bluuebunny/crossref_metadata_2025_split huggingface dataset:
Temperature Dependent Mechanical Behavior of Perfluorosolfonic Acid Membranes for Electrochemical Applications
Authors: Arthurs Claire , Kusoglu Ahmet 
Published: February 2020

Perfluorosulfonic acid (PFSA) membranes are the prototypical solid-electrolyte used in electrochemical devices such as polymer-electrolyte membrane fuel cells (PEMFCs) and electrolyzers [1]. To be commercially viable, polymer-electrolyte membranes (PEMs) in PEMFCs and electrolyzers must perform over a long operational time in both dry and wet environments. The ionic conductivity of PFSA membranes can be optimized by changing thickness, material (ionomer chemistry), and pretreatment to increase the ionic conductivity, and reduce power losses, thus improving cell efficiency. However, any effort to improve the transport functionality tends to undermine the membrane’s mechanical stability. [2] Therefore, a key challenge in PEM design is to improve transport of ions without compromising mechanical integrity and characterize the factors influencing mechanical stability of these materials in controlled environments.
Most past studies on the mechanical properties of PFSA membranes investigated only tension [2], although there are some exceptions [3][4]. Compression testing, however, is critical for understanding membrane behavior in electrochemical devices. For example, in fuel cells, hydration-related swelling of a constrained membrane generates partially reversed cyclic stresses, whereas in electrolyzers, PEMS undergo static compression as high as 40 MPa. Cyclic stresses combined with a harsh chemical environment make the PEMs susceptible to failure such as pinhole formation as well as crack initiation and propagation. High static stresses make creep response a great concern. To investigate how temperature and hydration state affect the membrane’s mechanical behavior and properties under compression in-situ, a compression setup with temperature control was used. PFSA membranes of varying chemistry, equivalent weight, thickness (from 50 to 200 µm), and thermal pretreatments were tested. Our results show that the mechanical behavior of PFSA membranes is different under compression than tension. Uniaxial compression and creep tests indicate that the PFSA membranes exhibit time-dependent nonlinear response over long periods of time. This work demonstrates the importance of studying the mechanical properties of these membranes under compression, which is more relevant for the various stress-states the membrane undergoes during operation.

Odgaard, M., Advanced Fluoride-Based Materials for Energy Conversion, in Advanced Fluoride-Based Materials for Energy Conversion. 2015, Elsevier. p. 325-374.

Kusoglu, A. and A.Z. Weber, New Insights into Perfluorinated Sulfonic-Acid Ionomers. Chemical Reviews, 2017. 117(3): p. 987-1104.

Kusoglu, A., et al., Effect of compression on PFSA-ionomer morphology and predicted conductivity changes. Journal of Membrane Science, 2012. 421(0): p. 283-291.

Kusoglu, A., et al., Role of Mechanical Factors in Controlling the Structure–Function Relationship of PFSA Ionomers. Macromolecules, 2012. 45(18): p. 7467-7476.
Capturing Hydroxyl Radical Generated from Oxygen Reduction on Fe/N/C Catalyst By Fluorescence Detection
Authors: Chen Lina , Tian Na , Zhou Zhiyou , Sun Shigang 
Published: February 2020

Low-cost ternary Fe/N/C catalyst has been considered as the most promising candidate to replace Pt for oxygen reduction reaction (ORR) in fuel cells. However, poor stability of Fe/N/C catalyst severely hampers its applications. A widely accepted mechanism for the instability of Fe/N/C catalysts is the oxidative attack by reactive oxygen species, especially by aggressive •OH radical. The •OH is speculated mainly via the decomposition of H2O2 intermediate through Fenton’s reaction. However, there are few reports about direct detection, especially quantitatively analysis of •OH radical during ORR on pyrolyzed Fe/N/C catalysts. The exact mechanism for generating •OH is unclear yet.
In this study, we use coumarin as a fluorescent probe to detect •OH generated from ORR on Fe/N/C catalyst. During the Fe/N/C ORR non-fluorescent coumarin will react with the •OH to generate the intense fluorescent 7-hydroxyl coumarin. According to the fluorescent intensity of 7-hydroxyl coumarin, the •OH can be quantitatively analyzed. Meanwhile, this probe molecule is highly specific to •OH radical, and is insensitive to O2, H2O2 and electrochemical oxidation.
We tested the •OH produced by the ORR at different potentials, and investigated its correlation with H2O2 intermediate. As shown in Figure 1, with potential decreased from 0.70 to 0.60 V, the amount of •OH generated from the ORR process on Fe/N/C catalyst increased and then declined, reaching a maximum at 0.65 V. This variation of •OH amount is greatly different from that of H2O2, and the latter increased linearly with decreasing potentials. Our result indicates that •OH is not mainly generated by the H2O2 decomposition.

