bluuebunny/crossref_metadata_2025_split huggingface dataset:
On the Potential of 3D Printed Micro Structured Porous Media to Enhance PEM Fuel Cell Performance
Authors: Schulz Volker Paul , Schmitz Sven , Auvity Bruno , Starke Thomas 
Published: February 2020

Over the last years, the additive manufacturing of metals with resolutions down to 50 µm has matured to be used in large-scale production [1]. The Germany-based company 3D MicroPrint uses the selective micro laser sintering (µSLS) together with extremely fine (Ø<5 µm) metal powder to generate micro structured parts.
3D MicroPrint is an industrial partner in a research project where the µSLS is used to manufacture different parts of polymer membrane electrolyte fuel cells (PEM-FC).
PEM-FCs are promising electrochemical devices for zero emission power sources. The transport of hydrogen and oxygen towards the reaction side and the removal of the produced water are essential for the PEM fuel cell performance. This gas transport towards the membrane electrode assembly (MEA) is governed by convection in flow channels of a bipolar plate and by diﬀusion in gas diffusion media (GDL).
In conventional PEM-FCs, the bipolar plates are either punched metal sheets or milled graphite plates. Standard GDLs are based on carbon paper which is treated with Polytetraﬂuoroethylene (PTFE).
In this study, we show a new approach to build up the gas supporting structures of PEM-FCs. Using the µSLS, there is an entirely new design space to build up the micro geometries of flow channels and gas diffusion. Additionally, the bipolar plate and the GDL can be combined and manufactured as a single part a so-called membrane separator.
In this contribution, we present different realizations of homogeneous and heterogeneous µ-3D printed parts used for as transport layers in PEM-FCs together with measured data on the fuel cell performance. One example of a homogeneous periodic structure used as GDL is shown in Fig. 1.
Based on these results, we outline the potential of additive manufactured microporous metal parts for PEM-FC applications.

Figure 1
(Invited) Elucidating Ion Transport Mechanisms in Polymerized Ionic Liquids
Authors: Liu Hongjun , Paddison Stephen J. 
Published: February 2020

Poor ionic conductivity typically hinders the utilization of ion containing polymers from functioning as a single ion conductor for energy storage or conversion applications. A provocative sub class of these materials are polymerized ionic liquids (polyILs) which have the potential to combine the desirable ion transport of an ionic liquid with the favorable mechanical properties of a polymer. However, the room temperature conductivity of polyILs is usually 2 or 3 orders of magnitude lower than that of low molecular weight ionic liquids, yet a decoupling of conductivity and structural dynamics in polyILs demonstrates the opposite at the normalized glass transition temperature (T
g/T). This seemingly conflicting observation can be reconciled by the fact that polyILs have higher T
g and lower dielectric permittivity at the same T
g/T than their molecular counterparts. Moreover, ionic conductivity of polyILs is found to be significantly slower than ion diffusion. Inverse Haven ratio shows a strong temperature dependence: saturating at 0.2 at higher temperature and decreasing at lower T. Pronounced reduction in conductivity is attributed to the cross correlation between the mobile ions since the ion pair diffusion is infeasible in polyILs. This speculation remains unverified.
We have recently undertaken atomistic molecular dynamics (MD) simulations to elucidate transport mechanism in polyILs and demonstrate the dynamical heterogeneity and cooperative motion of ion transport in polyILs establishing for the first time quantitative evidence of mobile ion hopping. The hopping of anions is found to be dominantly interchain in nature and is generally facilitated by five associating cations from two different chains. Intrachain hopping was found to be much less significant being mediating with fewer chains. The mobile anions tend to form string-like structures and move cooperatively; and the string length of concerted motion of mobile anions increases with decreasing temperature. Our results reveal the important role of a distance criterion in defining hopping events to correctly elucidate the components of the ion transport mechanism. This molecular-level information will provide an important step in both rationalizing experimental observations and the design of novel ion-containing polymers with superior transport properties.
Characterization of Surface Changes on Molybdenum Nitride Thin Films during the Oxygen Reduction Reaction Using Operando Grazing Incidence X-Ray Absorption Spectroscopy
Authors: Stevens Michaela Burke , Kreider Melissa E. , Gibbons Brenna M. , Gallo Alessandro , Mehta Apurva , Davis Ryan , King Laurie A. , Jaramillo Thomas F. 
Published: February 2020

