bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effect of Ionomer Content and Relative Humidity on IT-PEMFC Performances at 120 oc
Authors: Cho Min Kyung , Park Hee-Young , Cha In Young , Lee So Young , Yoo Sung Jong , Kim Hyoung-Juhn , Han Jonghee , Nam Suk Woo , Sung Yung-Eun , Jang Jong Hyun 
Published: February 2020

Due to its higher operating temperature (100 -120oC), intermediate temperature PEMFC (IT-PEMFC) is expected to provide improved heat and water management, CO tolerance, and electrode reaction kinetics. The previous researches regarding IT–PEMFCs have been focused on the material developments: proton exchange membranes and electrocatalysts, to achieve high performance and durability at elevated temperatures.
Maintaining hydration of membrane electrode assemblies (MEAs) to provide sufficient conductivity is one of the key issues in IT-PEMFC operation. When pressurized air feed is supplied with low humidity and high temperature, the sulfonated polymer membranes can be easily dried and, as a result, cell performances can be decreased severely. Therefore, the optimization of catalyst layer would be also very important, in order to achieve acceptable performances under unique operation conditions of IT-PEMFCs. However, there have been only reports regarding catalyst optimization of IT-PEMFC (1) (2). For conventional PEMFCs (~ 80oC), various groups have reported the effect of ionomer content (3), catalyst loading (4) and electrode thickness (5); but these results cannot be directly utilized to IT-PEMFCs that have much more severe drying problem.
In this study, the effect of ionomer content and relative humidity (RH) of inlet gas on single cell performance are examined under various RHs(10 ~ 35%). For this, MEAs were fabricated with ionomer content from 20 to 40 wt%. The cell performances were characterized through constant current operation and i-V polarization. In addition, impedance analysis was carried out in order to monitor the variation of ohmic resistances under various operating conditions.
References
1. Y. Song, H. Xu, Y. Wei, H. R. Kunz, L. J. Bonville and J. M. Fenton, Journal of Power Sources, 154, 138 (2006).
2. H. Xu, H. R. Kunz, L. J. Bonville and J. M. Fenton, Journal of The Electrochemical Society, 154, B271 (2007).
3. K.-H. Kim, K.-Y. Lee, H.-J. Kim, E. Cho, S.-Y. Lee, T.-H. Lim, S. P. Yoon, I. C. Hwang and J. H. Jang, International Journal of Hydrogen Energy, 35, 2119 (2010).
4. S. H. Ahn, S. Jeon, H.-Y. Park, S.-K. Kim, H.-J. Kim, E. Cho, D. Henkensmeier, S. J. Yoo, S. W. Nam, T.-H. Lim and J. H. Jang, International Journal of Hydrogen Energy.
5. J. W. Lim, Y. H. Cho, M. Ahn, D. Y. Chung, Y. H. Cho, N. Jung, Y. S. Kang, O. H. Kim, M. J. Lee, M. Kim and Y. E. Sung, Journal of the Electrochemical Society, 159, B378 (2012).
Surface Confinement of Oxygen in Carbon Supported Oxygen Reduction Catalysts
Authors: Chlistunoff Jerzy , Sansiñena José-María 
Published: February 2020

In 2011, we reported an oxygen adsorption phenomenon for heat treated, Fe/polyaniline based oxygen reduction catalysts.1 We found that the extent of oxygen adsorption correlated with the surface density of the active sites (Fe-N4 (2+2)) and determined the thermodynamic as well as kinetic parameters associated with the adsorption process.1

In our recent studies on oxygen reduction catalysis by macrocyclic complexes of transition metals such as porphyrins, phthalocyanines and corroles, we found the occurrence of similar phenomena. The surface confined oxygen can be easily detected by voltammetry, as its reduction produces a high reduction peak bearing typical “surface properties”, such as, e.g., the reduction current proportionality to the scan rate or the (approximate) axial symmetry (Fig. 1).
In this work, we compare the surface confinement of oxygen in presence of numerous carbon supported catalysts and their mixtures and conclude that an essential condition for the surface confinement of oxygen is, among others, a graphitic (π-electronic) structure of the catalyst support. This conclusion explains the proportionality between the magnitude of the phenomenon and the density of the active sites in heat treated ORR catalysts,1 where the active sites are believed to be embedded in graphene planes.2,3

Acknowledgement

The financial support from the University of California (grant 12-LR-237440) is gratefully acknowledged.