Figure 1
(Invited) Design of Catalyst Layer Structure for High Fuel Cell Performance
Authors: Lee Seon-Ho , Taning Ahmad Zulfikri , Woo Seunghee , Park Seok-Hee , Yim Sung-Dae 
Published: February 2020

The low Pt electrode is an important research topic for the commercialization of polymer electrolyte fuel cell (PEFC). Platinum nanoparticles act as a catalyst for the fuel cell electrode and promote the oxygen reduction reaction (ORR). In this process, the surface properties and structure of adjacent carbon supports and ionomer binders greatly affect the Pt catalyst. Therefore, the performance of the Pt/C catalyst in the fuel cell electrode is determined not only by the intrinsic activity of the catalyst itself, but also by the interface structure between the ionomer binder and the Pt/C catalyst. It has been reported that the ORR activity of the Pt/C catalyst in the fuel cell electrode is affected by the Pt poisoning of the sulfonic acid group tethered to the Nafion backbone as well as the oxygen permeability of the ionomer binder [1]. The difference in pore characteristics of the carbon support affects the optimum ionomer content [2] and Pt utilizaton [3] in the electrode. The surface properties of the carbon support also affect ionomer distribution and ionomer thickness on the catalyst surface, thereby altering the activity of the catalyst [4]. In spite of recent studies, understanding of complicated physicochemical phenomena in the microstructure of electrode is still very limited.
In this talk, we will discuss the fuel cell performance characteristics based on several electrochemical analyses according to the microstructure control of the catalyst layer. Various functional groups were introduced on the surface of Pt/C catalyst by post treatment and the catalyst layer was prepared to observe the ionomer distribution and ion transport characteristics according to functional groups. In addition, a multilayer catalyst layer having different ionomer contents in the thickness direction of the catalyst layer was prepared using an ultrasonic spraying process, and changes in hydrogen ion transfer and oxygen diffusion transfer characteristics in these catalyst layers were observed in a fuel cell. Finally, the electrochemical properties of the catalyst layer made of the ionomer dispersed in the high-boiling organic solvent will be introduced.
1. V. Yarlagadda, M. K. Carpenter, T. E. Moylan, R. S. Kukreja, R. Koestner, W. Gu, L. Thompson, A. Kongkanand, ACS Energy Lett. 3 (2018) 618.
2. Y. Liu, C. Ji, W. Gu, J. Jorne, H. A. Gasteiger, J. Electrochem. Soc. 158(6) (2011) B614.
3. Y.-C. Park, H. Tokiwa, K. Kakinuma, M. Watanabe, M. Uchida, J. Power Sources 315 (2016) 179.
4. A. Orfanidi, P. Madkikar, H. A. El-Sayed, G. S. Harzer, T. Kratky, H. A. Gasteiger, J. Electrochem. Soc. 164 (2017) F418.
Understanding Stability of the Transition Metal Carbides and Nitrides By Combining Experimental and Computed Thermochemical Properties
Authors: Matanovic Ivana , Garzon Fernando H 
Published: February 2020