Coupled water electrolysis systems and proton-exchange membrane fuel cells (PEMFC) are a promising technology for clean energy storage and conversion, respectively.1 The efficiency of the hydrogen PEMFC is limited, in part, by the poor performance of catalysts for the oxygen reduction reaction (ORR). Due to problems with low activity and conductivity, the majority of non-platinum group catalysts for the ORR are conductive-carbon-supported nanoparticulate transition metal nitrides and/or carbides. It is difficult to determine the active surface of these catalysts during reaction conditions due to their high surface area, inhomogeneous size and distribution, complicated support-catalysts interactions, and surface oxidation in air. To overcome these complications, our work has focused on the operando structural and compositional characterization of the surface of active molybdenum nitride thin films. These films, prepared via reductive sputtering,2 are an ideal template for study due to their tunable thickness, lack of carbon support, moderate electrical conductivity, and well-defined surface. Using a specifically designed electrochemical cell for grazing incidence x-ray absorption and diffraction, we have been able to characterize changes in our Mo
x
N surface under ORR conditions. These same surface changes are not apparent at similar non-ORR reducing conditions, supporting our hypothesis that we are characterizing the active surface during ORR.
­
This work highlights the role of nitrogen, oxygen vacancies, and electrical conductivity on electrochemical activity and allows us to probe the structure and thickness of the active surface layer as well as the active site geometry. Understanding the role and importance of nitride bulk and the distinct surface structure will allow us to re-think our typical rational design of catalyst materials and help us design more active and stable catalysts in the future.

References

(1) Seh, Z. W.; Kibsgaard, J.; Dickens, C. F.; Chorkendorff, I.; Nørskov, J. K.; Jaramillo, T. F. Combining Theory and Experiment in Electrocatalysis: Insights into Materials Design. Science (80-. ).
2017, 355, 1–12.
(2) Hones, P.; Martin, N.; Regula, M.; Francis, L. Structural and Mechanical Properties of Chromium Structural and Mechanical Properties of Chromium Nitride , Molybdenum Nitride , and Tungsten Nitride Thin Films. J. Phys. D Appl. Phys.
2003, 36, 1023–1029.
(Invited) Catalysts for Fuel Cells
Authors: Lopes Pietro Papa , Strmcnik Dusan , Wang Rongyue , Lv Haifeng , Becknell Nigel , Markovic Nenad M , Stamenkovic Vojislav 
Published: February 2020

The progress in platinum-based catalysts with the goal of improving their activity and durability in a proton exchange membrane fuel cell will be presented. The studies of the oxygen reduction reaction on well-defined surfaces have guided the approach to design of the real world nanostructured catalysts. Insights from single crystalline systems and thin film surfaces have yielded atomically precise information related to surface structure and alloying with other metals in the quest to improve their intrinsic catalytic activity. These experimental efforts are also producing information necessary for the design of catalysts with enhancing stability. Atomic level control of the positioning of elements within catalyst structure enables the design of shapes and surfaces that mimic the key descriptors discovered through research on well-defined surfaces. The meticulous characterization of nanoscale materials using extremely high-purity conditions and cutting-edge techniques provides greater understanding of their performance and degradation pathways. This knowledge enables implementation of these materials in membrane electrode assemblies (MEA) for demonstration of targeted performance in a fuel cell vehicle.
The catalyst, its support, water, ionomer, and gaseous reactants create challenging environment to control and engineer at the level that would be capable to address all technical targets that are necessary for wide deployment of this technology. The transition from high-purity liquid electrolytes into MEA still needs to be addressed before stepping into mass production of fuel cell stacks. The overall research strategy presented here exhibits the merits of a continuous pipeline from fundamental to applied research in the development of fuel cell technology.
(Invited) Pathways Towards High-Performance Reversible Alkaline Membrane Fuel Cells
Authors: Xu Hui , Wu Gang , Yan Yushan 
Published: February 2020

