bluuebunny/crossref_metadata_2025 huggingface dataset:
Ultra-Flexible Organic Electronics for Biomedical Application
Authors: Yokota Tomoyuki , Someya Takao
Published: July 2022

Since biometric sensing using light can noninvasively measure biological information from the outside of the body, various information can be obtained from dynamic things such as blood oxygen concentration and heart rate to static things such as fingerprints and veins. Among them, a flexible organic imager can be attracted to the body, so it is used as wearable electronics. Utilizing its flexibility, imagers capable of imaging fingerprints and veins, pulses that can be directly applied to the skin, blood oximeters, muscle contraction sensors, etc. have been reported.

In this study, we have developed ultra-flexible and lightweight highly efficient, ultra-flexible, air-stable, three-color, polymer light-emitting diodes (PLEDs) The total thickness of the devices, including the substrate and encapsulation layer, is only three micrometers, which is one order of magnitude thinner than the epidermal layer of the human skin. Due to the very thin substrate and neutral position, our device shows the highly flexibility and conformability. The PLEDs are directly laminated on the surface of skin and are used as indicators/displays. And also, we have developed a sheet-type image sensor that enables high-resolution and high-speed reading. Our conformable imager has pixel pitches as small as 50 µm, with resolutions of up to 508 dpi. Using our conformable imager, we succeed to take a high-resolution image of fingerprints and veins used for biometric authentication.
Probing the Density of States of Organic and Perovskite Semiconductors By Energy-Resolved Electrochemical Impedance Spectroscopy
Authors: van Geel Wietse Fransiscus Michel , Janssen René A.J.
Published: July 2022

The performance of thin-film photovoltaic cells is closely related to the energy alignment of the absorber layers and charge collection layers used for constructing the device and is further influenced by the presence of energetic disorder and defects in the photoactive material. This especially holds for novel organic and perovskite semiconductors, where film processing conditions, such as solvents used, thermal or solvent vapor annealing, and aging of the active materials are known to have an influence on the device performance. Knowledge about the energy of the relevant frontier orbitals such as HOMO and LUMO for organic semiconductors,[1]and valence (VB) and conduction (CB) bands for perovskites is key to designing more efficient materials. In addition, the energetic disorder, such as broadening of the band edges and states that appear in the bandgap are strongly affecting solar cell efficiencies. Knowledge about the density of states close to and inside the bandgap is very relevant in this respect.

In this work energy-resolved electrochemical impedance spectroscopy (ER-EIS) as advanced by Nádazdyet al.[2]is applied on various organic bulk-heterojunction and lead-halide perovskite semiconductors to map their energy landscape around and in the band gap. ER-EIS provides a direct electrochemical measurement of the HOMO/VB and LUMO/CB energies, but also resolves band tails and sub-bandgap states with a resolution of up to six orders of magnitude. This enables detection of subtle but important effects that are the consequence of layer processing conditions such as spin coat parameters, solvent combinations, thermal annealing time and temperature, and atmospheric exposure (vacuum, inert, air).

We will present experiments that aim to quantify relative changes in the energy landscape due to varying processing conditions and assign physical meaning to these changes (e.g. morphology and (un)intentional doping). The systems under investigation are well-known donor-acceptor bulk-heterojunction (e.g., P3HT:PCBM and PM6:Y6) and triple-cation mixed-halide perovskites (CsFAMA). The results shed new light on largely unknown defect states in the bandgap of solution-processed semiconductors.

[1] R. E. M. Willems, C. H. L. Weijtens, X. de Vries, R. Coehoorn, and R. A. J. Janssen, Relating frontier orbital energies from voltammetry and photoelectron spectroscopy to the open-circuit voltage of organic solar cells, Adv. Energy Mater.
2019, 9, 1803677.

[2] V. Nádazdy, F. Schauer, and K. Gmucová, Energy resolved electrochemical impedance spectroscopy for electronic structure mapping in organic semiconductors, Appl. Phys. Lett.
2014,
105, 142109.
Self-Reconstruction of Sulfate-Containing High Entropy Sulfide for Exceptionally High-Performance Oxygen Evolution Reaction Electrocatalyst
Authors: Nguyen Thi Xuyen , Su Yen-Hsun , Lin Chia-Chun , Ting Jyh-Ming
Published: July 2022

Novel earth abundant metal sulfate-containing high entropy sulfides, FeNiCoCrXS2 (where X = Mn, Cu, Zn, or Al), have been synthesized via a two-step solvothermal method. We show that sulfate-containing FeNiCoCrMnS2 exhibits superior OER activity with exceptionally low overpotential of 199, 246, 285, and 308 mV at current densities of 10, 100, 500 and 1000 mA cm-2, respectively, and surpassing its unary-, binary-, ternary-, and quaternary-metal counterparts. The electrocatalyst yields exceptional stability after 12000 cycles and 55 h of durability even at a high current density of 500 mA cm-2. Various in-situ and ex-situ analyses were used to investigate the self-reconstruction of the sulfides during the oxygen evolution reaction (OER) for the first time. The resulting metal (oxy)hydroxide is believed to be the true active center for OER. The remaining sulfate also contributes to the catalytic activity. Density function theory calculation is in a good agreement with the experimental result. The extraordinary OER performance of the high entropy sulfide brings a great opportunity for desirable catalyst design for practical applications.
(Invited) Dynamic Reconstruction of Lanthanum Nickelate Catalysts and Activation By Iron during OER
Authors: Twight Liam Peter , Tonsberg Alexandra , Dumpert Kora , Boettcher Shannon W.
Published: July 2022