Thermochemistry plays a key role in determining durability of the catalysts and catalytic supports, but is also critical in guiding the rational design of synthesis processes that lead to materials with advanced properties [1, 2]. In the last decade computations based on density functional theory have been used as an important tool in the calculation of thermodynamic properties, such as reaction enthalpies, free energies, and heat capacities. In this work we combine experimental thermochemical data available in the HSC Chemistry software and the data obtained using density functional theory calculations to study the stability of various transition metal carbides and nitrides in aqueous media as a function of pH, cell potential, and temperature.
Earth abundant transition metal carbides and nitrides have drawn considerable interest due to their low cost, unique chemical and physical properties, and high catalytic activity for variety of reactions, such as nitrogen electroreduction to ammonia, ammonia decomposition, alcohol electrooxidation, and biomass conversion. We will discuss the thermodynamics directed towards understanding oxidation of transition metal carbides and nitrides at different cell potentials, pH and temperatures. Namely, oxidation of the material will lead to the change in the geometric and electronic structure of the material, which can cause degradation and decrease in the catalytic activity. More specifically, transition metal carbides and nitrides based on molybdenum, iron, vanadium, and nickel will be considered to illustrate the importance of mapping out their stable phase as a function of pH, potential, and temperature. These diagrams can then be used to determine the stability of the materials in the aqueous media and guide the reaction conditions that will ensure highest durability for a targeted application.
[1] S. K. Nayak, A. D. Benavidez, I. Matanovic, and F. H. Garzon, Thermochemical analysis of Mo-C-H systems for synthesis of molybdenum carbides, Thermochim. Acta, 676, 27-32 (2019).
[2] S. K. Nayak, A. D. Benavidez, F. H. Garzon, Facile synthesis of high surface area molybdenum carbide nanoparticles, J. Am. Ceram. Soc., 00: 1– 7 (2018).
In Situ Characterization of Fe-N-C Electrocatalysts Synthesis By XPS and XRD
Authors: Chen Yechuan , Asset Tristan , Kodali Mounika , Artyushkova Kateryna , Atanassov Plamen 
Published: February 2020

As one of the most promising candidates to replace Pt-based electrocatalyst for oxygen reduction reaction in fuel cell, Metal-Nitrogen-Carbon (M-N-C) catalysts, especially Iron-Nitrogen-Carbon (Fe-N-C) materials, have attracted massive research interests in recent years. Typically, there are three main categories of synthesis approaches for Fe-N-C electrocatalyst, based on what chemicals are used as iron and nitrogen precursors: macrocyclic iron complexes, metal-organic frameworks, and various heterocyclic compounds. Despite these different approaches, it is found that numerous purified preliminary Fe-N-C products need further heat treatment to achieve better electrocatalysis performance. However, the reason why heat treatment is efficient, as well as the best parameters such as atmosphere, time and temperature, are still unclear and require intensive characterization for elucidation.
Here, we report in situ XPS for the investigation how carbon environment and nitrogen moieties change, in addition to in situ XRD, on a specific atomic-dispersed Fe-N-C material (made from nicarbazin via sacrificial support method[1]) during high temperature heat treatment. Figure 1 shows the change of surface contents via XPS C 1s and N 1s under ultra-high vacuum. It is found by rising the temperature from room to 750 °C, the graphitic C with a characteristic peak around 284.5 eV decreases from ~50 atomic % to ~20 %, resulting in a more fragmented carbon structure, while sp3 carbon and nitrogen-carbon have an obvious increase. After flash heating to 950 °C (the typical point used in 2nd heat treatment for this electrocatalyst synthesis) and followed cooling back to 150 °C, there is no reversibility of graphitic carbon. For N 1s shown in Figure 1B, comparing initial 150 °C and final 150 °C after cooling, it is found that pyridinic-N content drops from ~20 atomic % to 15%, and pyrrolic-N decreases from ~40 % to 30 % respectively. Meanwhile, metallic/amine nitrogen increases from ~10% to ~15% while graphitic-N/N+ grows from ~7 % to 20 %, resulting in a more efficient Fe-Nx bonding and surface ionic conduction. In addition, in situ XRD shows that there is no obvious crystalline formed during high temperature treatment, indicating that there is no agglomeration of iron particles. These in situ XPS and XRD results elucidate that extra heat treatment of Fe-N-C electrocatalyst after preliminary synthesis and purification is an essential procedure and can improve the electrochemical performance efficiently.
[1] M. J. Workman, M. Dzara, C. Ngo, S. Pylypenko, A. Serov, S. McKinney, J. Gordon, P. Atanassov, K. Artyushkova, J. Power Sources
2017, 348, 30-39.

