bluuebunny/crossref_metadata_2025_split huggingface dataset:
(Invited, Digital Presentation) High-Efficiency and Stable Perovskite LEDs and Displays with Nanophotonic Methods
Authors: Zhang Qianpeng , Zhang Daquan , Sun Xiaofei , Ren Beitao , Fan Zhiyong 
Published: November 2022

Perovskite light-emitting diodes (PeLEDs) have experienced rapid development in the past 8 years. The external quantum efficiencies (EQEs) of red, green, and near-infrared (NIR) PeLEDs have all surpassed the 20% milestone. Meanwhile, the blue PeLEDs also achieved EQEs higher than 10% and are catching up quickly with PeLEDs of other colors.
However, there are still two key problems remaining within the PeLEDs for their further development, namely the light extraction problem and the short lifetime problem. Therefore, in this report, we will discuss our recent work targeting addressing the above two critical problems.
First, our work on improving the light extraction efficiency by deploying the nanophotonic substrates will be introduced. Second, the improvement of the device’s operational lifetime at high luminance conditions with perovskite nanowires embedded in a porous alumina template will be discussed. Third, a full evaporation method that is compatible with industrialization will be shown. Last but not least, our endeavors on the displays based on perovskite materials will be covered.
References
[1] Q. Zhang, M. M. Tavakoli, L. Gu, D. Zhang, L. Tang, Y. Gao, J. Guo, Y. Lin, S. -F. Leung, S. Poddar, Y. Fu, Z. Fan, "Efficient metal halide perovskite light-emitting diodes with significantly improved light extraction on nanophotonic substrates," Nature Communications, 10 (1), 727 (2019).
[2] Q. Zhang, D. Zhang, L. Gu, S. Poddar, Y. Fu, L. Shu, and Z. Fan, “Three-dimensional perovskite nanophotonic wire array-based light-emitting diodes with significantly improved efficiency and stability,” ACS Nano, 14 (2), 1577-1585 (2020).
[3] Y. Fu, Q. Zhang, D. Zhang, Y. Tang, L. Shu, Y. Zhu, and Z. Fan, “Scalable All-evaporation Fabrication of Efficient Light-Emitting Diodes with Hybrid 2D-3D Perovskite Nanostructures,” Advanced Functional Materials, 30, 2002913 (2020).
[4] D. Zhang, Q. Zhang, B. Ren, Y. Zhu, M. Abdellah, Y. Fu, B. Cao, C. Wang, L. Gu, Y. Ding, K.-H. Tsui, S. Fan, S. Poddar, L. Shu, Y. Zhang, D.-B. Kuang, J.-F. Liao, Y. Lu, K. Zheng, Z. He, Z. Fan, “Large-scale Planar and Spherical Light-emitting Diodes Based on Arrays of Perovskite Quantum Wires”, Nature Photonics, 19, 284-290 (2022).
Porosity, Porosity Heterogeneity and Morphology Characterization of Microporous Layers of Commercial Gdls
Authors: Chen Yen-Chun , Buechi Felix N. , Karageorgiou Chrysoula , Eller Jens , Schmidt Thomas J. 
Published: November 2022

Porosity and morphology of MPLs have a remarkable influence on the performance of PEFCs. However, until now, MPL porosity is largely undetermined for all commercial gas diffusion layers and the MPLs are commonly thought of as a homogeneous layer in thickness and porosity. Many model studies are based on this picture. However, these assumptions are not evidence-based, and can lead to erroneous interpretations of MPL functions. The challenge of having realistic models of MPLs lies in the lack of descriptions of MPL properties on the representative millimeter scale, while its pore structure is on the nanometer scale.
Here, we use laboratory-based, X-ray tomographic microscopy (XTM) to determine the porosity, thickness and their spatial heterogeneity of microporous layers from 15 commercial GDL materials on the operation-relevant, millimeter scale. These properties are relevant to the diffusive transport through diffusion media (cf. Fick’s law).
The porosity distribution is measured by quantifying the volume fraction of a saturating liquid, n-decane, in the fully saturated MPL with a large field of view (FoV) of >10 mm2 and a voxel edge length (determining the image resolution) of 3.6 μm. With optimized X-ray quantum noise control, regional average porosity differences >4.7% can be determined with a 95% confidence level (for every 50 μm 50 μm regions). This resolution in porosity determination allows to define and quantify the degree of spatial porosity heterogeneity for every MPL—a property of MPL that was previously unclear.
Together with the MPL thickness heterogeneity (related to intrusion depth), the MPLs of the 15 commercially available gas diffusion layers from the three international manufactures Freudenberg, Sigracet® and CeTech, are characterized and classified into 5 groups. Contrary to the common homogeneous assumption, the majority of characterized MPLs (especially from Sigracet® and CeTech) actually come with various degrees of porosity and thickness heterogeneity. These differences among MPLs could result in very different water management properties of the respective GDL materials. The representative descriptions of MPL porosity, porosity heterogeneity and thickness heterogeneity also provides realistic input to modeling.