Accurate description of activity trends among perovskite oxide oxygen evolution catalysts using electronic descriptors requires that the bulk structure of the catalyst is comparable to that of the surface. Relatively few works thus far have addressed the dynamic nature of the catalyst structure during OER and the implications this has for rationalization of activity. Here the in-situ surface reconstruction of LaNiO3 particles and an analogous Ruddlesden-Popper phase, La2NiO4+
δ, is described using electrochemical and materials characterization techniques. Small, but characteristic redox features were observed during cyclic voltammetry of these materials corresponding to the Ni2+/3+ redox reaction in amorphous NiOxHy. The size of these redox features grow with prolonged cycling and chronoamperometry indicating that increased duration of electrochemical conditioning continuously induces reconstruction. The reconstructed species contributes to an increased surface area as determined by electrochemical impedance spectroscopy. Near doubling of the OER activity after intentional introduction of only 35 ppb Fe species is observed after cycling, consistent with the formation of NiOxHy on the crystalline surface and subsequent adsorption of Fe to form well-known and extremely active NiFeOxHy OER catalysts. This work brings into focus the importance of considering surface amorphization on perovskite catalysts in discussion of their activity.
Facile Spray Pyrolysis Synthesis of Ruthenium Single-Atomic Catalyst with High Activity and Stability for Hydrogen Evolution Reactions over a Wide pH Range
Authors: Yim Kyungmin , Koo Yoomo , Yoo Sung Jong , Kim Jinsoo
Published: July 2022

Electrochemical water splitting is an economic, green and sustainable route to produce hydrogen through the hydrogen evolution reaction (HER). Nowadays, ruthenium is an efficient catalyst with a desirable cost for HER. Doping Ru with a transition metal oxide was recently shown to greatly boost the activity and durability of the HER, even with small amounts of ruthenium based electrocatalysts. It also reduced total amount of Ru. Recent literature reported that Ru-O-Mo sites have better HER than Ru single atom due to significantly improved H2O adsorption. Among the various synthetic method, spray pyrolysis methods can produce rapidly large-scale production of uniformly mixed elements in spherical particles at one-step. In this study, we synthesized ruthenium doped MoO2 spheres (200~300nm) using ultrasonic spray pyrolysis method in various temperature from 500 oC to 800 oC. The synthesized catalysts were analyzed by XRD, FE-SEM, Raman, XPS and electrochemical analyzer. This research can provide a new strategy to synthesize highly active catalysts for HER over a wide pH range.
Optimal Geometrical Configuration of Metal Cations in Single Spinel CoxRh3-XO4 Nanoparticles to Promote Oxygen Evolution Reaction
Authors: Kwon Taehui , Hyerim Woo , Jin Dasol , Kim Myung Hwa , Lee Youngmi
Published: July 2022

Hydrogen (H2), which is widely considered as an ideal energy carrier to alternate traditional fossil fuels, can be produced by water electrolysis. Water electrolysis is a simple and promising technology due to its eco-friendly advantages. However, an anodic oxygen evolution reaction (OER) in water splitting devices provokes significant energy loss owing to its sluggish reaction kinetics. Therefore, designing advanced OER electrocatalysts is a very popular topic, among which spinel oxides have been widely studied for OER.

Hence, in this work, we construct single spinel of various Co
x
Rh3-x
O4 with 0.95 ≤ x ≤ 2.05 nanoparticles (NPs) as an outstanding OER electrocatalysts in alkaline condition. First, rhodium hydroxide and cobalt hydroxide were precipitated through acid-base reaction between dilute 0.1M NaOH and metal precursors solutions, then purified metal hydroxides was synthesized into Co
x
Rh3-x
O4 NPs via thermal annealing process. The morphology of Co
x
Rh3-x
O4 NPs was measured by field-emission scanning electron microscopy (FE-SEM) and high-resolution transmission electron microscopy (HR-TEM). The physical properties of Co
x
Rh3-x
O4 NPs were analyzed by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The electrocatalytic activity and stability of Co
x
Rh3-x
O4 NPs are studied toward OER in Ar-saturated 1 M NaOH aqueous solution with rotating disk electrode (RDE) voltammetry. Electrochemical impedance spectroscopy (EIS) was carried out to further investigate the electrochemical behaviors of the Co
x
Rh3-x
O4 NPs. Conclusively, we have identified which atomic ratio and configuration of Co and Rh cations can produce optimal synergistic effect toward OER. This research was supported by Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Science, ICT& Future Planning (NRF-2020R1A2B5B01001984).
Improvements in Performance and Cost Reduction of Large-Scale Rechargeable Zinc|Manganese Dioxide Batteries and a Future Roadmap Driven through Real World Applications
Authors: Yadav Gautam , Huang Jinchao , Weiner Meir , Yang Shinju , Vitale Kristen , Rahman Sanbir , Keane Kevin , Banerjee Sanjoy
Published: July 2022

Zinc|Manganese Dioxide (Zn|MnO2) are widely available as primary batteries for use in small-scale consumer electronics because of its low cost and high energy density. The last decade has seen a resurgence in research to make this chemistry rechargeable by materials engineering, additives and experimenting with various electrolytes. These important contributions have showed that Zn|MnO2 has all the prerequisites to be a post-lithium solution for grid-scale storage.

