bluuebunny/crossref_metadata_2025 huggingface dataset:
Density Functional Theory Study of the Interactions of Cl and α-Fe2O3 Surfaces: The Role of Cl in the Depassivation Process
Authors: Pang Qin , DorMohammad Hossein , Isgor O. Burkan , Árnadóttir Líney
Published: February 2020

Under the alkaline environment inside reinforced concrete, a protective passive film is formed on the iron surface. Chloride ions have been shown to be one of the aggressive ions that can cause depassivation of this passive film under the same condition but the atomistic mechanism of depassivation is not fully understood. Several hypotheses have been proposed for the role of Cl in the depassivation, such as ion exchange model and point defect model. Here we use density functional theory (DFT+U) calculations of Cl interactions with hematite (α-Fe2O3) to test these different hypotheses of Cl induced depassivation of iron passive film. The different hematite surfaces are used to represent the Fe (III) oxides which are the dominant structure in the outer layer of the passive film. On the flat (0001) surface, both pristine surfaces and surfaces with point defects are studied. Three point defects on the surface are considered, Fe vacancy, O vacancy and Fe-O pair vacancies. We found that the O vacancies enhanced the adsorption of Cl while the Fe vacancy weakens the adsorption. The insertion of the Cl into the sub surface was studied to investigate the stability of Cl staying in the bulk of oxide proposed in ion exchange model and was found to be endothermic for all four surfaces but surface defects have positive effects on the insertion of Cl, making it less endothermic with the smallest reaction energy of about 0.3 eV on the O vacancy surface. However, it is more difficult for Cl to stay in the sub surface lattice further away from the surface. The vacancy diffusion direction was studied by calculating the energy difference of vacancies in the different layers to investigate the point defect model. Fe vacancy is energetically more favorable in the deeper sub surface while O vacancy prefers to stay in the layers closer to the surface. The adsorbed Cl can affect the two diffusion process by making the two diffusion process more energetically favorable. These results indicate that the point defect model is the more promising model to explain the Cl-induced depassivation process.
Masking Contaminant-Induced SOFC Anode Degradation with H2
Authors: Reeping Kyle W. , Bohn Jessica M. , Walker Robert A.
Published: February 2020

Common contaminants in solid oxide fuel cell (SOFC) fuels, including chlorine and sulfur, are believed to induce anode degradation through one of several, temperature-dependent mechanisms. At relatively low operating temperatures, mechanisms propose that contaminants adsorb to the Ni electrocatalyst, blocking active sites and reducing conversion efficiency. This effect is largely reversible and anodes recover performance when the contaminant is removed from the fuel feed. At higher temperatures, contaminants react with Ni to form non-conducting or volatile materials, thus impeding electrochemical oxidation and destroying anode microstructure. Using both electrochemical measurements and operando vibrational Raman spectroscopy in SOFCs operating at 700°C, we have discovered that small amounts of excess molecular hydrogen added to both methane contaminated with chlorine and a biogas simulant contaminated with chlorine masks, but does not prevent, Cl-induced anode degradation. Once the hydrogen is removed from the incident fuel feed, anodes fail abruptly and irreversibly, implying that Cl-induced degradation proceeded while the hydrogen was present despite impedance and voltammetry data showing no apparent signs of performance loss. Effects are more pronounced and occur more rapidly in SOFCs operating with the biogas simulant (a 50-50 mixture (by mole fraction) of CH4 and CO2) than for methane. These results are discussed in terms of a new high-temperature degradation mechanism that considers site specific catalytic activity on Ni surfaces and steric requirements for –CH and H2 bond activation.
Plasma Etch Variation Control in Double Patterning Based Metal Hard Mask Open Process
Authors: Wang Shijing , Yao Da-Lin , Huang Jing-Yong , Hu Min-Da , Yuan Ke-Fang , Wang Yan , Zhou Jun-Qing , He Qi-Yang , Zhang Haiyang
Published: February 2020

At Cu/low-K interconnection based BEOL etch technology with double patterning scheme, metal hard mask (MHM) etch process is the key step to define final physical structure of Cu line. Gap fill and reliability performance are highly related with MHM pattern CD and profile. During double patterning-based MHM etch process, tri-layers (including organic and inorganic nonmetallic materials) and HM film (e.g. TiN metalloid material) etch processes are involved. Precondition, by-product and etch stop layers are different for each etch flow in double patterning-based MHM open process, which could easily induce final CD variation in first wafer and both trench patterns. First wafer effect with large CD variation in MHM etch process could induce interconnection fail and poor WAT/RE property. In this paper, we investigate double patterning-based MHM etch performance with different etch flow and wafer-less auto clean (WAC)/season process from the viewpoints of CD variation control. Variation control method and mechanism for double patterning-based MHM etch process are also addressed.
Electrochemical Fabrication of Freestanding Thin-Film Electrodes for Batteries and Catalysis
Authors: Yang Yang
Published: February 2020

In this work, a
freestanding and binder-free
NiS2/FeS holey film is developed using
a facile and scalable electrochemical route
. Both experimental study and computational investigation were performed to have an insightful understanding of the charge storage mechanism of this advanced energy material for LSBs. Such freestanding NiS2/FeS holey film provides unique merits for LSBs: i) Porous structure of holey film enables a large surface area for an enhanced ion/mass diffusion and reduced volume expansion; ii) The binder-free electrode combines the current collector (residual NiFe alloy) and active materials (sulfides) together, improving electron transport; iii) Sulfides are more stable as active materials than sulfur, showing only a small capacity decay while retaining high cyclability performance. A high volumetric capacity of 580 mAh cm-3 and a long-term stability over 1000 discharge-charge cycles were, therefore, achieved due to these merits.
Electrophoretic Deposition of Electrode Membrane for Solid Oxide Fuel Cells
Authors: Itagaki Yoshiteru , Yahiro Hidenori
Published: February 2020