Figure 1
Advanced Voltage Break Down Analysis By Statistical Open-Source Tool Case Study Based on Polymer Electrolyte Water Electrolysis
Authors: Dizon Arthur , Schuler Tobias , Weber Adam Z. , Danilovic Nemanja , Bender Guido 
Published: November 2022

The development of economical hydrogen-production methods is essential to establishing hydrogen as a viable fuel. One promising method of hydrogen production is proton-exchange-membrane water electrolysis (PEMWE), where water is converted electrochemically to hydrogen and oxygen gas. The PEMWE research efforts are multi-faceted and aim to improve material costs, operations costs, and safety, which require robust methods to accurately gauge PEMWE cell performance. Electrochemical cells can be fundamentally characterized in terms of a Tafel equation, which describes the relationship between the faradaic current density and applied potential as a log—linear relationship, respectively. Due to the complex and highly coupled chemistry and physics within the membrane—electrode assembly, the operational ranges of experimental PEMWE data used to extract Tafel parameters are often nebulous, which results in addition of a human element in estimating the appropriate data where a Tafel-kinetic model is assumed to be applicable.
In this work, an algorithm for extracting the Tafel slope was developed to assess the adherence of polarization data to a Tafel-kinetic model. The method was developed using experimental PEMWE data and is a systematic and statistical assessment that uses error propagation and Monte-Carlo simulations of fitted parameters to yield 95% confidence intervals (CIs). As shown in Figure 1a, the CIs are used to identify operational ranges where polarization data is consistent with a Tafel-kinetic model. The method was used to perform a voltage-breakdown analysis, which is shown in Figure 1b. A voltage-breakdown analysis is an analytical tool where voltage losses are quantified and associated with a specific mechanism, such as mass transfer, ohmic resistance, kinetics, and thermodynamics. The algorithm was implemented in a portable and open-source format, which was shown to reduce variability of analyses performed by members of the H2NEW consortia. Applicability of the algorithm should be transferrable to other electrochemical systems and may serve as a standardized method of extracting electrochemical kinetic parameters and performing voltage breakdown analyses.

Acknowledgements

This research is supported by DOE Hydrogen and Fuel Cell Technologies Office, through the H2NEW Consortia.

Figure 1
Study of Mechanical Properties of Membrane-Electrode Assemblies for Proton Exchange Membrane Fuel Cells By the Small-Punch Technique
Authors: Hernández Rebeca , Merino Susana , Plaza Daniel , Duque Luis , Folgado M. Antonia , Chaparro Antonio M , Serrano Marta , de Diego Gonzalo 
Published: November 2022

Mechanical properties of membrane-electrode assemblies (MEAs) are most relevant for the durability of proton-exchange membrane fuel cells (PEMFCs) [1]. During operation, the MEA must endure eventual changes in the static pressure of anodes and cathodes caused by changes in power demand, gases flow rate, and/or water generation, accompanied by hygrothermal cycles, that cause mechanical stresses in the membrane, leading to cracks and possible fatal failure [2]. In parallel, the mechanical properties of MEAs change irreversibly during power production as a consequence of membrane and electrodes corrosion [3]. Therefore, it is of interest to characterize the mechanical properties of MEAs before assembly, and after operation.
The small-punch is a new technique for testing mechanical properties of solids. It consists of measuring the deformation of a disc of the testing material with a ‘small puncher’, while recording the load (force) exerted by the puncher and the deflection produced on the specimen (Fig. 1a) [4]. The plot load vs deflection allows estimating mechanical strength, fracture toughness, impact, and tensile properties. Most interesting is that the disk specimen can be as small as a few millimeters, which makes the small-punch technique very appropriate when the amount of sample is limited, and for localized studies of mechanical properties.
In this communication, results of the small-punch technique are shown for the study of MEAs operated in single PEMFCs (Fig. 1b). The analysis is carried out of the local mechanical properties on new and degraded MEAs. First results show that local mechanical properties of the aged MEA correlate well with gas feeding conditions and reflect laterally inhomogeneous degradation (Fig. 1b).
Acknowledgement: The work is partially financed by the ELHYPORT project (PID2019−110896RB-I00), Spanish Ministry of Science and Innovation.
[1] X. Huang, R, Solasi, Y. Zou, M. Feshler, K. Reifsnider, D. Condit, S. Burtlatsky, T. Madden, J. Polymer Science: Part B: Polymer Physics, Vol. 44, 2346–2357 (2006).
[2] Z. Lu, M. Lugo, M.H. Santare, A.M. Karlsson, F.C. Busby, P. Walsh, J. Power Sources 214 (2012) 130-136.
[3] M. Pestrak, Y. Li, S.W. Case, D.A. Dillard, M.W. Ellis, Y-H. Lai, C. S. Gittleman, J. Fuel Cell Sci. Technol. (2010), 7(4): 041009.
[4] EN 10371:2021 Metallic materials - Small punch test method. CEN, Brussels (2021)