Reversible fuel cells have advantages over rechargeable batteries (Ni/MH or Li-ions) due to their high energy density, minimal self-discharge, and low cost. Reversible alkaline membrane fuel cells (AMFC) are attractive due to their ability to work with platinum-group-metal (PGM)-free catalysts. Major factors that limit the application of reversible AMFCs are low performance of bifunctional oxygen catalysts, alkaline membrane stability, and water management, which lead to high cost and low round-trip efficiency (RTE).
We have developed a variety of high-performance metal oxides/nanocarbon bifunctional oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) catalysts, which have demonstrated remarkable reversibility and stability under harsh voltage cycling from 0.0 V to 1.9 V, providing a solid foundation for enabling reversible AMFCs. However, during membrane and electrode (MEA) development, it was found that the alkaline membrane and ionomer degraded rapidly at high electrolysis voltages. Thus, hydroxide ion transfer paths across the membrane and in the electrodes were largely blocked. Although the introduction of diluted carbonate salt (e.g., NaHCO3) or base (e.g., KOH) solutions can help to retain the electrolysis operation to some degree, it leads to flooding and complicates the reversible fuel cell system.
In this work, we will present some solutions to the challenges of reversible AMFCs, thus realizing high-efficiency reversible fuel cell operations. First, oxidation-resistant alkaline membranes and ionomers that are stable under oxidation conditions will be discussed, to eliminate the need of carbonate salt (e.g., NaHCO3) or base (e.g., KOH) solutions. Second, high-performance bifunctional catalysts for hydrogen evolution reaction (HER)/hydrogen oxidation reaction (HOR) and ORR/OER catalysts will be elaborated. Furthermore, advanced MEAs will be designed to minimize water transport-associated reversible fuel cell performance loss. These combined efforts can improve the RTE to 50% at an appreciable current density (>500 mA/cm2).

Acknowledgement: The project is financially supported by the Department of Energy’s Fuel Cell Technology Office under the Grant DE-EE0006960.
(Invited) Molecular Engineering of Quaternary Ammonium Aromatic Polymers for Anion Exchange Membrane Fuel Cells
Authors: Bae Chulsung 
Published: February 2020

As a promising alternative to proton exchange membrane fuel cells (PEMFCs), anion exchange membrane fuel cells (AEMFCs) have received great attention in recent years. The high pH operating condition of AEMFCs allows use of non-precious metal catalysts and less expensive metal hardware. Recently, a power density over 1.0 W cm-2 has been achieved for AEMFC approaching close to that of PEMFCs. One of key requirements for high performance of AEMFCs is anion exchange membranes (AEMs) with high ion conductivity, good chemical stability and mechanical durability. New materials development using novel polymer backbones and side chain ionic functional groups have been extensively investigated over the past decade.
In this study, we will present the effects of different structures of polymer backbones and the location of ionic side chains on the membrane properties of AEMs and their fuel cell performance. Polymers made of soft backbone, such as polystyrene-b-poly(ethylene-co-butylene)-b-polystyrene (SEBS), and rigid backbones, such as polyarylenes containing biphenyl and terphenyl core groups (namely BPN and TPN series), have been evolved from my group at RPI over the past years. Because the backbone of those polymers are made of all carbon-carbon bonds, they showed excellent chemical stability under alkaline conditions. The high molecular weights (>100,000 g/mol) of those functionalized polymers also afforded good mechanical strength and high strain when made into film. A perspective of quaternary ammonium-functionalized polymers that have been developed from RPI will be presented with emphasis on synthetic strategy and materials performance in AEMFC test condition.
(Invited) High Performance Alkaline Membrane Fuel Cells Powered By Direct Ammonia
Authors: Achrai Ben , Tamir Gal , Kitayev Anna , Tal-Gutelmacher Ervin , Page Miles 
Published: February 2020

