based electrolytes and evaluates its impact on the cell OCV and overall performance of an GDC-based SOFC stack operating from 550 to 650°C.
The model incorporates both ionic and electronic current in the GDC electrolyte driving by the electrochemical gradient. The model employs irreversible electrodes and allows for a nonlinear potential distribution across the electrolyte to capture the distribution of oxygen defect concentrations following the work of Duncan et al3. In the current study, the model is used to analyze the relationship between leakage current and electrolyte thickness for a full stack cell wherein the conditions and effective oxygen partial pressure P
O2 can vary significantly particularly in the anode channels. Figure 1 plots average ionic, electronic, and total current density as a function of cell voltage for a cell with a 20 µm GDC electrolyte operating at 600°C. OCV deviation from theoretical value due to electrode/electrolyte interfaces overpotentials and Ohmic losses contributed by the ionic and electronic current. The effect of the leakage current on stack performance and efficiency provides a basis for understanding how fuel oxidation due to the leakage current impacts the relationship between stack current and fuel utilization. Results provide guidance for designing high-performance intermediate-temperature SOFCs with GDC electrolytes.
References
1. S. Baron, N. Brandon, A. Atkinson, B. Steele, and R. Rudkin, Journal of Power Sources, 126(1-2), pp. 58-66 (2004).
2. T. Nakamura, T. Kobayashi, K. Yashiro, A. Kaimai, T. Otake, K. Sato, J. Mizusaki, and T. Kawada, Journal of the Electrochemical Society, 155(6), pp. B563-B569 (2008).
3. K.L. Duncan, and E.D. Wachsman, Journal of the Electrochemical Society, 156(9), pp. B1030-B1038 (2009).
Incorporation of the Stefan-Maxwell Multicomponent Diffusion Model into a Pore Network Model of the PEMFC Electrode
Authors: Aghighi Mahmoudreza , Gostick Jeff T. 
Published: February 2020

Polymer electrolyte membrane fuel cells are one of the best candidates to replace internal combustion engines. The key requirement for commercial success of PEMFCs is to demonstrate optimal performance at high current density. However, because of liquid water generation, the power density is reduced by mass transport limitations at the cathode. Accordingly, precise modeling of mass transfer inside the porous structure of fuel cell electrodes is crucial.
Ordinary diffusion is the most commonly considered diffusion model for PEMFC in the literature. In most of these studies, the gas transport is considered as a binary system of oxygen diffusing through nitrogen (and sometimes water vapor). However, realistic simulation of fuel cell operation requires simultaneous modeling of both oxygen and water vapor transport in a stagnant film of nitrogen. In multicomponent diffusion, the fluxes of all of the species are important to consider since they might affect the diffusive transport of the other species.
A pore network modeling has been developed using the Stefan-Maxwell approach, to simulate the diffusion of gases mixtures inside fuel cell electrodes. Pore network models (PNM) provide an alternative approach for the continuum modeling in porous media. Rather than using finite element models of transport in the pore space, PNMs use pore-to-pore nodal balances to model species transport. They also enable the structural properties of the porous material to be incorporated directly into the model, rather than through constitutive relationships.
The SM model is notoriously difficult to solve numerically for pore networks, but some simplifications and solution schemes have been proposed in the literature [1,2] based on decomposing Jacobian matrix of the equations, which are less computationally expensive. In this work, these methods have been evaluated to determine an appropriate solution algorithm for the pore network. These advantages come at the expense of rigorous transport phenomena calculations since some simplification to the SM model are made.

References

1. Wood, J., L. Gladden, and F. Keil, Chemical Engineering Science, 2002. 57(15): p. 3047-3059.
2. Rieckmann, C. and F.J. Keil, 1997. 36(8): p. 3275-3281.

