bluuebunny/crossref_metadata_2025_split huggingface dataset:
(Invited) Leveraging Imaging Techniques to Accelerate the Advancement of Polymer Electrolyte Membrane Water Electrolyzers
Authors: Bazylak Aimy 
Published: February 2024

Polymer electrolyte membrane water electrolyzers (PEMWEs) are critically needed to meaningfully incorporate clean renewable energy into our energy, transportation, and manufacturing sectors, for without this energy conversion mechanism, the intermittency of renewable energy will always pose a prohibitive cost barrier to practical use. However, in addition to overcoming the intermittency issue of renewable energy, energy storage also has the power to transform current energy infrastructure, particularly when plagued by older systems that lack modularity and flexibility. For example, electricity grids are often constrained to move electricity in and out of a jurisdiction with careful predictions based on past use and future needs. This comes at a cost when electricity must be sold at a loss to prevent a catastrophic surplus of electricity in the grid. While the potential for PEMWEs is tremendous, we must reduce their capital and operating costs in order to reach widespread adoption. In recent years, important work in the field has contributed to advancing PEMWEs in a variety of areas from new materials to flow field design; however, experimental validation, particularly spatially resolved, is necessary to take a fully informed approach to tailoring these materials and architectures.
In this talk, I will discuss how we use X-ray and neutron imaging, both ex situ and operando, to provide high spatial and temporal resolution experimental performance and materials characterization for PEMWEs to inform our design process for new materials fabrication, new architectures, and operating parameters. We obtained nano-scale, 3D imaging of PEMWE catalyst layers to inform the stochastic simulations used to uncover the influence of pore size and ionomer distributions on electrical and ionic conductivities. We also used operando X-ray imaging to elucidate the influence of catalyst layer and porous transport layer interfacial conditions on liquid and gas transport behaviour. By applying neutron imaging, we elucidated the impact of temperature on the distribution heterogeneity of liquid water reactant at the catalyst layer. I will also discuss how we are using soft X-rays to perform synchrotron-based scanning transmission X-ray microscopy with absorption spectroscopy to uncover heterogeneity across performance and material characteristics for the PEMWE. Through these highly resolved techniques (in terms of time and space), we aim to advance our predictive models for designing next generation materials, interfaces, and flow configurations for high performance water electrolyzers.
Method for Systematic Validation of a Physically Based PEMFC Model By Spatially Resolved Impedance Measurements
Authors: Goosmann Tobias , Oppek Philipp , Weber Andre 
Published: February 2024

Loss mechanisms in PEM Fuel Cells related to charge transfer reactions or diffusive gas transport result in a strongly nonlinear performance, which is furthermore affected by operating conditions as temperature, relative humidity of the gases and stoichiometries. These dependencies have to be considered and validated in fuel cell models to ensure accuracy. Thus, the interpretation of the simulated results becomes more reliable.
Direct comparison of simulated and measured current/voltage-relation only allows to evaluate deviations in resulting cell voltages but exclude internal state variables of the model such as overvoltages due to different loss mechanisms. In consequence, simulated and measured values of voltage or current can concur by unnoticed compensation of different errors in magnitude and sign. Additionally, limited numbers of measurements and comparisons increase the probability and impact of this effect.
Aggravating, every single process within the cell depends on the comprehensive combination of all operating conditions and runs simultaneously with all other ones. A direct comparison of individual simulated and measured polarization curves therefore is not a suitable and sufficient validation.
We address this challenge by applying measurements of electrochemical impedance spectroscopy (EIS) during systematically varied operating conditions spatially resolved along the gas flow direction [1]. The loss processes within the cell can be separated by distribution of relaxation times (DRT) and quantified by a physico-chemical meaningful transmission line model. The resulting amount and distribution of resistances caused by loss processes is compared with the corresponding simulated values of a multiphysical model for observation and monitoring during operation [2]. These insights support the investigation of deviations between simulated and measured polarization curves and therefore the validation the model.
In this contribution, the resulting physical interpretation is discussed. Consequences and conclusions for the further development of the cell model are demonstrated.
[1]: P. Oppek et al., „ Spatially Resolved Deconvolution of Loss Processes in PEM Fuel Cells”, 241st ECS Meeting, Vancouver
[2] T. Goosmann et al. „Impedance-Based, Multi-physical DC-Performance-Model for a PEMFC Stack”, 241st ECS Meeting, Vancouver
Efficient High Temperature PEMFC Metallic Stack
Authors: Neofytidis Charalampos , Paloukis Fotios , Athanasopoulos Nikolaos , Neophytides Stylianos G. , Daletou Maria 
Published: February 2024

