bluuebunny/crossref_metadata_2025_split huggingface dataset:
(Invited) Development of Durable and Low Cost Membrane Humidifiers for Fuel Cell Systems
Authors: Huizing Ryan Nicholas 
Published: December 2020

In order to operate effectively, currently commercialized fuel cell proton exchange membranes require sufficient hydration to ensure good proton transport. Hydration also ensures that membrane in the fuel cell stack will have a longer operational lifetime. In order to ensure adequate hydration in the stack, most liquid-cooled PEM fuel cell systems use external humidification. Without external humidification, the fuel cell must be operated at a lower operating temperature to ensure that the stack will not dry out. Operating the stack at lower temperature requires that the coolant loop in the system must reject a greater amount of heat, necessitating a large radiator, which increase system volume. Furthermore, operating at lower fuel cell stack temperatures leads to a significant trade-off in terms of stack power output and acceptable environmental operating ranges.
Membrane humidifiers are an efficient form of external humidification that transport humidity through a membrane from the cathode exhaust to the incoming cathode supply air stream. In these humidifiers, membranes with a dense selective layer are used to transport water vapour without allowing oxygen and nitrogen to diffuse through the membrane. Since the membrane humidifier is coupled to the stack cathode exhaust and supply, in order to maintain its function, the membrane humidifier must not leak air or else reactant oxygen will bypass the stack through the humidifier. The humidifier must maintain a high level of water vapour transport and low air leakage over the lifetime of the device.
In this presentation we present our work developing low-cost selective membranes for fuel cell humidification. These membranes are functional over a wide temperature range (-30 to +110°C) and have high water vapour permeance. They are resistant to contamination, relative humidity cycling, freeze-thaw cycling, oxidation, hydrolysis, and acidic conditions that are present in the cathode exhaust.
This presentation will also discuss the incorporation of these flat-sheet membranes in to heat and mass exchangers (membrane humidifier cartridges). These cartridges are compact with a high membrane-to-volume ratio, high water vapour transport, and have low pressure loss. The membrane humidifiers are robust to a wide range of operating conditions. Furthermore, the design of these cartridges allows the humidifier to be manufactured at a low cost in high manufacturing volumes.
Finally, this presentation will discuss membrane-based heat and mass exchanger performance at different operating conditions. A performance model will be presented which summarizes humidifier performance as a function of membrane properties, exchanger design and architecture, and fuel cell operating conditions.
Voltage Control for a Polymer Electrolyte Fuel Cell System By Model Predictive Control Controller
Authors: Qi Yuanxin , Espinoza-Andaluz Mayken , Andersson Martin 
Published: December 2020

Due to its high power density, fast start up ability, low operating temperature, noiseless and environmental friendliness, polymer electrolyte fuel cells (PEFCs) have been regarded as the most promising alternative power sources for a variety of applications, such as transportation system, domestic system, stationary system and so on. Stable and effective control strategy is essential for the efficient and safe operation of PEFC systems. Voltage control is always a research hotspot in PEFCs’ control study. When using a PEFC system to supply power in a real application, it is of great significance to maintain a stable output voltage to avoid an adverse voltage drop under sudden load change, which can reduce the maintenance costs of the PEFC generation system. The output voltage of the PEFC system can be easily affected by the inlet flow rate of the reactant gas, i.e., the reactions inside the fuel cell system will be more sufficient with higher input flow rate of the reactant gas to produce higher electrical voltage, otherwise, less electrical voltage is generated. Therefore, the focus of this study is to control the output voltage of a PEFC system by regulating its hydrogen and air flow rates, which stands for a multi input and single output control problem.
Model predictive control (MPC) is an advanced method of process control with stronger robustness and faster response compared with conventional controllers. Its main advantage is that it allows the current timeslot to be optimized while keeping future timeslots in account. Moreover, the MPC is rather suitable for solving systems with constraints, which makes a good choice for the voltage control of the PEFC system since the fuel cell system is a complicated nonlinear and strongly coupled system, with many constraints that need to be considered to ensure the coordination and balance between every subsystem.
The first part of this study is to develop a PEFC system dynamic model, which is based on the NedStack PS6 of 6kW rated power. Its polarization behavior based on different reactant flowrates are evaluated. Then based on the developed model, a novel MPC controller is designed to control the PEFC system’s output voltage at 48V, assuming that the PEFC system can be an alternative power source for an electric bicycle with 48 V by regulating the input hydrogen and air flow rates. The following figure gives an overview of the voltage control of the PEFC system. It can be seen the input of the MPC controller contains the reference stack voltage, the state vector, the actual stack voltage and the current. It should be noted that the current is the our test signal.

