bluuebunny/crossref_metadata_2025_split huggingface dataset:
Droplet Dynamics and Removal from Polymer Electrolyte Fuel Cell Channels Using Acoustic Pressure Waves
Authors: Stolberg Preston R. , Coverdill Alexander , Mortazavi Mehdi , Benner Jingru , Chauhan Vedang , Santamaria Anthony D. 
Published: February 2020

Liquid water management in polymer-electrolyte-membrane (PEM) fuel cell reactant channels is critical to system performance, stability, and lifespan. A balance between cathode catalyst layer water generation and removal must be maintained to ensure proper membrane hydration while preventing flooding. Liquid water transport through the gas-diffusion-layer (GDL) results in droplet formation in reactant channels that may be removed via flow gas drag forces. This work investigates the effect that acoustic wave transmission in reactant flow gases has on liquid water droplets growing on the GDL surface. While recent and past work has shown this method may be useful toward preventing liquid buildup in reactant channels, fundamental analysis of the droplet behavior is lacking [1-3]. In this study experiments were performed using a transparent ex-situ flow channel of 3.5 (h) x 3.7 (w) mm cross section as shown in Figure 1a. Water droplet formation was controlled using a digital syringe pump injected through a port on the backside of the GDL. Air and Hydrogen were used to simulate both cathode and anode flow conditions. A speaker was connected in series with the feed gas and flow channel whereby acoustic signals were generated and passed through the reactant channel. Transducers measured pressure upstream and downstream of the droplet while a high speed camera captured images of the droplets motion from the side (Figure 1b). Early results show that pressure waves effect droplets pinning behavior on the GDL surface. Previous work has shown that a maximum contact angle hysteresis exists for droplet removal from GDLs. While gas flow causes droplet contact angle hysteresis, this work shows that oscillations caused by the acoustic waves may shift the droplet over the max hysteresis tipping point enabling removal.
References:

M. Schafer, J.S. Allen, Improved water removal from fuel cell flow channels via natural frequency excitation of free surfaces, ECS Transactions 41 (1), 1887-1896, 2011

Allen, Jeffrey S., "Water removal from gas flow channels of fuel cells" (2013), Patent#: 8524410, https://digitalcommons.mtu.edu/patents/120

Mortazavi, A.D. Santamaria, J.Z. Benner, V. Chauhan, Enhanced Water Removal from PEM Fuel Cells Using Acoustic Pressure Waves, Journal of The Electrochemical Society, 166 (7), F3143-F3153, 2019

Figure 1
Contamination of Pt Catalyst with Carbon Monoxide during Hydrogen Evolution
Authors: Yilmaz Abdurrahman , Pasaogullari Ugur 
Published: February 2020

Absorption of carbon monoxide (CO) on the platinum catalyst hampers the hydrogen oxidation and evolution reactions by affecting the reaction kinetics and reducing the electrochemical active surface area [1, 2]. In this paper, we use electrochemical impedance spectroscopy (EIS) to investigate the electrode poisoning on the hydrogen evolution reaction (HER) with the presence of CO. Single cell proton exchange membrane fuel cell (PEMFC) hardware with a low loading catalyst coated membrane (CCM) is operated in electrochemical hydrogen pump (EHP) mode. EIS data is collected every 5 minutes during poisoning with pure H2 or CO-H2 mixture on the anode and cathode. The Nyquist plot shows only one semicircle due to reaction kinetics, and this semicircle diameter increases significantly with time.
EIS measurements are performed in galvanostatic and potentiostatic modes. Both methods show that cathode poisoning has significant influence on hydrogen evolution, however, electrochemical surface area is significantly reduced at constant potential compared to constant current. At constant current operation, cell potential tends to increase accelerating the removal of CO. The highest impact on reaction kinetics is observed while both anode and cathode electrodes are poisoned at the same time. Anode electrode poisoning is more effective than cathode electrode poisoning on the rate of oxidation and evolution reactions at constant current. However, both electrodes have similar impacts at constant potential. Moreover, over potential of the anode electrode increases significantly during the CO poisoning at constant current operation compared to over potential of cathode electrode.
References

G.A. Camara, E.A. Ticianelli, S. Mukerjee, S.J. Lee and J. McBreen, 149(6), A748 (2002).