High temperature (HT) polymer electrolyte membrane fuel cells (PEMFCs) are highly beneficial for high power applications [1-3]. They can be used both in stationary, as well as portable power devices [1,4,5] combining the advantages of the PEM type cells (flexibility in dynamic operation, compactness) and high temperature operation (elimination of fuel humidification and carbon monoxide clean up).
This work focuses on the development, construction and testing of an efficient all-metallic HT-PEMFC stack with a power output of 1 kWe [6]. The selection of the proper polymer electrolytes allowed the operation of the stack within the range of 160-190oC. The Membrane-Electrode-Assemblies (MEA) and all components of the stack were designed and prepared in-house. The fuel cell stack characteristics and performance are affected by many parameters such as the materials, components’ design and proper assembly of the stack, as well as the operating conditions.
The stack accomplished 50% electrical efficiency with power output of 1070 W and a power density of about 0.18 W/cm2 at 180°C under pure H2 feed. The same performance was reached with reformate hydrogen feeds. The 1 kW electrical and 1 kW thermal power HT-PEMFC stack presented herein consists of thirty MEAs, metallic bipolar plates and an innovative cost-efficient internal pumpless two-phase equilibrium water-steam cooling. The effective design and construction of the latter secures temperature gradientless and isothermal operation of the stack and the production of high temperature superheated steam, which is an effective carrier of high-quality thermal energy with several commercial and industrial applications.

Acknowledgments

Funding from Region of Western Greece and European Regional Development Fund (RIS3) through DemoCHP DЕР7-0019758 and the Operational Program “Competitiveness, Entrepreneurship & Innovation” (EPAnEK), NSRF 2014-2020 through Solar2HyP Τ2ΕΔΚ-01877.

References

[1] K. Hooshyari et al., Energies 14 (2021) 5440.
[2] A. Chandan et al., Journal of Power Sources 231 (2013) 264–78.
[3] J. Zhang et al., Journal of Power Sources 16 (2006) 872–91.
[4] Y. Liu et al., Journal of Power Sources 311 (2016) 91–102.
[5] Z. Pu et al., Applied Energy 283 (2021) 116376.
[6] C. Neofytidis et al., Energy Conversion and Management 283 (2023) 116944.
Relevance of GDL Properties Regarding GDL Quality Assurance
Authors: Cremers Carsten 
Published: February 2024

Gas diffusion layers are an important part of all types of polymer electrolyte membrane fuel cells (LT-PEMFC, HT-PEMFC or AEMFC). Albeit the conversion reaction is not taking place in the GDL the contributions of the GDL to the function of the cell are essential. So, the GDL needs to homogenise the distribution of reacting gases over the electrode area compensating inhomogeneities created by the channel fin structure of the flow-field of the bipolar plate and at the same time cause a focussing of product streams towards the channels. The GDL needs to conduct electric current between the catalyst layer and the bipolar plate at high current density and transport released thermal energy. The GDL also needs to distribute mechanical pressure of the stack compression.
In order to accomplish all those tasks, the GDL needs to feature the right properties with high homogeneity through-out its area and with high reproducibility batch to batch. Unfortunately, a rather high number of properties can be assigned to a GDL. So, the review paper by Yuan et al. on properties for different LT-PEMFC components1 lists about 15 different properties for GDL which influence their function. As many of these properties are difficult to measure measuring all of them is not a viable approach to the quality assurance of GDL as part of their industrial production.
Within the project QM-GDL Fraunhofer ICT together with the other partners of the project is analysing the relevance of the different properties, comparing the expected impact of deviation from the designed values and the effort, and determining the actual values. The goal is to determine the most relevant parameters which will allow to assure proper functioning of the GDL if their values are controlled keeping the effort for measurements at a reasonable value.
In the presentation the approach for the selection of relevant parameters will be explained at a number of examples. Also, a tentative list of parameters will be presented and discussed.
The presented work is part of the project QM-GDL which receives financial support by the German Federal Ministry of Digital Infrastructures and Traffic under Grant Agreement 03B11016E. The content of the presentation is in the sole responsibility of the author.