SOFC electrode with the bi-layered structures were prepared with electrophoretic deposition (EPD) methods. The thicknesses of each layer were well controlled with the deposition time and applied voltage in the EPD process. The bi-layered structures exhibited the lowered cathodic potential loss compared to the mono-layered ones. The decrease in thickness of the first layer and the increase in that of the second layer effectively reduced both polarization and ohmic resistances. Bilayer structures consisting of active and current collecting layers were fabricated. The examined bi-layered structures, LSM/LSM-YSZ, exhibited the minimal polarization resistance when the thicknesses were 10 and 4 micrometers at 600oC, respectively. It was deduced that the effective thickness of the active layer is around 4 mm under the current condition. We also prepared layered anode films by EPD method. The layered structure of anodes formed by EPD were also effective to reduce electrode over-potential.
Encapsulation of Aluminium and Titanium-Aluminium Nanorods into Oxide Matrix By Powerful Pulsed Discharge Method
Authors: Ferreira Mario G. S. , Zheludkevich Mikhail , Lisenkov Aleksey
Published: February 2020

Encapsulated metal nanostructures were prepared using the powerful pulsed discharge method. Metal nanorods were obtained in porous titania and alumina matrix by direct electrodeposition from 1-ethyl-3-methylimidazolium chloride-based ionic liquids. The deposition process was characterized by cyclic voltammetry. Morphology of the encapsulated structures was studied by SEM. It was found that the most efficient method for electrodeposition of pure aluminium into titania nanotubes is the potential cycling method, while for deposition of the Al-Ti alloy in alumina pores a pulsed method with three different steps is preferable . Closing the titania nanotubes was found to be possible both with empty and metal-filled channels, whereas with alumina matrix this procedure can be performed only when pores are filled with conductive material. The obtained results throw light on the mechanism of porous film encapsulation under high-voltage pulses and allow preparing encapsulated nanostructures in the oxide films.
Electrodeposition to Form Nanoporous Gold at Microdisc Electrode Arrays for Electrochemical Sensing Applications
Authors: Rohan James F. , Nagle Lorraine C , Barry Fiona
Published: February 2020

In this work we report on the controlled electrodeposition of gold-silver alloys at microdisc arrays to form nanoporous gold (NPG) upon silver removal. NPG is characterised by a sponge-like 3D network composed of interconnecting nanopores and nanoligaments. It is also chemically inert, corrosion resistant and biocompatible. These characteristics make NPG an attractive electrochemical platform for many applications such as electrocatalysis[1, 2] and biosensing[3]. We will show that simulated and corresponding experimental measurements for electrodes based on the microdisc array offer the potential for signal amplification arising from individual radial diffusion occurring at each microdisc. Through further post-processing of the microdisc array we will describe an electroless deposition process for conformal nanoscale active materials deposition to enhance analysis for specific analytes such as for phosphate detection.

Nagle, L.C. and J.F. Rohan, Nanoporous gold anode catalyst for direct borohydride fuel cell. International Journal of Hydrogen Energy, 2011. 36(16): p. 10319-10326.

Nagle, L.C. and J.F. Rohan, Nanoporous Gold Catalyst for Direct Ammonia Borane Fuel Cells. Journal of the Electrochemical Society, 2011. 158(7): p. B772-B778.

Galvin, P., et al., Nanoenabling electrochemical sensors for life sciences applications. Journal of Materials Research, 2017. 32(15): p. 2883-2904.
Controlled Superlattice Assembly – a Step Towards Superlattice Devices
Authors: Yu Yixuan , Yu Dian , Orme Christine A.
Published: February 2020

Ordered assemblies of nanocrystals called superlattices are promising materials for next generation devices. detectors and sensors. However, traditional methods to assemble nanocrystals lack the control needed for device integration. To fill this gap we show that electrophoretic deposition can be used to drive nanocrystal assembly. We will demonstrate that field-driven assembly can deposit well-ordered superlattices with diffraction peaks out to (2,2,8) over large (cm2) areas. Moreover, the process is amenable to wafer-level deposition, reversible and several orders of magnitude faster than conventional solvent evaporation or co-solvent techniques. The electric field controls the nanocrystal flux making the deposition process akin to vapor deposition. To demonstrate this new level of control, we use the field to systematically change the growth rates and nucleation density. These are confirmed using in situ quartz crystal microbalance to measure growth rates and ex situ imaging to measure nucleation density. We use nickel and silver nanocrystals to illustrate that films can grow either via a layer-by-layer or by an island formation mechanism and that ligands play a central role in determining whether nanocrystals assemble into thin films or colloidal crystals. This new level of control allows us to tune the correlation length, which we expect to have advantages for fundamental studies and to benefit device performance.

