bluuebunny/crossref_metadata_2025 huggingface dataset:
About the Necessity to Consider Membrane Electrolyte Degradation Statistically
Authors: Dlugosch Thomas , Kirsch Sebastian , Friedrich K. Andreas
Published: February 2020

One key factor for the commercialization of fuel cell vehicles is a sufficient membrane durability. In this context, car manufactures work on reliability accelerated stress test procedures (AST) to measure membrane lifetime. There have been many lifetime investigations for polymer electrolyte membrane fuel cells (PEMFCs) especially for the perfluorinated sulfonic acid (PFSA) membrane [1-3]. For comparison of membrane lifetimes, it is necessary to ensure reproducibility of the experimental lifetime data. However, in part of the literature lifetime of membranes was derived from few repetitions – if not none – of single cell experiments only [e.g. 3-5]. Random failures due to membrane production variations, cell assembly inaccuracies and statistical defects cannot be quantified without statistical analysis. Accordingly, some conclusions in literature might have been blurred due to insufficient repetition of measurements.

In this work, we stress the necessity to generate statistically relevant membrane degradation data. The development of the open circuit voltage (OCV) and the H2-crossover current (iH2) is shown in Figs. 1-2 for one specific AST and nine cells. It can be seen, that in the range of reproducibility lifetime can be 1000 or 20000 cycles. At the conference more evidence for the wide nature of the lifetime distribution will be presented. Accordingly, the distribution in voltage loss and hydrogen crossover development cannot be neglected if clear conclusions about membrane life shall be derived. Without a high number of repetitions the statistical significance is not assured. Some of the recent conclusions in literature about impact on membrane lifetime will be considered critically from this point of view.

References:

Zhang, et al., J. Power Sources 195 (2010) 1142–1148

Zhang, et al., J. Power Sources 205 (2012) 290– 300

Chandesris, et al., Int. J. Hydrog. Energy 42 (2017) 8139 – 8149

Zhang, et al., Int. J. Hydrog. Energy 39 (2014) 15989 - 15995

J. Parnian, et al., J. Membr. Sci. 556 (2018) 12-22

Figure 1
Graphene-Based Proton Transmission and Hydrogen Crossover Mitigation in Electrochemical Hydrogen Pump Cells
Authors: Bukola Saheed , Creager Stephen E
Published: February 2020

The relative rates of transmembrane proton and hydrogen gas transmission are of high importance in most PEM-based electrochemical energy conversion devices. Membrane separators that simultaneously have high rates of proton transmission and low rates of gas transmission are highly desired but this property combination is difficult to achieve because most modifications that could give higher proton transmission rates through a membrane, tend also to give higher gas crossover rates. This presentation will present results indicating that one monolayer of CVD single-layer graphene embedded between two polyelectrolyte membranes can give this desired membrane property combination. Proton transmission occurs through single-layer graphene in a PEM sandwich structure with area-specific resistance values less than 40 mΩ cm2, which is less than the resistance of most PEM membranes. Hydrogen crossover rates in PEM / graphene / PEM sandwich structures were measured by a limiting current method and found to be reduced by more than eight times relative to values in similar membranes without graphene. The lecture will present data on these points and discuss the mechanism(s) by which graphene might provide this desirable set of membrane properties.
Modeling Impact of Ce on Fuel-Cell Performance and Durability
Authors: Ehlinger Victoria Marie , Kusoglu Ahmet , Weber Adam Z.
Published: February 2020

Throughout the lifetime of a polymer-electrolyte fuel cell, the membrane undergoes chemical degradation that causes defects to form and grow, contributes to a loss of performance, and can lead to cell failure. A combination of accelerated stress tests (ASTs)1-2 and modeling studies3-4 have been performed on this topic to better understand membrane degradation mechanisms and how to mitigate them5-6. During fuel-cell operation, formed peroxide radicals due to reactant gas crossover attack the polymer backbone and end chains, leading to membrane thinning and formation and growth of defects such as cracks and pinholes. This study builds upon our previous modeling study on membrane degradation to analyze the addition of chemical scavengers into the fuel-cell membrane to mitigate the effects of chemical degradation via radical attack. The developed model is transient and 1D across the fuel-cell sandwich. The transport and concentration of cerium is modeled using an ion-transport model based on concentration solution theory, thereby allowing the evaluation of how water gradients also move cerium ions throughout the ionomer, resulting in nonintuitive distributions. The model results also show how drive-cycle testing impacts the performance of the cell and the location of cerium, where relaxation of the applied gradients help redistribute the cerium in the ionomer. The purpose of the study is to optimize the cerium amount in both the membrane and catalyst layers by balancing effects of mitigation of chemical degradation and performance due to the impact of cerium on the ionomer material properties. For the latter, a key feature is accounting for the nonlinearities induced by the impacts of cerium on membrane and catalyst-layer ionomer properties.

Acknowledgements

The authors would like to thank Hans Johansen for helpful discussions and Los Alamos National Laboratory for providing material property data. Funding support was supplied by the Fuel Cell Performance and Durability Consortium (FC-PAD), by the Fuel Cell Technologies Office (FCTO), Office of Energy Efficiency and Renewable Energy (EERE), of the U.S. Department of Energy under contract number DE-AC02-05CH11231.