At Urban Electric Power, we have been commercializing proton-insertion Zn|MnO2 batteries in cylindrical and prismatic form factors between 70 to 140Ah nameplate capacity. These batteries contain improved materials and electrode designs with improved utilizations of the cathode and anode theoretical capacity. Both the cathode and anode can achieve 40 to 60% of their theoretical capacity, which is currently the best in alkaline electrolytes and scaled-up cells. These improvements not only reflect the performance but also the manufacturability of cells on a large scale. In this talk, we will present the methodological approach we pursued to achieve these performance metrics and reduce the cost to <$80/kWh. We also cycled these cells according to various protocols that represent real world applications. For example, we found that the newly improved Zn|MnO2 cells can achieve >6 years of performance for solar microgrid applications, which is better than lead acid batteries, the current battery of choice. We have also manufactured gelled Zn|MnO2 batteries that can be considered as “non-spillable” and thus, “non-hazardous” according to transportation regulations. These non-spillable cells manufacturing process and performance will also be presented in the talk. The talk will also expand on the future generations of Zn|MnO2 that are currently under development at Urban Electric Power like the conversion battery which access the complete 2nd electron capacity of the electrodes and the high voltage (>2.5V) battery. These batteries expand the application space of Zn|MnO2 batteries which make it a viable contender for post lithium-ion batteries.
Techno-Economic Comparison of Different Organic Flow Batteries Based on Experimental Data Versus a Vanadium Flow Battery
Authors: Gerlach Daniel , Trupp Sabine , Noack Jens , Le Boulch Chloé , Pinkwart Karsten , Bischof Katharina , Roznyatovskaya Nataliya , Skyllas-Kazacos Maria
Published: July 2022

The challenges of climate change are becoming more and more relevant to society. This also increases the need for a wider use of renewable energies, which, due to their fluctuating availability, also increases the need for the possibility of intermediate storage in other forms of energy. Flow batteries (FB) store electrical energy chemically in electrolytes and are scalable in terms of power and energy. This advantage can best be used in stationary applications; flow batteries are one of the most promising technologies here. The capacity of the batteries is largely determined by the active species of their electrolytes which is why this is mostly focused. The success of a technology is primarily related to economic factors. For this reason, it is important to compare the costs of different technologies. All important influencing factors must be taken into account for the different technologies and related to the technical properties such as performance and efficiency. Nearly no results are available for a cost assessment of organic flow batteries, but the large spectrum of organic active species makes it increasingly worth investigating.

Therefore, an existing techno-economic model [[1]] based on a 10 kW / 120 kWh vanadium flow battery (VFB) was optimized and a laboratory scale FB for further research was developed. With this laboratory scale FB, a VFB with electrolytes with different molarities was first examined in 3 likewise standardized test cycles, which contain both the behavior at different electrical currents and aging tests. The same tests were then carried out with aqueous organic FBs (AOFB), with MV / 4-HO-TEMPO and AQS / BQDS in different molarities being selected as RedOx pairs. Those AOFBs were analyzed and compared with the results of the lab-scale VFB. In addition to the most examined parameters such as energy density and power density, temperature and cell resistance were examined, too. A system for evaluating the toxicity of electrolytes was also developed in order to be able to include an initial assessment of the social acceptance of such an FB in the evaluation. In this lecture the first results of this techno-economic approach will be presented. In addition, a rating scale for assessing toxicity is also presented.

[1] J. Noack, L. Wietschel, N. Roznyatovskaya, K. Pinkwart, and J. Tübke, Energies, 9, 627 (2016).

Figure 1
(Invited) The Pathway to Widespread Commercialization of Redox Flow Batteries
Authors: Perry Mike L.
Published: July 2022

Large-scale electric-energy-storage (EES) systems have the potential to transform the electric grid. The deployment of recent EES systems have predominately been Li-ion batteries (LiBs), which are being used primarily for Ancillary Services (e.g., frequency regulation) and other grid applications (e.g., load following) that require relatively short discharge durations (i.e., ≤ 4-h at rated power). At these relatively low energy/power ratios, LiBs can be lower cost than the historical EES baseline, which is pumped-storage hydropower (PSH). However, since the cost of most conventional batteries scales linearly with energy capacity, the energy-storage cost ($/kWh) is not necessarily lower for uses that require longer discharge times. For these long-duration energy-storage (LDES) applications (i.e., ≥ 5-h at rated power), EES systems with independent power and energy components, e.g., PSH, redox flow batteries (RFBs), reversible fuel cells, and electrofuels, have an inherent cost advantage, since one can readily increase the energy/power ratio by selectively adding more energy capacity, without the added cost of excessive power components. LDES applications have the potential to be a substantially larger market than short-duration EES; however, the requirements for LDES systems are also inherently more challenging. The primary commercialization challenge is capital cost (i.e., $/kWh installed). In addition to fully decoupled power and energy, RFBs have other unique attributes that make this battery architecture ideally suited for grid-scale LDES, namely: long cycle life even with deep cycles, inherently superior safety, and easy recyclability. Largo Clean Energy (LCE) is a vertically-integrated developer of all-V RFBs (VRFBs), and LCE’s MW-scale product is arguably the most advanced RFB system available on the market today. This talk will primarily focus on: 1) what LCE has already done to substantially reduce the cost of VRFBs, 2) how VRFBs can potentially enable the commercialization of other types of RFB systems, and 3) future opportunities to further reduce the capital cost of a variety of RFB systems.

