bluuebunny/crossref_metadata_2025_split huggingface dataset:
Modeling and Sizing of a Y-Shaped Laminar Flow Micro-Fluidic Fuel Cell
Authors: Espinoza Andaluz Mayken , Zhang Xiaoqiang , Yang Danan , Andersson Martin 
Published: February 2024

The high demand for portable and desktop electronic devices requires mobile energy sources. Electronic devices, in general, are small when they are portable and require autonomy, sustainability, efficiency, and large enough periods of operability. In that sense, microtechnology, a type of technology related to the manufacture of prototypes or three-dimensional high-precision products in various materials ranging in size from tenths of microns to a few millimeters, has reached a boom in microfabrication of devices that are not exclusively electronic. Applications in several fields show that micro-energy sources are a focal point for commercializing prototypes in the mobility sector.
The energy demand to supply micro-devices has been increasing in recent years. Considering the power output of the laminar flow microfluidic fuel cell (LFFC), it is a suitable solution to provide the required electrical energy in small devices. The absence of electrolytes and no requirement of platinum as catalytic material are two of the most important advantages of this type of fuel cell. The current study provides detailed information about the design and characteristics of an LFFC. A complete analysis of the different channel shapes is considered in this study, with the Y-shaped channel being selected as the best option. The impact of the inclination degree for the inlet channels has been considered to evaluate the average velocity the flow acquires in the channel. In addition, the voltage-current behavior considering the materials, fuel/oxidant, and design characteristics has been obtained through modeling approaches.

Figure 1. Velocity profile and Reynolds number in the mid-plane of the Y-channel design

Figure 1
Projected Fuel Cell Stack Costs Using Non-PGM Cathode Electrocatalysts
Authors: Swider-Lyons Karen , Patel Sejal , Rainford Chris 
Published: February 2024

Platinum is typically used at the cathode of the cathode of proton exchange membrane fuel cells (PEMFCs) to overcome the kinetic limitations of the oxygen reduction reaction (ORR) to water. Pt is a noble metal that is mined mainly in South Africa and Russia. At present costs of $965 per troy ounce ($31 per gram), the cost of Pt in the cathode is approximately 40% of the total cost of each PEMFC membrane electrode assembly (1,2). Supply chain concerns have been raised that there is insufficient Pt in the world to support the conversion of all automobiles to hydrogen, or that increasing the demand of Pt through mass commercialization of fuel cells would drive up its demand and then cost (1,3). Researchers have therefore looked for catalysts that do not contain Pt or other precious metals (3). Oxygen reduction without Pt is possible, and all living creatures and plants use cytochrome enzymes with reactive iron or copper sites as part of a catalytic cycle to reduce O2 to reactive oxygen. Significant improvements have been gained in the performance of fuel cells with non-PGM cathodes by improving the density of sites and improving the catalyst durability (4).
We estimate the cost impact of eliminating Pt from the cathode of a heavy-duty fuel cell stack. The calculations are based on the comparison of Plug fuel cells with Pt cathodes, compared to literature polarization curves for cells and stacks containing PGM-free cathodes (note that the anodes still contain Pt). We carry out a sensitivity analysis using different costs to the non-PGM catalysts. Our primary finding is that eliminating Pt from the cathode does little to reduce stack costs because the performance of the fuel cells with non-PGM cathodes is low, and larger stacks are needed to meet performance requirements. We will also discuss how using a non-PGM cathode affects projected recycling costs.
References:
[1]. A. Kongkanand, M. F. Mathias, J. Phys. Chem. Lett. 2016, 7, 1127−1137
[2]. B.D. James, J. Huya-Kouadio, C. Houchins, D. Desantis, Strategic Analysis, Inc. Technical Report. DOI: 10.13140/RG.2.2.36532.55683.
[3]. C. Sealy, Materials Today, 2008, 11, 65.
[4]. F. Jaouen, E. Proietti, M. Lefevre, R. Chenitz, J.-P. Dodelet, G. Wu, H. T. Chung, C. M. Johnston, P. Zelenay, Energy Environ. Sci., 2011, 4, 114.
Anode Defects’ Propagation in Polymer Electrolyte Membrane Fuel Cells Stack
Authors: Bultel Yann , BAS Corine , Dubelley Florence , Micoud Fabrice , Rosini Sébastien , Nayoze-Coynel Christine 
Published: February 2024