Work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.
(Keynote) Surfactant and Halide Control in Gold Nanorod Synthesis
Authors: Murphy Catherine
Published: February 2020

Gold nanorods have been of continuing interest to many scientists due to their brilliant optical properties that are dictated by particle shape. Nanorods exhibit both transverse and longitudinal plasmon bands that are tunable from the visible into the near-infrared. Applications areas include plasmon-based sensors, diagnostics, imaging agents, and even photothermal therapeutics due to reasonably efficient light-to-heat conversion. The primary synthesis of these materials starts with a gold salt, and various reduction steps with various reducing agents, in the presence of particular surfactants and ions, do produce gold nanorods of tunable aspect ratio; yet the details of the synthetic steps and the "true" source of the symmetry-breaking anisotropy to produce rods instead of spheres are still the subject of debate. In this talk we will examine the state of the art in gold nanorod synthesis, including recent work that used a design-of-experiment multifactorial approach to gain deeper mechanistic insights into synergistic effects between the various reagents in the synthesis.
Atomic Layer Deposition Using Self-Terminated Electrodeposition Reactions
Authors: Moffat Thomas P. , Liu Yihua , Ahn Sang Hyun , Ritzert Nicole L. , Wang Rongyue , Gillette Eleanor , Gokcen Dincer , Hangarter Carlos , Tan Haiyan , Bendersky Leonid , You Hoydoo , Bertocci Ugo
Published: February 2020

Recently, an inexpensive “wet form” of ALD based on self-terminated electrodeposition reactions was uncovered that enables controlled formation of ultrathin films of Pt, Ir and iron group metals and alloys thereof. Common to all these systems is the role of reaction intermediates, namely adsorbed H or OH-, in the quenching of metal deposition reactions. Further details on the mechanisms of self-terminated deposition reactions will be discussed. Likewise, the utility and relevance of the process to the synthesis of nanoparticles and thin films, and the study of bimetallic electrocatalysts, will be outlined.
Electrochemical Synthesis of H2O2 Via Water Electrolysis
Authors: Siahrostami Samira , Shi Xinjian , Abroshan Hadi , Zheng Xiaolin , Nørskov Jens
Published: February 2020

Hydrogen peroxide (H2O2) is a crucial chemical with a wide range of applications in various industries, including paper bleaching, textile manufacturing and environmental protection for distillation, detoxification and color removal of wastewater. Electrochemical production of hydrogen peroxide (H2O2) offers small scale decentralized process which is highly desirable for remote usages. Both oxygen reduction (eq. 1) and water oxidation (eq. 2) reactions could be exploited to produce H2O2.

O2 + 2(H++e-) ---> H2O2 E0 = 0.7 V (1)

2H2O ---> 2(H++e-) + H2O2 E0 = 1.76 V (2)

These reactions are simple and remarkable, but in practice selectivity toward the desired H2O2 product is an issue since these are not the thermodynamically favored reactions for oxygen reduction and water oxidation. Over the past years, several efforts have been made to find selective, and active catalysts for these reactions.1–4 In this work, by combining density functional theory (DFT) calculations and experiment, we provide leads to design suitable electrocatalysts with high selectivity and activity for H2O2 synthesis from both processes.3

References

(1) Siahrostami, S.; Verdaguer-Casadevall, A.; Karamad, M.; Deiana, D.; Malacrida, P.; Wickman, B.; Escudero-Escribano, M.; Paoli, E. a; Frydendal, R.; Hansen, T. W.; Chorkendorff, I.; Stephens, I. E. L. S.; Stephens, I. E.; Rossmeisl, J. Nat. Mater.
2013, 12 (12), 1137–1143.

(2) Verdaguer-Casadevall, A.; Deiana, D.; Karamad, M.; Siahrostami, S.; Malacrida, P.; Hansen, T. W.; Rossmeisl, J.; Chorkendorff, I.; Stephens, I. E. L. Nano Lett.
2014, 14 (3), 1603–1608.

(3) Siahrostami, S.; Li, G.-L.; Viswanathan, V.; Nørskov, J. K. J. Phys. Chem. Lett.
2017, 1157–1160.

(4) Shi, X.; Siahrostami, S.; Li, G.-L.; Zhang, Y.; Chakthranont, P.; Studt, F.; Jaramillo, T. F.; Zheng, X.; Nørskov, J. K. Nat. Commun.
2017 (SEPT), 1–12.
N/S-Me (Fe, Ni) Doped Porous Carbon Derived from Metal–Organic Frameworks As Efficient Electrocatalysts for Oxygen Reduction Reactions
Authors: Dong Fang , Tang Qiaowei , Liu Junyu , Liu Cong , Qiao Jinli
Published: February 2020

In the past few decades, polymer electrolyte membrane fuel cells (PEMFCs), as a kind of clean, efficient energy sources, which is considered to be the most promising solution to solve the increasingly serious energy crisis and reduce the environmental pollution, have experienced continuously increasing attention1. Oxygen reduction reaction (ORR) in fuel cells plays a decisive role in determination of performance, and electrocatalysts with high-performance ORR are essential for practical applications. However, the commercialization of PEMFCs has long been hindered by the utilized expensive Pt-based catalyst for cathodic ORR2 3. To solve the bottleneck, non-platinum-group-metal electrocatalysts with low cost, high activity and durability have been intensively pursued as alternatives to Pt for the ORR4. Recent years witnessed the dramatic interest in using nitrogen/sulfer-doped porous carbon as one of the promising ORR catalysts. Herein, we present N/S-Me (Fe, Ni) doped porous carbon derived from a metal–organic frameworks MOF-67 (ZIF-N/S-Me-PC) as highly efficient ORR electrocatalysts. The catalytic ORR activities of ZIF-N/S-Me-PC are studied by linear sweep voltammetry (LSV), employing rotating disk electrode (RDE) and rotating ring-disk electrode (RRDE) techniques to quantitatively obtain the ORR kinetic constants and the catalysts' possible reaction mechanisms. In comparison to the commercial Pt/C (20%), the electrocatalyst ZIF-N/S-Me-PC exhibits a pronounced positive shift in Eonset. In addition, it also demonstrates excellent long-term stability and durability during the 5000-cycle continuing-oxygen-supply (COS) accelerating durability tests (ADTs). Catalytic ORR activities were thoroughly examined by scanning electron microscopy (SEM), X-ray diffraction (XRD), low-temperature N2 adsorption and X-ray photoelectron spectroscopy (XPS).