Acknowledgements

Many thanks to my flow-battery collaborators at Largo Clean Energy and at Raytheon Technologies Research Center (formerly known as UTRC), as well as many other outstanding colleagues on multiple UTRC-led ARPA-E projects and JCESR collaborations on flow batteries.
Half-Cell Flow Batteries: A Powerful Approach to Evaluating Cycling Stability of a Redox Active Electrolyte
Authors: Liu Tianbiao
Published: July 2022

Aqueous redox flow batteries (ARFBs) represent one promising energy storage technology for integration of renewable energy and balancing the electricity grids because of their technical merits of decoupled energy and power, sustainable and tunable redox active materials, and non-flammable and low cost aqueous supporting electrolytes. Despite numerous new flow battery chemistries reported in the last decade, the cycling life of ARFBs is still primarily limited by the chemical stability of redox active electrolytes. This presentation discusses the proper use and data interpretation of a half-cell flow battery to evaluate the cycling stability of a single redox active electrolyte. Specifically, the half-cell flow battery studies of K4[Fe(CN)6]/K3[Fe(CN)6] at alkaline conditions using balanced and unbalanced cell configurations will be discussed and compared. Our results reveal that the capacity loss of the K4[Fe(CN)6]/K3[Fe(CN)6] half-cell is attributed to cyanide ligand dissociation and then subsequent redox degradation. The reported half-cell flow battery methodology can be widely applied to develop new redox active electrolyte materials.
(Invited) Low-Temperature Molten Sodium Batteries for Large-Scale Storage: Fundamental Studies of Metal Halide Catholyte and Cathode Materials
Authors: Maraschky Adam M. , Lee Rose Y. , Percival Stephen J. , Gross Martha M. , Peretti Amanda S. , Spoerke Erik D. , Small Leo J.
Published: July 2022

Low-cost, long-duration energy storage is a vital resource needed for a robust electric grid powered by renewables. Low-temperature (<130 °C) molten sodium batteries (MNaBs) with NaI-metal halide molten salt catholytes have been developed to meet this need. This battery chemistry avoids the safety concerns caused by metal dendrites and flammable organic solvents found in Li-metal or Li-ion batteries. It also offers higher voltages and drastically reduces the expensive high temperature material requirements compared to other MNaBs, such as sodium-nickel chloride (ZEBRA) batteries, which operate near 300 °C. Among the key challenges to wide-spread utilization of these emerging molten Na batteries for large-scale, long-duration applications is catholyte stability and performance at high current densities while cycling at temperatures just above the melting point of Na (98 °C). To optimize the catholyte, we have examined a variety of electroactive molten salt chemistries, including mixtures of NaI with AlCl3, AlBr3, and GaCl3. To better understand the catholyte properties during cycling, we have performed electrochemical kinetics studies and mathematical modeling of the iodide-triiodide speciation. Results reveal a dependence between catholyte speciation and usable capacity and current densities for the given catholyte compositions. Additional experiments, including cyclic voltammetry and chronoamperometry, probe the interactions between the cathode current collector and the molten salts, revealing potential impacts on electrochemical kinetics and stability during cycling. Insights from these fundamental studies serve as the foundation for the informed design of high-performance cathodes in new scalable molten sodium batteries.

Sandia National Laboratories is a multi-mission laboratory managed and operated by National Technology and Engineering Solutions of Sandia, LLC., a wholly owned subsidiary of Honeywell International, Inc., for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-NA0003525.
Beyond the Norm: Synthesis and Electrochemical Study of High Concentrated NaPF6 Electrolytes
Authors: Ould Darren Michael Charles , Menkin Svetlana , O'Keefe Christopher A. , Coowar Fazlil , Barker Jeremy , Grey Clare P. , Wright Dominic S.
Published: July 2022

The global drive towards decarbonisation means there is increasing need for large-scale energy storage, which has focussed research efforts into sodium-ion batteries (SIBs).1 SIBs are well suited to grid-storage applications due to the wide abundance, even distribution and low cost of sodium deposits.2 This contrasts to the better known and understood lithium-ion batteries (LIBs), where lithium is much less abundant. Additionally, the use of sodium has other sustainability implications, which are desirable for grid-scale applications, as it allows cobalt-free cathodes to be used and the copper current collectors at the anode to be replaced by aluminium.

Currently SIBs use NaPF6 as the chosen electrolyte salt,3 however commercial supplies of this are often of low-grade and contain NaF (a hydrolysis product of NaPF6), making it unsuitable for battery use.4 Alternatively, pre-made electrolyte solutions of NaPF6 may be purchased, but the cost can be prohibitive and limits solvent exploration.

