bluuebunny/crossref_metadata_2025_split huggingface dataset:
Surface Texture Design of FBR-ALD Pt/C Catalyst to Enhance PEMFC Performance
Authors: Baek Ji-Hu , Jung Myung-Jin , Lee Sung , Jung Yu-Jin , Lee Woo-Jae , Kwon Se-Hun 
Published: November 2022

Proton exchange membrane fuel cell (PEMFC) is an efficient electrochemical energy conversion device that directly generates electricity from the chemical energy of fuels without the emission of greenhouse gases. The most reliable catalyst in PEMFC is Platinum (Pt) metal nanoparticles (NPs) that exhibit excellent electrochemical activity and stability compared to other catalysts. However, using of Pt catalyst is limited due to its very high cost and low abundance on Earth. Therefore, it is important to use Pt catalyst efficiently for making the PEMFC economically viable. In this regard, several synthesis techniques have been developed to reduce the loading and uniform distribution of Pt NPs on carbon support with high electrochemically active surface area (ECSA). One of the most efficient techniques to uniformly deposit Pt NPs with a controllable size on carbon support is to use a fluidized bed reactor (FBR) atomic layer deposition (ALD). Our group recently demonstrated that FBR-ALD Pt/C catalysts can exhibit high fuel cell performance and high endurance even with low Pt NPs loading by optimizing the surface of carbon supports combined with proper ALD process parameters [1]. However, it is still challenging to further improve the fuel cell performance by rational designing the Pt NPs surfaces in order to make FBR-ALD into a viable commercial production.
In this study, a unique way to improve the fuel cell performance was suggested to design and optimize atomic scale surface textures of Pt NPs. During the FBR-ALD of Pt NPs, in-situ surface modulation of Pt NPs was applied via a proper protective oxide deposition and etching. A careful surface studies was performed to analyze the surface morphology, distribution and uniformity of Pt NPs. Electrochemical performances were evaluated and optimized by measuring cyclic voltammetry (CV) and oxygen reduction reaction (ORR). Finally, a fuel cell performance was studied through membrane electrode assembly (MEA) characteristics.
References

W. J. Lee, S. Bera, H. C. Shin, W. P. Hong, S. J. Oh, Z. wan, S. H. Kwon, Adv. Mater. Interfaces 6, 1901210 (2019).
PBI-Membrane for High-Temperature PEMFC
Authors: Azizi Kobra , Hjuler Hans , Seselj Nedjeljko , Jensen Jens Oluf , Li Qingfeng , Cleemann Lars Nilausen 
Published: November 2022

High-temperature proton exchange membrane fuel cells (PEMFCs) are particularly attractive because of the potential benefits of faster electrode kinetics, high tolerance to fuel impurities, no humidification requirements, and simplified system design.1 The present work focuses on ongoing work based on membrane electrode assemblies (MEAs) for high temperature proton exchange membrane fuel cells. HT-PEMFCs were operated at 160-170 °C using humidified synthetic reformate. We have illustrated that an increase in the pressure of the in-going gases to 2 barG increases - as expected - the performance, E.g. the power density was improved from 0.32 W/cm2 at 0 barG to 0.48 W/cm2 at 2 barG at 170 °C. More data will be shown at the meeting.
Fig 1: a) IV curves b) dependence of power density on back pressure, operating conditions: backpressure (0.4–2 barG), temperature: 170 °C, and λRef/ λAir (1.3 /2.5)
Continuous operation and more than 290 start stop cycles have been performed in order to study the degradation effects of both continuous operation and of repeated start stops. Start stop cycles led to a degradation of 0.01 mV/cycle.
The durability of HT-PEMFC can now be considered similar to low temperature PEMFC. We have proved more than 15,000 hours in single cells at 0.3 A/cm2. The degradation rate is around 4 μV/h for approx. 13,000 hours. Graphs of single cell performance during operation have shown very stable behavior for over 10,000 with an overall degradation of 9 μV/h at a current density of 0.4 A/cm2.
Reference
1) O. Jensen, D. Aili, H. A. Hjuler, Q. Li, High Temperature Polymer Electrolyte Membrane Fuel Cells - Approaches, Status and Perspective, ISBN 978-3-319-17081-7; DOI 10.1007/978-3-319-17082-4, Springer International Publishing, New York, 2015.