X.-Z. Yuan, C. Nayoze-Coynel, N. Shaigan, D. Fisher, N. Zhao, N. Zamel, P. Gazdzicki, M. Ulsh, K. A. Friedrich, F. Girard and U. Groos, Journal of Power Sources,
491 (2021).
Next Generation Fluorine-Free Proton Exchange Membranes for Electrochemical Energy Applications
Authors: Andrenacci Sara , Sandru Eugenia , Fortin Patrick 
Published: February 2024

Most commercially available proton exchange membrane (PEM)-based fuel cell and electrolyser systems currently employ perfluorinated sulfonic acid (PFSA)-based PEMs, e.g., Nafion. The use of these fluorinated polymers presents serious health and environmental concerns as their production, degradation, and disposal results in the release of hazardous perfluorinted compounds that have been shown to accumulate in the environment and are toxic to living organisms.[1] Developing non-toxic, safe-by-design hydrocarbon PEMs is therefore crucial to ensure that renewable technologies that rely on proton exchange membranes remain an environmentally friendly solution. Additional shortcomings of PFSA-based PEMs include their expensive synthetic cost, inherently high hydrogen crossover, and limited operating temperature range due to poor thermo-mechanical properties above 90 °C. Hydrocarbon (HC)-based membranes offer advantages over their perfluorinated counterparts in these specific areas, however, the main drawback of HC-PEMs is that they require a much greater density of sulfonic acid groups to achieve similar proton conductivities as PFSA-based polymers.[2] This leads to greater water uptake and excessive swelling which ultimately leads to reduced mechanical stability of HC membranes.
More recently there has been an increasing number of reports exploring the use of block copolymer strategies to limit the water uptake and swelling properties of hydrocarbon PEMs while maintaining good ionic conductivity.[3] As the ion, liquid, and gas transport properties of the membrane are largely attributed to the hydrophilic blocks (i.e., with sulfonic acid groups) and the mechanical, chemical, and thermal stability of the resulting membrane is determined by the hydrophobic blocks (i.e., no sulfonic acid groups), it is postulated that the resulting membrane properties can be tuned by varying the fraction of hydrophilic/hydrophobic blocks.
The overall goal of this project is to synthesise hydrocarbon block copolymer PEMs with reduced gas crossover and enhanced the mechanical properties while maintaining sufficiently high ionic conductivity, ultimately leading to higher performance and greater durability inelectrochemical energy conversion and storage systems, e.g., fuel cells and electrolysers. In this project we have compared the ex-situ properties of novel hydrocarbon block copolymers with PFSA-based Nafion membranes, e.g., water uptake and swelling, conductivity measurements, oxidative stability via Fenton's test, etc., as well as in-situ performance tests in single cell fuel cell and electroylzers.
[1]Feng, M.; Wang, Z. et al.
Sci. Rep.
2015, 5, 9859.
[2]Holdcroft, S. Chem.
Mater. 2014, 26, 381.
[3]Guiver, M. et al.
Chem.
Rev.
2017, 117, 4759.
Species Transport in Hydrophilic Nafion-Coated Cu Catalysts for CO2 Electroreduction
Authors: Adesina Peace O. , Elliott James , Lapkin Alexei A 
Published: February 2024