References

1 M.J. Wu, E.G. Zhang, Q.P. Guo, Y.Z. Wang, J.L. Qiao, K.X. Li, P.C. Pei, Appl. Energy, 175, 468 (2016).

2 Q.W. Tang, L.M. Wang, M.J. Wu, N.N. Xu, L. Jiang, J.L. Qiao, J. Power Sources, 365, 348 (2017).

3 M. Sahoo, S. Ramaprabhu, Energy, 119, 1075 (2017).

4 M.J. Wu, Q.W. Tang, F. Dong, Z.Y. Bai, L. Zhang, J.L. Qiao, J. Catal, 352 , 208 (2017).
In-Situ Studies of Carbon Removal from Ni-YSZ Anodes Using Mixtures of O2 and H2
Authors: Tsoi Stanislav , Maza William A , Kirtley John D , Steinhurst Daniel A , Walker Robert A , Owrutsky Jeffrey C.
Published: February 2020

There is interest in understanding the chemical mechanisms in order to improve approaches for reforming fuels and regenerating components in solid oxide fuel cells. Chemical and electrochemical oxidative removal of carbon from Ni-YSZ anodes is studied using a suite of experimental techniques. After carbon is deposited on the anodes during methane exposure, it is removed with a series of the oxidizing mixtures containing a fixed O2 concentration and varying H2 concentrations. The CO and CO2 produced are monitored in real time using IR emission and mass spectrometry. Concurrently, near IR imaging of the anode is employed to monitor the surface temperature and electrochemistry to track the open circuit potential of the cell. The data demonstrate monotonically increasing amount of CO and decreasing amount of CO2 with the increasing H2 concentration. In addition, a control experiment of carbon removal with H2O yields relative amounts of evolved CO and CO2 close to those observed with the 1:2 O2:H2 mixture. The results implicate atomic O and -OH as primary chemical removal agents, the latter being effective at oxidizing carbon to CO and the former at oxidizing CO to CO2. In a separate experiment, electrochemical removal of the pre-formed carbon via cell polarization indicates an efficient oxidation of electrochemically accessible carbon to CO and a slow oxidation of CO to CO2. Addition of H2 gas during the polarization removal experiments leads to electrochemical generation of water inside the anode, which further accelerates oxidation of carbon. Thus, the present work clarifies mechanisms of carbon removal from the anodes of SOFCs.
(Invited) Membranes with Recombination Catalyst for Hydrogen Crossover Reduction: Water Electrolysis
Authors: Bessarabov Dmitri
Published: February 2020

Hydrogen and oxygen crossover phenomena through a solid polyelectrolyte membrane constitute one of the important safety concerns in PEM electrolysis.

Hydrogen gas crossover in PFSA membranes during water electrolysis is a dynamic variable, characterised by complex functional relationships between the membrane water content, nature of the membrane, and operational conditions.

Mitigation strategies to reduce gas crossover may include various approaches, based on the mechanism of interaction of hydrogen and the membrane matrix. These approaches may include passive solutions, reactive solutions, and combinations thereof. The most straightforward solution to reduce crossover is to increase membrane thickness; however, this leads to higher resistance to proton transport. Another rather straightforward approach includes developing mixed-matrix membranes, by adding fillers into the membrane matrix. By selecting a membrane material with a low diffusion coefficient and low water content, one can also reduce gas crossover. It is known that sulfonated hydrocarbon PEMs have significantly lower gas permeability than PSFA membranes (Bessarabov and Millet, 2018).

The reactive approach includes promoting the process of hydrogen consumption by introducing Pt into either the CL and/or the current collector. The first membranes with Pt were fabricated for the purpose of self-humidification, for fuel cell applications (Watanabe et al., 1998). According to Ito et al. (2016) and Abdalla et al. (2017), it is critical for safe PEM electrolysis. The very well understood mechanism of hydrogen consumption involves recombination of hydrogen and oxygen on a Pt catalyst.

This paper will describe morphology of Pt catalyst that was developed for the recombination purposes and embedded in the PFSA membranes. Experimental data for hydrogen reduction permeation will be presented. Catalyst was characterized by HR TEM.

References.

Abdalla, S., Al-Marzouki, F., Obaid, A., 2017. Safety considerations during production and consumption of hydrogen using proton exchange membrane electrolysis. J. Renew. Sustain. Energy 9, 013101

Bessarbov, D. and Millet, P. PEM Water Electrolysis, Elsevier, 2018 (in press)

Ito, H., Miyazaki, N., Ishida, M., Nakano, A., 2016. Cross-permeation and consumption of hydrogen during proton exchange membrane electrolysis. Int. J. Hydrogen Energy, 41 (45), 20439–20446

Watanabe, M., Uchida, H., Emori, M., 1998. Analyses of self-humidification and suppression of gas crossover in Pt-dispersed polymer electrolyte membranes for fuel cells. J. Electrochem. Soc. 145 (4), 1137–1141
(Invited) Pyrochlore-Type, Acid-Stable Electrocatalysts for Oxygen Evolution Reaction
Authors: Yang Hong
Published: February 2020