Herein, this talk will detail the synthesis of high-grade NaPF6 from the addition of NH4PF6 with sodium metal in THF solvent. By performing the reaction under anhydrous conditions, NaPF6 can be prepared in the absence of hydrolysis products (NaF), as confirmed by solid-state NMR spectroscopy and powder X-ray diffraction. With high-grade NaPF6 in hand, we have looked at the effects of using higher concentration electrolyte solutions of NaPF6 (>1 M) in ethylene carbonate:diethyl carbonate (EC:DEC 1:1 v/v) solvent. This showed the degradation dynamics of sodium metal-electrolyte interface are different for more concentrated (>1 M) electrolytes, although there is a trade-off with bulk conductivity compared to 1 M solutions. Lastly, the performance of the synthesized NaPF6 has been tested in commercial 2- and 3-electrode pouch cells by Faradion Ltd, UK.5

References:

1 D. Kundu, E. Talaie, V. Duffort and L. F. Nazar, Angew. Chem. Int. Ed., 2015, 54, 3431–3448.

2 C. Vaalma, D. Buchholz, M. Weil and S. Passerini, Nat. Rev. Mater., 2018, 3, 18013.

3 A. Ponrouch, D. Monti, A. Boschin, B. Steen, P. Johansson and M. R. Palacín, J. Mater. Chem. A, 2015, 3, 22–42.

4 A. Bhide, J. Hofmann, A. Katharina Dürr, J. Janek and P. Adelhelm, Phys. Chem. Chem. Phys., 2014, 16, 1987–1998.

5 D. M. C. Ould, S. Menkin, C. A. O'Keefe, F. Coowar, J. Barker, Clare P. Grey and D. S. Wright, Angew. Chem. Int. Ed., 2021, 60, 24882–24887.

Figure 1
Tuning the Intermolecular Interactions of Sulfonated Ionomer Via Polymer Blending
Authors: Senathiraja Thivani , Cornelius Chris
Published: July 2022

Morphology of proton exchange membranes defines the proton conductivity and the durability of the membranes. One cost-effective approach to manipulate the morphology of the sulfonated ionomers is via polymer blends. In this study, varying compositions of Penta Block Copolymers (PBC) with two different ion-exchange capacity (IEC) of 1.0 and 2.0 were blended with poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) to create 2wt% homogenous solution-cast membranes in chloroform. Unmodified PPO membrane possessed higher thermal decomposition temperatures of 427.41°C, and unmodified PBC(1.0) and PBC(2.0) decomposed at 399.85 °C and 400.805 °C, respectively. Both PBC(1.0)-PPO and PBC(2.0)-PPO blend membranes exhibited a similar trend for the changes in decomposition temperature with composition. As the PPO blend ratio increased, the decomposition temperature of PBC(1.0)-PPO and PBC(2.0)-PPO increased by 6.5% and 6.6%, respectively. These changes may be attributed to the increase in thermal stabilities due to PPO’s inherently high glass transition temperature. Water Uptake (WU) studies revealed that PBC(1.0) and PBC(2.0) membranes blended with PPO have reduced WU% as the PPO blend ratio increases. Unmodified PPO is highly hydrophobic and has a WU of 1.52%, while unmodified PBC(1.0) and PBC(2.0) portrayed WU of 14.44% and 74.5%, respectively. When hydrophobic PPO blends with the hydrophilic sulfonated ionomers, the ionic channels are hindered, lowering the WU%. For instance, WU of PBC (1.0)-PPO blend in the ratio of 50:50 is halved compared to PBC (1.0)-PPO blend of 90:10 ratio. Similarly, WU of PBC (2.0)-PPO blend in the ratio of 50:50 is lowered by 72.25% compared to PBC (2.0)-PPO blend of 90:10 ratio. In conclusion, the study shows that polymer blending significantly alters the membrane’s intermolecular interactions and changes the membrane’s durability and water uptake. The impact is more evident as the IEC of the sulfonated ionomers is increased. Proton conductivity studies and morphological transitions will be incorporated in future investigations.

Figure 1
Impact of Sulfonated Poly(Ether Ether Ketone) Pretreatments on Proton Exchange Membrane Fuel Cells Performances and Durability
Authors: Daoudi Meriem , Ferri Evelise , Tougne Claire , El Kaddouri Assma , Perrin Jean-Christophe , Dillet Jérôme , Salah Touhami , Mainka Julia , Gonon Laurent , Mareau Vincent H , Mendil-Jakani Hakima , Dufaud-Niccolai Véronique , Espuche Eliane , Gain Olivier , Lottin Olivier
Published: July 2022

Many works have been devoted to the development of low cost ionomers as alternative to perfluorosulfonic acid membranes for Proton Exchange Membrane Fuel Cells (PEMFC) applications. Among them, sulfonated Poly(Ether Ether Ketone) (sPEEK) membranes. Before use, sPEEK membranes must be pretreated to ensure a complete protonic substitution and removal of residual reagents/solvent. This is generally ensured by soaking the membrane in an acid solution -at room temperature or higher, usually at 80°C1- followed by a rinsing step in water at room temperature. In addition to these pretreatment steps, it was reported2 that an hydrothermal treatment in water at high temperature for a few hours to a few days can improve the membrane nanostructure, water uptake and proton conductivity with expected positive effects on performances. Herein, we studied the impact of sPEEK membrane pretreatment on fuel cell performances and durability using two different batches of Fumapem E730 from Fumatech, acquired in 2019 and in 2020. Five different protocols were tested. The first consists only in membrane acidification and rinsing, while the four others also include a hydrothermal treatment in water at 80°C from 1 hour to 72 hours, and possibly an additional hydro alcoholic treatment. The 2020 batch membranes subjected to a hydro alcoholic pretreatment followed by a 72-hours hydrothermal pretreatment achieved the best performances and the lowest high frequency resistance (Rhf) when tested in a fuel cell. Their performances even exceeded those of a Nafion XL membrane. This could be explained by a better ionomer nano-structuration and therefore a better protonic conductivity. These performances are compared to those of the 2019 batch. In addition, the impact of pretreatment is investigated via Accelerated Stress Tests (AST) combining load (hence potential) and load-driven humidity cycling, and open-circuit voltage.