References

R. Borup, et al., Chem. Rev., 107, 3904 (2007)

F. A. de Bruijn, et al., Fuel Cells, 8, 3 (2008).

R. Singh, et al., J. Electrochem. Soc., 165, F3328 (2018)

K. H. Wong and E. Kjeang, J. Electrochem. Soc., 166, F128 (2019).

M. Zatón, et al., Sustainable Energy & Fuels, 1, 409 (2017).

F. D. Coms, et al., in The Chemistry of Membranes Used in Fuel Cells: Degradation and Stabilization, 1st ed., S. Schlick Editor, John Wiley & Sons, Inc. (2018).
Iron-Nitrogen-Carbon (Fe-N-C) Active Sites Imaging By Scanning Transmission Electron Microscopy (STEM)
Authors: Asset Tristan , Kumar Kavita , Dai Sheng , Xu Mingjie , Yan Xingxu , Chen Yechuan , Li Xiaoyan , Pan Xiaoqing , Maillard Frederic , Dubau Laetitia , Atanassov Plamen
Published: February 2020

Iron-nitrogen-carbon electrocatalysts (i.e. Fe-N-C) are of interest for the oxygen reduction reaction because they can solve the geological and economic constraints associated with the use of Pt-based electrocatalysts. However, the nature and the stability of their active sites is yet to be fully understood. The presence of nitrogen and atomically dispersed Fe is believed to result in the presence of various moieties, i.e. Fe-Nx, N-pyridinic, N-pyrrolic, etc. Such assumptions are based on the fitting of the N1s peak observed by X-ray photoelectron spectroscopy (XPS) 1,2 and, for the Fe-Nx moieties, extended X-ray absorption fine structure (EXAFS) 3. Imaging a non-model Fe-N-C electrocatalyst at an atomic scale could provide additional insights onto the exact structure of those moieties, and, in combination with electrochemical ageing, ease the assessment of their stability. Here, we discuss the multiplicity of actives sites in an Fe-N-C electrocatalyst synthesized by the sacrificial support method. We use a combination of XPS, EXAFS, scanning transmission electron micrographs (STEM) and electron energy loss elemental mapping (EELS – see Figure 1) to unveil the presence, additional to Fe-Nx, of other active sites, e.g. Fe-NxCy or nitrogen moieties. Then, we investigate the stability of said moieties (with a focus onto Fe-Nx) using a combination of step-cycles (10,000 cycles; 0.6 – 1.0 V vs. RHE, 3s – 3s, in Ar-saturated 0.1 M H2SO4, T = 80°C) and STEM (see Figure 1), showing that, in these experimental conditions and for this specific family of Fe-N-C electrocatalysts, the atomically dispersed Fe forms clusters – but not nanoparticles – during the ageing process.

(1) Artyushkova, K.; Serov, A.; Rojas-Carbonell, S.; Atanassov, P. J. Phys. Chem. C
2015, 119, 25917–25928. (2) Matanovic, I.; Artyushkova, K.; Strand, M. B.; Dzara, M. J.; Pylypenko, S.; Atanassov, P. J. Phys.
Chem. C
2016, 120 (29225–29232), 6–13. (3) Zitolo, A.; Goellner, V.; Armel, V.; Sougrati, M.; Mineva, T.; Stievano, L.; Fonda, E.; Jaouen, F. Nat.
Mater.
2015, 14 (September), 937–942.

Figure 1
High-Throughput Anion Exchange Membrane Characterization at NREL
Authors: Meek Kelly M , Antunes Christopher M , Strasser Derek , Owczarczyk Zbyslaw R. , Neyerlin Ami , Pivovar Bryan S.
Published: February 2020

Alkaline fuel cells (AFCs) are of high interest because they utilize lower cost catalyst and separator materials relative to polymer electrolyte membrane fuel cells. AFCs require anion exchange membranes (AEMs) that have high alkaline chemical stability, high hydroxide ion conductivity, and adequate thermal/mechanical properties. While numerous AEMs have been developed as solid-state electrolytes for AFCs, there is still disagreement in literature on standard membrane testing procedures and optimal membrane chemistry to ensure peak long-term AFC performance. Currently, NREL is developing tools and protocols to allow for high throughput, parallel characterization of AEM materials. More specifically, NREL has received membranes from more than 10 partners and has tested more than 50 membranes using these approaches. This is allowing us to gain valuable insight into different backbone and cation strategies. In many cases these ex-situ results can be compared to fuel cell performance and durability. Technical investigations include conductivity, ion exchange capacity, mechanical performance, chemical stability, thermal properties, water uptake, swelling, and fuel cell performance. Structure-property relationships that are determined to improve membrane performance and durability will be discussed, lending insight into optimal backbone and cation strategies to employ in development of AEMs.

Figure 1
P2G System Technology Development Aiming at Building a CO2-Free Hydrogen Society
Authors: Sakamoto Masaki , Izuhara Daisuke , Sotouchi Hiroko , Aoyagi Fukuo
Published: February 2020

The government's "Basic Energy Plan" decided on April 11, 2014 has been decided to promote initiatives aimed at realizing "hydrogen society", a society that utilizes hydrogen in everyday life and industrial activities It was. Following this, the Ministry of Economy, Trade and Industry will formulate the "Hydrogen / Fuel Cell Strategy Roadmap" in June 2014 and aim to establish a CO2-free hydrogen supply system around the year 2040.

According to the Government's "Long-Term Energy Supply and Demand Outlook" published in July 2015, the renewable energy ratio to total electricity generation in FY 2030 is estimated to be 22 to 24%. On the other hand, renewable energy has large output fluctuations due to the influence of the natural environment, and geographically unevenly, there are concerns such as suspension of connection to the transmission and distribution electric power network. One solution to this problem would be the Power-to-Gas system utilizing the conversion using electric power from renewable energy into hydrogen. The obtained hydrogen can reduce CO2 emissions by replacing fossil fuels in heating sector.