Multiple important electrochemical processes including hydrogen generation from water reply on acid-stable electrocatalysts for oxygen evolution reaction (OER). The material choice of OER electrocatalysts in acid is often limited to only two major types of oxides (e.g., RuO2 and IrO2). Recently, ternary compounds have been reported to have excellent OER performance. Among them, our group developed pyrochlore-type electrocatalysts of various compositions. Yttrium ruthenate (Y2Ru2O7-δ) was shown to have significantly enhanced performance towards OER in acid media over both RuO2 and IrO2 catalysts at current density about 1 mA/cm2 [1]. It has an onset overpotential of 190 mV in 0.1-M perchloric acid solution. Tafel plots show the Y2Ru2O7-δ catalyst had enhanced activity from 55 mV/dec for the first cycle to 46 mV/dec for the 10,000th cycle. In comparison, the OER performance for RuO2 catalyst degraded from 61 mV/dec for the first cycle to 72 mV/dec for the 10,000th cycle under the same testing conditions. A range of techniques including X-ray absorption spectroscopy (XAS) and computational tools such as density functional theory (DFT) calculation have been used to understand the structural origins of enhanced performance. Our preliminary data suggest a low valence state in yttrium ruthenate (Y2Ru2O7-δ) favors the high OER activity, while lowered band center energy for the overlap between Ru 4d and O 2p orbitals contributes to the stability. A systematic study on the structural origin for high OER performance has further been carried out using a series of A2Ru2O7-δ pyrochlore-type electrocatalysts and will be presented in this talk. Strategies for improving the overall performance of these OER catalysts will also be discussed [2,3].

References:

M. Kim,# P.-C. Shih,# K.-C. Tsao, Y.-T. Pan, X. Yin, C.-J. Sun, H. Yang, J. Am. Chem. Soc., 2017, 139, 12076-12083 (#: equal contribution).

M. Kim, X. X. Chen, Y.-T. Pan, P.-C. Shih, H. Yang, J. Electrochem. Soc., 2017, 164, F1074-F1080.

M. Kim, X. X. Chen, P.-C. Shih, H. Yang, ACS Sustainable Chem. Eng., 2017, 5, 10190-10917.
The Bifuctional Electrocatalyst SiO2-SO3H Supported Pt for Unitized Regenerative Fuel Cells
Authors: Jung Ho-Young , Jung Ji-Hyun , Lim Min-Hwa
Published: February 2020

For enhance the electrochemcial performance of URFC system, the novel combination of sulfonated silica-supported Pt electrocatalyst were synthesized. The investigated electrochemical surface area values are 23.02 and 22.96 m2/g for the Pt black and 80 wt% Pt/SiO2-SO3H catalysts, respectively. The bifunctional (oxygen reduction reaction (ORR) and oxygen evolution reaction (OER)) performance in URFC system were carried out through fuel cell and water electrolyzer modes for Pt/C, Pt/SiO2, and Pt/SiO2-SO3H electrocatalysts. The determined round-trip energy conversion efficiency of Pt/C, Pt/SiO2, and Pt/SiO2-SO3H are 45.3, 44.6 and 46.1 %, respectively. Comparatively, the Pt/SiO2-SO3H electrocatalyst shows an improved electrocatalytic performance than Pt/C and Pt/SiO2 electrocatalysts. Due to presence of sulfonic acid functional group on the support material (SiO2–SO3H), the proton conduction has intensified in the catalyst layer during the URFC unit cell operation. Based on the performance data, the sulfonated silica-supported Pt electrocatalyst (Pt/SiO2-SO3H electrocatalyst) identified as a efficient bifuntional electrocatalyst material for further development in URFC applications.

Key Words : Unitized regenerative fuel cell (URFC), Electrocatalyst, Sulfonated silica (s-SiO2), Oxygen reduction reaction (ORR)

Figure 1
Stainless Steel Based Water Oxidation Catalyst Electrode for Solar-Chemical Production
Authors: Lee Minoh , Hwang Yun Jeong , Min Byoung Koun
Published: February 2020

Solar-chemical production inspired from nature has attracted substantial attention due to a need for developing sustainable future energy as well as chemical resources. Water oxidation catalyst is a vital element for achieving photoelectrochemical solar-chemical production system. In this study, we demonstrate a highly efficient and scalable water oxidation (OER) catalyst electrode using low cost and earth abundant material, stainless steel (SS). Since surface modification of SS is facile in conjunction with the segregation phenomena of added elements from the iron matrix by thermal or electrochemical treatments we applied two ways to synthesize active OER catalyst electrodes. First, Ni-rich cratered structures were spontaneously formed on the SS surface by harsh electro-oxidation. The chemical composition changes of Fe and Ni on the catalyst surface dramatically was found to enhance water oxidation activity showing an overpotential value of 504 mV at 10 mA/cm2 in a CO2-saturated bicarbonate electrolyte. Active SS surface was also synthesized by a sulfide precursor layer formation by sulfurization followed by its removal by an electro-oxidation process. Interestingly, a newly exposed catalytic layer after eliminating the Fe-S overlayer has a nanoporous structure with changed elemental composition, resulting in a significant improvement in OER performance with an overpotential value of 265 mV at current density of 10 mA/cm2 in alkaline electrolyte condition. The details of the synthetic method and characterization of OER catalyst electrodes will be discussed in the presentation.
Mixed Oxides/Phosphides As Efficient Electrocatalysts for Oxygen Evolution Reaction
Authors: Zhang Lei , Chang Chun , Lu Shih-Yuan
Published: February 2020