Acknowledgements

This work was funded by AFCC and the NSERC CRD program.
Characteristics of Pd-Pt Nanoparticles with Core-Shell Structure on Polybenzimidazole-Wrapped Graphene for Fuel Cell Electrocatalyst
Authors: Kim Chaerin , Fujigaya Tsuyohiko , Nakashima Naotoshi 
Published: February 2020

Introduction

Pt has received unremitting interest in the proton-exchange polymer electrolyte fuel cell (PEFC) technology as electrocatalysts for both the hydrogen oxidation and oxygen reduction reactions [1]. However high cost limits its application and the reduction of the amount of Pt in the catalyst is required (it was ca. 48.83 $ per gram at the beginning of 2014) [2].To reduce the usage of Pt, arranging Pt as shell on proper metal core is promising “core-shell approach”. This strategy is attractive and practical because only the outmost few layers of Pt atoms in a catalyst are actually needed in facilitating a reaction while most atoms in the bulk are more or less wasted [3, 4]. Among various metal, we chose Pd as a core metal due to the stability under strong acidic condition in PEFC [5]. Here, we attached Pd-Pt core-shell nanoparticles on Graphene which are ideal materials as conductive supporting due to the large surface area, remarkable electric conductivity and excellent electrochemical durability. This study, we utilize polybenzimidazole (PBI) as a polymeric anchor to load Pd-Pt core-shell nanoparticles on to the surface of Graphene.

Experiments

Graphene wrapped with PBI (Graphene/PBI) (5.0 mg) was added to a 60-vol% aqueous ethylene glycol (EG) solution (20 mL) and dispersed by sonication. Pd (OAc)2 (3.3 mg) dissolved in the methanol (5.0 mL) was added to the Graphene/PBI dispersion, and then the mixture was heated at room temperature for 3 h. H2PtCl6 •6 H2O (0.45 mg) dissolved in a 60 vol% aqueous EG solution (20 mL) was added to the Graphene/PBI/Pd dispersion and the mixture was stirring for room temperature for 24 h. The solid material was collected by filtration and washed with water and then dried under vacuum to obtain Graphene/PBI/Pd-Pt (Figure 1).

Results and Discussion

To inspect the structure of Pd-Pt core-shell nanoparticles, we observed scanning transmission electron microscopy (STEM). STEM operated at 200 kV are presented in Figure 2.
Figures 2a and 2b show the STEM image of a Graphene/PBI/Pd-Pt. Figures 2c and 2d show the EDS mapping of Pd (red) and Pt (blue). It is obvious that Pd is surrounded by Pt as indicated in overlay (Figure 2e). The results strongly indicate the successful formation of Pd-Pt core-shell structure on Graphene/PBI.

Conclusions

We fabricated Graphene/PBI/Pd-Pt core-shell composite. STEM results indicate that the Graphene /PBI/Pd-Pt core-shell catalyst exhibited the core-shell nanostructure.

References

N. Nakashima et. al,
Adv. Funct. Mater
. 18, 1776 (2008)

T.Fujigaya et. al,
Adv. Mater. 25,1666–1681(2013)

R. R. Adzic et. al,

Angew. Chem. Int. Ed.
49, 8602 (2010)

Y. Xia et. al.
Science

.
324, 1302 (2009)

Y. Xia et. al.
Chem. Soc. Rev.

41, 8035-8049 (2012)
Performance Variation of Flexible Polymer Electrolyte Fuel Cell with Ag Nanowire Current Collector under Torsion
Authors: Park Taehyun , Chang Ikwhang , Lee Jinhwan , Ko Seung Hwan , Cha Suk Won 
Published: February 2020