Ionomer coated catalysts have increasingly been utilized in the electrocatalytic reaction of CO2 to multi-carbon products on Cu-based GDEs1,2. Their proton conductivity coupled with the Donnan exclusion due to the charged immobilized ions have served as a means of tailoring the microenvironment of the catalyst to desired products. Whilst there are experimental efforts geared towards the tuning of the local environment to desired products, there is a lack of supporting computational models that elucidate ionic species profile within the Nafion coated catalyst in the presence of fixed negative sulfonate ion charges from Nafion and the negative charges from the electrocatalysts.
On the other hand, hydrated Nafion ionomer in the presence of a supporting electrolyte forms a biphasic polymer matrix which allows the transport of CO2 in both the hydrophilic and hydrophobic regions of Nafion ionomer3. Recent literature has highlighted the transport of CO2 in hydrophobic domains but in not in hydrophilic domains4. In this work, we look a closer look at CO2 transport in hydrophilic domains. We combine mass transport generalized modified Poisson-Nernst-Planck (GMPNP) equations and molecular dynamics to elucidate the transport of reactant/product species in the local environment of Nafion coating on planar Cu catalysts.
We find that the thickness of the Nafion coating, the presence of immobilized sulfonic charges, ionic concentration of electrolyte impacts the availability of CO2, pH and the concentration of cations which are important parameters for CO2 reduction reaction. We also provide a relationship between the pKa of Nafion and the local dielectric constant of the reaction’s microenvironment using molecular modelling and the corresponding impact of Nafion’s ability to effectively minimize carbonate reactions. Our results underscore the need to manage the catalyst-ionomer microenvironments for CO2 reduction on copper electrodes. This model in conjunction with further experimental endeavours can serve as a benchmark for other intricate porous catalyst models that are significant for optimizing catalyst performance for large scale CO2 reduction operations.

Bibliography

Bui, J. C. et al. Engineering Catalyst–Electrolyte Microenvironments to Optimize the Activity and Selectivity for the Electrochemical Reduction of CO2 on Cu and Ag. Acc. Chem. Res.
17, acs.accounts.1c00650 (2022).

Kim, C. et al. Properties of the ionomer under CO 2 R-related environments Tailored catalyst microenvironments for CO 2 electroreduction to multicarbon products on copper using bilayer ionomer coatings. doi:10.1038/s41560-021-00920-8 (2022).

Ren, X., Myles, T. D., Grew, K. N. & Chiu, W. K. S. Carbon Dioxide Transport in Nafion 1100 EW Membrane and in a Direct Methanol Fuel Cell. J. Electrochem. Soc.
162, F1221–F1230 (2015).

García de Arquer, F. P. et al. CO2 electrolysis to multicarbon products at activities greater than 1 A cm−2. Science (80-. ).
367, 661–666 (2020).

Figure 1
Ionomer-Dependent Oxygen Evolution Reaction in a Half-Cell and a Liquid Electrolyzer
Authors: Mora Joy Marie , Li Guangfu , Chuang Po-Ya Abel 
Published: February 2024