Figure 1
Catalyst Layer Resistance, Utilization, and Degradation in PEM Electrolysis
Authors: Padgett Elliot , Bender Guido , Haug Andrew , Lewinski Krzysztof A. , Sun Fuxia , Yu Haoran , Cullen David A. , Steinbach Andrew , Alia Shaun M 
Published: November 2022

Proton exchange membrane (PEM) electrolysis is a promising route for renewable hydrogen production. However, to enable widespread, low-cost hydrogen generation, PEM electrolyzers must make advances in performance and durability with greatly decreased loadings of iridium as the anode oxygen evolution catalyst. The ionic and electronic resistance of the anode catalyst layer is an important consideration, as high internal resistance lowers catalyst utilization and cell performance while accelerating degradation. Catalyst layer resistance (CLR) is relatively well-understood in fuel cells and other porous electrode systems. However, characterization of CLR is not routinely used in the PEM electrolysis community, and the impacts of CLR for PEM electrolysis are not widely understood.
Here we will present in-situ methods for measuring CLR in electrolysis cells using a non-faradaic H2/H2O condition as well as methods for calculating the associated voltage losses. These methods are applied to anode catalyst layers based on IrO2 nanoparticles as well as dispersed nano-structured thin film (NSTF) Ir catalysts. Trends of CLR, performance, and durability with electrode properties such as loading and interactions between the porous transport layer and catalyst layer will be discussed. We will also present investigation of characteristic uneven degradation of the catalyst layer caused by CLR and strategies for mitigating this degradation mechanism.
Optimization Strategies for Commercialization of High-Temperature Pemfcs
Authors: Seselj Nedjeljko , Martinez Alfaro Silvia , Azizi Kobra , Bompolaki Eftychia , Gromadskyi Denys , Hromadska Larysa , Hjuler Hans , Cleemann Lars Nilausen 
Published: November 2022

The increasing requirement for renewable energy places high-temperature proton exchange membrane fuel cells (HT-PEMFCs) on the forefront of “green” energy-generating power devices. Compared to certain PEMFC technologies, HT-PEMFCs possess faster electrode kinetics, high tolerance to fuel poisons and impurities, no humidification requirements, simplified cooling and system design.1 Herein we present optimization strategies of membrane electrode assemblies (MEAs) for HT-PEMFCs, focusing mainly on the (1) component characterization, (2) MEA fabrication, and (3) testing protocols. A selection of gas diffusion electrodes (GDEs) was tested, as well as the presence/absence of a microporous layer (MPL) on the cell performance. The catalyst layer (CL) has been modified in the terms of fabrication methods, catalyst type, platinum (Pt) content, as well as a variety of binders and additives. The PEM optimizations focused on varying and testing: (1) the molecular weight (Mw) of polybenzimidazole (PBI) for membrane casting, (2) PEM thickness, and its (3) acid doping levels (ADL). The MEAs were then fabricated at altering hot-pressing conditions and their performances were compared. The MEA testing focused on activation, humidity levels, high current operations, elevated temperature and pressure operations, as well as long-term stationary and dynamic durability protocol studies. The material fabrication optimizations resulted in higher onset and peak-of-life voltages, as well as longer cell durability. Together with optimized cell testing, we have achieved power densities of more than 0.8 W/cm2, with stationary durability of more than 13,000 hours at 0.3 A/cm2 current density, with the degradation rate of 4 μV/h. Originally the dynamic durability was demonstrated with more than 290 start-stop cycles showing the performance degradation of up to 100 µV/cycle, however, new tests show degradation rates of less than 46 µV/cycle. The performance and durability that we have demonstrated here position HT-PEMFCs as matured technology that can enter the mass market as a commercial and reliable electrochemical power device, to answer the ever-increasing societal energy demands in the age of climate change.