Alkaline exchange membrane fuel cells (AEMFCs) have gained significant attention in recent years owing to several advantages over the industry-standard proton exchange membrane fuel cells (PEMFCs) such as lower cost materials (e.g., non-PGM electro-catalysts, hardware, etc.)
Less commonly cited are potential advantages of AEMFCs with respect to alternative fuels. Ammonia is a particularly attractive carbon-free fuel, being liquid at room temperature under ~7 atm, resulting in very high volumetric energy density and simplified distribution relative to hydrogen which is typically compressed to 200-700 atm. Furthermore, ammonia cannot be used as a fuel in PEMFCs since in the acidic environment ammonia exists primarily as ammonium which displaces the H+ ions that impart conductivity to the polyelectrolyte.
One of the key challenges in direct ammonia fuel cells is to execute the sluggish ammonia oxidation reaction (AOR) effectively. Previous successful attempts at operating direct ammonia fuel cells, therefore, all utilized high-temperature approaches such as solid oxide fuel cells (SOFCs) operated at ~600-850 °C [1] or alternatively, alkaline fuel cells (AFCs) operated at ~140 °C with concentrated KOH solutions as the electrolyte [2]. Additionally, a few attempts have been made to operate at lower temperatures with ammonia as a fuel, yielding very low power densities (<20 mW/cm2) [3-4].
In this study, we report for the first time, a direct NH3/O2 AEMFCs operated completely free of liquid electrolyte – in both the membrane-electrode assembly and the fuel feed. Utilizing operating temperatures of 100-120 °C to minimize losses from the AOR, and optimizing operation conditions and MEA design, yielded a peak power density of 270 mW/cm2 with no added electrolyte, and 450 mW/cm2 with the addition of dilute (1M) KOH to the fuel feed. Optimization was also carried out to stabilize performance over several hours with minimal voltage loss, thereby demonstrating sustained ammonia oxidation in the absence of any hydroxide additives. This work thus demonstrates the applicability of a high-performance direct ammonia-powered AEMFCs.
[1] Hagen A., "Use of alternative fuels in solid oxide fuel cells." Fuel 2.2H2 (2007): H2.
[2] Simons E.L., Cairns E.J., Surd D.J., "The performance of direct ammonia fuel cells." Journal of The Electrochemical Society 116.5 (1969): 556-561.
[3] Rong L., Tao S., "Direct ammonia alkaline anion-exchange membrane fuel cells." Electrochemical and Solid-State Letters 13.8 (2010): B83-B86.
[4] Kuntke P., Sleutels T.H.J.A., Saakes M., Buisma C.J.N., "Direct ammonia fuel cell performance using PtIr/C as anode electrocatalysts." international journal of hydrogen energy 39.10 (2014): 5148-5152.
The Effect of Length of Spacer on the Anodic Oxidation of Bisamides
Authors: Becker James Y. , Golub Tatiana 
Published: February 2020

Previously we studied the anodic oxidation of different types of amides, including cyclic ones [1-3]. Recently we investigated [4] the anodic oxidation of bisamides (from diaminoalkanes) involving 2-4 methylene groups as spacers between the two amide functionalities. Those with 3 and 4 methylene groups behave similar to monoamides. They both undergo mostly mono- and dimethoxylations at the alpha-position to 'N' atom. However, when the spacer contains two methylene groups only, the anodic process affords mostly fragmentation products due to CH2-CH2 bond cleavage: RCONHCH2OCH3 exclusively, or along with RCONHCHO, depending on the supporting electrolyte used. The scheme below describes the outcome in both cases:

References
[1] Golub T.; Becker J. Y., Org. Biomol. Chem. 2012, 10, 3906-3912.
[2] Golub T.; Becker J. Y., J
. Electrochem. Soc. 2013, 160, G3123-G3127.
[3] Golub T.; Becker J. Y., Electrochim. Acta
2015, 173, 408–415.
[4] Golub T.; Becker J. Y., Beilstein J. Org. Chem.
2018,
14, 861–868.