References

1) J. Chlistunoff, J. Phys. Chem. C, 115, 6496-6507 (2011).
2) M. Lefèvre, J.-P. Dodelet, P. Bertrand, J. Phys. Chem. B, 106, 8705-8713 (2002).
3) M. Lefèvre, E. Proietti, F. Jaouen, J.-P. Dodelet, Science, 324, 71-74 (2009).

Fig. 1. Cyclic voltammetry (100 mV s-1) of oxygen reduction catalyzed by carbon (XC72) supported cobalt phtalocyanine showing the predominantly surface character of the oxygen reduction peak. Catalyst ink composition: 46.5 mg XC72; 0.8 mg CoPC; 8 cm3 isopropanol; 55.9 μl 5% Nafion. Catalyst loading 0.1 mg (for XC72).

Figure 1
Development and Characterization of Membrane and Catalyst Materials for the Cucl(aq)/HC(aq) Electrolytic Cell
Authors: Hall Derek M. , Lotfi Roghayyeh , Kim Soohyun , Lvov Serguei N. 
Published: February 2020

Recent developments in membrane and electrocatalyst characterization techniques for materials used in the CuCl(aq)/HCl(aq) electrolytic cell have significantly increased the amount of experimental data available in literature. Rotating disc electrode (RDE) and membrane conductivity cells capable of operating in highly concentrated HCl(aq) were developed to characterize the material performance of key MEA materials for this electrolytic cell. Specifically, exchange current density and transfer coefficient values for platinum and carbon as the electrocatalyst material for the anode reaction of this electrolytic cell were quantified in highly concentrated HCl(aq)1. Additionally, conductivity and permeability parameters of hot-pressed Nafion 117 were characterized for applications in highly concentrated HCl(aq) and CuCl(aq) solutions2. Though these fundamental properties are now available, there remained a need for a simple model to connect these properties appropriately to overall cell performance. While equilibrium thermodynamics of this electrolytic cell was carefully studied3, the cell electrode kinetics and transport in the membrane have not been modeled yet. Principles of non-equilibrium thermodynamics have the potential to incorporate membrane transport properties and electrochemical kinetic data together into a simple but useful model of this electrolytic cell. The use of linear phenomenological equations with phenomenological coefficients can be used to model the effects of permeability and conductivity on the ohmic resistance of the electrolytic cell. In addition to linear non-equilibrium processes, non-linear nonequilibrium thermodynamic expressions of the electrochemical reactions can be used to model the effects of electrocatalyst properties on the overall cell performance. As a result, suitable electrocatalysts and membrane materials were identified and their effects on the electrolytic cell performance were quantified in the form of a non-equilibrium thermodynamic model.
References:
1. D. M. Hall, E. G. LaRow, R. S. Schatz, J. R. Beck, and S. N. Lvov, J. Electrochem. Soc., 162, F108–F114 (2015).
2. R. Schatz, S. Kim, S. Khurana, M. Fedkin, and S. N. Lvov, ECS Trans., 50, 153–164 (2013).
3. D. M. Hall, N.N. Akinfiev, E. G. LaRow, R. S. Schatz, and S. N. Lvov, Electrochim. Acta, 143, 70-82 (2014).
Electrochemical Performance of 100cm2 Class Direct Carbon-Molten Carbonate Fuel Cell (DC-MCFC)
Authors: Choi Sun Hee , Park Dong-nyeok , Ham Hyung Chul , Yoon Sung-Pil , Han Jonghee , Nam Suk Woo 
Published: February 2020