Figure 1
Online Measurements of Hydrogen Impurities in PEMFC Single Cells and Short Stacks
Authors: Becker Hans , Smith Graham , Bacquart Thomas , Hinds Gareth 
Published: December 2020

Impurities can easily contaminate pure hydrogen at various points in the supply chain. The maximum allowed impurity concentrations in hydrogen, sold for automotive PEMFC use, are regulated by the ISO 14687 standard. Imposing too strict limits on hydrogen quality increases the cost of hydrogen unnecessarily but too lax limits risk the performance and durability of PEFMCs. It is therefore imperative that the specified limits are based on rigorous and realistic studies of impurity behaviour in fuel cells. As part of the European Union funded projects HYDRAITE and MetroHyVe2, NPL is investigating the impact of fuel impurities on the performance and durability of fuel cells. The overall aim is to develop new testing standards and provide more reliable information to ISO committees for the continuous revision of fuel quality standards.
Impurity studies are being carried out primarily on commercial short stacks tested with a hydrogen recirculation loop and a dead-end anode. This operation mode is typical in real systems as it gives a very high fuel utilisation, however it also causes fuel impurities to concentrate well above their inlet level. Standard fuel cell testing is coupled with online measurements of the concentration of a range of contaminants inside the anode recirculation loop. For example, a Gas Chromatograph with a methanizer and flame ionising detector (GC-methanizer-FID) is used to provide information on CO2, CO, and CH4; while Selected Ion Flow Tube - Mass Spectrometry (SIFT-MS) is used to analyse isotopically labelled impurities and probe the concentrations of other species as a function of time.
Our results will first show the power and limitations of using online gas analysis with isotopically labelled impurities to monitor processes related to CO poisoning in single cells. We will then demonstrate that certain hydrocarbon impurities have little impact on stack performance despite being stringently regulated. Finally, we will present information on rates of O2 and CO2 crossover, drawing conclusions relevant for setting the next iteration of hydrogen fuel standards. This work provides vital underpinning metrological support for the development of more robust business cases for large scale deployment of hydrogen in automotive applications.
Investigation of Multilayered Catalyst Layers for Polymer Electrolyte Fuel Cells by Electrospray Deposition
Authors: Arai Hikaru , Irita Masaru , Katayama Noboru 
Published: December 2020

Due to problems such as environmental pollution and global warming, fuel cells are attracting attention as an energy source with low environmental load. As a type of fuel cells, there is a growing demand for polymer electrolyte fuel cells that can operate at low temperatures and are suitable for miniaturization. Improved power generation performance is required to increase the penetration of this technology.
The performance of a fuel cell depends on the structure of the catalyst layer (CL), which is directly involved in the reaction. The structure of the CL mainly depends on the composition and the coating method. Recently, a method has been proposed in which ion and gas transportation is made more efficient and the performance is improved by changing the ionomer distribution in the thickness direction. However, in order to change the ionomer distribution, precise control of the coating amount is required, and there are few actual formation examples and the coating method is limited. Therefore, coating methods that have not yet been investigated should also be considered. In this study, the electrospray deposition (ESD) method was used to prepare the CLs, and the comparison of the power generation performance and the effect on the CL structure were investigated.
In order to change the ionomer distribution in the thickness direction, multi-layered CLs with different ionomer to carbon ratio (I/C ratio) were formed, and the power generation performance was compared with that of the homogeneous CLs. Several homogeneous CLs with different I/C ratios were formed and the CLs were observed with scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS). The maximum output power density was 274 mW cm-2 and 312 mW cm-2 for the homogeneous and three-layer CLs, respectively. Therefore, it was found that the structure in which the distribution of ionomers is changed in the thickness direction is effective in improving the performance of the CL formed by ESD. The SEM-EDS observation revealed that the agglomeration of particles became more pronounced and the CL became thinner as the I/C ratio increased. The result suggest that it is necessary to take into account the change in thickness with the amount of ionomer in order to form an ideal CL structure using ESD.
Investigating the Influences of Polystyrene-Based Hydroxide Ion Conducting Ionomer on Electrode in Anion Exchange Membrane Fuel Cells
Authors: Chae Ji Eon , Lee So Young , Song Kwang Ho , Kim Hyoung-Juhn 
Published: December 2020