With the increasing demand for energy supply and awareness of climate crisis, green energy generation has attracted intensive and extensive research attention during the past decades. Hydrogen, as a high energy density non-carbon energy source, has been one of the spotlights and its green production has been one of the top research topics in scientific community. Among the many existing hydrogen generation processes, water splitting (H2O → H2 + 1/2O2) driven by renewable energies is considered a dream everlasting process for hydrogen supply. Water splitting however is obstructed by one of the two reactions involved, the oxygen evolution reaction (OER, 4OH- → O2 + 2H2O + 4e- in alkaline solutions), because of its high over-potentials and sluggish kinetics caused by the four electron transfer process. Consequently, extensive efforts have been devoted to develop more efficient catalysts to lower the over-potential and thus energy consumption and to accelerate the kinetics of the OER. Mixed oxides or phosphides have been found to exhibit positive synergistic effects and achieve ultralow over-potentials for the OER. In this presentation, two recent examples are offered to illustrate this point, one involving mixed NiO/NiCo2O4 nanocrystals grown in situ from skeleton of 3D porous nickel network and the other concerning hollow nanocubes composed of well-dispersed mixed metal-rich phosphides, Ni5P4 and Fe3P, in N-doped carbon.
Modified Separator Performing Dual Physical/Chemical Roles to Inhibit Polysulfide Shuttle Resulting in Ultra-Stable Li–S Batteries
Authors: Abbas Syed Ali , Kaisar Nahid , Wang Pen-Cheng , Chu Chih-Wei
Published: February 2020

we describe a modified activated expanded graphite chitosan (AEG/CH) coated separator for Li–S batteries in which the shuttling phenomenon of the lithium polysulfides is restrained through two types of interactions: activated expanded graphite (AEG) flakes having a high surface area of 368 m2g-1interacted physically with the lithium polysulfides, while chitosan (CH), was used to bind the AEG flakes on the separator, interacted chemically through its abundance of amino and hydroxyl functional groups. Moreover, the AEG flakes facilitated ionic and electronic transfer during the redox reaction. Live H-cell discharging experiments revealed that the modified separator was effective at curbing polysulfide shuttling; moreover, XPS analysis of the cycled separator confirmed the presence of lithium polysulfides in the AEG/CH matrix. Using this dual functional interaction approach, the lifetime of the pure sulfur-based cathode was extended to 1000 cycles at 1C-rate (1C = 1670 mA/g), decreasing the decay rate to 0.021% per cycle—a value that is among the best reported to date. A flexible battery based on this modified separator exhibited stable performance and could turn on multiple light emitting diodes. Such modified membranes with good mechanical strength, high electronic conductivity, and anti-self-discharging shield appear to be a scalable solution for future high-energy battery systems.
Investigation of Al2O3 Wet-Chemical Coatings on Cathode Materials of Lithium-Ion Batteries
Authors: Han Binghong , Key Baris , Lapidus Saul , Garcia Juan , Iddir Hakim , Vaughey John T. , Dogan Fulya
Published: February 2020

Coating targeted particles using a wet-chemical method is a simple, effective, and easy-to-scale-up method to coat protective oxide layers. Previous studies have shown that wet coating Al2O3 on the surface of Li-ion battery cathode materials can effectively prevent their chemical and structural degradation during charging-discharging processes, and improve the lifetime of batteries. However, there are still a limited number of systematic investigations of the wet coating process for Al2O3 coatings on cathode materials. The selection of precursors, solvents, coating loadings, annealing conditions, and even the compatibility between the Al2O3 coating and the underlying cathode material, are synthetic variables that can change the interfacial structure and electrochemical performance of the coated cathode. In this work, we used the wet-chemical method to synthesize a series of Al2O3-coated LiNixMnyCo1-x-yO2 (NMC) particles, with various precursor-solvent combinations, Al2O3 loadings, annealing conditions, and cathode compositions. Using nuclear magnetic resonance, electron microscopy and high-resolution X-ray diffraction techniques, we have shown that the structural and chemical evolutions of the surface coatings are highly dependent on annealing temperatures, cathode compositions and precursor-solvent combinations. Higher annealing temperature lead to a more homogeneous, smoother, and conformal coating on cathode materials with the formation of LiAlO2 phase. Organic solvents in place of water also lead to a more evenly and strongly bonded coatings, particularly under low-temperature treatment. We have also found that the crystallization temperature of the coating layers is precursor dependent. In addition, we have discovered that decreasing Mn content facilitates the diffusion of surface aluminum into the bulk in samples that have undergone high-temperature annealing. This facilitates a transfer of aluminum cations from the surface coating to become a bulk dopant. This is confirmed by local Al chemical environment evolution, local lattice distortion and surface morphology changes. Density functional theory calculations indicate that the incompatibility between Mn and Al could be the reason of the composition dependence of surface Al insertion. Finally, we demonstrate that the diffusion of Al into the bulk, the low temperature treatment, and the aqueous coating process lead to poor cyclability and low capacity in charging-discharging process, indicating the importance of the optimized wet coating protocols and coating-cathode compatibility to the electrochemical performance of coated cathodes. This work is important to the development of better coating methods for the next generation cathode materials in Li-ion batteries.
In-Situ X-Ray Diffraction Study on Failure Mechanisms of Nickel-Rich Nmcs
Authors: Wang Shanyu , Yan Mengyu , Yang Jihui
Published: February 2020