N.R. Elezovic, Lj. Gajic-Krstajic, V. Radmilovic, Lj. Vracar and N.V. Krstajic, Electrochim. Acta, 54, 1375 (2009).

Figure 1
Ionomer Aggregation in Dispersions: Revealing the Role of Solvent By a Fully Atomistic MD Study
Authors: Tarokh Atefeh , Karan Kunal , Ponnurangam Sathish 
Published: February 2020

Ionomer dispersions are a key ingredient for fabrication of fuel cell catalyst layers. The structural characteristics of ionomer (e.g. Nafion) in dispersions and thereby in the colloidal catalyst ink (comprising Pt/C catalyst and ionomer in a solvent/media) has been speculated to play an influential role in the structure, property and performance of CLs made thereof [1-5]. How or why the chains of the sulphonic acid containing perfluorinated ionomers interact with each other in organic solvents or water or water-alcohol mixtures to form aggregates is not understood. The shape and size of aggregates are still under debate [6]. Furthermore, the commonly deployed x-ray, neutron and light scattering techniques for characterization of ionomer dispersion are limited in their capabilities to shed light on the internal structure of the aggregates, i.e. chain entanglement and coiling, solvent induced swelling, as well as the clustering or dissociation of sulphonic acid. Our all-atom Molecular Dynamics (MD) study aims to reveal the role of solvents on the aforementioned aggregation behavior and aggregate characteristics. Nafion ionomer in common lab solvents such as toluene, IPA, ethanol, glycerol, formic acid, formamide and water was simulated. The results reveal that depending on the solvent ionomers aggregate either due to ionic interactions between protonated sulphonate ion pairs (Figure 1a) or due to hydrophobic effects (Figure 1b). Interesting structure is observed for mixture of alcohol and water (Figure 1c), consistent with the structure proposed by Los Alamos researchers (Welch et al)[6].
The presentation will discuss the results in further details including aggregate shape/size, chain conformation, ionic cluster shape/size, and acid deprotonation for various solvents. A new aggregation phase diagram will be introduced.

References:

[1] Uchida et al, 1995, J Electrochem Soc, 142, 463 ; [2] Malek et al, 2007, J. Phys. Chem. C, 111, 13627; [3] Ghelichi et al, 2016, J Macromolecules, 49,1479; [4] Mashio et al, 2016, Electrochim Acta, 202,14; [5] Mabuchi et al, 2017, J Electrochem Soc,80, 577; [6] C.Welch et al, 2012, American Chemical Society, 1,1403.

Figure 1
Elucidating the Structural Composition of a Fe-N-C Catalyst By Nuclear and Electron Resonance Techniques
Authors: Wagner Stephan , Auerbach Hendrik , Tait Claudia , Martinaiou Ioanna , Shyam Kumar Chethala Neelakandhan , Kübel Christian , Sergeev Ilya , Wille Hans-Christian , Behrends Jan , Wolny Juliusz , Schünemann Volker , Kramm Ulrike Ingrid 
Published: February 2020

Today, state of the catalysts in proton exchange fuel cells are platinum-based. Cost estimates show that basically the catalyst is one of the most expensive components in the FC stack. While platinum is very active for the hydrogen oxidation reaction, large quantities (approx. 80 % of the overall Pt content) are required on the cathode for the oxygen reduction reaction (ORR).
Thus, alternative catalysts are required. Fe-N-C catalysts achieve very promising ORR activities in PEFC applications. The most active ones are prepared from zinc immidazole frameworks in combination with an iron source (and nitrogen precursor), that are then pyrolysed at temperatures of 900 °C or even higher. This makes it very likely that inorganic spectator species are formed.
In order to get some more fundamental insight, in this work we focused on the characterization of a Fe-N-C model catalyst. The material was prepared from iron porphyrin supported on carbon with low iron loading at 600 °C followed by acid leaching. For this condition, previous results indicate that still the overall amount of FeN4 centers remain intact, but transforms to slightly different local environments.
Herein, we will show by the use of nuclear inelastic scattering (also known as Nuclear Resonance Vibrational Spectroscopy), low temperature Mössbauer spectroscopy and Electron Paramagentic Resonance spectroscopy that the above given conclusion was wrong: even for these mild preparation conditions large amounts of spectator species are found, that overlay in room temperature Mössbauer spectroscopy with the so-called D1 doublet, previously assigned as ORR active site by us and others.
Nevertheless, still the catalyst contains about 50 % FeN4 centers, thereof a partial fraction that is coordinated by oxygen molecules.
These results underline the importance of in-depth analysis of Fe-N-C catalysts as the amount of spectator species should be decreased in best case to zero, in order to avoid side reactions.
Fuel and Water Management in Direct Methanol Fuel Cells
Authors: Blankenau Isaac , Marten Lauren , Li Xianglin 
Published: February 2020