Alkaline anion exchange membrane fuel cells (AEMFCs) are an attractive alternative to proton exchange membrane fuel cells because they have the advantage of cost savings due to the use of non-noble metal catalysts. Since AEMFCs has a charge carrier of hydroxide ions, anion exchange membranes having various cationic groups substituted on the hydrocarbon polymer backbone have been actively studied for high hydroxide conductivity, mechanical properties and durability. In addition, the electrode ionomer of the core material of the membrane electrode assembly acts as a binder for uniformly dispersing the catalyst and fixing the catalyst layer and anion exchange membrane. It also serves as a transport pathway for hydroxide ions produced from the cathode to the anode. In particular, it is important that the electrode ionomer greatly affects the catalyst layer type and fuel cell performance.
Herein, polystyrene-based copolymers with variable molecular weight are prepared by radical polymerization of styrene, grafted with bromo-alkyl chains of different length (C3 or C6) through Friedel-Crafts acylation, and quaternized to afford a series of hydroxide ion–conducting ionomers. The performance of anion-exchange membrane fuel cells (AEMFCs) constructed using the prepared electrode ionomers is affected by several ionomer properties, and a maximal power density of 407 mW cm−2 and a durability exceeding that of a reference cell with a commercially available ionomer are achieved under optimal conditions. Thus, the developed approach is concluded to be well suited for the fabrication of next-generation electrode ionomers for high-performance AEMFCs.
Modeling Synergistic Fuel Cell Membrane Degradation with Mitigating Effects of Cerium
Authors: Ehlinger Victoria Marie , Kusoglu Ahmet , Weber Adam Z. 
Published: December 2020

During operation, polymer-electrolyte-membrane (PEM) fuel cells undergo mechanical and chemical degradation mechanisms, which behave synergistically and lead to accelerated membrane degradation over time. This study builds upon previous modeling work on mechanical degradation as described by a pinhole in the membrane and the effects of cerium on chemical degradation.1 By combining these two models, analysis can be carried out on the coupled degradation methods and how the mitigation effects of cerium disrupt the degradation cycle. The mechanical model represents a pinhole in the membrane using an effective void fraction, which allows for increased gas crossover through the membrane and impacts the membrane transport and mechanical properties. A microkinetic model for the chemical degradation is included in the model, including attack of the membrane polymer by hydroxyl radicals as well as the mitigation reaction for quenching of hydroxyl radicals with cerium. A concentrated solution theory approach is used to model the transport of cerium ions throughout the cell.2 The model results show how the location of cerium in the cell can be used to prevent chemical degradation. In addition, the model shows how cerium slows down the rate of pinhole growth by reducing the gas crossover and membrane thinning rate. Finally, the model can be used to optimize the distribution of cerium in the membrane and catalyst layers by balancing trade-offs between lowering degradation rates and decreasing fuel cell performance.
Acknowledgements: Funding support was supplied by the Fuel Cell Performance and Durability Consortium (FC-PAD), by the Fuel Cell Technologies Office (FCTO), Office of Energy Efficiency and Renewable Energy (EERE), of the U.S. Department of Energy under contract number DE-AC02-05CH11231. The authors would like to acknowledge Grace Anderson and Claire Arthurs for their work on membrane characterization experiments.