At the Agency for Natural Resources and Energy, the report of the "CO2 Free Hydrogen Working Group" was compiled in March, In the report, technical issues such as low cost and high efficiency of various technologies including water electrolysis equipment, improvement of durability, improvement of utilization rate were taken as technical issues.

In this research, we demonstrate technological development from hydrogen production using renewable energy to transportation, storage and use in the real society, and establish the basic technology for practical application of "Power to Gas system".

The applicability of the water electrolyzer was confirmed by grasping the electrical characteristics of the water electrolyzer (the ability to absorb unstable power, responsiveness, etc.) from the data of the evaluation equipment. In addition, it was expected that 74% could be achieved with the year-round water electrolyzer system efficiency.

In the future business model using the 1.5 MW PEM type water electrolyzer, the MEA performance for achieving the required system efficiency of 80.5% is based on the voltage efficiency has already been achieved.

Assuming a system at the stage of practical use, we concluded that direct utilization for industrial use and utilization as a CO2-free fuel for the heat demand for industrial use are effective. In line with this conclusion, we have determined the specifications of a pure hydrogen boiler assumed as a hydrogen utilization device, by investigating the tolerance of fluctuations and the partial load operation in line with actual plant operation.

ACKNOWLEDGEMENT

This work was partially supported by the New Energy and Industrial Technology Development Organization (NEDO) of Japan.
Characterization of Cerium Dioxide Thin Films Prepared By Plasma-Enhanced Atomic Layer Deposition for Solid Oxide Fuel Cells
Authors: Jeong Wonyeop , Lee Sanghoon , Ryu Sangbong , Cho Gu Young , An Jihwan , Cha Suk Won
Published: February 2020

Solid oxide fuel cells (SOFCs) are considered to be the next generation of energy conversion devices because of their environmental friendliness and high efficiency. Particularly due to its high operating temperature, it has high fuel flexibility and does not require water management. However, the high operating temperature that causes these advantages accelerates the degradation of fuel cell components, thereby reducing the durability and limiting the usable materials. Therefore, in recent years, a lot of research has been conducted to lower the operating temperature of the SOFCs.

One method of lowering the operating temperature of SOFCs is to apply an electrolyte having good ionic conductivity at low temperatures(400-600℃). Potential examples are doped ceria materials. One of the well-known ceria-based electrolytes is Gd-doped ceria (GDC), which exhibits ion conductivity 1-2 times higher than yttria stabilized zirconia, YSZ, which is the most commonly used electrolyte in SOFC. GDC has good ionic conductivity, but when exposed to a reducing environment, Ce4+ is reduced to Ce3+ and begins to have electronic conductivity, which causes a decrease of open circuit voltage (OCV). Therefore, in order to apply GDC as an electrolyte, an additional blocking layer must be added so that it is not exposed to the hydrogen environment of the anode. This additional layer increases not only the thickness of the electrolyte but also the interfacial resistance between the layers, thereby increasing the ohmic resistance. Therefore, the fabrication of GDCs with thinner and better surface properties is critical to improving the performance of low temperature SOFCs.

In this study, CeO2 thin film was fabricated using atomic layer deposition (ALD) as a preceding step for the fabrication of GDC thin films. Oxygen plasma was used to oxidize the precursor to widen the ALD window and to produce the highly crystalline CeO2. The growth rate of CeO2 was determined by controlling precursor and oxidizer exposure time, and the thickness of thin film per cycle was confirmed. The surface morphology was observed by scanning electron microscope (SEM), and dense and pinhole-free thin film surface was confirmed. In addition, X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) analyses were performed and the characteristic crystalline peaks and chemical compositions were compared with those of the thermal ALD CeO2 thin films.
(Invited) Solid State Batteries: Energy Density, Cycle- and Manufacturability
Authors: Soloveichik Grigorii L.
Published: February 2020

Conventional Li-ion batteries (LIBs) are close to practical limits in energy density and cost. The major disadvantage of LIBs is the presence of a flammable electrolyte and a porous separator, which makes them hazardous and restrict the choice of electroactive materials. Solid state batteries (SSBs) could be potentially safer and more energy dense if dendrite-free Li anode is used. The Advanced Research Projects Agency (ARPA-E), which funds high risk, high reward transformational research to reduce energy related emissions, reduce imports of energy from foreign sources, improve energy efficiency, and ensure US technological lead in advanced energy technologies, focuses on the development and scale up of membrane component for solid state batteries as well as full cells with high energy density.

According the Integration and Optimization of Novel Ion-Conducting Solids (IONICS) program, a thin (≤20 μm) solid state (ceramic or polymer) electrolyte has to demonstrate ASR ≤5 Ohm-cm2 with high current density and movable areal capacity in Li metal cells. Several major risks for SSBs with Li metal anode have been identified: 1) low electrolyte conductivity, 2) incompatibility of solid membrane with Li metal, 3) anode volume change, 4) dendrite formation, and 5) non-uniform Li plating/segregation, and mitigation strategies will be examined. These issues are related mainly to cyclability, while the cell architecture (e.g. thickness, porosity, non-active materials) defines the energy density and affects its manufacturability, which remains mostly uncharted territory for solid state batteries.