Reliability and durability are key considerations to successfully deploy Proton Exchange Membrane Fuel Cells (PEMFCs). Defects induced by manufacturing processes and fuel cell operating conditions may shorten the lifetime of PEMFC due to membrane electrode assembly (MEA) components degradations. If the degradation mechanisms occurring along ageing are now well-known, the propagation of these defects to other materials or to other locations in the stack was poorly investigated in the literature. Recently, we investigated a defect-propagation in MEA via accelerated stress tests combining load and load-driven humidity cycling, and open-circuit voltage. Results highlighted a defect propagation in term of anode and cathode ECSA losses. Significant membrane thinning is also observed for the defective segments. If, the defect propagation was investigated at the cell scale, it has been barely studied in the literature at the stack level.
The objective of this work is to quantify the impact of MEA manufacturing defects on the performance and durability in stack and to analyze how these defects can propagate within healthy areas of the same MEA or to healthies MEAs within a stack.
Tests were carried out on two stacks with metallic bipolar plates. The stacks were assembled using 35 defect-free MEAs for the healthy stack and using 30 homogeneous MEAs and 5 MEAs with controlled anode defects over 25% of the active area (absence of anode catalyst layer) for the faulty one. The two stacks were operated on a test bench able to control operating conditions and electrochemical characterizations were regularly made in order to evaluate the impact of the defects on the stack behavior.
The initial characterization of the stack contained faulty MEAs showed, as expected, that the defects in the anode active layers have a significant effect on the performance of the cells from the conditioning stage. The analysis of the degradation rate showed that the cells directly in contact with the defected MEAs were the ones whose performance degraded the fastest, which implies that the presence of defects within the stack induces a propagation of the performance decrease. This phenomenon could be linked to a significant increase in hydrogen leakage through the membrane identified both by off-line electrochemical characterization and by thermal camera measurements in post-mortem analysis. The mechanism of degradation is still difficult to understand but the presence of defects within the stack could lead to constriction of the current lines around the defect and to localized heating which could degrade the membrane relatively rapidly.

Figure 1
Supercapacitive Electrolyzer for Decoupled Hydrogen Production
Authors: Toledo Carillo Esteban , García-Rodríguez Mario , Sanchez-Moreno Lorena , Dutta Joydeep 
Published: February 2024

The production of green hydrogen is an energy vector and key component to tackle the decarbonization goals. Electrolysis of water for production of green hydrogen using renewable energy sources is an attractive approach, but the integration of electrolysis technologies with these sources is still facing challenges such as membrane degradation and gas crossover. Decoupled electrolysis is a promising approach to overcome these challenges. In this approach, the generation of hydrogen and oxygen can be separated in time or space, which allows for efficient and reliable integration with renewable energy sources. Symes et.al. developed a two-step electrochemical system that separates the water oxidation and hydrogen evolution reactions using an electron-coupled proton buffer. However, most decoupling designs still require the use of membranes for separation of redox mediator, which can be susceptible to degradation and have limited lifetimes. Researchers have introduced solid-state mediators to build membraneless electrolyzers using battery-like materials. The use of solid-state mediators eliminates the need for membranes and can provide improved performance and stability.
In this work, we introduce a membraneless architecture decoupled hydrogen production in a hybrid cell combining the standard electrocatalytic reactions of water splitting with a capacitive storage mechanism. This innovative approach increases the flexibility and robustness of the hydrogen production system, allowing for operation in both acidic and alkaline conditions. The supercapacitive electrolyzer was assembled using the bifunctional catalyst cobalt-iron phosphide prepared by electrodeposition and a commercial activated carbon cloth as a capacitive electrode. The results of this work demonstrate the potential of membraneless electrolysis for green hydrogen production. The hybrid cell achieved an energy consumption of 48 kWh/kg at a nominal current density of 10 mA/cm2 in a 5 x 5 cm2 cell. Faradaic efficiencies over 99% were achieved at 100 mA/cm2. The cycle stability of the single cell was demonstrated over 20 h of operation (100 cycles) at a current density of 20 mA/cm2 with no apparent electrode degradation. Moreover, the simplicity of the cell design in this study not only facilitates quick scaling of production but also offers significant advantages in terms of operational cost and maintenance, as membraneless electrolyzers eliminate the need for expensive and complex components. To further enhance the performance of the hybrid cell for green hydrogen production, it is possible to reduce the ohmic contribution of the capacitive electrode and lower the overpotential required for the bifunctional catalyst to facilitate efficient water splitting.
Hydrogen Fuel Cell Aiming at Vehicle Propulsion: Onboard or Off-Board Electricity Generation?
Authors: Santos Andrade Tatiana , Thiringer Torbjörn 
Published: February 2024