Figure 1
Alkyl Phosphonic Acids: An Alternative to Phosphoric Acid in HT-Pemfcs
Authors: Maurya Sandip , Lim Katie , Hu Zhendong , Jia Hongfei , Klein Jeffrey Michael , Kim Yu Seung 
Published: November 2022

Phosphoric acid has received the most attention as a choice of electrolyte for a high-temperature proton exchange membrane fuel cell (HT-PEMFC). Phosphoric acid has many attractive properties such as high anhydrous conductivity, good compatibility with hydrocarbon membranes, and thermal stability [1], which enables high fuel cell performance under anhydrous and elevated operating temperatures (140-180 oC) [2-3]. However, phosphoric acid has undesirable properties such as high catalyst poisoning, high evaporation rate at > 200 oC, and low acid retention from the doped membrane. Alkyl phosphonic acid may correct some of the drawbacks of phosphoric acid, improving fuel cell performance and durability.
In this presentation, we report the technical challenges and possible resolutions for HT-PEMFCs using alkyl phosphonic acid doped membranes. We focus on the effects of alkyl phosphonic acid on hydrogen oxidation and oxygen reduction reactions of Pt-based catalysts. In addition, we discuss the membrane selection of robust operation of alkyl phosphonic acid-based HT-PEMFC.

References:

[1] A.S. Lee, Y.-K. Choe, I. Matanovic, Y.S. Kim, Journal of Materials Chemistry A, 7 (2019) 9867-9876.
[2] K.H. Lim, A.S. Lee, V. Atanasov, J. Kerres, E.J. Park, S. Adhikari, S. Maurya, L.D. Manriquez, J. Jung, C. Fujimoto, I. Matanovic, J. Jankovic, Z. Hu, H. Jia, Y.S. Kim, Nature Energy, 7 (2022) 248-259.
[3] V. Atanasov, A.S. Lee, E.J. Park, S. Maurya, E.D. Baca, C. Fujimoto, M. Hibbs, I. Matanovic, J. Kerres, Y.S. Kim, Nature Materials, 20 (2021) 370-377.
Cationic Ionomer Thin Films for Alkaline Electrochemical Energy Conversion
Authors: Kushner Douglas , Katzenberg Adlai , Luo Xiaoyan , Kusoglu Ahmet 
Published: November 2022

Ionomers are used as the solid-electrolyte in many electrochemical energy conversion technologies where they offer many functionalities such as ion conduction, electrical insulation, and water transport. These ionomers are found as nanometer-thick electrolyte thin films within the catalyst layers of fuel cells, electrolyzers, and hydrogen-based redox flow batteries where electrochemical reactions take place. The ionomer performance and durability are strongly related to their properties governed by a myriad of parameters such as chemical structure, water uptake, and morphology, all of which are stimulated differently by the external environment. Typically, the ionomer consists of the same ion-conducting polymer used as the electrode separator but exhibit disparate properties from the bulk membrane when nanometer thickness coatings are confined to a hard substrate (as in a catalyst layer), where the behavior is influenced by the ionomer affinity with the air and hard interfaces. Two motifs of ionomers exist, one as an acidic polymer (e.g. Nafion) and the alternative, and less studied, alkaline polymer (e.g. Sustainion).
This talk will focus on filling in the gaps between the disparate properties of alkaline ionomers in the thin film motif that have been extensively studied for acidic ionomers. Aspects such as different backbones (e.g. perfluorinated, aliphatic, aromatic) and side chains (e.g. length, functional group) are explored in X-ray scattering, hydration, and transport measurements. Small-angle X-ray scattering is used to probe the morphology of these different polymer thin-films. Quartz crystal microbalance and spectroscopic ellipsometry under different states of humidity are used to probe hydration and free volume. The resulting correlations provide insights on not only how different polymer respond to the confined environment but how chemistry can be tuned to boost performance in alkaline electrochemical energy devices.
Self-Adhesive Ionomers for Durable Alkaline Water Electrolysis
Authors: Shah Parin , Chen Mengjie , Groenhout Katelyn , Tee Hui Min , Park Habin , Kohl Paul 
Published: November 2022