Electrocatalytic oxygen evolution reaction (OER) is an important area of research due to its significance in water electrolysis, which contributes to the clean-energy storage and conversion techniques. OER exhibits irreversible and sluggish kinetics, which necessitates a high overpotential to achieve the desired reaction rate. In an alkaline medium, non-precious metals (such as Ni, Fe, Co) or metal-free materials (such as 3d-transition metal oxides and heteroatom-doped carbons) can replace expensive iridium and ruthenium oxides, which is otherwise required in an acidic medium to facilitate the reaction. However, developing new catalysts for alkaline OER is limited by the scaling relations among adsorption energetics of key intermediates (i.e., OOH*, OH*, and O*).
The electrochemical reaction kinetics depends critically on the nature of the interface between catalyst and the electrolyte where an electrical double layer (EDL) forms during OER. The current understanding of the EDL structure involves the interfacial interactions between adsorbates and catalyst layer (CL) which can be modified to improve the reaction efficiency. Ionomers are essential components of the CL and are vital in uniformly dispersing catalyst particles in ink solution. The ionomers also act as binder for the catalyst particles in the CL, helping to improve the electrode’s durability and stability over time. In addition, despite the fact that ionomers affect the properties of EDL, the impact of ionomer on the reaction pathway is often overlooked in electrocatalytic research.
In this study, we investigate the role of ionomer in the catalyst layer by comparing different polymer dispersions, including PTFE, Nafion, and commercial As-4. The results indicate that the Nafion-contained CL performs better than other polymer CLs in TF-RDE/RRDE, as it facilitates direct O*-O* coupling. In contrast, anionic ionomer demonstrates superior long-term stability in alkaline liquid electrolyzers, despite oxidization degradation.
Nanocellulose as a Sustainable Polymer Electrolyte
Authors: Lyth Stephen Matthew , Bayer Thomas , Nishihara Masamichi , Sasaki Kazunari 
Published: February 2024

Polymer electrolyte membranes in fuel cells and electrolyzers will play a key role in the hydrogen economy. These membranes are generally made of sulfonated fluoropolymers, which have excellent proton conductivity, impressive redox stability, and good gas barrier properties. However, the complex synthetic processes mean that they remain expensive. Their synthesis also involves ecologically damaging perfluorosulfonic acids (PFSAs), otherwise known as “forever chemicals” due to their persistence in the environment. More sustainable and lower cost hydrocarbon electrolytes should therefore be investigated.
Cellulose is the most abundant biopolymer in nature, and is derived from plant matter. It is used at vast scale and low cost to make paper and cardboard. Cellulose can be chemically or mechanically treated to break up the fibers to form “nanocellulose”. Nanocellulose is a low-cost nanomaterial which can be formed into thin membranes which are much stronger than conventional cellulosic paper.
We propose nanocellulose as an alternative electrolyte to replace sulfonated fluoropolymers in fuel cells. We confirmed that unmodified nanocellulose can conduct protons due to acidic hydroxyl groups. We also showed that nanocellulose membranes present a much better barrier to hydrogen compared to Nafion, and can successfully be used as an electrolyte in fuel cells. However, the current-voltage performance of unmodified nanocellulose was insufficient due to a high membrane resistance.
We went on to improve the proton conductivity by introducing sulfonic acid groups and reduced the membrane resistance by using spray deposition to create thinner membranes, resulting in significantly improved fuel cell power density of 160 mW/cm2. We also implemented crosslinking with sulfosuccinic acid to simultaneously improve the ionic conductivity, increase strength, and reduce swelling in water. This work shows that nanocellulose is a promising new class of polymer electrolyte which could significantly reduce the cost and improve sustainability of fuel cell and electrolyser systems.
1. Cellulose Nanocrystals Crosslinked with Sulfonic Acid as Sustainable Proton Exchange Membranes for Electrochemical Energy Applications, O. Selyanchyn, T. Bayer, D. Klotz, R. Selyanchyn, K. Sasaki, S. M. Lyth, Membranes 12 (7), 658 (2022)
2. Spray Deposition of Sulfonated Cellulose Nanofibers as Proton Conducting Membranes for Fuel Cells, T. Bayer, B. Cunning, R. Selyanchyn, B. Smid, S. Fujikawa, K. Sasaki, S. M. Lyth, Cellulose, 28, 1355–1367 (2021)
3. Proton Conductivity in Cellulosic Materials: A Review, O. Selyanchyn, R. Selyanchyn, S. M. Lyth, Frontiers in Energy Research: Fuel Cells, 8, 596164 (2020)
4. High Temperature Proton Conductivity in Nanocellulose: Paper Fuel Cells, T. Bayer, R. Selyanchyn, S. Fujikawa, K. Sasaki, and S. M. Lyth, Chemistry of Materials, 28 (13), 4805–4814 (2016)