In response to the global energy crisis and climate change, hydrogen has been pointed out as promising fuel to be part of the green energy transition. Thus, countries worldwide have released policies to support and increase the hydrogen industry. Therefore, investigations regarding how hydrogen can be utilized best as a fuel should be addressed to evaluate its potential applications. Since transportation is responsible for 37% of the carbon emissions from the end-use sectors, it is of interest to consider hydrogen fuel for vehicle propulsion. There are two main alternatives that might be considered for the electricity generation from hydrogen: 1) a hydrogen fuel cell onboard the electric vehicle or 2) a hydrogen fuel cell off-board powering the electric vehicle.
Therefore, in this work, we propose the modeling and simulation from hydrogen fuel to wheels of the two different systems using the WLTP as the driving cycle reference. For the onboard system, the following components were considered: the vehicle dynamics, the gear, the motor, the inverter, the battery, and the fuel cell system on board (fuel cell vehicle powertrain). For the off-board system, the following components were considered: the vehicle dynamics, the gear, the motor, and the inverter for the battery electric vehicle powertrain, followed by the charger, the grid, and the fuel cell system off-board. The components were modeled as further described.
The vehicle dynamics were modeled mathematically and the weight difference between the vehicles was taken into account. The gear was a single-step gear. The motor was an eight-pole PMSM and the inverter three-phase IGBT. The battery for both was modeled as a lithium-ion battery with different sizes, with the battery for the fuel cell vehicle being much smaller. Capacity values similar to commercialized vehicles were used (4 and 300 Ah). The fuel cell was modeled as a commercialized fuel cell with 63% peak efficiency. For the fuel cell vehicle, a control strategy was implemented to split the power demand between the fuel cell and the battery. The control strategy was based on the state of charge of the battery and the power demand for each point of the cycle.
The simulation results have shown a slightly higher efficiency and lower hydrogen consumption for the onboard system compared to the off-board system. Even though there were more losses associated with the battery and the fuel cell in the onboard system, the losses associated with vehicle weight and the off-board power electronics related to the off-board system were more significant to the overall energy consumption. Thus, the results suggest that if hydrogen is available as a fuel aimed at vehicle propulsion using it onboard is more efficient than using it off-board.
Miniature Fuel Cell with Monolithically Fabricated Si Electrodes- Application of a PDMS Flow Channel for Operando Observation -
Authors: Hayase Masanori , Yoshimura Gaku , Sakai Yuta , Yamaguchi Takeo 
Published: February 2024

Miniature fuel cells have attracted attention as an ultimate portable power source, and we have developed monolithically fabricated Si electrodes for the miniature fuel cells [1,2]. In the fuel cells, two Si electrodes with porous Pt catalyst layer are pressed onto either side of a PEM (polymer electrolyte membrane) , and the prototype fuel cells showed promising performances of over 500mW/cm2 output at 313K with H2-O2. However, the high output was obtained with only small reaction area. Along with enhancement of the reaction area, the performance dropped. We assumed that the performance drop is caused by flooding due to increased water production, which was ignored because MEMS fuel cells are dimensionally small and the outputs are also small. In this study, we attempted to observe the behavior of produced water on the fuel flow channel using a novel transparent channel cover as shown in figure 1. Furthermore, it was assumed that the produced water stays in the concave portions on the catalyst layer, and stripe-shaped projections were formed on the channel cover to prompt drainage of the produced water from the fuel channels.
The transparent fuel channel cover was fabricated with PDMS using soft lithography techniques. Initially, a mold for the cover was made with a dry film resist. Micro stripe pattern with 40μm width were made. Considering the PDMS shrinkage during polymerization, the mold pattern had to be formed a few percent larger than the desired shape. Figure 2 shows the whole view of the PDMS channel cover on a miniature fuel cell with Si electrodes. The reaction on the Si substrate was 1mm and 4mm long. Within the area, 100μm x 100μm sections were etched down to the backside catalyst layer. Magnified view on the reaction area is shown in figure 3. It was found that the stripes were finely aligned on the concave portions on the Si electrode.
Figure 4 shows the polarization curves of the power generation tests. Results with the novel fuel channel cover with stripes showed higher output compared to the conventional simple cuboid straight shape cover. Figure 5 shows the microscopic view of the channel. While produce water droplets were observed on downstream area in the conventional cuboid shape channel, no droplets were observed with the novel channel cover. It was assumed that drainage of the produced water was successfully prompted and smooth fuel supply to the catalyst layer was realized by the novel fuel channel cover.