Low-temperature water electrolysis using anion conductive polymer electrolytes has several potential advantages over acid-based polymer electrolyzers. However, the formation of durable, high surface area electrodes remains a challenge. In particular, the adhesion and connectivity of high surface area, particulate catalysts to the porous transport layer is critically important to the long-term cell lifetime.
In this study, a family of covalently bonded, self-adherent, hydroxide conducting ionomers has been synthesized and tested under alkaline electrolysis conditions. The ionomers are based on hydroxide conducting poly(norbornene) polymers used in fuel cell and electrolyzers. Ionomers used in electrolysis electrodes, especially at the oxygen gas producing anode, must provide adhesion between the catalyst particles, porous transport layer and solid polymer membrane. Simple mixtures of ionomer and catalyst can suffer from poor catalyst adhesion because only physical adhesion is used to bind the components together.
The terpolymer and tetrapolymer ionomers used in this work have been functionalized to provide cites for chemical bonding of bis(phenyl)-A-diglycidyl ether to the ionomer, catalyst, and porous transport layer. The resulting electrodes show excellent adhesion of the catalyst particles to the porous transport layer, as determined by adhesion measurements. Electrolyzer results show stable voltage performance over long periods of time.
Molecular Dynamics Study on the Microscopic Mechanism of Mechanical Properties of Nafion Membrane
Authors: Wang Haoran , Mabuchi Takuya , Ji Jiayuan , Huang Sheng-Feng , Tokumasu Takashi 
Published: November 2022

As the core component of new energy vehicles, the safe operation of polymer electrolyte fuel cells has become more important with the rapid development of the new energy field. Since polymer electrolyte membrane (PEM) works at a hydrated environment, the mechanical properties of its hydrated state must remain stable. At present, studies have shown that the increase of water content will reduce the mechanical properties of materials, such as the decrease of Young's modulus, but the microscopic mechanism has not been elucidated. This presents a challenge to the work to develop novel PEMs. We tried to use the method of coarse-grained (CG) molecular dynamics (MD) simulation to study the microscopic mechanism of the mechanical properties of basic PEM Nafion membrane under different water content conditions. The purpose of this study is to seek to demonstrate the microscopic mechanism by which macroscopic mechanical properties are determined from the MD perspective, thereby providing general guidance for the future development of novel PEMs. More specifically, we tested the Nafion membrane (CG model with 4 beads on the main chain and 2 beads on the side chain) under tensile and compressive stress (strain 0-0.5) at different water contents (2-14). Quantified micro-parameters make it possible to establish macro-micro relationships. Considering that our chosen Nafion is the basic model, it may have good generality to other complex models.
At the macroscopic level, our results show that increasing the water content reduces Young's modulus of the material. The decreasing rate of Young's modulus shows a slowing trend. This is in good agreement with previous research. At the microscopic level, our results show that the coordination number between any two types of atoms except water molecules within the same volume decreases with increasing water content, suggesting that the increase in water molecules forces other atoms to away from each other, thereby increasing the spacing between molecules. Therefore, the dominant force on this distance scale, that is, the electrostatic attraction between positive and negative ions is reduced. We have a reason to think that this is the main micromechanical factor to change macroscopic mechanical properties.
In addition, the results of polymer chain entanglement parameters show that the degree of entanglement of polymer chains deepened with the increase of water content. The complex entangled structure will increase the difficulty of the polymer deformation. We believe that this is one of the micromechanical factors to decrease the Young's modulus. The study of these mechanisms may help in the development of new Nafion materials.
(Invited) Understanding and Tuning the Cell Reversal Tolerance of PEM Fuel Cell Anodes: Application-Relevant Design Parameters for Precious Metals Catalysts
Authors: Maric Robert , Strasser Peter , Gebauer Christian 
Published: November 2022