Figure 1
One-Pot Synthesis of Gram-Level Shape-Controlled Pt-Ni Catalysts with Enhanced Electrocatalytic Properties for PEMFC
Authors: Cai Xin , Lin Rui 
Published: February 2020

Proton exchange membrane fuel cells (PEMFC) are one of the most effective ways to solve energy and environmental problems due to their high efficiency, environmental protection and stability. As the most efficient redox catalyst, Platinum (Pt) remains the first choice for PEMFC catalysts. However, the low reserves and high prices of platinum have made it difficult to reduce the cost of PEMFC and affect its commercial application. Therefore, improving the utilization and activity of Pt is still the focus of current research on fuel cell catalysts.
In recent years, the development of catalyst has been focused on the shape-controlled platinum alloy nanoparticles. It is reported that more highly active Pt-M (111) crystal faces can be exposed in the shape-controlled catalysts, which increases the activity of the catalyst and the utilization of Pt. However, these high performance catalysts were usually prepared by multistep synthesis method with difficult preparation and poor reproducibility, which also has a low yield in one-batch. Thus, a facile yet efficient synthesis strategy is necessary for enabling atomic-scale engineering and mass production of nanocatalysts for real world applications. Herein, we report a relatively effective and simple one-pot synthesis of novel shape-controlled Pt-Ni catalysts and its single production is around 0.5g. By controlling the reaction time, the catalysts with different morphology were prepared and their electrocatalytic properties were studied. The nanoframe catalyst possess the best ORR activity and durability. In this regard, this method can be a promising way for mass production of the high performance shape-controlled Pt-Ni alloy electrocatalyst.
Iron and Nitrogen Doped Carbide Derived Carbon and Composite Catalysts for Fuel Cell Cathodes
Authors: Ratso Sander , Sahraie Nastaran Ranjbar , Sougrati Moulay Tahar , Käärik Maike , Kook Mati , Saar Rando , Vlassov Sergei , Kisand Vambola , Paiste Päärn , Jia Qingying , Leis Jaan , Mukerjee Sanjeev , Jaouen Frederic , Tammeveski Kaido 
Published: February 2020

Producing renewable energy is one of the most important electrochemical challenges in the 21st century. Currently the focus is mainly on enhancing the oxygen reduction reaction (ORR) on the cathode of the fuel cell and to utilize non-noble metal catalysts instead of the expensive and scarce Pt-based catalysts that are currently prevalent. Iron and nitrogen doped nanocarbons have emerged as a possible replacement. Here, we study a catalyst material synthesized from carbide-derived carbon (CDC, a carbon material made by removing the metal atoms from a carbide) and composites of CDC and carbon nanotubes (CNT). To dope this material, 1,10-phenanthroline and iron(II)acetate were used in a ball-milling and pyrolysis procedure.1,2 The composites were created by adding CNTs, dicyandiamide and additional iron(II)acetate before repeating the ball-milling and pyrolysis process. The surface morphology was examined by scanning electron microscopy (SEM), and elemental composition by X-ray photoelectron spectroscopy (XPS), porosity analysis was done by N2 adsorption/desorption and the bulk elemental composition was studied by inductively coupled plasma mass spectroscopy (ICP-MS). The speciation of iron was studied using 57Fe Mössbauer spectroscopy.
These CDC-based Fe-N-C catalysts show promising half-wave potential for ORR of 0.81 V vs RHE in 0.5 M H2SO4. For a same Fe content of 0.5 wt% in the catalyst precursor, the Fe-N-C catalyst derived from CDC-2 (derived from TiC) showed ca. 5 times higher activity at 0.8 V vs. RHE than that derived from CDC-1 (derived from B4C). The residual presence of boron in CDC-1 seems to be the main reason for the lower activity of CDC-1 derived catalysts, leading to the preferential formation of iron boride instead of ORR-active FeNxCy moieties. Higher Fe contents were investigated for CDC-2, but lead to unmodified activity, which is explained from Mössbauer spectroscopy measurements by the increasing formation of ORR-inactive Fe species at high Fe content. The addition of CNTs to create a core-shell composite with a CNT shell surrounding the CDC cores increased the stability of the catalyst in acidic media.