Figure 1
Effect of Plasmon Stimulation on the Extraction of Photosynthetic Electrons from Thylakoid Membranes
Authors: Kim Yong Jae , Hong Hyeonaug , Yun JaeHyoung , Kim Seon Il , Ryu WonHyoung 
Published: February 2020

Because of extremely high internal quantum efficiency of photosynthesis, photosynthetic bio-solar energy conversion has drawn much attention recently in the field of renewable energy. Thylakoid membranes (TMs) are the place where photosynthesis occurs. Since TMs can be easily isolated from plants or algae and remain stable after isolation, they are widely used in photosynthetic energy transfer systems. However, despite its high conversion efficiency from photons to photosynthetic electron (PE), their overall efficiency is limited due to limited absorption of incident photons and low extraction efficiency of PEs. Therefore, several approaches were developed to increase PE extraction by improving electrical connections between TMs and electrodes such as amine or carboxyl modified carbon nanotube electrode, titanium oxide (TiO2) modified electrode or reduced graphene oxide (rGO) modified electrode. Furthermore, PE extraction can also be increased by stimulating photosynthesis to produce more PEs. Recently, it was demonstrated that photosynthesis stimulation could be achieved by inducing localized plasmon field very close to the light energy harvesting complexes within isolated photosystem I or II.
In this study, we aimed to enhance PE extraction by stimulating photosynthesis using plasmon induced resonance energy transfer (PIRET). Gold nanorod (AuNR) was used to induce plasmonic field close to the TMs for photosynthesis stimulation and the geometry of AuNR was carefully selected to match its plasmon resonance wavelength with the absorption wavelengths of photosystem I or II within TMs. Therefore, AuNRs of 17 nm width and 45 nm length were chosen to have their plasmon resonance peak at 675 nm. On the other hand, since plasmonic energy can be transferred only in a few nanometer ranges, AuNR should be located very close to TM. Therefore, a tethering molecule which can link AuNR and TM was added to attach the AuNRs to TMs. The tethering molecule has poly ethylene glycol (PEG) chain and two functional groups of thiol group (-SH) and succinimide ester (NHS ester) group at each terminal end. To make AuNR-PEG-TM conjugation, the tethering molecule solution was added to an AuNR in distilled water (DIW) suspension to form AuNR-PEG-NHS. Then, a TM solution with phosphate buffer saline (PBS) was added to the mixture so that AuNR-PEG-TM conjugation was finally formed. Each intermediate product was characterized using SEM, TEM, optical, fluorescence spectroscopy, and XPS analysis. The PE currents from AuNR-PEG-TM was measured and compared to PE currents from pure TM. With the AuNR-PEG-TM conjugation, the PE current was increased by 400% compared to the PE currents of pure TM.
Side-Selective Modification of Photosystem I Protein and Preparation of Oriented Photo-Electrochemical Films
Authors: Wolfe Kody 
Published: February 2020

The directional orientation of photoreactive protein complexes extracted from plants, algae, and cyanobacteria is of crucial importance to the performance of biologically-modified, photo-active electrodes. The photo-electrochemical response of such protein complexes is inherently directional and achieving uniform orientation is necessary to mitigate problems such as electron-hole recombination, low net charge transfer due to competing electrochemical reactions, and loss of direct electron transfer to the electrode. [1] Previous efforts to control orientation have explored bio-conjugation [2] and electrostatic interactions with self-assembled monolayers (SAMs) [3] to improve photocurrent generation. However, the ability to efficiently modify, deposit, and characterize the orientation of such bio-electrode films has not been demonstrated.
To achieve controlled orientation, an extraction-modification procedure has been developed based on side-selective functionalization of photosystem I (PSI), a photo-active protein complex derived from spinach. Reactive amine groups on the surface of PSI can be leveraged to incorporate a variety of new functional groups through solution-based modification reactions. The functional group chosen for modification can be tailored to achieve oriented deposition on the substrate electrode. Herein we explore modification strategies utilizing the thiol-gold affinity and polyethylene glycol (PEG) “capping”. The deposition kinetics, monolayer structure, and electrochemical reactivity of the modified PSI monolayers have been studied to better understand the ability to control PSI orientation on gold electrodes. Controlled orientation will allow for the future development of oriented PSI based devices such as biohybrid photovoltaics or electrochemical photocatalysis membranes, and this facile modification procedure may be implemented with other membrane bound proteins and protein complexes.
[1] G. LeBlanc, et al, Langmuir, 30 (37), 10990–11001, 2014.
[2] R. F. Simmerman, et al, Bioconjugate Chem, 26 (10), 2097–2105, 2015.
[3] K. A. Manocchi, et al, Langmuir, 29 (7), 2412–2419, 2013.