The shared vision of a hydrogen economy, in which sustainable hydrogen covers a substantial fraction of a nation’s energy demand, unites supporters from science, industry, and politics to engage in cooperative exchange and collaborative work. Several publicly and privately funded initiatives support research and innovation activities on renewable hydrogen production, distribution and storage, as well as fuel cell technologies for transportation and stationary applications with the goal of achieving set climate neutrality goals and limit the impact of human-driven climate change [1].
In this context, proton exchange membrane (PEM) fuel cells are considered to play a pivotal role in the decarbonization of the mobility sector, as they allow a simple power scaling through a modular stack design, offer a refueling time and range comparable to conventional combustors, but in contrast, are pollutant- and emission-free when green hydrogen is used [2]. In applications with high lifetime requirements, the management of challenging operating conditions is of key importance. Recently, particular attention was paid to cell reversal events triggered by hydrogen starvation, which – without proper countermeasures – lead to a sharp decline in performance within seconds as the carbon-supported catalyst significantly corrodes at the anode [3].
Among other remedies, the incorporation of a co-catalyst, like iridium oxide [4], that favors the harmless oxygen evolution reaction (OER) of water over the destructive carbon oxidation reaction (COR) is broadly employed to improve the intrinsic stability of Pt/C-based anode catalysts. However, the scarcity of platinum and especially iridium makes sophisticated catalyst and electrode concepts indispensable to serve the stability requirements in a resource-saving way. Based on the latest findings and developments, we derived a wide range of material requirements and material adjustments, which in combination enhance the tolerance against hydrogen starvation induced degradation. Incremental improvements of the Pt/C-based anode catalyst form the foundation [5], which is further extended by a broad screening of several iridium-based co-catalysts under application-relevant conditions [6]. As will be emphasized, a careful selection of the anode catalyst system properties not only results in a significant increase in the initial cell reversal tolerance but is also crucial to maintaining this stability after operation under reductive H2 conditions.

References

[1] V. Masson-Delmotte et al., In Press, IPCC: Global Warming of 1.5°C (2018).
[2] O. Gröger et al., J. Electrochem. Soc., 162 (14) A2605-A2622 (2015).
[3] M. F. Tovini et al., J. Electrochem. Soc., 168 064521 (2021).
[4] K. H. Lim et al., J. Electrochem.
Soc., 164 (14) F1580-F1586 (2017).
[5] R. Marić, C. Gebauer, F. Eweiner, and P. Strasser, to be submitted.

[6] R. Marić, C. Gebauer, F. Eweiner, and P. Strasser, to be submitted.
Improved Oxygen Reduction Reaction (ORR) Kinetics Via Interfacial Engineering
Authors: Gawas Ramchandra , Snyder Joshua David , Tang Maureen 
Published: November 2022

Sluggish oxygen reduction reaction (ORR) kinetics, even on the best available catalyst (Pt), is one of the major challenges in widespread commercialization of polymer electrolyte membrane fuel cells (PEMFC).1 Significant advances have been made towards making highly active Pt catalysts through nanostructuring, alloying, size, and shape control to mitigate these kinetic losses.2 An additional strategy for ORR activity enhancement is though the targeted engineering of the electrochemical interface. For example, Ionic liquid (IL) interlayers improve the ORR kinetics on bulk and nanostructured catalysts for both Pt and alloyed-Pt materials.3 Along with the kinetic enhancement, ionic liquid interlayers also mitigate the sulfonate adsorption on Pt and improve the durability of Pt/C thin films.4,5

Despite remarkable improvement in performance at half-cell and MEA-level, the mechanism of this improvement is not completely understood. In this work, we combine single crystal voltammetry with microkinetic modeling to analyze the mechanism of ORR enhancement in presence of ionic liquids. With iterative feedback between single crystal voltammetry and microkinetic model output, we establish the importance of accounting for lateral interactions between adsorbed oxygenated species by using real data informed adsorption isotherms. With our experimentally validated model, we show that the mechanism of impact of ILs on ORR activity is through exclusion of water and reduction in electrochemical interface solvation, yielding lower spectator hydroxyl coverages and a reduced barrier for hydroxyl removal, resulting in higher surface site availability during the ORR. This improved understanding will help design Pt-interfaces to moderate the interaction of the interfacial water network with Pt active sites, providing another strategy for improving ORR kinetics.
References:

Debe, M. K. Electrocatalyst approaches and challenges for automotive fuel cells. Nature
486, 43–51 (2012).

Kulkarni, A., Siahrostami, S., Patel, A. & Nørskov, J. K. Understanding Catalytic Activity Trends in the Oxygen Reduction Reaction. Chem. Rev.
118, 2302–2312 (2018).