This study has designed and setup experiments to measure the performance of MEAs made from Johnson Matthey’s gas diffusion electrodes (anode: 3 mg/cm2 Pt and 1.5 mg/cm2 Ru; cathode: 1.25 mg/cm2 Pt). The polarization curves of MEAs with fuel and water management layers, which are porous materials with different wettability and mass transfer resistance, have been experimental measured with dilute methanol solutions (3M or less). In addition, the water crossover, and methanol crossover, as well fuel efficiency, energy efficiency have been estimated from changes of weight and concentration of methanol solutions before and after constant current discharge experiments.
Results show that adding a fuel management layer between the methanol channel and the MEA can significantly reduce the water and methanol crossover rate and increase the fuel and energy efficiency. The net water flux across the electrolyte membrane could be less than the water flux caused by electro-osmotic drag flux. In other words, the water flux by diffusion and convection could be from cathode to anode when a fuel management layer is applied. However, the fuel management layer also reduces the water flux from the channel to the MEA and increases the ohmic resistance of the electrolyte membrane. A water management layer between the MEA and cathode channel is recommended to reduce the water loss through the cathode, reduce the water and methanol and water crossover rate, and increase the fuel efficiency. This water management layer does not deteriorate the water flooding since the operating current of methanol fuel cells (<0.5 A/cm2) are typically much lower than that of proton exchange membrane. The limiting current with or without the water management layer keeps almost the same. In addition, if a fuel management layer is applied to reduce the methanol crossover, a thinner electrolyte membrane is recommended because it requires less water to be hydrated and it has relatively low ohmic resistance.
(Invited) Solid State Electrolyte for Li-Metal Based High Capacity Battery Application
Authors: Wu James J. 
Published: February 2020

NASA future missions demand safe, high specific energy (>400 Wh/kg) batteries. Current state-of-the-art (SOA) lithium-ion batteries (LIBs) can only provide ~150-200 Wh/kg in energy capacity, which is unable to meet NASA’s future energy goals, and also pose safety issues due to the use of liquid flammable electrolyte. There are intense on-going development activities to increase battery energy density. The use of Li metal as an anode material has emerged as one highly attractive option for achieving high-energy, next generation batteries. This is because Li has many advantages. It is the lightest metal, but also has the highest theoretical capacity. It also has the lowest potential, which boosts whole cell voltage, and Li metal is 100% active material and requires no binder. Thus, Li metal is an ideal anode material for high energy battery chemistries. Lithium metal based advanced battery chemistries are envisioned to be mission enhancing and, in many cases, mission enabling for future space and aeronautic applications.However, the reliable use of this exceptionally high capacity anode in a commercial rechargeable battery has not been achieved due to safety and reliability concerns resulting from thermal runaway and short-circuit issues due to dendritic growth on the Li metal anode from lithium plating during charge-discharge cycles.
A solid state electrolyte, such as garnet/ceramic or solid polymer nanocomposite electrolyte, is a promising approach to make Li metal safely cycling. The solid state electrolyte is non-flammable and eliminates leakage and fire hazard by replacing the liquid flammable electrolyte. However, the low-ionic conductivity and high interfacial impedance are the key issues to be overcome. In this presentation, the research activities on solid state electrolyte development funded by the NASA Advanced Energy Storage System program and by the NASA Center Innovative Fund will be presented, and the progress and results will be also discussed.
(Invited) Electrocatalysis and Photoelectrochemistry Based on Modified Titanium Dioxide Nanomaterials
Authors: Chen Aicheng , Dondapati Jesse , Van Der Zalm Joshua , Chen Shuai , Prins Scott 
Published: February 2020