The purpose of flexible and bendable fuel cell is to support future electronics, wearable electronics for example, which require more electrical energy than current portable electronics. As widely used lithium-ion battery technology is converging to its maximum ideal energy density, it is inevitable to find other solutions to cope with the increase of energy consumption of developing electronics. In addition, one of the most highlighted electronics in future is wearable electronic device. It has different characteristic that it requires flexibility and bendability. For this reason, flexible polymer electrolyte fuel cell (PEFC) was researched in our previous report [1]. Here, electrochemical performances of the cell were evaluated under bent position and decreasing tendency of the maximum power density was observed with increase of bending. However, the performances of flexible PEFC under various positions, torsion for example, should also be evaluated in order to investigate if it is possible to operate in fully bendable electronics such as wearable electronics.
This study shows the performance variation of flexible PEFC under torsion. Ag nanowires percolation network which can be stretched upto strain of 370% with less than 30 % increase of electrical resistance was adopted as material for current collector [2]. Polydimethylsiloxane (PDMS) was used to fabricate bendable fuel cell stack. Cross-sectional sizes of flow channels on flow-field plates for anode and cathode were 1 x 1 mm2 and 2 x 1 mm2, respectively. Degrees of torsion were 0, 5, 10, 15 and 20°. The results showed that maximum power density of flexible PEFC decreases as torsion increases. From the previous results [1], it is speculated that compressive stress perpendicular to membrane-electrode assembly (MEA) decreased with increase of torsion degree. In order to investigate causes of performance loss, electrochemical impedance spectra were measured. It showed that ohmic and faradaic resistances of the cell increased with increase of torsion. It corresponds with the previous results that ohmic and faradaic resistances increase when normal compressive stress to MEA decrease. However, it was found that decreased percentage of maximum performance of the cell was less than 35 %, meaning that flexible PEFC can be used for flexible electronic devices if overdesigned.

Acknowledgement

This work was supported by the Global Frontier R&D Program on Center for Multiscale Energy System funded by the National Research Foundation under the Ministry of Education, Science and Technology, Korea (2011-0031569).

Reference

[1] I. Chang et al., Bendable polymer electrolyte fuel cell using highly flexible Ag nanowire percolation network current collectors, J. Mater. Chem. A, 2013, 1, 8541-8546.
[2] P. Lee et al., Highly Stretchable and Highly Conductive Metal Electrode by Very Long Metal Nanowire Percolation Network, Adv. Mater., 2012, 24, 3326-3332.
Potentiality of Hydrocarbon Membrane for Durability Improvement of Pt and PtCo Alloy Catalyst and Pt Loading Reduction
Authors: Izuhara Daisuke , Umeda Hiroaki , Ito Yumiko , Shintaku Yuta , Adachi Shinya 
Published: February 2020

One of the major cost drivers in polymer electrolyte fuel cells (PEFCs), particularly for automotive application, is the use of platinum-based electrodes to facilitate electrochemical reactions such as hydrogen oxidation and oxygen reduction. Improving the durability of Pt and PtCo alloy catalyst shall reduce total active area and/or Pt loading per unit active area without any sacrifice in performance of fuel cell stacks, and it can also significantly be beneficial to the reduction of total Pt usage on fuel cell vehicles (FCVs). Catalyst durability during fuel cell operation remains a key challenge to developing the fuel cell system with acceptable overall cost in automotive applications.
Toray has been developing advanced hydrocarbon (HC) membranes to give a better total solution in terms of overall cost reduction of fuel cell systems, which includes i) the potentiality for durability improvement of Pt and PtCo alloy catalyst and Pt loading reduction due to less Pt particle dissolution, ii) no emission of super acids such as HF and perfluorosulfonic acids, iii) low gas crossover, and iv) environmental friendliness, in comparison with conventional PFSA membranes.
We will describe in the meeting that Toray HC membrane would potentially improve the durability of PtCo alloy catalyst owing to less Pt particle dissolution, and thereby reduce total active area and/or Pt loading per unit active area by 45% ((1-0.24V/0.43V)x100) vs Nafion HP as a reference in case judging at 1000 hours in the accelerated chemical and mechanical durability test. We hope Toray HC membranes could help to form a pathway toward FCV wide commercialization.
ACKNOWLEDGEMENT
This work was partially supported by the New Energy and Industrial Technology Development Organization (NEDO) of Japan.
Analysis of the Electrochemical Performance of Ptni/MWCNT in Alkaline Media
Authors: Valenzuela-Muñiz Ana Maria , Alonso-Lemus Ivonne , Escobar Beatriz , Verde Gomez Ysmael 
Published: February 2020