References:

(1) Jun, M.-S.; Choi, Y.-W.; Kim, J.-D.. J. Membr. Sci.
2012, 396, 32–37. https://doi.org/10.1016/j.memsci.2011.12.008.

(2) Mendil-Jakani, H.; Zamanillo López, I.; Mareau, V. H.; Gonon, L. Phys. Chem. Chem. Phys.
2017, 19 (24), 16013–16022.

Figure 1
Influence of Carbon Support Type, Presence of Platinum and Ionomer Content on Agglomeration in Catalyst Layers
Authors: Kariuki Nancy N. , Park Jaehyung , Lindell Matthew , Haug Andrew , Myers Deborah J.
Published: July 2022

Polymer electrolyte fuel cell (PEFC) energy conversion systems have found application in transportation applications due to their high power density, low operating temperature, high energy conversion efficiency, and speed of refueling.1 One of the key components of a PEFC is the membrane electrode assembly (MEA), which consists of a proton exchange membrane (PEM), such as a perfluorosulfonic acid (PFSA), sandwiched between two catalyst layers (CLs) serving as anode and cathode. Several studies of CL microstructure−performance relationships suggest that the electrode microstructure characteristics, such as the extent of the catalyst−ionomer interaction, continuity of the ionomer phase, and pore size distribution are critical for performance.2-4 However, successful implementation of novel materials for PEFC electrodes is hindered by the lack of a fundamental understanding of the complex, multicomponent nature of the CL, the interplay of its components, and their independent and cooperative effects on the effective properties and performance.

In this work, ultra-small angle X-ray scattering (USAXS) was employed to investigate the effects of carbon support type, presence of platinum, and ionomer loading on catalyst agglomeration in CLs. Particle size distributions (PSDs), obtained from fitting the scattering data using the maximum entropy (MaxEnt) method, were used to determine the size of carbon aggregates and agglomerates from carbon-ionomer and platinum-carbon-ionomer CLs. Three types of carbon supports were chosen for the investigation: high surface area carbon (HSC), Vulcan XC-72, and graphitized Vulcan XC-72. CLs with a range of perfluorosulfonic acid (PFSA) ionomer loadings (0.2-1.0 ionomer to carbon ratio, I/C) were studied in order to evaluate the effect of ionomer on the CL agglomerate structure. The CL agglomerate structure will be correlated with electrochemical performance to reveal the interplay of the components, and their independent and cooperative effects on performance.

References

B.D. McNicol, D. A. J. Rand, K. R. Williams, J. Power Sources 100 (2001) 47–59.

F. C. Cetinbas, X. Wang, R. K. Ahluwalia, N. N. Kariuki, R. P. Winarski, Z. Yang, J. Sharman, and D. J. Myers, J. Electrochem. Soc., 164, (2017) F1596–F1607.

Y.-C. Park, H. Tokiwa, K. Kakinuma, M. Watanabe, M. Uchida, J. Power Sources 315 (2016) 179-191.

S. Holdcroft, Chem. Mater., 26 (2014) 381−393.

This work was supported by the U.S. Department of Energy, Energy Efficiency and Renewable Energy, Hydrogen and Fuel Cell Technologies Office under the auspices of the Fuel Cell Performance and Durability Consortium (FC-PAD). The Advanced Photon Source was supported by the U.S. Department of Energy, Office of Science User Facility. Argonne National Laboratory is managed for the U.S Department of Energy by the University of Chicago Argonne, LLC, also under contract DE-AC-02-06CH11357.
Fabrication and Performance Evaluation of Tubular Catalyst Layer for Proton Exchange Membrane Fuel Cell
Authors: Pedram Sara , Jankovic Jasna
Published: July 2022

Over the past several decades, planar proton exchange membrane fuel cells (PEMFCs) received considerable attention due to their simple structure, manufacturing, and easy integration. However, current PEMFC electrode designs are disadvantaged by high cost, insufficient mass transport, nonuniform reactant, current and temperature distribution, and limited water removal. The development of a novel tubular fuel cell design could address these challenges. Tubular-shaped PEMFC offers several advantages over planar one, including lower pressure drop, efficient water removal, reduced mass transport losses, and cost reduction owing to removing one of gas diffusion layer/bipolar plate (GDL/BPP) side.

This work developed a carbon nanofiber (CNF)/Pt-based cathode for a tubular fuel cell. The tubular CNF support for Pt catalyst was fabricated employing the electrospinning method. Polyacrylonitrile (PAN) was used as the precursor. The electroless deposition of Pt using the chloroplatinic acid solutions was applied to produce well-dispersed low Pt loading nanowires. The tubular CNF/Pt electrodes were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), ex-situ cyclic voltammetry to determine the CF and Pt morphology and feasibility of the prepared layer in PEMFC application. SEM images indicated that increasing the Pt precursor concentration in the plating bath leads to higher Pt loading and larger Pt clusters on the CNF surface. The calculated electrochemical active surface area (ECSA) trend imparts that high Pt loading is less favorable as thick Pt layers lead to low Pt utilization and increased material costs. ECSA results agreed with SEM images, suggesting that the medium Pt concentration (1.5 g L-1 Pt precursor) developed a homogenous Pt distribution and comparable Pt surface area of 24 m2 gPt
-1 for the Pt loading of 0.046 mg cm-2, proving the feasibility of the proposed process.
Operating Proton Exchange Membrane Fuel Cells at a Constant Relative Humidity
Authors: Bielefeld Nikolaj M. , Sørensen Rasmus D. , Jørgensen Mikkel , Kure Kristoffer S. , Berning Torsten
Published: July 2022