V. M. Ehlinger, A. Kusoglu and A. Z. Weber, Journal of The Electrochemical Society, 166, F3255 (2019).

A. R. Crothers, R. M. Darling, A. Kusoglu, C. J. Radke and A. Z. Weber, Journal of The Electrochemical Society, 167, 013548 (2020).
Enabling > 4C Fast Charging of Li-Ion Batteries with Graphite/Hard Carbon Hybrid Anodes to Overcome Energy/Power Density Tradeoffs
Authors: Chen Kuan-Hung , Goel Vishwas , Namkoong Min Ji , Wied Markus , Müller Simon , Wood Vanessa , Sakamoto Jeff , Thornton Katsuyo , Dasgupta Neil P. 
Published: December 2020

Li-ion batteries with high energy density and fast-charge capability are required to realize the widespread use of electric vehicles. However, current graphite-anode-based Li-ion batteries are unable to achieve fast charging without adversely impacting battery performance. This is because when graphite anodes are subjected to fast charging conditions, large cell polarizations reduce the accessible capacity and induce Li plating on the anode surface. The formation of metallic Li on the graphite anode surface results in irreversible loss of Li inventory, leading to significant capacity fade. In contrast to graphite, hard carbon is known to exhibit enhanced power performance. However, the high redox potential, low first-cycle efficiency, and low material density have prevented the adoption of hard carbon in high-energy-density battery systems. Thus, there is a unmet need to develop Li-ion technology to achieve both high energy density and power performance.
In this work, we demonstrate hybrid anodes fabricated by mixing graphite and hard carbon to achieve fast-charging Li-ion batteries with high energy density, using industrially relevant multi-layer pouch cells (> 1Ah) and electrode loadings (3 mAh/cm2). Standard roll-to-roll slurry casting was performed to fabricate the hybrid anodes, demonstrating the compatibility with existing Li-ion manufacturing. By tuning the blend ratio of graphite and hard carbon, it is shown that the battery performance can be tailored to simultaneously achieve high energy density and power performance. As a result of the hybrid anode design, we demonstrate pouch cells with > 96% and > 93% capacity retention over 100 cycles of 4C and 6C fast-charge cycling respectively. Synchrotron tomography was employed to investigate the microstructure effects (porosity, tortuosity, and pore size) on the electrochemical performance. Electrochemical dynamic simulations were also performed to provide mechanistic insight into the origins of the improved fast-charging performance of the graphite/hard carbon hybrid anodes.
(Invited) Designing Electrocatalysts for Controlling Selectivity of Oxygen Reduction Reaction
Authors: Joo Sang Hoon 
Published: December 2020