Figure 1. Performance of Blue World Technologies MEAs: (A) from different production batches showing small performance scatter, and (B) i-V and power curves at elevated pressures.
Reference:
1. O. Jensen, D. Aili, H. A. Hjuler, Q. Li, High Temperature Polymer Electrolyte Membrane Fuel Cells - Approaches, Status and Perspective, ISBN 978-3-319-17081-7; DOI 10.1007/978-3-319-17082-4, Springer International Publishing, New York, 2015.

Figure 1
Highly Durable Pt-Based Core-Shell Catalysts with Metallic and Oxidized Cobalt Species for Boosting the Oxygen Reduction Reaction
Authors: Oezaslan Mehtap , Janssen Marek , Weber Philipp , Park Daseung , Klein Jochen 
Published: November 2022

A self-supported Pt-CoO alloy catalyst has recently been reported as a new concept for Pt-based catalysts combining high surface area with high ORR activity. [1] Very recently, the presence of cobalt oxide species within Pt-Co catalyst after electrochemical dealloying in acidic media has also been reported by Weber et al. [2] However, the elemental distribution particularly for light elements like oxygen as well as the influence of the Co oxide on the ORR activity are still unclear to date.
We prepared a disordered PtCoOx alloy catalyst using wet-impregnation - freeze-drying - thermal annealing method. [3] After electrochemical activation by dealloying, the less noble metal is dissolved from the nanoparticle surface and the remaining Pt surface atoms are forming a protective particle shell referred to as core-shell catalyst. [2, 3] Using high resolution scanning transmission electron microscopy in combination with electron energy loss spectroscopy (STEM-EELS) we were able to explore the detailed structure of the activated PtCoOx catalyst with a Pt-enriched shell. Based on the EELS elemental maps of Pt, Co and O, we observed that oxygen is mainly located at the interface between the Pt-enriched shell and the PtCoOx alloy core. Thus, the CoOx species are highly stable during the electrochemical dealloying in acidic media. The ORR mass activity (0.56 ± 0.14 A mgPt
-1 at 0.9 VRHE) of the PtCoOx core-shell catalyst is 2.5-times higher, whereas the ORR specific activity (592 ± 171 µA cmPt
-2 at 0.9 VRHE) is 3-times higher than that for commercial Pt/C (0.24 ± 0.05 A mgPt
-1, 187 ± 29 µA cmPt
-2). The stability of the CoOx species and the electrochemical catalyst durability were tested by using an accelerated stress test (AST, 10,000 cycles from 0.5 to 1.0 VRHE) in acidic media. Here, the PtCoOx core-shell catalyst showed an improved electrochemical durability compared to Pt/C and maintains 85% of the initial ECSA, 54% of the initial ORR mass activity and 68% of the initial ORR specific activity, respectively. From the STEM-EELS and XPS measurements, we revealed an increase of the thickness of the Pt-enriched shell of several monolayers after the AST protocol. Very surprisingly, the cobalt oxide in the sub-surface layers still remains, but it is less narrowly distributed than before the AST experiment.
Thus, we suggest that the Co oxide species in PtCoOx alloy catalyst might have a positive effect on the ORR performance and durability and could even be a yet undiscovered alternative to metallic cobalt.
Reference:
[1] G.W. Sievers et al., Nat. Mater., 2021, 20, 208-213;
[2] D.J. Weber et al., J. Mater. Chem. A, 2021, 9, 15415-15431;
[3] M. Oezaslan et al., J. Electrochem. Soc., 2012, 159, B394-B405.
Local Hydrophobicity of Atomically Dispersed Fe-N-C Catalysts and Its Impact on the Oxygen Reduction Reaction in Membrane Electrode Assembly
Authors: Atanassov Plamen , Liu Yuanchao , Murphy Eamonn , Mamania Divija Nitin , Khedekar Kaustubh , Zenyuk Iryna V. 
Published: November 2022

