bluuebunny/crossref_metadata_2025_split huggingface dataset:
Properties and Parameters of Importance for Enhanced Performance and Performance Stability of Anion Exchange Membrane Fuel Cells – a Modeling Study
Authors: Brandon Simon , Yassin Karam , Rasin Igal G , Dekel Dario R. 
Published: February 2020

Research and development of anion exchange membrane fuel cells (AEMFCs) has placed a large focus on cell performance. For example, one of the main goals of anion exchange membrane (AEM) materials development has been the increase of their hydroxide conductivity, which directly enhances AEMFC performance. Although crucially important, achieving high performance is not enough since robust AEMFCs must exhibit both high performance AND high performance stability (i.e. longevity).
In this contribution we present results from one-and-three dimensional modeling studies aimed at elucidating the impact of a number of key AEM material properties, as well as AEMFC design and operating parameters, both on performance and on performance stability.
Using a one-dimensional model of AEMFC operation [1], which includes AEM chemical degradation analysis capabilities [2], we discuss the relative importance of membrane conductivity, membrane thickness and membrane water diffusivity. In particular, we demonstrate that although conductivity is an important AEM property where cell performance is concerned, its impact on longevity is minimal. Thus developing an AEM which promotes enhanced cell performance and cell performance stability requires a focus both on conductivity and on other properties and/or parameters which do impact stability. Our results show that one of these is AEM water diffusivity which strongly influences AEMFC performance stability and should therefore (in addition to conductivity) be on the list of important properties and parameters to be tailored in the next generation of AEMs.
In addition to our one-dimensional analysis, we employ a full three-dimensional model of an AEMFC to explore additional properties and parameters of importance. In particular, we discuss the impact of system geometry (flow field patterns) as well as gas flow rates (gas stoichiometry) on performance, and propose possible related routes to process improvement.
References:

R. Dekel, I.G. Rasin, M. Page, S. Brandon, J. Power Sources 375 (2018) 191

R. Dekel, I.G. Rasin, S. Brandon, J. Power Sources 420 (2019) 118
Electrolysis Cell Performance and Durability - a Contradiction in Terms?
Authors: Bensmann Boris , Suermann Michel , Trinke Patrick , Immerz Christoph , Broda Agata , Hanke-Rauschenbach Richard 
Published: February 2020

In the current stage the focus of PEM water electrolysis cells development is on improving durability and reliability. Over the next decade growing attention has to be paid to reduce capital and operating cost as well as to increase flexible operation in order to fulfil the needs of the costumers, e.g. reducing the systems total cost of ownership (TCO). In most cases, however, achieving the desired cost reduction and higher flexibility contradicts durability and reliability expectations as well as performance requirements.
TCO reductions can be achieved by changing the operating conditions, e.g. increasing temperature, current density, operating pressure or load flexibility, but also by e.g. reducing the catalyst loading or membrane thickness. With respect to the operating conditions, it seems problematic as the different parameters also act as stressors for certain degradation phenomena in the system. On the other hand, reducing the so far oversized materials used, increases the vulnerability of the components with regard to degradation and thus limits the durability and reliability of the system.
This contribution discusses this described interplay between performance and durability in more detail. First, stressors (e.g. high compartment pressures) are attributed to certain degradation effects (e.g. voltage increase) appearing in the cell. Concerning such a general analysis, there is much information available about the response of the electrochemical cell to certain stressors and the relations are well known. However, only less can be said about the origin of this measureable effects. But to achieve the required performance while maintaining or even increasing the durability, a deeper understanding of the underlying degradation phenomenon (e.g. loss of ionic conductivity) is required. It is shown on the example of the membrane as critical component in electrolysis cells that standard electrochemical characterization methods, if evaluated properly, can already provide important information about the origin of such measured effects.
Starting from this, new materials can be developed or adequate mitigation strategies can be implemented to suppress degradation. It is also shown that additionally applied comprehensive modelling of electrolysis cells can support these efforts and can potentially be used for optimized cell design, considering performance and durability requirements.
Effect of Microscopic Oxygen Bubbles on Measured OER Catalyst Stability - a Comparative Study between RDE and MEA Measurements
Authors: El-Sayed Hany A , Tovini Mohammad Fathi , Weiß Alexandra , Gasteiger Hubert A. 
Published: February 2020