Figure 1
Heteroatom (N, P, B) Doped Hierarchical Porous Carbons from Coal Tar Pitch with High Specific Surface Area for Oxygen Reduction Reaction
Authors: Dong Fang , Qiao Jinli 
Published: February 2020

Heteroatom (N, P, B) Doped Hierarchical Porous Carbons from Coal Tar Pitch with High Specific Surface Area for Oxygen Reduction Reaction
Fang Dong, Jinli Qiao*

College of Environmental Science and Engineering, Donghua University, 2999 Ren’min North Road, Shanghai 201620, China.
*qiaojl@dhu.edu.cn
In the past few decades, fuel cells, as a kind of clean and efficient energy sources, which is considered to be the most promising solution to the increasingly serious energy crisis of energy conversion equipment, has attracted significant attention.1 Oxygen reduction reaction (ORR) in fuel cells plays a decisive role in determination of performance, and electrocatalysts with high-performance ORR are essential for practical applications. Up to now, the platinum or its alloyed nanoparticles have been used to catalyze the sluggish ORR, however, their high cost as well as the limited natural abundance hinder the development and commercialization of the interrelated technologies.2 The development of new ORR catalysts free of noble metals is thus the next challenge for the long-term viability and sustainability of fuel cells. Due to the introduction of porous structure, porous carbon materials with high specific surface area, porous rich and aperture can be adjusted, which has the advantages of high chemical stability and good electrical conductivity, and this has been widely used in the aspects such as catalysis, adsorption and electrochemical energy storage.3 Recent years witnessed the dramatic interest in using nitrogen-doped porous carbon as one of the promising ORR catalysts. Besides N, other heteroatoms have also been introduced into carbon materials and they also show enhanced catalytic activity for ORR.4 In this work, we choose N, P and B as doped heteroatoms to fabricate the hierarchical porous carbons derived from coal tar pitch. The catalytic ORR activities of the heteroatom (N, P, B) doped hierarchical porous carbons from coal tar pitch are studied and the results show that heteroatom (N, P, B) doped with hierarchical porous carbon from coal tar pitch has high specific surface area and high catalytic activity for ORR.
References
1 M.L. Xiao, J.B. Zhu, L.G. Feng, C.P. Liu, W. Xing, Advanced Materials, 27, 2521 (2015).
2 M. Sahoo, S. Ramaprabhu, Energy, 119, 1075 (2017).
3 L. Osmieri, R. Escudero-Cid, A.H.A. Monteverde Videla, P. Ocón, S. Specchia, Applied Catalysis B: Environmental, 201, 253 (2017).
4 M.J. Wu, Q.W. Tang, F. Dong, Z.Y. Bai, L. Zhang, J.L. Qiao, Journal of Catalysis, 352 , 208 (2017).
(Invited) Current Status of Solid Oxide Fuel Cell Technology and Commercialization
Authors: Singhal Subhash C. 
Published: February 2020

After almost four decades of research and development, considerable progress has now been made in the development and commercialization of solid oxide fuel cells (SOFCs) for clean and efficient power generation. The main advantages of SOFCs are low emissions, fuel flexibility, and high efficiency. The SOFC power generation systems are now sold commercially with units totaling over 500 MW installed or on order, for small residential units (~1 kWe), commercial and industrial systems (100-400 kW), and microgrids (several MW). The most important need to further accelerate commercialization of SOFC technology is to significantly reduce the overall cost of such systems while maintaining adequate performance and performance stability with time. This overview focuses on the designs, materials, processing, and performance of solid oxide fuel cells, and discusses the progress in the deployment of power generation systems built with various design solid oxide fuel cells and their operating experiences. Challenges in reducing cell and system costs are also summarized.
SOFCs can also be operated in reverse operating mode for hydrogen and syngas production through electrolysis of steam and mixtures of steam and carbon dioxide; interest in such solid oxide electrolysis has greatly increased during the last decade. Application of solid oxide cells for electrolysis is also discussed in this overview.