Non-precious metal electrocatalysts with atomically dispersed transition metal sites have shown promising performance for the oxygen reduction reaction (ORR) in proton exchange membrane fuel cells. The Fe-N-C catalysts, with single iron atom coordinated by nitrogen atoms (FeNx) on carbonaceous supports, exhibits outstanding ORR activity as compared to its other metal counterparts (M-N-C). [1] The Fe-N-C catalysts synthesized via sacrificial support method (SSM) showed superior ORR performance and this family of Fe-N-C electrocatalysts is so far the only commercially available PGM-free catalysts for fuel cell application. [2] For membrane electrode assembly (MEA) performance, the pore structure [3] and surface hydrophobicity [4] of the carbon matrix are of particular significance, because the high current throughput requires good oxygen transport and well-controlled water management on cathodes. In this talk, we present the local hydrophobicity of SSM-based Fe-N-C electrocatalysts [1] and its impact on the ORR macrokinetics in MEA. Specifically, nitrogen physisorption and water vapor physisorption were used to study the pore morphology and the local surface hydrophobicity, respectively. As shown in Figure 1, the sacrificial templated Fe-N-C catalyst showed a large amount of mesoporosity while its surface was very hydrophobic, as indicated by the little water uptake through whole pressure range. Such porosity and local hydrophobicity features were further correlated to its macrokinetic performance in a study of water partial pressure dependence under MEA configuration.

Reference

[1] T. Asset and P. Atanassov, Joule, 2020, 4, 33.
[2] https://pajaritopowder.com

[3] Y. Huang, Y. Chen, M. Xu, T. Asset, P. Tieu, A. Gili, D. Kulkarni, V. de Andrade, F. de Carlo, H. S. Barnard, A. Doran, D. Y. Parkinson, X. Pan, P. Atanassov, and I. Zenyuk, Materials Today, 2021, 47, 53.
[4] L. Liu, S. J. Tan, T. Horikawa, D. D. Do, D. Nicholson and J. Liu, Adv Colloid Interface Sci, 2017, 250, 64.

Figure 1
Which Properties Should Anion-Exchange Membranes Have to Achieve a Longer Fuel Cell Lifetime?
Authors: Yassin Karam , Rasin Igal G , Brandon Simon , Dekel Dario R 
Published: November 2022

The substantial advancements and availability of new cost-effective materials have drawn significant attention to the technology of anion-exchange membrane fuel cells (AEMFCs). The anion exchange membrane (AEM) is a core component in AEMFCs, essential for conducting hydroxide ions and, more importantly, controlling water transport between the fuel cell electrodes. In this contribution, we apply the computational methodology outlined in Refs. [1,2] to explore the effects of various membrane properties on AEMFC performance and its stability. We specifically consider the following parameters: (A) water diffusivity, (B) membrane thickness, (C) ion exchange capacity (IEC), (D) maximum hydration level (λmax) corresponding to ionomer/water contact (maximum number of water molecules per functional group), (E) hydroxide conductivity, and (F) degradation rate constant of the AEM functional group.
First, we describe our modeling approach, which includes a one-dimensional isothermal and time-dependent model of AEMFC operations. The model considers the chemical degradation process of the ionomeric materials in the cell, transport phenomena through the anode and cathode gas diffusion layers, anode and cathode catalyst layers, and the membrane. Finally, the electrochemical reactions, hydrogen oxidation in the anode and oxygen reduction in the cathode, are described by Butler-Volmer kinetics. We present our main findings, demonstrating that membrane water diffusivity and λmax have the most significant impact on AEMFC lifetime, followed by membrane thickness and IEC, attributed to enhanced water distribution across the cell. We also demonstrate the significance of improving functional group stability to performance stability, while AEM hydroxide conductivity shows a negligible effect on AEMFC lifetime. Finally, we perform dimensional analysis and provide an analytical, useful correlation to estimate the AEMFC lifetime of selected membranes from the literature and compare it to the measured operation time. In conclusion, this work highlights important AEM parameters aimed at improving AEM designs in order to enhance the performance stability of AEMFCs.
[1] D.R. Dekel, I.G. Rasin, S. Brandon, Predicting performance stability of anion exchange membrane fuel cells, J. Power Sources. 420 (2019) 118–123. https://doi.org/10.1016/j.jpowsour.2019.02.069.
[2] K. Yassin, I.G. Rasin, S. Brandon, D.R. Dekel, Elucidating the role of anion-exchange ionomer conductivity within the cathode catalytic layer of anion-exchange membrane fuel cells, J. Power Sources. 524 (2022) 231083. https://doi.org/10.1016/j.jpowsour.2022.231083.