Recent advances and trends in the development of novel approaches to materials for solid state batteries, their design and manufacturing of large format full solid electrolyte cells with different cathodes that is being funded by ARPA-E via RANGE, IONICS and OPEN 2018 programs will be discussed.
(Invited) Measurement of Polarization Resistance of LSM + YSZ Electrodes on YSZ Using AC and DC Methods
Authors: Virkar Anil
Published: February 2020

Most of the measurements of electrode polarization are conducted using electrochemical impedance spectroscopy (EIS). The electrochemical devices, however, operate in a DC mode. Thus, frequency-dependent circuit elements (capacitances, constant phase elements, inductances) have no significance on the actual operating current and voltage of a device. The objective of the present work was to measure electrode polarization resistance using both EIS and DC technique and compare the results.

A solid cylinder of 8YSZ of diameter ~1.17 cm and length ~5.00 cm was made by powder pressing in an isostatic press using a polymer mold and sintering at 1600oC in air for 4 h. Platinum electrodes/probes were painted along the circumference at four places approximately 1.2 cm apart. The strip width was ~2 mm. The sample was fired at 900oC. LSM + YSZ electrodes were applied on the two circular end faces and fired at 1000oC for 2 h. Pt wires were attached to the four Pt electrodes. Gold mesh was adhered to the circular LSM + YSZ electrodes. The sample was secured in a ceramic fixture and placed in a tubular furnace. Measurements were conducted in O2-N2 gas mixtures containing 100%, 10%, 5% and 1% O2. For DC studies, a DC voltage was applied in the range of 0.05 V and 0.38 V across the sample. At each applied voltage, the corresponding current was measured and potentials at all four probes was measured. From the measured potentials and the current, the ionic resistance of the cylinder was determined, from which the ionic resistivity was determined. From the voltage measured between one of the end electrodes and a probe, the ionic resistance between the end electrode and the probe, and the net current density, overpotential at the electrode was determined. This was done as a function of current. Also, from these measurements, electrode polarization resistance was determined. For EIS studies, done only under no applied DC voltage, spectra were obtained between electrode-1 and probe-2 and between probe-2 and electrode-2. From these measurements, the polarization resistances of the two electrodes were determined separately. EIS spectra were also obtained across electrode-1 and electrode-2. The spectra across electrode-1 and probe-2 and across probe-2 and electrode-2 were summed point by point. These spectra were then compared with the spectra across the entire sample.
High Performance Reversible Solid Oxide Cells with Porous La0.6Sr0.4FeO3-Δ Oxygen Electrodes
Authors: Guan Chengzhi , Chen Kongfa , Zhou Jing , Wang Jian-Qiang , Zhou Xiao-Dong
Published: February 2020

As a mixed electronic and ionic conductor (MIEC), (La,Sr)FeO3-δ has been extensively studied to replace manganite based materials as oxygen electrode of intermediate temperature (600-800oC) reversible solid oxide cells (RSOCs). However, compared to Sr doped LaCoO3 material, the electrochemical performance of cobalt-free (La,Sr)FeO3-δ needs to be improved to meet the requirements of commercial applications. Contrary to the conventional solid-state reaction and sol-gel method, molten salt synthesis (MSS) is a simple, versatile, and environmental-friendly approach to synthesize highly active perovskite catalysts with controllable compositions and morphologies. Especially, the corrosion effect of molten salts and the salt-removal process in MSS process have potential to manufacture particles with open porous topographic structure, resulting in large specific surface area. Therefore, it’s promising to use the MSS method to enhance the activity of cobalt-free (La,Sr)FeO3-δ.

In this study, the MSS method was employed to synthesize perovskite La0.6Sr0.4FeO3-δ (LSF) at 850oC as the oxygen electrode of a button solid oxide cell. In the material preparation procedure, moderate chloride composite was added in the reactants, forming a liquid environment to accelerate the reaction. At 800 °C, the button cell exhibits a peak power density of 1.73 Wcm-2 using pure H2 as fuel and reaches an electrolysis current density of 1.50 Acm-2 under 1.3 V in 50% CO2/50% H2, both of which are much better than the reference cell with a La0.6Sr0.4FeO3-δ electrode prepared by sol-gel method. The button cell also demonstrates a stable performance under a constant current density of 0.5 Acm-2 in SOFC mode for 200 hours. We also discussed the mechanism for the ultra-high electrochemical performance of La0.6Sr0.4FeO3-δ by charactering the difference between LSF powders synthesized by MSS method and sol-gel method. The results show that LSF using MSS powders possess a great plenty of pores in the grains. Meanwhile, the valance and the coordinator number of Fe atoms are reduced owing to the poor solubility of oxygen and the corrosion in the molten chlorides, leading to more oxygen vacancies. Therefore, we concluded that the combining effect of the microstructure and the enhanced amount of oxygen vacancies make the porous LSF electrode exhibits attractive electrochemical performance in both SOFC mode and SOEC mode.

Figure 1
(Invited) Mixed Protonic-Electronic Membrane Reactors; Converting Hydrocarbon Resources and CO2 to Fuels
Authors: Wachsman Eric D.
Published: February 2020

Membrane reactor technology holds the promise to circumvent thermodynamic equilibrium limitations by in-situ removal of product species, resulting in improved chemical yields. Recent advances in mixed-conducting oxide-membrane technology present the possibility for a dramatic reduction in the cost of converting petroleum, coal and biomass derived feed stocks to hydrogen and other “value added” hydrocarbons. We have developed novel membrane reactor technology, based on high temperature proton conductors, that can convert a wide range of hydrocarbons to pure H2, and syngas for synthesis of liquid fuels and chemical feed stocks. By simultaneous H2permeation and catalysis, we have demonstrated the ability to increase water gas shift yields >70% over thermodynamic limitations. Similarly, we have demonstrated increases in steam reforming yields, and the ability to reform CH4with CO2.