Snyder, J., Fujita, T., Chen, M. W. & Erlebacher, J. Oxygen reduction in nanoporous metal-ionic liquid composite electrocatalysts. Nat. Mater.
9, 904–907 (2010).

Li, Y., Hart, J. L., Profitt, L., Intikhab, S., Chatterjee, S., Taheri, M. & Snyder, J. D. Sequential Capacitive Deposition of Ionic Liquids for Conformal Thin Film Coatings on Oxygen Reduction Reaction Electrocatalysts. ACS Catal.
9, 9311–9316 (2019).

Li, Y., Intikhab, S., Malkani, A., Xu, B. & Snyder, J. Ionic Liquid Additives for the Mitigation of Nafion Specific Adsorption on Platinum. ACS Catal.
10, 7691–7698 (2020).

Figure 1
Electronic Perturbation of Platinum Alloy By Transition Metal-Doping Towards Improved ORR Activity and Stability
Authors: Zaman Shahid , Xia Bao Yu 
Published: November 2022

As of today, Pt-based catalysts are the predominant ORR catalysts that meet the desired activity requirements of ORR in fuel cells. However, their broader applications are still challenging due to highly sluggish ORR kinetics, limited stability and higher cost of Pt. In order to develop novel electrocatalyst materials, herein we report surface tuning of binary PtCo alloy through transition metal doping, which reveals superior ORR activity achieving a mass activity of 2.07 A mgPt
-1 at 0.9 V vs. reversible hydrogen electrode (RHE) and excellent durability with minor degradation after 30000 cycles. The ternary PtCoMn@NGNS alloy prepared through facile molten salt pyrolysis reveals a strong metal-support interaction via metal-nitrogen-graphene coordination.
Furthermore, Mn dopants alter the electronic structure of Pt alloy, which improves the oxygen-intermediate binding energy on the interface and suppress the Co dissolution through unique configuration, resulting in enhanced activity and durability of the catalyst. According to the DFT calculations, the surface Mn extensively adsorbs an OH, resulting in increased surface Co stability and overall ORR catalytic performance. Therefore, it is understandable that the development of ternary Pt alloy results in considerable changes in the structural and electrical characteristics of metal overlayer, which varies dramatically from monometallic surfaces.
Our experimental results corroborated by theoretical calculations show that electronic perturbation of PtCo by Mn doping stabilizes the Co and causes significant strain in the Pt(111), which accounts for the increased ORR performance. The strained lattice of Pt caused by Co alloying and surface segregation of Mn both play important roles in the increased ORR activity. Similarly, the Pt3CoMn-OH configuration diminishes Co dissolution and improves overall stability. It is anticipated that such a facile preparation of high-performance electrocatalysts will advance the practical applications of ORR catalysts.
Figure 1:

Figure 1
Polymer Electrolyte Fuel Cell Electrodes with Improved Durability
Authors: Liyanage Wipula Priya Rasika , Yang Gaoqiang , Komini Babu Siddharth , Spendelow Jacob S. 
Published: November 2022

Proton exchange membrane fuel cells (PEMFC) are a promising clean energy conversion device for both transportation and stationary power applications. Current PEMFCs contain high loadings of expensive and rare platinum (Pt) based catalysts, which presents an obstacle to widespread commercialization in clean energy applications. While extensive efforts have been devoted to increase the catalytic activity of Pt while reducing the loading and to stabilize Pt particles1, state of the art Pt catalysts typically consist of 2-5 nm Pt nanoparticles supported on carbon (Pt/C). Small Pt particles are vulnerable to degradation due to Ostwald ripening, coalescence, and support corrosion during dynamic operation of the fuel cell. Therefore, before the broader commercialization of PEMFCs can be achieved, the durability and robustness of fuel cell electrodes need to be improved. In this work, we present an alternative novel strategy for improving fuel cell performance durability with a new electrode architecture containing carbon-free catalyst.

Acknowledgement:

We gratefully acknowledge support from the Laboratory Directed Research & Development Program at Los Alamos National Laboratory.
References:

Kim YS, Welch CF, Mack NH, Hjelm RP, Orler EB, Hawley ME, Lee KS, Yim SD, Johnston CM. Highly durable fuel cell electrodes based on ionomers dispersed in glycerol. Physical Chemistry Chemical Physics. 2014;16(13):5927-32.