Fast screening of OER catalysts for their intrinsic activity and stability is pivotal for the development of PEM electrolyzers.1 With respect to OER activity, catalyst screening is very well-established using different measurement techniques such as rotating disk electrode (RDE), flow-channel methods, or full cell measurements in an electrolyzer, where comparable activities are obtained. On the other hand, accelerated stability testing of OER catalysts has been reported to result in different stability lifetimes based on the testing method. For example, stability tests using the RDE technique result in magnificently shorter catalyst lifetimes than those using an electrolyzer.2

We have recently discovered that the use of an RDE-based galvanostatic test is not reliable to investigate the OER catalyst stability as the “apparent” catalyst degradation associated with this test is mostly due to a measurement artefact.3 During the OER galvanostatic test, oxygen gas bubbles form and accumulate in the pores of the catalyst layer, shielding the active surface area of the catalyst, therefore resulting in an increasing potential, mistakenly interpreted in the literature as catalyst degradation.4, 5

In this contribution, we present a comprehensive study in which we demonstrate how the accumulation of microscopic oxygen bubbles in the pores of the electrocatalyst layer during the OER results in an artefact that falsifies the estimated catalyst lifetime. We will show that this artefact exists in all RDE-based stability tests including galvanostatic, potentiostatic, and potential cycling techniques. Furthermore, we will show that the same artefact also exists during the stability test carried out using a membrane electrode assembly (MEA) in an electrolyzer, but to a much lesser extent compared to that associated with the RDE technique. We will also discuss how to mitigate this accumulation of gas bubbles in an MEA, and discuss possible protocols that enable the OER catalyst stability testing using RDE-based techniques.
References

L. Wang, F. Song, G. Ozouf, D. Geiger, T. Morawietz, M. Handl, P. Gazdzicki, C. Beauger, U. Kaiser, R. Hiesgen, A. S. Gago and K. A. Friedrich, J. Mater. Chem. A,
5(7), 3172–3178 (2017).

S. Cherevko, Current Opinion in Electrochemistry,
8, 118–125 (2018).

Hany A. El-Sayed, Alexandra Weiß, Lorenz F. Olbrich, Garin P. Putro, and Hubert A. Gasteiger, Journal of the Electrochemical Society,
166(8), F1-F7 (2019).

H.-S. Oh, H. N. Nong, T. Reier, M. Gliech and P. Strasser, Chem. Sci.,
6(6), 3321–3328 (2015).

H.-S. Oh, H. N. Nong, T. Reier, A. Bergmann, M. Gliech, J. Ferreira de Araújo, E. Willinger, R. Schlögl, D. Teschner and P. Strasser, J. Am. Chem. Soc.,
138(38), 12552–12563 (2016).
Operando Sub-Second Neutron Imaging of Cationic Species Migration in a Proton Exchange Membrane Water Electrolyzer
Authors: Zlobinski Mateusz , Babic Ugljesa , Gubler Lorenz , Schmidt Thomas J. , Boillat Pierre 
Published: February 2020

In recent years, it became clear that implementing energy storage on a large scale is a necessary route for the power production sector to maintain a stable and sustainable grid with increasing share of intermittent renewable sources of energy. Proton exchange membrane water electrolyzers show promise especially because of their suitability to be coupled to renewables in remote areas decentralizing the energy grid. There are, however, some challenges, which have to be tackled before market penetration can occur. One of the most pressing issues is the susceptibility of the proton exchange membrane to feed water impurities in form of cations [1], [2]. Titanium porous transport layers, piping and other system components will introduce slight amounts of cations during normal operation (Fe, Na, Cu, Ca, Ti), which over a longer period will become the cause of significant overpotential [3]. It is therefore necessary to understand the contamination mechanism of proton exchange membranes and its impact on the electrochemical performance of the cell.
Motivated by the fact that the reversible degradation is one of the key factors which dictate the operability of an electrolyzer, we carried out experiments which bring further insights into the influence and behavior of the cationic species in the proton exchange membrane water electrolyzer under operation and standby conditions. Neutron imaging techniques were employed to observe the model contaminant in form of Gd3+, which is a perfect fit due to its large neutron cross-section. We found that under the effect of the electric field the cations migrate and accumulate near cathode catalyst layer/porous transport layer interface. A sub-second imaging setup enabled us to correlate the position of cations within the membrane with electrochemical data. Subsequently we regenerated the cell by operating it with diluted sulfuric acid (below 1mMol/L) injected into cathode compartment during the neutron imaging. Influence of the accumulation of the cations near the cathode catalyst layer on the electrolyzer performance and optimal operando regeneration procedures will be discussed.
[1] S. Sun, Z. Shao, H. Yu, G. Li, and B. Yi, “Investigations on degradation of the long-term proton exchange membrane water electrolysis stack,” J. Power Sources, vol. 267, pp. 515–520, 2014.
[2] X. Wang, L. Zhang, G. Li, G. Zhang, Z. G. Shao, and B. Yi, “The influence of Ferric ion contamination on the solid polymer electrolyte water electrolysis performance,” Electrochim. Acta, vol. 158, pp. 253–257, 2015.
[3] U. Babic, M. Suermann, F. N. Büchi, L. Gubler, and T. J. Schmidt, “Critical Review—Identifying Critical Gaps for Polymer Electrolyte Water Electrolysis Development,” J. Electrochem. Soc., vol. 164, no. 4, pp. F387–F399, 2017.