More recently we have developed single-step gas to liquid reactors that convert natural gas to C2+products with high yields and no unwanted oxidation byproducts. The direct utilization of CH4and CO2to simultaneously produce C2+hydrocarbons (C2and aromatics) and syngas (CO and H2) on opposite sides of a mixed protonic-electronic conducting SrCe0.7Zr0.2Eu0.1O3-δmembrane reactor is demonstrated. On one side (interior) of the membrane reactor, direct non-oxidative methane conversion (DNMC) over an iron/silica catalyst produces C2+hydrocarbons and H2. On the other side (outer surface) of the membrane, permeated H2(driving the DNMC reaction) reacts with a CO2sweep gas to form CO and water via the reverse water gas shift (RWGS) reaction. This novel single H2-permeable membrane reactor simultaneously addresses both reduction of greenhouse gas (CO2 and CH4) emissions as well as production of value-added hydrocarbon products (C2+, CO, and H2) with in situ gas separation.
(Invited) Titanate-Based Electrodes for Solid Oxide Cells
Authors: Barnett Scott A , Zhang Shan-Lin , Zhu Tenglong , Lu Matthew Yunching , Mogni Liliana Veronica
Published: February 2020

This talk describes solid oxide cell electrodes based on Sr(Ti0.3Fe0.7)O3 (STF). For oxygen electrodes, the substitution of a small amount of Co (up to 15%) for Fe substantially reduces polarization resistance, e.g., from 0.7 to 0.2 Wcm2in air at 600 oC.[1] The oxygen transport rate coefficients and polarization resistance RP
values are increased by a factor of ~ 3 times by Co substitution, and are generally much better than those for the widely used (La,Sr)(Co,Fe)O3 electrodes. Electrode and cell stability are markedly improved compared to LSCF cathodes. PrOxinfiltration into Co-substituted STF yields a substantial reduction in RP
, to values useful for low-temperature (<600 oC) solid oxide cells. For fuel electrodes, Sr(Ti0.3Fe0.7)O3 yields good performance at ≥ 800 oC and hydrogen-rich fuels, but the performance suffers at lower temperature and in depleted fuel due to slow H2 dissociative adsorption.[2] The substitution of 7% Ni for Fe in Sr deficient STF substantially reduces RP
under these conditions.[3] The Ni substitution results in the exsolution of Ni and Fe from the perovskite, yielding Ni-Fe nanoparticles that decorate the oxide electrode surfaces and promote hydrogen dissociative adsorption. Perovskite stoichiometry, which changes during exsolution, is found to play an important role in electrode performance; initially Sr-deficient anodes yield much lower RP
values. RP
values for Ni-substituted STF are comparable those of Ni-YSZ anodes.

References：

[1] S.-L. Zhang, H. Wang, M.Y. Lu, A.-P. Zhang, L.V. Mogni, Q. Liu, C.-X. Li, C.-J. Li, S.A. Barnett, Energy & Environmental Science (2018, DOI: 10.1039/C8EE00449H).

[2] T. Zhu, D.E. Fowler, K.R. Poeppelmeier, M. Han, S.A. Barnett, Journal of The Electrochemical Society
163 (2016) (8) F952.

[3] T. Zhu, H.E. Troiani, L.V. Mogni, M. Han, S.A. Barnett, Joule (2018) 10.1016/j.joule.2018.02.006.
High-Temperature Membrane for Water Removal in in-Situ Process
Authors: Lee Tae Hyun , Dorris Stephene E , Ma Beihai , Balachandran Uthamalingam
Published: February 2020

Water is a main by-product of many chemical processes, such as the production of hydrocarbons from synthesis gas, condensation reactions, and oxidative dehydrogenation. In most cases, water must be removed before or during product purification. Current water removal technologies, including direct condensation, azeotropic distillation, and vacuum or reactive distillation, are energy intensive. We are investigating use of in-situ water removal membranes to circumvent the energy-intensive conventional approaches for separating water at low temperatures and pressures. The water removal membranes would provide a continuous flux of water at constant temperature and pressure while avoiding the energy-consuming steps of conventional separation methods. Large energy losses associated with water removal could be avoided, and process efficiency significantly improved.

Water is undesirable as a primary by-product at the reaction site because it could lower the reaction rate by decreasing the catalyst activity. Removal of water at the reaction site, therefore, can prevent catalyst deactivation, and it also can increase the reaction yield by shifting the equilibrium conversion to the desired products. Because the existing polymer-based membrane technologies have a temperature limitation, we are developing ceramic membranes for separating steam under process conditions over a wide temperature range (200-900ºC). Preliminary results of the steam permeation rate measurement with dense ceramic membranes made of ionic conductor will be presented in this talk.
(Invited) Monolithically Integrated Gallium Nitride and Silicon Photoelectrode for Efficient and Stable Artificial Photosynthesis
Authors: Mi Zetian
Published: February 2020