With an ever-increasing population, the importance of industrial processes to ensuring enough food and energy are produced to meet increasing demand cannot be understated. Unfortunately, these processes often produce byproducts that become waste and cause ecological damage. A large concern arises when these waste products enter the water system, resulting in serious consequences for the environment. Various methods have been explored towards the removal of these pollutants. Catalysis plays a key role in chemical production, energy conversion and storage, air purification, water treatment, food processing, and the life sciences. In this presentation, we report on the preparation and modification of TiO2 nanostructured materials as advanced electrocatalysts and photocatalysts for environmental applications and water disinfection.
TiO2 nanopores and nanotubes were directly grown on a titanium substrate using anodization processes. Scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, and X-ray diffraction were employed to characterize the formed TiO2 nanostructures. The electrocatalytic and photocatalytic activities of the nanoporous and nanotubular TiO2 were investigated by the degradation of phenolic pollutants and lignin, a byproduct of the pulp and paper industry, as the model pollutants. The formed TiO2 nanostructures were further treated using electrochemical methods in enhance their catalytic activities. The effectiveness of electrochemical and photoelectrochemical degradation of phenolic species and lignin was determined by UV-Visible spectroscopy and total organic carbon analyzer. The effect of the growth time, the morphology, and the electrochemical treatment on the performance of the formed nanoporous and nanotubular TiO2 is discussed. In addition, the increasing lack of drinking water around the globe is of great concern. The synergistic effect of the integration of photocatalysis and electrocatalysis on bacterial disinfection is highlighted.
(Invited) In Situ/Operando X-Ray Characterization of Electronic Structure in Energy Materials Systems
Authors: Lee Jonathan R. I. , Ogitsu Tadashi , Wood Brandon C. , Bagge-Hansen Michael , van Buuren Tony 
Published: February 2020

Characterizing the evolution in electronic structure of energy materials systems, e.g., (photo)electrochemical, electrocatalytic, etc., during operation is essential for fully understanding their behavior; the structure-property relationships derived from operando studies of functioning energy systems is critical for informing the tailored design of materials with enhanced performance as part of a feedback loop. Synchrotron-based soft x-ray spectroscopies, including both x-ray absorption spectroscopy (XAS) and x-ray emission spectroscopy (XES), are ideally suited to the in situ/operando study of energy material structure. As element specific probes of the unoccupied and occupied electronic density of states, XAS and XES can yield insight into the bonding and composition/structure of materials across multiple length scales; moreover, these techniques are equally applicable to ordered and amorphous systems, and have the sensitivity to address structural changes in low concentration additives/dopants and bulk materials alike. Significantly, the advantages of XAS/XES are only fully realized via the close coupling of in situ experimental methods and advanced ab initio modeling, especially for highly complex, multi-component systems, to identify and interpret key spectroscopic signatures. We demonstrate the benefits of a combined experiment/simulation approach via the investigation of nanostructured carbon aerogel (CA) electrodes operating in prototypical electric double-layer capacitors. Simulations are leveraged to interpret spectral changes consistent with complex, reversible, and highly influential structural transformations: profound bias- and time-dependent evolution of the electronic structure under applied bias connotes both mesoscale (distortion of the porous networks) and nanoscale (specific adsorption) phenomena central to device performance. Although XAS/XES have the potential for impact across multiple EMN consortia, further discussion will focus on ongoing work centered around our combined experiment/simulation node within HydroGEN.
This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.
(Invited) HydroGEN Supernode: Linking Low Temperature Electrolysis/Hybrid Materials Properties to Electrode Performance
Authors: Alia Shaun M , Bender Guido , Ulsh Michael , Mauger Scott A , Pivovar Bryan S. , Dinh Huyen N , Weber Adam Z. , Danilovic Nemanja , Kusoglu Ahmet , Colon-Mercado Hector 
Published: February 2020