It is well known that the outstanding properties and characteristics of multi-walled carbon nanotubes (MWCNT) make them attractive materials for diverse applications. For electrocatalytic systems, MWCNT are being exhaustively studied all over the world, and it is been corroborated that this type of materials are appropriate to be used as support of metallic nanoparticles, having a synergistic effect in the electroactivity. However, it has been found also that the MWCNT characteristics as quality (graphitization grade) and purity (amount of amorphous carbon) have a direct influence on the metal anchorage, the electrocatalytic activity as well as the stability. On the other hand, Pt-Ni system is attracting the attention in recent years for its application as PEM fuel cell electrode. The addition of a non-noble metal (Ni in this case) could decrease the cost of the electrocatalyst as well as improve the performance. The research group involved in the present work has been working during years in the design and synthesis of PtNi/MWCNT electrocatalysts using homemade MWCNT of high quality and purity, and analyzing their performance in acidic media for the application in PEM fuel cells. The obtained results are interesting and promising, high activities have been achieved as well as good stability. Nevertheless, in order to diversify the applications, as well as have a complete understanding of the PtNi/MWCNT systems, studies in alkaline media are necessary. Hence, the aim of this paper was to study the electrochemical performance in alkaline media of PtNi/MWCNT homemade electrocatalysts towards the PEM fuel cell reactions. In order to achieve this goal, the studies were performed in a conventional three electrodes cell, using a glassy carbon rod as working electrode, a Pt wire as counter electrode, a Ag/AgCl (KCl Sat) electrode as reference, and 1M NaOH solution as electrolyte. The interesting results obtained as well as the discussion will be presented at the conference.
Acknowledgments: Authors recognize the support to FOMIX-QRoo under grant no. QR00-2011-001-174895
Glycerol Electrooxidation on Well-Shaped Pd Nanoparticles Modified By Bi-Adatoms
Authors: Coutanceau Christophe , Zalineeva Anna , Baranton Stève 
Published: February 2020

The electrochemical conversion of glycerol gains more and more attention because glycerol is a by-product of biofuel industries, and for its potency for electric energy or hydrogen and added-value-chemical cogeneration [1]. Due to complex oxidation pathways a large number of useful chemicals may be produced [2]. The control of activity and selectivity can be provided by the electrode potential and the formulation of electrocatalysts. In alkaline medium, palladium is a catalytic metal active for the electrooxidation of small organic molecules [3–5]. Many electrocatalytic reactions on Pd surface are known to be structure sensitive [6,7]. The activity and selectivity of Pd catalysts can also be tuned by modification with p-group atoms, such as Bi [8,9]. Moreover, it has been proposed that the structure of the electrodes (unsupported, self-supported or carbon supported Pd-Bi catalysts) has an important effect on the electrocatalytic behavior, influencing the activity as well as the selectivity of the reaction.
Here, the synthesis of preferentially-shaped Pd nanoparticles, their physico-chemical characterization and their surface modification by spontaneous bismuth adsorption are described, as well as their activity towards glycerol electro-oxidation.
In order to better, understand the role of palladium surface and bismuth modification on polyol oxidation, electrochemical measurements have been carried out on palladium nanocubes and nanooctahedrons with high amount of {100} and {111} surface nanodomains, respectively, and nanospheres without preferential surface orientation. Glycerol electrooxidation has been studied and compared on both nanoparticles, before and after modification by Bi adatoms; in situ infrared spectroscopy measurements of glycerol electrooxidation on Bi-modified Pd surfaces were also performed to determine adsorbed intermediates and reaction products versus Bi surface coverage.
1- M. Simoes, S. Baranton, C. Coutanceau, ChemSusChem 5 (2012) 2106.
2- A. Behr, J. Eilting, K. Irawadi, J. Leschinski, F. Lindner, Green Chemistry 10 (2008) 13.
3- C. Bianchini, P.K. Shen, Chemical Reviews 109 (2009) 4183.
4- E. Antolini, Energy & Environmental Science 2 (2009) 915.
5- M. Simoes, S. Baranton, C. Coutanceau, Applied Catalysis B: Environmental 93 (2010) 354.
6- F.J. Vidal-Iglesias, R.M. Aran-Ais, J. Solla-Gullon, E. Garnier, E. Herrero, A. Aldaz, J.M.
Feliu, Physical Chemistry Chemical Physics 14 (2012) 10258.
7- M. Shao, J. Odell,M.Humbert, T. Yu, Y. Xia, Journal of Physical Chemistry C 117 (2013) 4172.
8- M. Simoes, S. Baranton, C. Coutanceau, Applied Catalysis B: Environmental 110 (2011) 40.
9- A. Zalineeva, S. Baranton, C. Coutanceau, Electrochem. Comm. 34 (2013) 335.
Pd-Based Bimetallic and Trimetallic Catalyst for Direct Formic Acid Fuel Cells
Authors: Hu Shuozhen , Noborikawa Jennifer , Haan John , Scudiero Louis , Ha Su 
Published: February 2020