Artificial photosynthesis, i.e., the chemical transformation of sunlight, water, and carbon dioxide into high energy-rich fuels is one of the keys to sustainable carbon-free, storable, and renewable source of energy. Although significant progress has been made for decades, the development of low cost, efficient, long-term stable semiconductor photocatalysts/photoelectrodes has remained challenging for the large-scale practical application of this frontier technology. Recently, gallium nitride (GaN), the semiconductor that has been widely used in LED lighting and power electronics, has emerged as a highly promising material for artificial photosynthesis. With the incorporation of indium, the energy bandgap of GaInN solid solution can be varied across nearly the entire solar spectrum. Significantly, GaInN are the only known semiconductors whose energy band edges can straddle water redox potentials under deep visible and near-infrared light, which is essential for the efficient generation of solar fuels through water splitting and CO2 reduction. We have recently discovered that the surface of III-nitride nanostructures can be tuned to be nitrogen (N)-rich, which can protect against photo-corrosion and oxidation. With the use of such N-rich GaN nanostructures, we have demonstrated the first artificial photosynthesis system that is capable of direct solar water splitting with stability >500 hrs at an efficiency level significantly above the natural photosynthesis. GaN-based nanostructures can be directly integrated with low cost, large area Si wafer. For example, the monolithic integration of an In0.5Ga0.5N top light absorber (energy bandgap ~1. 7 eV) with a Si bottom light absorber (energy bandgap ~1.1 eV) promises a solar-to-hydrogen conversion efficiency up to 30%. We have performed a detailed investigation of the design, synthesis, and photoelectrochemical performance of InGaN/Si double-junction photocathodes. We have demonstrated that InGaN/Si photocathodes can perform unassisted solar water splitting with relatively high efficiency in 0.5 M sulfuric acid under AM1.5G one-sun illumination. Long-term stable operation has also been demonstrated for GaN/Si photocathodes without using any extra surface protection. The unique GaN/Si photoelectrode also provides a powerful platform for the efficient transformation of CO2 to chemical fuels. By coupling with various photocatalysts, the selective conversion of CO2 and water to syngas, methanol, formic acid, and methane has been achieved with high Faradaic efficiency under sunlight illumination. With the use of GaN nanostructures, we have further demonstrated photochemical methanol to ethanol conversion, which enables the direct transition of a toxic fuel (methanol) to a more versatile and safe alternative (ethanol). We will also discuss photochemical nitrogen-fixation on GaN nanostructures, which contributes to the conversion of highly energy-intensive Haber-Bosch industry into mild, clean and sustainable process.
Nanoconfined Pores of Poly(4-vinylpyridine) Polystyrene and Poly(tert-butyl methacrylate)Polystyrene Block Copolymers: Electroanalytical Study and Carbon Dioxide Reduction
Authors: Ghebremichael Habte , Sidorenko Alexander
Published: February 2020

The performance of electrocatalysis and chemical synthesis within nanodomains is of interest as a novel means of producing chemical products. Self-assembled block copolymers (BCPs) provides us with a means of conducting these reactions. BCPs undergo a phenomenon known as microphase separation where two immiscible polymer subunits undergo reorganization to form highly ordered nanodomains. The incorporation of a small organic molecule within BCPs followed by extraction of these small molecules allows for the production of nanoporous domains that can function as nanovessels for chemical reactions. Polystyrene-Poly(4-vinylpyridine) and Poly(t-butyl methacrylate)-Poly(4-vinylpyridine) is used in this study as the BCPs of interest. Electrochemistry allows us to analyze and perform chemical synthesis within these nanoporous domains. One reaction we are looking at is the electrochemical reduction of carbon dioxide (CO2RR). Due to the nature of these nanovessels, reactions that are energetically unfavorable in the macroscale may prove feasible due to many factors including, reduce degrees of freedom for the reactants, high concentration of protons within these pores, and highly charged electronic environment.
(Invited) Computational Discovery of Metal-Organic Frameworks for Hydrogen Storage: Combining High-Throughput Screening, Machine Learning, and Experimental Demonstration
Authors: Siegel Donald J
Published: February 2020

Metal organic frameworks (MOFs) are promising materials for the storage of hydrogen fuel due to their high surface areas, tunable properties, and reversible gas adsorption. Although several MOFs are known to exhibit high hydrogen densities on a gravimetric basis, realizing high volumetric capacities a critical attribute for maximizing the driving range of fuel cell vehicles remains a challenge. Here, MOFs that achieve high gravimetric and volumetric H2 densities simultaneously are identified computationally, and demonstrated experimentally. The hydrogen capacities of ~100,000 MOFs drawn from databases of known and hypothetical compounds were predicted using empirical correlations and direct atomistic simulations. Based on these predictions, promising MOF candidates were synthesized and evaluated with respect to their usable H2 capacities. Several MOFs predicted to exhibit high capacities displayed low surface areas upon activation, highlighting the need to understand the factors that control stability. Consistent with the computational predictions, several MOFs were experimentally demonstrated to exhibit an uncommon combination of high usable volumetric and gravimetric capacities. Importantly, the measured capacities exceed those of the benchmark compound MOF-5, the record-holder for combined volumetric/gravimetric performance. Multiple machine learning algorithms were trained on this computationally-generated database. The relative accuracy of these algorithms were compared, with the most promising algorithm applied to predict H2 capacities in an additional 400,000 MOFs. Our study illustrates the value of computational screening in pinpointing materials that optimize overall storage performance.
(Invited) Overview of Research and Development within the Hydrogen Materials—Advanced Research Consortium (HyMARC)
Authors: Stetson Ned T , Stavila Vitalie , Gennett Thomas , Allendorf Mark D.
Published: February 2020