Ni-rich layered LiNi1-x-yMnxCoyO2 (NMC, 1-x-y ≥ 0.5) are among the most promising candidates for next-generation high-energy-density lithium-ion batteries for electric vehicle applications, primarily due to their high energy density and good rate capability. Their poor cycle stability and thermal instability, especially at high operating voltages (> 4.3 V), however, could cause shortened life, induce thermal runaway, and thus largely hinder their usages. To overcome these drawbacks, the intrinsic failure mechanisms of Ni-rich NMC need to be clarified. In this work, in-situ X-ray diffraction was performed on LiNi0.6Mn0.2Co0.2O2 (NMC622) and LiNi0.8Mn0.1Co0.1O2 (NMC811) cycled at different voltage windows (2.8-4.2 V, 2.8-4.4 V, and 2.8-4.6 V), and the phase evolutions and failure mechanisms were systematically investigated. NMC622 shows reversible structural evolutions and an excellent cycle stability in 2.8-4.2 V and 2.8-4.4 V, while a new and inactive phase (presumably the spinel) was clearly observed when charged beyond 4.4 V. For NMC811, the inactive phase emerges at lower voltages ~ 4.3 V, and grows quickly with prolonged cycles in 2.8-4.4 V and 2.8 - 4.6 V. The appearance of the inactive phase seems to be triggered by the transition from hexagonal H2 to H3 phase, along with a large lattice shrinkage in the c-axis. The continuous growth of the electrochemically inactive phase mainly contributes to the poor cycle stability of Ni-rich NMCs at high voltages ≥ 4.4 V, which is further corroborated by our electrochemical impedance spectroscopy analysis.
High-Performance Lithium–Sulfur Batteries Based on Layered Double Hydroxides–Carbon Nanotubes Composite Cathode and a Dual-Coated Graphene–Polypropylene–Al2O3 Separator
Authors: Hwang Jang-Yeon , Sun Yang-Kook
Published: February 2020

Li–S batteries are becoming attractive due to their tremendous merits. In Li–S batteries, the sulfur (S8) undergoes a two-electron redox reaction with Li, which can provide a high theoretical capacity of 1675 mA h g−1 and can achieve high energy densities (2600 Wh kg−1) that are three-fold higher than those of transition metal oxide cathodes.1,2 Although Li–S battery technology has made great progress due to such intensive research efforts,3-5 effective approach for high performance Li–S battery to deliver a high capacity and good capacity retention with high sulfur loading has not been suggested yet.

Herein, a novel lithium–sulfur cell design is proposed, which consists of sulfur and magnesium–aluminum-layered double hydroxides (MgAl-LDH)–carbon nanotubes (CNTs) composite cathode with a modified polymer separator produced by dual side coating approaches (one side: graphene and the other side: aluminum oxides). The composite cathode functions as a combined electrocatalyst and polysulfide scavenger, greatly improving the reaction kinetics and stabilizing the Coulombic efficiency upon cycling. The modified separator enhances further Li+-ion or electron transport and prevents undesirable contact between the cathode and dendritic lithium on the anode. The proposed lithium–sulfur cell fabricated with the as-prepared composite cathode and modified separator exhibits a high initial discharge capacity of 1375 mA h g−
1 at 0.1 C rate, excellent cycling stability during 200 cycles at 1 C rate, and superior rate capability up to 5 C rate, even with high sulfur loading of 4.0 mg cm−
2. In addition, the findings that found in postmortem characterization of cathode, separator, and Li metal anode from cycled cell help in identifying the reason for its subsequent degradation upon cycling in Li–S cells.
Operando Multi-Modal Synchrotron Investigation for Structural and Chemical Evolution of Metal Sulfide Additives in Li-S Battery
Authors: Lin Cheng-Hung , Sun Ke , Zhao Chonghang , Williams Garth J. , Bai Jianming , Dooryhee Eric , Thieme Juergen , Stavitski Eli , Attenkofer Klaus , Gan Hong , Chen-Wiegart Yu-chen Karen
Published: February 2020

The Lithium-Sulfur (Li-S) battery with metal sulfide additives attracts more interests in recent years due to its potential to provide higher energy density, to increase electric capacity, and to improve the electrical conductivity of the insulated sulfur electrode. This multi-functional design on cathode showed initial promise; however, complicated interactions at the system level are accompanied by some detrimental side effects. The metal sulfide additives that promote a chemical conversion as the reaction mechanism, e.g., CuS and FeS2, to increase the theoretical capacity of the Li-S system can cause undesired parasitic reactions, such as the dissolution of the additive in the electrolyte. Studying such complex reactions presents a challenge because it requires experimental methods that can track the chemical and structural evolution of the system during an electrochemical process. To address the fundamental mechanisms in these systems, structural and chemical evolution of CuS additive in Li-S battery was conducted via operando multi-modal synchrotron techniques in this work. Transformation of phase and chemical state in S-CuS hybrid electrode during cell discharge/charge was investigated by X-ray Powder Diffraction and X-ray Absorption Spectroscopy. The Cu ion dissolution and its migration from cathode to anode during battery reaction were monitored by X-ray Fluorescence Microscopy. With the combination of operando multi-modal synchrotron approach, a new reaction mechanism was understood and proposed in this study.

Figure 1
Solid-State Stretchable Fabric-Based Lithium Ion Battery
Authors: Moradi Ghadi Bahar , Ardebili Haleh
Published: February 2020

Recent efforts in the development of stretchable and wearable energy storage devices including lithium ion batteries, have been strongly motivated by tantalizing applications such as smart garments, wearable communication, flexible display devices, and medical implants. This study focuses on the development and characterization of a stretchable fabric-based lithium ion battery composed of fabric-based electrodes and a solid polyethylene oxide (PEO) based electrolyte. Specifically, several stretchable fabrics were considered including cotton and silver based fabrics. Mechanical and electrochemical performances of the fabric-based battery are characterized, and furthermore, the materials and fabrication processes are optimized.
Carbon Nanofibers (CNFs) Coated Ni Foam As 3D Integrated Current Collector and Sulfur Host in Li-S Batteries
Authors: Zeng Zhipeng , Liu Xingbo
Published: February 2020

Tremendous attention has been paid to the energy conversion and storage devices for their rapidly growing market and more requirement for nowadays’ applications, ranging from portable electronics, electric tools to large renewable energy systems. The high theoretical capacity (1672 mAh g-1) and energy density (2600 Wh kg-1) for sulfur electrode make it be a very promising candidate for electric and hybrid electric vehicles among the various candidates. However, the commercialized process for this promising material is still greatly hindered by a series of issues, including the insulating of sulfur, large volume change, and the “shuttle effect” of polysulfides.