Acknowledgement

This work was partly performed under the Cooperative Research Program of “NJRC Mater. &Dev.”

References

[1] M. Kobayashi, T. Suzuki, M. Hayase, Journal of Power Sources, 267, 622-628 (2014).
[2] R. Shirai, et al., Journal of The Electrochemical Society, 166(15), D834 (2019)

Figure 1
Casting Electrodes on PEEK Reinforced Sulfonated Polyphenylsulfone Membrane
Authors: van Treel Niklas , Qelibari Regina , Titvinidze Giorgi , Klose Carolin , Münchinger Andreas , Cruz Ortiz Edgar , Vierrath Severin 
Published: February 2024

Researchers are exploring the potential of proton exchange membranes made from hydrocarbon polymers that do not contain fluorine. These polymers possess desirable properties that could make them more environmentally friendly and cost-effective compared to current perfluorinated sulfonic acids (PFSA). Hydrocarbon polymers have a unique structure that maintains high proton conductivity while reducing gas crossover, thus presenting a promising alternative to PFSA membranes [1]. Previous studies have demonstrated the potential of hydrocarbon membranes in electrolyzers using sulfonated polyphenylene sulfone (sPPS) [2]. However, sPPS has a high ion exchange capacity (2.17 – 3.57 meq/g), leading to excessive water uptake that causes the membrane to swelling and impedes upscaling, such as casting anodes directly onto the membrane. To overcome this issue, a woven, open-mesh PEEK substrate was incorporated into the membrane. The reinforced membrane exhibited a significant reduction in water uptake of up to 53% at room temperature and 43% at 60°C compared to the initial membrane. This improvement made it possible to cast the anode directly onto the membrane, resulting in a homogeneous surface (Fig. 1 left). In addition, preliminary electrolysis tests showed promising performance with low membrane resistance of 69 mΩcm² for a 74 µm thick membrane (Fig. 1 right).

Literature: [1] Miyake, J.; Taki, R.; Mochizuki, T.; Shimizu, R.; Akiyama, R.; Uchida, M.; Miyatake, K. Design of flexible polyphenylene proton-conducting membrane for next-generation fuel cells. Sci. Adv.
2017, 3(10), eaao0476. DOI: 10.1126/sciadv.aao0476
[2] Klose, C.; Saatkamp, T.; Münchinger, A.; Bohn, L.; Titvinidze, G.; Breitwieser, M.; Kreuer, K.; Vierrath, S. All‐Hydrocarbon MEA for PEM Water Electrolysis Combining Low Hydrogen Crossover and High Efficiency. Adv. Energy Mater.
2020, 10 (14), 1903995. DOI: 10.1002/aenm.201903995

Figure 1
Reinforced Membranes with PTFE Matrix and Sulfonated Hydrocarbon Electrolyte for PEM Fuel Cells
Authors: Pratama Juniko Nur , Lee Hyejin , Shin Dongwon , Bae Byungchan 
Published: February 2024

Proton exchange membrane fuel cells (PEMFCs) have emerged as a promising technology for clean energy conversion with various potential applications. Due to its cost-effectiveness, sulfonated hydrocarbon has been researched as an alternative to Nafion, a commercial proton exchange membrane. However, sulfonated hydrocarbon's mechanical and chemical stability remains a critical challenge that needs to be addressed, as the membrane must withstand harsh operating conditions, such as wet-dry mechanisms in high-temperature operations. To compete with perfluorosulfonic acid (PFSA), sulfonated hydrocarbon should be reinforced with a polytetrafluoroethylene (PTFE) substrate. However, there are significant issues with incompatibility between sulfonated hydrocarbon and PTFE substrate.
To improve the impregnation, simple and reproducible chemical treatment has been developed to enhance the hydrophilicity of PTFE using a mixture of acids and oxidizing agents. Moreover, surfactant was added to increase compatibility and improve impregnation. After the reinforced membrane was fabricated, the membranes were characterized, including their water uptake and dimensional stability. The reinforced membrane also showed superior mechanical properties, including gas permeability, tensile strength, and dynamic mechanical analysis. To evaluate the degree of impregnation, the transparency of the reinforced membrane was checked for haziness and further analyzed with scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS) mapping to quantify the impregnation degree. Finally, the performance and durability of the reinforced membrane were measured by single-cell and wet-dry cycling tests.
Alkaline-Stable Poly(phenylene-co-arylene ether) Block Copolymer-Based Anion Exchange Membranes with Alkyl Side Chain
Authors: Kwon Hugeun , Lee Hyejin , Shin Dongwon , Bae Byungchan 
Published: February 2024