Proton exchange membrane fuel cells are currently being commercialized for numerous applications ranging from electric vehicles to stationary applications to miniature type of fuel applications. For the miniature fuel cells, it is desirable to operate at very high current densities in order to maximize the power density. Because at high current densities, the waste heat generation and removal becomes a substantial practical problem, gas diffusion layers (GDL) made out of perforated metals have recently become of interest. Here, a chemical etching process is applied to create uniform holes of equal size(around 80 microns) in a metal sheet. While this type of GDL has superior heat transfer properties and has been found to keep the fuel cell at an almost constant temperature, the uniformly sized holes must be kept from flooding. On the other hand, it is known that the fuel cell membrane must be kept hydrated in order to have a satisfactory proton conductivity.

The purpose of this work is to investigate the possibility of maintaining a relative humidity of 100 % across the entire length of the flow channel. This is to keep the membrane perfectly hydrated while at the same time preventing flooding. The height and width of the flow channels in these fuel cells are in the range of 200 microns, causing a high pressure drop, and as the pressure decreases along the flow channel, the relative humidity would decrease. However, the relative humidity can then be maintained by adding water as a result of the electro-chemical chemical reaction in the fuel cell. Thereby, conditions for which the relative humidity stays constant at 100% over the entire channel length can be calculated, assuming the current density is uniform and that for simplicity all the product water exits the cell at the cathode side.

In this work, a model will be constructed and solved in the Engineering Equation Solver (EES). The output of the model will be the required stoichiometric flow rate to maintain a constant relative humidity for different channel geometries, pressure gradients and temperatures.
Strain Evolution in Pt-Ni Alloy Nanoparticles during Electrochemical Ni Leaching Revealed By Bragg Coherent Diffraction Imaging
Authors: Kawaguchi Tomoya , Komanicky Vladimir , Latyshev Vitalii , Cha Wonsuk , Maxey Evan , Harder Ross , Ichitsubo Tetsu , You Hoydoo
Published: July 2022

Alloy catalysts such as Pt-M (M: other metal elements) have been extensively developed to improve the sluggish oxygen reduction reaction (ORR) that limits the efficiencies of fuel cells and metal-air batteries. Their catalytic activity is potentially enhanced by strain induced in a nearly pure Pt "shell" formed by dissolving the alloyed metal (M) from the surface. It is, therefore, of great importance to reveal the strain distribution on the Pt shell in situ so that we can exploit this mechanism to design new alloy catalysts. Yet, it has been challenging to analyze the strain on the shell because it inevitably requires a technique that can image the strain field of the nanoparticles with high spatial resolution.

In this study,1 we successfully revealed the strain of the exemplary Pt-Ni alloy nanoparticles in detail from the 3D images obtained by using a novel synchrotron technique, “Bragg Coherent X-ray Diffraction Imaging” (BCDI), which can directly image minute atomic displacement field owing to the X-ray coherence. Pt-Ni nanoparticles with compositions of Pt2Ni3 (Ni rich), Pt1Ni1 (moderate Ni), and Pt3Ni2 (Ni poor) were observed by BCDI during cyclic voltammetry cycles, in which the less noble metal Ni electrochemically leached from the alloy. This cycling induced tensile strain inside particles in all the compositions, implying that the formation of a Pt shell on the surface strained the core of the particle because of the lattice mismatch between the Pt-Ni alloys and Pt. The strain in the shell was evaluated from a core-shell elastic model using the parameters obtained in the 3D images.

A compressive circumferential strain in the shell was observed in all the compositions, and the Pt1Ni1 particle showed the largest compressive circumferential strain of 5%. Since the compressive strain is reported to facilitate the enhanced ORR,2 the compositional dependence of the strain magnitude observed in this study was in excellent agreement with the previous study performed with nm-size particles where Pt1Ni1 exhibits the highest activity among a wide range of compositions.3
A similar strain-activity relation was also inferred in a powder X-ray diffraction studies of core-shell Pt
x
Co1-x
alloys,4 suggesting it is a widely applicable phenomenon. The present study demonstrated that the strain on alloy nanoparticles can be quantitatively determined by BCDI during electrochemical reactions, which enables us to exploit surface strain in designing a wide range of electrocatalysts.