With this in mind, we developed the CNFs coated Ni foam both as the sulfur host and the current collector. The Ni foam was coated with two types of carbon layers. The inner one is relatively compact carbon layer rich in micropores, and the outer one is carbon nanofiber layer. After heat treatment at elevated temperature, sulfur was either physically impregnated into the micropores or chemically bond to C and Ni atoms. The surface and cross-section morphology were characterized by SEM and TEM and the chemical bond states were analyzed by XPS. The 3D conductive network, micropores, and chemical binding synthetically resulted in the high stability and excellent rate capability of the electrode, showing the potential application in developing high-performance Li-S batteries.
Core-Shell Architectured High Energy Cathode Nanocrystals to Stabilize the Electrode-Electrolyte Interface
Authors: Kwon Bob Jin , Dogan Fulya , Key Baris , Jokisaari Jacob , Freeland John W , Kim Chunjoong , Klie Robert F , Cabana Jordi
Published: February 2020

Stabilization of high energy cathode-electrolyte interface is required to meet the criteria for the power source and stable cycling performance in Li-ion batteries. [1] The undesired reactions at the interface could be minimized by introducing redox-inactive ions on the surface of active materials without affecting original properties. [2] To demonstrate the roles of passivating layers more effectively, high energy nanocrystals were introduced due to its high surface area that can induce access of charges with electrolytes, accelerating chemical degradation at the interface. [3] A synthetic method based on colloidal chemistry was employed to grow a thin shell enriched in Al3+ in the same reaction environment where the particles were grown in dispersible form, ensuring effective coverage of all surfaces. The resultant core-shell nanocrystal consists of active lithium transition metal oxides as a core and enriched Al3+ shells as a passivating layers to suppress the unfavorable reaction on the surface. Careful post-synthetic annealing was used to produce the final heterostructures and tailor the specific chemistry of the shells. The modified nanocrystals improved capacity retentions in various conditions, such as elevated temperature and high applying potentials compared to the bare counterpart where a shell is not presented, strongly suggesting a role of protective layers. The chemical identity and specific structural information of the bulk and passivation layers were mainly characterized by a combination of solid state nuclear magnetic resonance (NMR), X-ray photoelectron spectroscopy (XPS), scanning transmission electron microscopy (STEM), and X-ray absorption spectroscopy (XAS).

Reference

Lee, K. T.; Jeong, S.; Cho, J. Acc. Chem. Res, 2013, 46, 1161-1170.

Kim, C.; Phillips, P. J.; Xu, L. P.; Dong, A. G.; Buonsanti, R.; Klie, R. F.; Cabana, J. Chem. Mater, 2015, 27, 394-399.

Bruce, P. G.; Scrosati, B.; Tarascon, J. M. Angew. Chem. Int. Ed, 2008, 47, 2930-2946.
A Novel High-Voltage Binder for High-Capacity Cathode of Lithium-Ion Batteries
Authors: Pham Hieu Quang , Kim Gwansu , Jung Hyun Min , Song Seung-Wan
Published: February 2020

An increase in the energy density of lithium-ion batteries has long been a competitive advantage for advanced wireless devices and long-driving electric vehicles. Li-rich layered oxide, xLi2MnO3∙(1−x)LiMn1−y−z
Ni
y
Co
z
O2 (LMNC), is a promising high-capacity cathode material for high-energy batteries, whose capacity increases by increasing the charge cut-off voltage to above 4.6 V vs. Li/Li+.1,2 Li-rich layered oxide cathode however suffers from a rapid capacity fade during the high-voltage cycling because of instable cathode-electrolyte interface, and the occurrence of metal-dissolution, particle cracking and structural degradation, particularly, at elevated temperatures.2 Herein, we report the development of a novel high-voltage binder (P), which mitigates the cathode degradation problems through superior binding ability to conventional polyvinylidenefluoride (PVdF) binder and the formation of robust surface structure at the cathode. While P-LMNC//graphite full-cell with 1M LiPF6/EC:EMC without any electrolyte additive shows a stable cycling performance over 100 cycles even in the harsh operation condition of 55 ○C between 2.5 and 4.7 V at 0.2C delivering capacity retention of 89% and high cyclic coulombic efficiencies close to 100%, a very rapid capacity fade and poor coulombic efficiencies are observed with PVdF-LMNC//graphite full-cell.3 This is so far the best and first performance ever reported for high-voltage full-cell at elevated temperature without any electrolyte additive. The detailed studies of surface composition and formation mechanism, and their relation to high-voltage and high-temperature cycling performance would be presented in the meeting.

Acknowledgements

This research was supported by National Research Foundation of Korea (NRF-2015R1D1A1A01060838) and Chungnam National University.

References

H. Q. Pham, K.-M. Nam, E.-H. Hwang, Y.-G. Kwon, H.-M. Jung, S.-W. Song, J. Electrochem. Soc., 161, A2002 (2014).

H. Q. Pham, E.-H. Hwang, Y.-G. Kwon, S.-W. Song, J. Power Sources, 323, 220, (2016).

H. Q. Pham, G. Kim, H. M. Jung, S.-W. Song, Adv. Func. Mater., in press (2017).