One of major difficulties in developing direct carbon fuel cells is the high anode polarization in the carbon oxidation, which ultimately leads to the large loss of overall performance in direct carbon fuel cells. The molten carbonates (having the high ionic conductivity and good stability under CO2 environments) have been suggested to deal with this issue because they can facilitate the carbon oxidation by extending the electrochemical reaction sites from three phase boundary of anode to the bulk carbon surface. The molten carbonate fuel cell (MCFC) is the ideal choice for applying such molten carbonates into direct carbon fuel cells. Note that the molten carbonates such as Li2CO3 and K2CO3 are used in the electrolyte material in MCFC. However, the underlying mechanism in operating and developing MCFC-based direct carbon fuel cells is still unclear.
In this work, we present the effect of various operating parameters such as temperature, molten carbonate/carbon ratio and different Ni thin layers inserted between matrix (electrolyte support) and carbon green sheet on the electrochemical performance of 100cm2 class direct carbon - molten carbonate fuel cell (DC-MCFC). In addition, we attempt to understand the oxidation behavior of carbon in wet carbon anode (the composite of carbon and molten carbonates) of DC-MCFC. We find that in DC-MCFC, CO is produced via two electron transfer reaction [C (s) + CO3
-2 → CO2 (g) + CO (g) + 2e-] and is further oxidized with CO3
-2[CO(g) + CO3
-2 → 2CO2 (g) + 2e-] at CCV condition, indicating that CO is responsible for determining the DC-MCFC performance.
(Invited) Imaging and Quantitative Chemical Mapping of PEM-FC Catalyst Layers By Scanning Transmission X-Ray Microscopy
Authors: Hitchcock Adam P 
Published: February 2020

Low temperature, hydrogen-fueled, proton exchange membrane fuel cell (PEM-FC) based engines are being developed rapidly for near-term implementation in mass production, personal automobiles. Materials and process research aiming to further optimize these systems is focused on understanding and controlling various degradation processes (carbon corrosion, Pt migration, cold start), and reducing cost by reducing or eliminating Pt in the electro-catalyst, especially for the oxygen reduction reaction (ORR), and optimizing the nanoscale distribution of the cathode components. Soft X-ray scanning transmission X-ray microscopy (STXM) [1] is a powerful tool to study PEM-FC catalyst layers (membrane electrode assemblies, MEA). STXM provides spectroscopic identification and quantitative mapping of chemical components with 30 nm spatial resolution in both 2D projection and 3D spectro-tomography. For a given radiation dose, it provides much more chemical information than analytical transmission electron microscopy (TEM) and thus it has significant advantages for mapping ionomer in MEA cathodes [2, 3], which has proven to be a very challenging component to detect by TEM due to the high sensitivity of ionomer to radiation damage. This tutorial will describe the instrumentation, methodology and data analysis involved in applying STXM to PEM-FC catalyst layers, and illustrate its capabilities with results from recent studies [4, 5].
STXM performed on BL 10ID1 at the Canadian Light Source and on BL 5.3.2.2 at the Advanced Light Source. Research supported by AFCC, NSERC, Canada Research Chairs, and the Catalyst Research for Polymer Electrolyte Fuel Cells (CaRPE-FC) network.
[1] A.P. Hitchcock, Soft X-ray Imaging and Spectromicroscopy in Handbook on Nanoscopy, eds.G. Van Tendeloo, D. Van Dyck and S. J. Pennycook 2012. (Wiley)
[2] D. Susac, V. Berejnov, A.P. Hitchcock, and J. Stumper, ECS Transactions 41 (2011) 629.
[3] D. Susac, V. Berejnov, A.P. Hitchcock and J. Stumper, ECS Transactions 50 (2012) 405
[4] A.P. Hitchcock, et al., J. Power Sources 266 (2014) 66
[5] V. Lee, et al. J. Power Sources 263 (2014) 163

Figure 1
(Invited) Modeling of and Novel Approaches to Water Management in Polymer Electrolyte Fuel Cells
Authors: Wang Chao-Yang 
Published: February 2020

This lecture will discuss profound importance of water and thermal management in polymer electrolyte fuel cells. The science of water management in fuel cells will be scrutinized in two aspects: macroscopic phenomena and microscopic interfacial phenomena [1-4]. We shall review current advances in fundamental understanding and development of modeling tools for various length scales, as schematically summarized in Figure 1. In addition, we will discuss novel approaches to water management that have emerged most recently.

References

[1] C.Y. Wang, Chem. Rev., 104 (2005) 4727.
[2] P.K. Sinha, P.P. Mukherjee and C.Y. Wang, J. Mat. Chem., 17 (2007) 3089-3103.
[3] T. A. Trabold, J. P. Owejan, J. J. Gagliardo, D. L. Jacobson, D. S. Hussey, and M. Arif, Use of neutron imaging for proton exchange membrane fuel cell (PEMFC) performance analysis and design, in Handbook of Fuel Cells, Eds. W. Vielstich, A. Lamm and H. Gasteiger, Wiley and Sons Ltd., Vol.6, 2009.
[4] U. Pasaogullari and C.Y. Wang, Modeling and Diagnostics of Polymer Electrolyte Fuel Cells, in Modern Aspects of Electrochemistry, Springer, 2009.