Hydrogen fuel cells have the potential to solve some of the biggest problems in transportation applications. When used to power vehicles they offer comparable range, with similar refueling times, as gasoline vehicles, with the added benefit of zero emissions at the point of use. Current onboard storage technologies employ compressed hydrogen gas at 70 MPa, which has an energy density of only about one seventh of that of gasoline. Liquid hydrogen, with a normal boiling point of 20 K, has close to twice the energy density of 70 MPa compressed hydrogen. While liquid hydrogen is currently the primary way large quantities of hydrogen is transported and stored, it is energy intensive to produce, and is not suitable for small-scale or long-term storage. Condensed-phase materials, such as metal hydrides, nanoporous sorbents and liquid hydrogen carriers, have the potential to meet the Department of Energy’s (DOE) capacity targets for onboard storage as well as for bulk transport and storage, at significantly reduced operating pressures and relevant temperatures. However, none of the existing materials can meet all the DOE technical targets. To address the limitations of current materials, the DOE Fuel Cells Technologies Office established the Hydrogen Materials Advanced Research Consortium (HyMARC), which includes scientists and engineers from five U.S. National Laboratories and six DOE User Facilities. This presentation will provide an overview of the HyMARC effort, including specific examples illustrating how this project facilitates and promotes the discovery of novel hydrogen storage materials and technologies. Recent material advances pioneered by HyMARC researchers include, for example, the discovery of Metal-Organic Frameworks capable of binding multiple hydrogen molecules to a single metal ion site, interface-driven reactions in nanoscale metal hydrides, and graphene-encapsulated hydrides. These developments are providing guidance for material discovery efforts and are creating new synthesis, modeling, and characterization capabilities that can accelerate materials discovery.
Quantitative Measurements of the Gas Evolution in Li-Ion Batteries Via Oems (Online Electrochemical Mass Spectrometry)
Authors: Zheng Haotian , Liu Kewei , Croy Jason R. , Zhang Zhengcheng , Yao Yan , Liao Chen
Published: February 2020

Confronted with the fast-growing marked demand for high energy and power Li-ion batteries in electrical vehicles and hybrid electrical vehicles. Numerous efforts have been applied to develop battery systems with higher charge voltage to achieve higher cell energy. However, a more severe capacity fading is usually observed for the high voltage cell, accompanied with sever battery swelling, which could be attributed to more side reactions. Online electrochemical Mass Spectrometry (OEMS) is an analytical technique that combines electrochemical half-cell experimentation with mass spectrometry. It allows in-situ mass resolved determination of gaseous or volatile electrochemical reactants, reaction intermediates and products in real time. In this work, we will discuss the setup of a laboratory grade OEMS and reported the initial test towards several popular NMC cathode//Graphite lithium ion batteries with different electrolyte choices, and comparison of our results with reported literature will be presented.
Peltier Heats of LiFePO4 electrodes from a Thermoelectric Cell
Authors: Gunnarshaug Astrid Fagertun , Kjelstrup Signe , Bedeaux Dick , Burheim Odne Stokke , Vie Preben J. S.
Published: February 2020

Temperature is known to affect ageing and performance of lithium ion batteries [1]. We need to improve the understanding of the heat sources in the electrode compartments in order to accurately model internal temperature profiles. Reports of reversible heat effects local to electrode surfaces in lithium-ion batteries are therefore important, but are scarce in literature [2].

The reversible heat production at a battery electrode interface is investigated in this experimental work, measuring the Peltier heat of the electrode LiFePO4 electrode. The Peltier heat at an electrode can be found by measuring the change in electric potential across the cell with two identical electrodes when a temperature difference is applied [3]. We present the Seebeck coefficient and Peltier heat of a symmetric pouch cell consisting of two commercial LiFePO4 electrodes and a 1M LiPF6 and Ethylene Carbonate (EC) /Diethyl Carbonate (DEC) (50:50 w%) electrolyte-soaked separator. The electrodes have been thermostatted to the wanted temperatures T and T+ ΔT, respectively.

Al (s,T) | LiFePO4 (s,T) | EC, DEC, LiPF6 | LiFePO4 (s,T + ΔT) | Al (s,T+ ΔT)

We show that the thermoelectric effect is time-dependent due to a build up of concentration gradients within the cell, and the establishment of not only one, but two Soret equilibria. The initial Seebeck coefficient gives the Peltier heat of one electrode for a homogeneous electrolyte in a battery [4]. We derive equations that will describe the approach of the cell to steady state, and use this to estimate the initial value. The consequences of the Peltier heat of LiFePO4 for battery discharging and charging will be discussed.

Acknowledgment

The authors are grateful to the Research Council of Norway through its Centres of Excellence funding scheme, project number 262644, PoreLab. We acknowledge ENERSENSE for financial support. The group of authors also acknowledge the Research Council of Norway (RCN) project no. 228739, for funding through the project "Life and Safety for Li-ion batteries in Maritime conditions (SafeLiLife)".

References

[1] J. Vetter, P. Novak, M. Wagner, C. Veit, K.-C. Möller, J. Besenhard, M. Winter, M. Wohlfahrt-Mehrens, C. Vogler, ´ A. Hammouche, Ageing mechanisms in lithium-ion batteries, J. Power Sources 147 (12) (2005) 269 – 281.

[2] Frank Richter, Astrid Gunnarshaug, Odne Stokke Burheim, Preben J. S. Vie, and Signe Kjelstrup. Single Electrode Entropy Change for LiCoO2 Electrodes. ECS Trans., 80(10):219-238, 2017.