Figure 1
In-plane Mass Transport in Polymer Electrolyte Membrane Electrolyzer Porous Transport Layers with Through Pores
Authors: Kim Pascal Junseob , Lee ChungHyuk , Lee Jason Keonhag , Fahy Kieran F. , Bazylak Aimy 
Published: February 2020

The porous transport layer (PTL) is a key component in the polymer electrolyte membrane (PEM) electrolyzer for transporting reactant liquid water to the active sites while facilitating oxygen gas removal. Most current PTL designs use an expanded foam structure with uniform porosity. The interactions between the PTL and flow fields typically leads to non-uniform reactant and product distributions due to the necessarily open and closed regions (channels and lands in the flow fields). These non-uniform distributions hinder performance in the cell; therefore, structures tailored to particular flow field geometries would benefit the technology and be of significant interest to the field.
Mesh-type PTLs are promising for their ease of fabrication with controllable structures at low manufacturing costs, yet the nature of two-phase flow within the mesh-type PTLs is not well understood in the literature. Furthermore, mesh structures have not been optimized to be used with conventional flow fields. In this study, the effect of mesh structures on the mass transport properties of a PEM electrolyzer is investigated through customized porous transport layers and synchrotron X-ray imaging. Two porous transport layers were compared: a PTL with straight pores under the channel and the land and another PTL with straight pores under only the channel (Figure 1). The pores under the land were inaccessible for both liquid water and gas, and as a result, reactions were localised under the channel regions. Moreover, the presence of pores under the land region led to a reduced electrical contact area, thereby contributing to increased ohmic resistance. We observed that pores under the land resulted in higher mass transport resistances exhibited by an increase in gas volume in the pores under the channel. Overall, the PTL with pores only under the channel exhibited relatively superior electrochemical performance; thus, we recommend that mesh PTL should be designed with minimal pores under the land.
Figure 1: Schematic of the anode half of PEM electrolyzers installed with a mesh PTL with a) pores under the channel and land regions, and b) pores under only the channel region of the flow fields.

Figure 1
Investigation of the Microstructure and Rheology of Iridium Oxide Catalyst Inks for Low-Temperature Polymer-Electrolyte-Membrane Water Electrolyzers
Authors: Khandavalli Sunilkumar , Park Jaehyung , Kariuki Nancy N. , Myers Deborah J. , Ulsh Michael , Mauger Scott A 
Published: February 2020

Low-temperature polymer electrolyte membrane water electrolyzers (PEMWE) are an attractive clean energy technology to produce hydrogen (H2) as an energy carrier for several applications such as transportation and grid-scale energy storage and distribution (as supported by the US Department of Energy’s H2@Scale initiative). A critical component of PEMWE membrane electrode assemblies (MEA) is the catalyst layer (CL), where the electrochemical reactions occur. The microstructure of the CL plays a key role in MEA performance by affecting porosity, connectivity, etc. The CL microstructure is formed by the catalyst particles and an ionomer - which acts both as a binder for catalyst particles and as a proton conducting medium. The interactions between the ink components (catalyst-ionomer-solvent), and the ionomer concentration in the ink, which dictates the ink microstructure and the processing behavior during coating and drying, play a critical role in the formation of the CL microstructure.
In this talk, an investigation of catalyst-ionomer interactions, microstructure and rheological behavior of the catalyst inks will be presented. The ink consists of iridium oxide (IrO2) catalyst particles and Nafion ionomer dispersed in a mixture of 1-propanol and water. A combination of rheology, ultra-small/small angle x-ray scattering, dynamic light scattering, and electrophoretic mobility were used to understand inter-particle and particle-ionomer interactions and characterize microstructure. Our results show that iridium catalyst dispersions in the absence of ionomer are agglomerated. When ionomer is added to the dispersion it adsorbs to the surface of IrO2 and provides stabilization through both electrostatic and steric mechanisms. As the ionomer content increases, we see increasing interparticle interactions. The stability and microstructure evolution as a function of ionomer concentration in the ink will be discussed. As well as their relation to device performance.
Catalyst Effects on Gas Phase HCl Oxidation in PEM Electrolyzer
Authors: Likit-anurak Kris , Lopata Joseph Steven , Shimpalee Sirivatch , Weidner John W. , Khunatorn Yottana , Meekins Benjamin Highsmith 
Published: February 2020