The oxygen reduction reaction (ORR) is arguably one of the most important electrochemical reactions affecting the efficiency of energy conversion devices such as fuel cells [1] and metal-air batteries [2]. Oxygen (O2) can be reduced in two ORR pathways are possible: the four-electron (4 e–) pathway to generate water (H2O) by complete reduction and the two-electron (2 e–) pathway to hydrogen peroxide (H2O2) involving partial O2 reduction [3,4]. Although the 2 e– pathway ORR has been regarded as an adverse side reaction that impedes the efficient 4 e– pathway, it has recently garnered a surge of interest as a means of the electrochemical production of H2O2.
In this presentation, we present a catalyst design strategy for controlling catalytic selectivity of ORR. We have developed a general synthetic strategy that can produce atomically dispersed precious metal catalysts of Os, Ru, Rh, Ir, and Pt, which served as model catalysts for unravelling catalytic activity and selectivity trends for the ORR [5]. The atomically dispersed precious metal catalysts generally showed higher selectivity for H2O2 production, due to their isolated geometry, than their nanoparticle counterparts for the ORR. Among the atomically dispersed catalysts, the H2O2 selectivity was changed by the types of metals, with atomically dispersed Pt catalyst showing the highest selectivity. A combination of experimental results and density functional theory calculations revealed that the selectivity trend of atomically dispersed catalysts could be correlated to the binding energy difference between *OOH and *O species. In terms of 2 e− ORR activity, the atomically dispersed Rh catalyst showed the best activity. We also present our recent results on the design of carbon-based and non-precious metal catalysts for the selective 2 e– ORR for H2O2 production [6,7].
References
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5. H. Kim, D. Shin, J. Lee, D. S. Baek, T. J. Shin, Y.-T. Kim, H. Y. Jeong, J. H. Kwak, H. Kim, S. H. Joo, ACS Nano 14, 1990 (2020).
6. J. Sa, J. H. Kim, S. H. Joo, Angew. Chem. Int. Ed. 58, 1100 (2019).
7. M. Ko, L. T. M. Pham, Y. J. Sa, J. Woo, T. Nguyen, J. H. Kim, D. Oh, P. Sharma, J. Ryu, T. J. Shin, S. H. Joo, Y. H. Kim, J.-W. Jang, Nat. Commun. 10, 5123 (2019).
Strategies to Enhance the Activity and Durability of MEA for High Temperature PEMFC
Authors: Park Hyanjoo , Kim Hoyoung , Bang Hotea , Tran Dinh Son , Yeo Kyeongrim , Kim Soo Kil 
Published: December 2020

High temperature polymer electrolyte membrane fuel cells (HT-PEMFCs) using phosphoric acid (PA)-doped polybenzimidazole (PBI) membrane have advantages of enhanced electrode kinetics, improved carbon monoxide (CO) tolerance, and simplified water management [1], while poisoning of the catalysts by phosphate adsorption to deactivate them remains as an issue [2]. In addition, the deliquescence of PA (absorption of moisture when exposed to the humid atmosphere) resulted in the un-even distribution of PA [3], therefore deterioration in the MEA performance.
To mitigate these issues, we have tried to optimize the structures of the commercial electrode and controlled the hydrophilicity of the electrode through additional deposition of very small amounts of Pt (anode) [4] or PtCu (cathode) using pulse electrodeposition. It was confirmed that the cell performance was improved by adjusting the hydrophilicity, improving the distribution of PA, and changing the formation of the triple phase boundary (TPB) of the catalyst layer. The performance loss due to the deliquescence of PA in the commercial PBI membrane when exposed to various humidity conditions was mitigated through an additional PA dosing method on the electrode [5].
Apart from the activity, the durability of the modified MEAs exhibited different aspects. Various MEAs were fabricated by selectively combining the results of the pulse electrodeposition and PA dosing, and the durability tests for the MEAs were performed with repeated cycles of turning on (180°C) and turning off (room temperature). 40 cycles of repeated temperature variation deactivated most of the MEAs regardless of the modifications, while the amounts of the deterioration were the functions of the modification methods. Interestingly, the performance deterioration was more obvious in the observation of the peak powers while the change in the cell potential at low current density region (200 mA/cm2) was not substantial, implying the deterioration was greatly related to the mass transport management. The different behaviors in the durability according to the modification methods along with the materials characterization using electrochemical and spectroscopic analyses will be introduced at the conference.
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[2] S. Kaserer, K. M. Caldwell, D. E. Ramaker, C. Roth, J. Phys. Chem. C, 117 (2013) 6210-6217.
[3] S. Jahangiri, I. Aravi, L. I. Sanli, Y. Z. Menceloglu, E. Ozden-Yenigun, Polym. Advan. Technol., 29 (2018) 594-602.
[4] D.-K. Kim, H. Kim, H. Park, S. Oh, S. H. Ahn, H.-J. Kim, S.-K. Kim, J. Power Sources, 438 (2019) 227022-227030.
[5] H. Park, H. Kim, D.-K. Kim, W. J. Lee, I. Choi, H.-J. Kim S.-K. Kim, Int. J. Hydrogen Energy, (2019) DOI:10.1016/j.ijhydene.2020.03.039.