[3] K. S. Førland, T. Førland, and S. Kjelstrup. Irreversible Thermodynamics: Theory and Applications. Tapir, Trondheim, 2001.
Correlating Directly Recycled Cathode Performance to Aging Conditions
Authors: Wang Han , Whitacre Jay
Published: February 2020

Traditional recycling of lithium-ion battery cathode materials draws the most attention currently due to the valuable metal elements contained, especially cobalt. There are three dominate recycling approaches that may be used to recover useful materials from the aged cathode powders: pyrometallurgical, hydrometallurgical and direct physical.(1-3) The former two methods are already operating at scale. However, they suffer from significant energy input and complex chemical process respectively, which makes the recycled products less environmental-friendly and economically competitive. Recently, processing methods have been developed with less energy and cost input by making directly recycling the cathode material for reuse in a new battery. This is appealing in cases where there is a large amount of identical or very similar cathode materials in use. (2, 4)

In this work, we show “direct recycled” products of differently cycled Li(NixCoyAlz)O2 cathode via a solid-state processing method with different parameters. We assess the materials product performance in terms of electrochemical specific capacity, phase purity and consistency. Furthermore, we correlated interaction among aged conditions of cathode, solid-state process parameters and recycled product performance. Figure 1 shows that when treated with the same solid-state process parameters, the recycled cathode materials show different electrochemical performance depending on conditions of the aged cathode materials.

In this talk, we will discuss our approach and results, as well as suggest a technical path forward for the implementation of large-scale direct recycling of cathode materials from aged lithium-ion batteries.

Reference:

L. Gaines, Sustain Mater Techno, 17 (2018).

H. Wang, S. Frisco, E. Gottlieb, R. Yuan and J. F. Whitacre, J Power Sources, 426, 67 (2019).

R. E. Ciez and J. F. Whitacre, Nat Sustain, 2, 148 (2019).

H. Wang and J. F. Whitacre, Energy Technol-Ger, 6, 2429 (2018).

Figure 1
Oxidative Pyrolysis of Si/Polyacrylonitrile Composites As an Unconventional Approach to Fabricate High Performance Lithium Ion Battery Negative Electrodes
Authors: Hu Jiazhi , Meyer Andrew W , Huang Xiaosong , Cheng Yang-Tse
Published: February 2020

High performance Si/polyacrylonitrile (PAN) composite negative electrodes are fabricated by a robust process of oxidative pyrolysis at a temperature between 250 and 400oC. Multiple techniques, including XRD, SEM, EDX, TGA, XPS, EIS, Raman, TEM, and nanoindentation, are employed to investigate the structural, chemical, and mechanical properties of the Si/PAN composite electrodes before and after oxidative pyrolysis. With increasing temperature, oxidation, dehydration, aromatization, and intermolecular crosslinking take place in PAN, resulting in a stable cyclized structure which functions as both a binder and a conductive agent in the Si/PAN composite electrodes. Meanwhile, PAN reacts with oxygen, forming volatile products and producing progressively porous Si/PAN composites with increasing temperature. With a Si mass loading of 1 mg/cm2, a discharge capacity of ~1600 mAh/g at the 100th cycle is observed from the 400oC treated Si/PAN composite electrode when cycled at a rate of C/3. This 400oC treated electrode also shows good rate capability. It exhibits a specific discharge capacity of ~500 mAh/g at 3C compared to the nearly zero capacity for those treated at lower temperatures. This facile method of synthesizing Si-based composite negative electrodes can potentially be applied to other Si/polymer systems for further increasing the power/energy density of lithium ion batteries.
Investigating the Electrochemical Effect of Core-Multi Shell Structured Nickel-Rich NMC Cathode Materials
Authors: Chung Youngmin , Shin Youngho
Published: February 2020

Nickel-rich nickel manganese cobalt (NMC) oxide is a high energy density cathode material for lithium-ion batteries. However, surface-related fast capacity fading has been a major obstacle to its practical application. In this work, to address this issue, nickel-rich core-multi shell structured NMC oxide Li[Ni0.9-x-yMn0.05+xCo0.05+y]O2 (x and y ≤0.15) materials with multiple outer layers of stable NMC compositions were synthesized via co-precipitation method using a specially developed continuous stirred-tank reactor (CSTR).

We have used scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) with cross-sections of the grided particle samples, and inductively coupled plasma mass spectrometry (ICP-MS) to understand the contribution of core and outer shell layers and total composition of the synthesized core-multi shell structured NMC materials. The synthesized cathodes consisted of high-nickel NMC90/5/5 (LiNi0.9Mn0.05Co0.05O2) core and NMC333, NMC622, and NMC811 outer shells have an overall composition of NMC811 or NMC622 depending on outer shell ratio.

The analyzed concentration distribution inside the particles indicates that the nickel composition decreases linearly from the center of the particle to the surface and that the manganese and cobalt concentrations increase. The NMC811 and NMC622 of the core-multi-shell structure with optimized outer shell layer improve cycling capacity, capacity retention (92% after 100 cycles) and rate capability as compared to commercial materials having the same overall composition due to the unique microstructure of the stabilized particle surface by increasing the stable Mn4+ ratio at the shell. Electrochemical impedance spectroscopy (EIS) and differential scanning calorimetry (DSC) results showed that the high stability of core-multi shell structured NMC materials is responsible for the reduction in surface and charge transfer resistance by decreasing the reaction with the electrolyte.