Electrolysis of HCl exhibits promise for large-scale production of hydrogen with the additional benefit of converting a low-value byproduct (HCl) into a more valuable feedstock (Cl2). However, most of the available publications in literature use aqueous phase HCl as the electrolyte [1-3]. Previously, gas phase hydrogen bromide (HBr) was shown to electrolyze at current densities an order of magnitude greater than that of aqueous HBr [4]. Aqueous HBr electrolysis was limited by slow diffusion in the liquid phase. We show here that gas phase HCl also exhibits higher reactions rates, as reflected by higher current densities, when compared to aqueous phase.
The purpose of this work was to study the efficiency and durability of the anode catalyst (RuO2 and IrRuO2), the role of the polymer membrane (Nafion vs. polybenzimidazole), and the operating parameters (temperature, HCl flow rate, and current density) in a proton exchange membrane (PEM) electrolyzer. We found that crossing over of chorine from anode to cathode can poison the catalyst at the cathode, resulting in less durability and shorter lifetime of the electrolyzer. We also discuss how operating temperature, HCl flow rate, and hydration affect the performance of the electrolyzer.
References:

Huskinson, J. Rugolo, S.K. Mondal, M.J. Aziz, Energy & Environmental Science. 5 (2012) 8690.

Mohammadi , S.N. Ashrafizadehb, A. Sattari, Chemical Engineering Journal 155 (2009) 757–762.

Barmashenko and J. Jo"Rissen, Journal of Applied Electrochemistry 35 (2005) 1311–1319

Sivasubramanian, R.P. Ramasamya, F.J. Freireb, C.E. Hollanda, J.W. Weidner, International Journal of Hydrogen Energy 32(4) (2007) 463-468.
(Invited) The Evolution of Membrane Electrode Assemblies for Automotive Applications
Authors: Martinez Alex 
Published: February 2020

Membrane Electrode Assemblies (MEAs) have evolved significantly in recent years to become a complex piece of technology. Currently, MEAs incorporate a variety of catalyst types and supports which need to be integrated into layers for both anode and cathode electrodes. In addition, the additives used in the membrane have also become more complex, to mitigate gas crossover and degradation that can be caused by metal ion impurities, thus enabling the deployment of thinner membranes (<15 mm). Further, different approaches to maximising the power per cost lead to different power density requirements. For example, the performance target set by the US-DOE is 1.0 W/cm2, whereas in EU funded program GAIA1 the target is a demanding 1.8 W/cm2. This forces MEA developers to carefully design each component to enable mass commercialization.
This presentation will document recent advances at JM in the design of MEAs for the transportation industry, with an emphasis on the integration of scaled-up alloy catalysts in cathode layers. Results from advanced catalyst characterisation using state of the art TEM and XPS facilities will be provided; these results have helped identify the mechanisms that compromise catalyst stability and activity and have allowed the synthesis of new materials and layers that will enable thrifting of Pt to levels that will help mass commercialization. In addition, with the help of 1D testing and the use of simulation tools such as OpenFCST, insights will be provided into proton and oxygen transport limitations at high current densities. Finally, a detailed analysis will also be provided that highlights the importance of understanding catalyst and ionomer surface compositions to give high kinetic activity whilst also enabling high performance at high current densities in H2/Air, in order to reach 1.8 W/cm2.