T. Kawaguchi et al., Nano Letters, 21, 5945–5951 (2021).

H. Wang et al., Science, 354, 1031–1036 (2016).

C. Wang et al., Advanced Functional Materials, 21, 147–152 (2011).

D. Wang et al., Nature Materials, 12, 81–87 (2013).
Electrochemical Trends of Atomically Dispersed Metal-Nitrogen-Carbon Materials As Oxygen Reduction Reaction Catalysts and Active Supports
Authors: Ly Alvin , Wang Hanson , Murphy Eamonn , Huang Ying , Guo Shengyuan , Liu Yuanchao , Zenyuk Iryna V. , Atanassov Plamen
Published: July 2022

Platinum-based catalysts currently remain the best option for polymer electrolyte membrane fuel cell (PEMFC) applications. Meanwhile, atomically dispersed metal-nitrogen-carbon (MNC) materials have been the frontrunner for platinum-group metal free catalysts for the oxygen reduction reaction (ORR)1. Considering that the platinum-based nanoparticles are preferably supported on carbonaceous materials, it would be intuitive to use MNC catalysts as a support for platinum nanoparticles to further increase the activity and performance of the catalyst layer in a PEMFC. In this work, we synthesized and investigated a series of MNC materials (Mn-N-C, Fe-N-C, Co-N-C, Ni-N-C, and Cu-N-C) using a previously described method2 to elucidate the electrochemical trends of possible interactions between the MNC materials as a support and standard Pt nanoparticles. Recent works3,4 have shown that combining MNC catalysts with Pt catalysts not only improves the activity of the overall composite catalyst, but also improves the stability of both counterparts. As shown in Figure 1, the supported Pt nanoparticles on MNC materials outperforms the same type of Pt nanoparticles when supported on an industry standard carbon.

Reference

Asset, T. & Atanassov, P. Iron-Nitrogen-Carbon Catalysts for Proton Exchange Membrane Fuel Cells. Joule
4, 33–44 (2020).

Murphy, E. et al. Using Atomically Dispersed Bimetallic Active Sites to Probe the Nitrate Reduction Mechanism to Ammonia. ECS Meet. Abstr.
MA2021-02, 1559 (2021).

Ao, X. et al. Atomically dispersed Fe–N–C decorated with Pt-alloy core–shell nanoparticles for improved activity and durability towards oxygen reduction. Energy Environ. Sci.
13, 3032–3040 (2020).

Qiao, Z. et al. Atomically dispersed single iron sites for promoting Pt and Pt3Co fuel cell catalysts: performance and durability improvements. Energy Environ. Sci. (2021).

Figure 1
Synthesis of Nitrogen-Doped Wood-Based Carbon Materials and Their Application for Oxygen Reduction
Authors: Tamasiunaite Loreta , Upskuviene Daina , Balciunaite Aldona , Jasulaitiene Vitalija , Niaura Gediminas , Drabavicius Audrius , Plavniece Ance , Volperts Aleksandrs , Dobele Galina , Zhurinsh Aivars , Norkus Eugenijus
Published: July 2022

Recently, great attention has been focused on biomass-derived electrocatalysts for the oxygen reduction reaction (ORR). In the present study, the wood-derived nitrogen-doped carbon nanomaterials with graphene-like structures have been synthesized from wood biomass using a chemical activation method with NaOH to achieve a high specific surface area (SSA). Then, the activated carbon materials have been doped with nitrogen using dicyandiamide (DCDA) as a cheaper nitrogen precursor. The synthesized catalyst's morphology, structure, and composition have been characterized using TEM, XPS, Raman Spectroscopy, and ICP-OES. The activity of the prepared catalysts was evaluated for ORR in the 0.1 M KOH solution employing the rotating disk electrode (RDE) method. The nitrogen-doped carbon materials have been shown a high electrocatalytic activity and stability for the oxygen reduction reaction. The number of electrons transferred per O2 molecule is close to 4.0.

Acknowledgment

This project has received funding under the Baltic Research Programme project “Sustainably produced nanomaterials for energy applications (SuNaMa)” (No. S-BMT-21-12, LT08-2-LMT-K-01-055).
(Digital Presentation) Temperature-Dependent Study for Electrochemical Surface Area on a Catalyst Layer Used in a PEFC
Authors: Espinoza R. , Munoz Kevin , Santana Jordy , Espinoza Andaluz Mayken , Andersson Martin
Published: July 2022

Electrochemical Surface Area (ECSA) is the portion of the catalyst layer electrochemically available to participate in electrode reactions inside a Polymer Electrolyte Fuel Cell (PEFC). ECSA is an important metric that diagnoses the performance/degradation of a catalytic layer and allows the development of new electrodes. This study aims to describe the behavior of the ECSA as a function of cell operating temperatures based on a self-designed experimental based on two approaches. The first is through an analytical-theoretical analysis, and the second is through empirical correlations that fit the experimental curves obtained. The primary variable to study in the present work is temperature. Based on previous studies, the temperature is one of the most influential variables that affect fuel cell efficiency.

A single PEFC with an active area of 25cm2, a woven carbon cloth gas diffusion layer, a microporous layer, catalytic layer support with 0.5 mg cm-2 of Platinum on carbon, and Nafion 212 ® membrane were used to perform this study. The temperature range was varied in the range of 40 - 80 oC in steps of 10 °C, and a 100% of Relative Humidity on inlet gases, i.e., hydrogen and nitrogen, were settled at 100%. The characterization of the ECSA was performed with an in-situ cyclic voltammetry test, and the voltage sweep was conducted from 0 to 0.8 V. Finally, the volumetric flow was fixed at 0.1 L/min for both gases hydrogen on the anode side and nitrogen on the cathode side. The results show that the electrochemical surface area (ECSA) of the cathode catalyst decreases drastically as the operating temperature of the cell increases; this is due to the decrease of active sites by the fewer hydrogen ion pathways reaching higher temperatures. Consequently, the empirical correlation proposed for the electrochemically active area in this study helps the catalyst layer's diagnosis and predicts the level of performance for different temperatures.

Figure 1