Direct formic acid fuel cell (DFAFC) has generated great attraction in the field of energy systems, especially when it combines with carbon dioxide (CO2) electrochemical reduction unit. This whole system is referred as regenerative direct formic acid fuel cell. In regenerative DFAFCs, formic acid is oxidized at the anode of fuel cell to produce electricity along with CO2 and water (H2O). These CO2 and H2O then can be reduced to formic acid through an electrochemical reduction process using renewable energy sources, such as solar energy or wind energy. Therefore, the CO2-derived fuels hold interesting prospects for future energy systems based on non-fossil energy sources. In the regenerative DFAFC system, formic acid is used as the energy carrier and it is important to efficiently oxidize formic acid at the fuel cell’s anode to achieve a high system performance. Among the anode catalysts, Pd-based bimetallic or trimetallic catalysts have attracted a lot attention due to their better activity and stability than pure Pd toward formic acid oxidation [1-3]. In addition, the lower cost due to the use of less expensive transition metals makes these Pd-based bimetallic catalysts promising material for developing cheaper DFAFC.
In this study, we synthesize PdCu/C and PdNi/C alloys via metal salt reduction method. The nominal atomic ratio of Pd:Cu and Pd:Ni is 3:1. TEM images shows the particle sizes are about 5 nm, 7 nm, and 6 nm for Pd/C, PdCu/C and PdNi/C, respectively. Then, PdCu/C and PdNi/C are physically mixed by weight ratio of 1:1 and annealed at 400 °C in Ar. To make comparison, PdCu/C and PdNi/C are also annealed at the same condition separately. Cyclic voltammetry results indicate that, before annealing, PdCu/C shows the best activity toward formic acid oxidation (See Figure 1 (a)). When the samples are annealed at 400 °C, both the PdCu/C and physical mixture samples show the activity enhancements, while the activity of PdNi/C sample is not affected by the annealing process, as shown in Figure 1 (b). Based on the CV data, it is clear that the physical mixture sample is most affected by the annealing process as it shows the most activity enhancement. Consequently, after the annealing process, the physical mixture sample shows the best activity. For an example, at 0.1V (vs. Ag/AgCl), the annealed physical mixture sample shows the current density of 2.71 mA/cm2, which is a factor of 1.5 higher than that of annealed PdCu/C sample. To investigate the effect of the annealing process to different samples and their electrochemical activity toward the formic acid oxidation, TEM and X-ray photoelectron spectroscopy are used.

References

1. Suo, Y. G., Hsing, I. M., Electrochimica Acta, 2011, 56 (5): p. 2174-2183.
2. Dai, L., Zou, S. Z., Journal of Power Sources, 2011, 196 (22): p. 9369-9372.
3. Du, C. Y., Chen, M., Wang, W. G., Yin, G. P., Acs Applied Materials & Interfaces, 2011, 3 (2): p. 105-109.