References

GAIA, Grant Agreement Number 826097, http://www.gaia-fuelcell.eu/

Acknowledgements

The GAIA project has received funding from the Fuel Cells and Hydrogen 2 Joint Undertaking under grant agreement No 826097. This Joint Undertaking receives support from the European Union’s Horizon 2020 research and innovation programme, Hydrogen Europe and Hydrogen Europe Research.
Perovskite Solar Cells Using Tin Oxide As Electron Transport Layer
Authors: Workman Maniell , Chen Zhi David , Sarvari Hojjat , Liu Guoduan , Graham Kenneth , Park So Min 
Published: February 2020

Abstract

Solar Energy has many challenges and disadvantages preventing its widespread use and implementation. Current silicon solar panel technology is still more expensive than coal and oil. The need for alternative energy sources has driven research for high efficiency and low-cost solar cells. The previous electron transport material (ETL) is TiO2, which needs high processing temperature (~400°C), which limits many applications using flexible substrates. Tin oxide layer can be processed at low temperatures (<200°C). It is promising for applications for flexible substrates.
My research is focused on perovskite solar cells utilizing tin oxide nanoparticle as ETL. Tin oxide layer was spin coated and annealed in order to create a conductive electron transport material. In this study, we will compare two precursor materials: SnCl4 nanoparticles in ethanol solution and SnO2 nanoparticles in aqueous solution. We found that the ETL using SnCl4 nanoparticles results in much poorer performance of solar cells with a power conversion efficiency (PCE) of 12.32% (Figure 1) and the ETL using SnO2 nanoparticles results in much better solar cells with PCE of approximately 18.13% (Figure 2). Therefore, SnO2 nanoparticle is a promising ETL material for high efficiency perovskite solar cells.
a)b)
Figure 1: a) I-V curves of a solar cell with SnO2 ETL using SnCl4 precursor. Poor performance (12% PCE) and large hysteresis observed. b) I-V curves of a solar cell with SnO2 ELT using SnO2 nanoparticle precursor. Lower hysteresis and higher PCE (18%) observed.

Figure 1
Adherent Light-Induced Al Plating on Si for Substitution of Ag in Si Solar Cells
Authors: Ricci Lewis , Tseng Mao-Feng , Shin Woo Jung , Tao Meng , Liu Yunyu , Jiang Fangdan , Xing Guoqiang 
Published: February 2020

Silver (Ag) is one of the most expensive materials used in the manufacture of silicon (Si) solar cells today as the front electrode. The current Si cell manufacturing cost from Si wafers is ~$0.10 per cell and Ag accounts for about half of that cost. Another key issue is the limited reserve of Ag on our planet, with a US Geological Survey estimated amount of 530,000 metric tons [1]. Even if the entire Ag reserve was used for cell manufacturing, we could only supply ~5% of the 2100 global energy demand [2]. Based on material cost, abundance, and resistivity, only two suitable replacements for Ag exist, Cu and Al. Al bears the advantage over Cu since it eliminates the need for a barrier layer such as Ni. Al is also less prone to oxidization often experienced by Cu. We reported light-induced Al electroplating on Si solar cells using a Lewis acidic chloroaluminate ionic liquid [3], demonstrating direct Al plating on Si without a seed layer.
This talk focuses on surface preparation and Al plating processes to promote strong adhesion and low contact resistance between plated Al and cell emitter. Sheet resistance and surface morphology of the emitter were monitored as a function of laser power for SiNx removal. Electrochemical capacitance-voltage profiling determined the laser power at which the emitter surface dopant profiles were preserved. A process to remove laser damage and clean the Si surface after laser patterning was developed by etching Si in 1 wt% NaOH. It was found by atomic force microscopy that ~23 s was the minimum time to completely remove the original Si surface which was damaged and contaminated. Al deposits on substrates prepared by this surface cleaning process showed strong adherence in the Scotch tape test. Al plating was performed at different temperatures. The resulting film thickness and morphology were investigated with scanning electron microscopy. The lowest film resistivity was less than 8 µΩ-cm which was obtained at a plating temperature of 50°C and showed a grain size of 2–5 µm.
[1] U.S. Geological Survey, Mineral Commodity Summaries (2017).
[2] M. Tao, Terawatt Solar Photovoltaics: Roadblocks and Opportunities (Springer, London, 2014).
[3] L. Wang, W.-H. Huang, W. J. Shin, M. Tao, B. Deng, and D. Wang, J. Electrochem. Soc., 165, D381 (2018).