Figure 1
(Invited) Combinatorial Study of Fundamental Electrocatalyst Performance - the Scanning Flow Cell Coupled to Online Analytics
Authors: Cherevko Serhiy , Schuppert Anna K. , Grote Jan-Philip , Geiger Simon , Zeradjanin Aleksandar R. , Keeley Gareth , Mayrhofer Karl J.J. 
Published: February 2020

Continuous electrochemical flow reactors for efficient conversion of electrical energy into chemicals and vice versa, i.e. fuel cells and electrolyzers, become increasingly important for our energy sustainability and environmental concerns. One bottleneck for the commercialization are the electrocatalyst materials, which constitute the core of electrochemical energy conversion devices. While the optimization of kinetic activity of catalysts and efficiency of whole cells has been widely explored, the highly important stability of the materials and selectivity for reactions has often been neglected. In this presentation I will demonstrate how fundamental investigations of electrocatalyst activity, stability and selectivity can be performed online and in parallel, and what can be learned from these studies for large scale applications. The focus will be on the recent methodological developments from our group, in particular the scanning flow cell (SFC) coupled to online analytics, which also allows for combinatorial analysis. The potential of this approach will be demonstrated by results on the essential oxygen electrochemistry on noble metal catalysts as used in low-temperature fuel cells and electrolysers.

1. Katsounaros, I.; Cherevko, S.; Zeradjanin, A.R.; Mayrhofer, K.J.J.; Oxygen Electrochemistry as a Cornerstone for Sustainable Energy Conversion; Angewandte Chemie – International Edition 2014, 53, 102 – 121.

2. Topalov, A.A.; Cherevko, S.; Zeradjanin, A.R.; Meier, J.C.; Katsounaros, I.; Mayrhofer, K.J.J.; Towards a comprehensive understanding of platinum dissolution in acidic media; Chemical Science, 2014, 5, 631-638.

3. Cherevko, S.; Topalov, A.A.; Zeradjanin, A.R.; Katsounaros, I.; Mayrhofer, K.J.J.; Gold dissolution: towards understanding of noble metal corrosion; RSC Advances 2013, 3, 16516-16527.
Anodic Olefin Coupling Reactions: Controlling the Reaction Pathways of Radical Cation Intermediates and Efforts Toward Artemisolide
Authors: Perkins Robert J , Moeller Kevin D 
Published: February 2020

Intramolecular anodic olefin coupling reactions provide a useful method to quickly construct complex ring systems. These reactions have been shown to be compatible with a range of nucleophiles to form a variety of cyclic compounds while conserving or increasing the functionality of the original substrate.
Though a powerful synthetic tool, anodic olefin coupling reactions do not always proceed well. Radical cations are very reactive intermediates and are thus susceptible to side reactions such as eliminations and polymerization. When the desired intramolecular cyclization is relatively slow, these side reactions outcompete cyclized product formation entirely. Two examples are provided in Scheme 1.1,2 In the first example, simultaneous formation of a 6-membered ring and a quaternary carbon using an allyl silane as a trapping nucleophile led to only elimination products along with other general decomposition. The same problem presents itself in the second example, where the coupling of a furan and enol ether to form a 7-membered ring is too slow to compete with the elimination.
To circumvent this problem, new methodology is being developed that incorporates an additional nucleophile into the electrolysis substrate to allow intramolecular trapping of both ends of the radical cation.3 By tethering an extra alcohol nucleophile to the end of an enol ether to quickly trap the radical cation, cationic decomposition pathways can be avoided, allowing for the desired cyclization occur (Scheme 2).
In the talk to be presented, the development of this methodology will be discussed along with ongoing efforts to apply this methodology towards the synthesis of the 5:7:5-fused core skeleton of the natural product Artemisolide.
References:
1. Tinao-Wooldridge, L.V.; Moeller, K.D.; Hudson, C.M. J. Org. Chem.
1994, 59, 238
2. Redden, A.; Moeller, K.D. Org. Lett.
2011, 13, 1678.
3. Redden, A.; Perkins, R.J.; Moeller, K.D. Angew. Chem. Int. Ed.
2013, 52, 12865.