Proton exchange membranes (PEMs) are desirable materials as they can be applied to their potential and wide range of electrochemical applications. However, in most electrochemical applications of PEMs for energy production, precious metals such as platinum are essential as catalysts due to the highly acidic media of the system. Anion exchange membranes (AEMs) have been studied recently to replace these PEMs. However, AEM-based electrochemical devices mainly operate under strongly basic conditions. Under those conditions, AEM is prone to decomposition. As a result, membrane scientists have adopted polymers of ether-free backbone, but their IEC is generally more than 2.0 meq/g to achieve high conductivity. The high IEC results in excessive water uptake, making the AEM fail chemically and mechanically during long-term operations.
To develop high-performance AEMs, we have synthesized new phenylene-based block copolymers. They have phenylene chains as hydrophilic segments for high chemical stability, in which hydrophobic parts are composed of arylene ether. This configuration is beneficial in solubility because the hydrophobic arylene ether block mitigates the poor solubility of phenylene. Moreover, a flexible alkyl chain was introduced as conducting moiety into hydrophilic phenylene. Thus, the enhanced solubility promoted the membrane’s efficient hydrophilic/hydrophobic morphological separation. The block copolymer-based AEM showed lower HFR (141 mΩ·cm2) than the Fumatech membrane (168 mΩ·cm2) in single-cell performance at 70 °C.
Hydroxide Conducting Naphthalene-Containing Polymers and Membranes Via Polyhydroxyalkylations
Authors: Luong Triet Nguyen Dai , Chen Si , Jannasch Patric 
Published: February 2024

Anion exchange membranes (AEMs) are critical components of alkaline membrane water electrolyzers and fuel cells that are under development today [1,2]. Consequently, there is a strong demand for highly conductive and alkali-stable AEMs. In this context, polyhydroxyalkylation has emerged as one of the most efficient synthetic pathways to chemically resistant polymer backbones for AEMs. In these Friedel-Crafts type polycondensations, an electron-rich aromatic compound reacts with an activated ketone or aldehyde to produce an aryl-ether-free polymer. The desired quaternary ammonium cations are then usually introduced through a Menshutkin reaction [3,4].
In the current work, we have employed naphthalene-based compounds as monomers in polyhydroxyalkylations to prepare a series of high-molecular weight poly(naphthalene alkylene)s with various naphthalene contents. These polymers were then quaternized and cast into AEMs. Here, we will discuss the influence of the naphthalene monomer type and content on AEM properties such as solubility, water uptake, ion conductivity, ionic clustering, thermal and alkaline stability, and also the prospects of using these AEMs in electrochemical systems.
References:
[1] Chen, N., Wang, H.H., Kim, S.P. et al. Poly(fluorenyl aryl piperidinium) membranes and ionomers for anion exchange membrane fuel cells. Nat. Commun.
12, 2367 (2021).
[2] Li, D., Park, E.J., Zhu, W. et al. Highly quaternized polystyrene ionomers for high performance anion exchange membrane water electrolysers. Nat. Energy
5, 378–385 (2020).
[3] Olsson, J.S., Pham, T.H., Jannasch, P., Poly(arylene piperidinium) hydroxide ion exchange membranes: synthesis, alkaline stability, and conductivity. Adv. Funct. Mater.
28, 1702758 (2017).
[4] Pan, D., Bakvand, P.M., Pham, T.H., Jannasch, P. Improving poly(arylene piperidinium) anion exchange membranes by monomer design. J. Mater. Chem. A
10, 16478–16489 (2022).