The HydroGEN Energy Materials Network (EMN) supernode in low temperature electrolysis combines capabilities from the National Renewable Energy Laboratory (NREL), Lawrence Berkeley National Laboratory (LBNL), and Savannah River National Laboratory (SRNL) to perform relevant and ground-breaking research outside of EMN-funded projects. The low temperature electrolysis supernode focuses on: evaluating and bridging the gap between rotating disk electrode half-cell activity and membrane electrode assembly single-cell performance; and understanding how electrode composition and processing parameters affects device performance.
Ex-situ testing has been used to screen a variety of catalysts and correlate oxygen evolution activity to in-situ performance. Gaps between half- and single-cells were attributed to differences in configuration and standardized test parameters. While non-kinetic loss in membrane electrode assemblies are primarily due to resistance (ohmic), significantly larger transport losses are found in rotating disk electrodes due to electrode orientation and agitation. Differences in kinetics between these methods is primarily due to temperature. Increasing half-cell temperature and using flow cells can be used to bridge the gap between ex- and in-situ performance. Various oxygen evolution catalyst types, including different surfaces (metal/oxide), supports, surface areas, and components, were evaluated to address test differences across these material sets.
Additionally, electrode composition and processing parameters were evaluated for their affect in electrolysis performance. Although catalyst layer uniformity may not significantly affect device performance at high loading, coating methodology is critical at low loading. Various spray coating parameters, including ink composition (ionomer content, water/alcohol ratio), drying temperature, and deposition rate were evaluated and found to alter the resulting performance in membrane electrode assemblies. Ionomer content was further correlated to half-cell tests, where low content may adversely impact ink stability (catalyst layer uniformity) and the catalyst layer interface, while high content may lower performance through contaminant effects. Parameters from spray coating tests were applied to slot die and gravure coating methods to transfer this understanding to larger-scale processes. Efforts to tune coating parameters utilize rheology studies and ex-situ characterization to assess catalyst-ionomer-solvent interactions and ionomer thin films. Multiscale modelling was used to evaluate membrane electrode assembly performance and separate kinetic, transport, and ohmic losses. Composition and processing parameters were additionally applied to hybrid cycles.
Intrinsic Properties of Silicon-Electrolyte Interphase (SiEI) Studied through Individual Inorganic Components
Authors: Han Sang-Don , Wood Kevin N , Stetson Caleb , Norman Andrew G , Brumbach Michael , Coyle Jaclyn , Xu Yun , Harvey Steve , Teeter Glenn , Zakutayev Andriy , Burrell Anthony 
Published: February 2020

The stabilization of a silicon-electrolyte interphase (SiEI) is a great challenge which limits the ability to approach theoretical capacity limits (about 3,600 mAh g-1, almost 10 times higher than that of graphite) in silicon (Si) anodes for next-generation lithium-ion batteries (LiBs). The SiEI is a less studied topic relative to the research devoted to battery components, in part, because of its complexity, reactivity and continuous evolution.1 However, the SiEI plays a key role in prevention of further electrolyte reduction and desolvation of Li+ions, which is directly related to electrochemical performance, lifetime and safety of batteries. For example, the unstable SiEI leads to irreversible capacity losses, poor cycling stability and a limited cycle life.2-4

In this study selected known SiEI components (i.e., SiO2, Li2Si2O5, Li2SiO3, Li3SiOx, Li2O and LiF) were prepared as amorphous thin films. The chemical composition, homogeneity, morphology and local electronic structure across the surface and the bulk were characterized using X-ray photoelectron spectroscopy (XPS), electron energy loss spectroscopy (EELS), time-of-flight secondary ion mass spectrometry (ToF-SIMS), atomic force microscope (AFM), and scanning-spreading resistance microscopy (SSRM). In addition, the physical, electrochemical and mechanical properties of individual constituents were characterized using electrochemical impedance spectroscopy (EIS), operandoXPS with an electron gun, and AFM (force distance curve) and scanning probe microscopy (SPM)-based nanoindentation.
This study delineates the components which are critical for stabilizing the SiEI. These findings enable rational design of new electrolyte additives and functional binders for the development of next generation LiBs.

References

1. M. Gauthier, T. J. Carney, A. Grimaud, L. Giordano, N. Pour, H.-H. Chang, D. P. Fenning, S. F. Lux, O. Paschos, C. Bauer, F. Maglia, S. Lupart, P. Lamp and Y. Shao-Horn, J. Phys. Chem. Lett.2015,6, 4653.
2. B. Philippe, R. Dedryvere, M. Gorgoi, H. Rensmo, D. Gonbeau, and K. Edstrom, Chem. Mater.2013, 25, 394.'
3. T. Jaumann, J. Balach, M. Klose, S. Oswald, U. Langklotz, A. Michaelis, J. Eckerta, and L. Giebelera, Phys. Chem. Chem. Phys.2015, 17, 24956.
4. B. T. Young, D. R. Heskett, C. C. Nguyen, M. Y. Nie, J. C. Woicik, and B. L. Lucht, ACS Appl. Mater. Interface2015, 7, 20004.