Figure 1
Modeling Two-Phase Transport on the PEM Water Electrolyzer
Authors: Han Bo , Steen Stuart M. , Mo Jingke , Zhang Feng-Yuan 
Published: February 2020

Understanding multi-phase and multi-component transport in a porous electrode plays a crucial role in optimizing the actual electrode structures and maintaining the performance of a polymer electrolyte membrane (PEM) water electrolyzer, which has attracted more attention for renewable energy storage and hydrogen production due to its higher efficiency/density and a more compact design. Since the electrode microstructure and transport mechanisms of a PEM water electrolyzer is quite complex, until recently, it has been very difficult to provide a comprehensive understanding of these mechanisms. Although some experiments and few simple numerical models have been carried out for investigating the two-phase transport phenomena in a PEM water electrolyzer, many fundamental issues still remain, particularly concerning the effects of gas-liquid two-phase transport inside porous liquid/gas diffusion layer (LGDL) with various surface wetting properties, pore structures on the electrolyzer performance.
In this study, a comprehensive two-phase transport model has been developed as an efficient numerical scheme for direct modeling the effects of two-phase transport on the electrolyzer performance, particularly for liquid water and oxygen transport in the anode porous gas diffusion layer. The liquid water saturations are found to decrease significantly along the LGDL thickness direction with larger contact angles. But for smaller contact angles, the saturation values along the LGDL thickness direction are almost identical. Further numerical results for the gas-liquid two-phase transport behaviors and electrolyzer performance with effects of LGDL pore morphology will also be presented. Results obtained from the present model will provide fundamental understandings of gas-liquid transport behaviors in a porous electrode and can be employed as the useful information to design and optimize the electrode microstructure and improve the performance of PEM water electrolyzers.
Model-Based Regional Comparison of Autonomy and Battery Utilization of Energy Storage Integration with Solar Power
Authors: Lawder Matthew T , Subramanian Venkat R. 
Published: February 2020

For intermittent renewable energy sources to be utilized beyond small penetration levels in the electric grid they must be coupled with some form of energy storage (see Figure 1). Solar power varies on two time scales. Solar trends vary seasonally, but instantaneous solar power can also vary on a minute-to minute basis because of cloud cover. This variability creates a need for a flexible form of energy storage.
We used a model-based approach to study the autonomy (the percentage of time the system meets demand) and battery utilization (amount of capacity used) of a battery system tied to solar generation during yearly operation.1 Along with the variation in solar insolation seen throughout the year, we include a demand schedule which allows for different system load demands to be studied. Including demand allows for the study of different types of grid systems ranging from regional utility scale to Microgrid scale. In the study we look at Microgrid systems which include energy storage and distributed energy generation2 and include both islanded and grid-tied demand structures. Grid charging options have been incorporated into the study and allow for an economic analysis of battery utilization strategies.
We used an electrochemical and transport based battery model battery model for the energy storage aspect of the system.3 For the solar portion of the model we will assess both ideal insolation curves as well as site based insolation data. For the real-site data, several solar monitoring sites within the US were studied. The real data from solar sites was obtained through an NREL database and will offer a contrasting look at how much the coupled system can be affected on a daily and seasonal basis.4

Comparisons for solar charging versus grid charging will be studied from an autonomy, utilization, and economic stand-point. System wide metrics will be used to assess the system’s operation.

Acknowledgements

The authors acknowledge financial support from the Solar Energy Research Institute in India and the United States (SERIIUS), as well as, Washington University in St. Louis’ McDonnell Academy Global Energy and Environmental Partnership (MAGEEP).

References

1. C. Protogeropoulos, B. J. Brinkworth, and R. H. Marshall, International Journal of Energy Research,
21, (1997)
2. R. H. Lasseter, Journal of Energy Engineering-Asce,
133, (2007)
3. S. Santhanagopalan, Q. Z. Guo, P. Ramadass, and R. E. White, Journal of Power Sources,
156, 620(2006)
4. National Renewable Energy Laboratory. (2013). Solar Resource Data. Available: http://www.nrel.gov/rredc/solar_data.html

Figure 1