bluuebunny/crossref_metadata_2025_split huggingface dataset:
Theoretical Study on Oxygen Dissociation Reaction on LaSrCoO3
Authors: Ishimoto Takayoshi , Sato Kenji , Tada Tomofumi , Amezawa Koji , Koyama Michihisa 
Published: February 2020

Introduction

Doped lanthanum cobaltite and its derivatives are used as cathode materials in solid oxide fuel cell (SOFC). For a high catalytic activity, the improvement of properties governing the cathode performance is important. It is generally regarded that one of the important factors is electronic structure of cathode material. It is known that the Co ion in doped lanthanum cobaltite shows three spin states, such as low spin (LS), intermediate spin (IS), and high spin (HS). Hong et al. pointed out that the change of electronic structure due to the difference of spin states affect the formation energy of oxygen vacancy in LaCoO3 bulk system. Although it is expected that the high catalytic materials for oxygen adsorption and dissociation on oxide surface are proposed by the controlling the electronic structure of doped lanthanum cobaltite, the effect of electronic structure due to the difference of spin states of Co ion is unclear for the surface reactions on doped lanthanum cobaltite. In this study, we analyzed the stability of oxygen vacancy and surface reaction of oxygen under the different spin states of Co ion in Sr doped LaCoO3by using density functional theory (DFT) calculation.

Computational Details

We used LaSrO-terminated (001) surface of cubic LaSrCoO3 crystal structure. Half of La atoms were substituted by Sr atoms in LaO layers to analyze the effect of segregation of Sr in La6Sr6Co8O28 slab model. GGA-PBE with PAW potentials were applied with cutoff energy of 600 eV and 2x2x1 k-points. The initial spin configuration was constrained, such as LS, IS, and HS states, to obtain the different electronic structures. All DFT calculations were performed by using VASP.

Results and Discussion

We first analyzed the oxygen vacancy formation energy on the surface of La6Sr6Co8O28. The vacancy formation energies of one oxygen on surface under the LS, IS, and HS states were 0.92, 1.03, and 0.95 eV, respectively. The vacancy formation energies of two oxygen on surface under the LS, IS, and HS states were 3.27, 2.36, and 1.90 eV, respectively. The oxygen vacancy formation became unstable when the number of oxygen vacancy increases in all spin states. The oxygen vacancy formation energy for HS was the smallest compared with LS and IS states for two oxygen vacancy systems. We found that the difference of spin state of Co ion affects the oxygen vacancy formation energy on surface of LaSrCoO3. In addition, we analyzed the stability of oxygen vacancy under the different Sr configurations to understand the effect Sr segregation. Details are discussed in the presentation.

Acknowledgement

The activities of INAMORI Frontier Research Center are supported by KYOCERA Corporation. All calculations are performed on the HA8000 computer systems in Research Institute for Information Technology, Kyushu University.

Reference

[1] W. T. Hong, M. Gadre, Y. -L. Lee, M. D. Biegalski, H. M. Christen, D. Morgan, and Y. Shao-Horn, J. Phys. Chem. Lett., 4, 2493 (2013).
Improving the Lifetime and Cycle Life of NMC/Graphite Li-Ion Cells Charged to 4.4 or 4.5V
Authors: Dahn Jeff 
Published: February 2020

Significant extra capacity and energy density can be obtained from NMC/graphite cells by increasing the upper voltage cutoff from 4.2V to 4.5V. However, when this is done, parasitic reactions between the charged NMC electrodes and the electrolytes accelerate and cell lifetime is compromised.
In this lecture, I will review recent work in our laboratory that has focussed on increasing the lifetime of NMC/graphite Li-ion cells charged to 4.4 or 4.4V. This work has centered around:
1) Quantifying parasitic reactions using Ultra High Precision Coulometry, Isothermal Battery Microcalorimetry and Automated Cycling/Impedance Spectroscopy measurements;
2) Reducing the rate of parasitic reactions through the use of electrolyte additives;
and
3) Using surface science techniques, e.g. XPS, to understand how these electrolyte additives function.
The results of this work are NMC622/graphite, NMC532/graphite, NMC422/graphite and NMC111/graphite cells which have improved properties for high voltage use.
This work has been carried out by a large number of graduate students and post doctoral fellows including Dr. Mengyun Nie, Dr. Jian Xia, Dr. Lenaic Madec, Dr. David Hall, Dr. David Yaohui Wang, Lin Ma, Kathlyne Nelson, Laura Downie, Remi Petibon, Julian Self, Leah Ellis, Deijun Xiong and Chris Burns. Collaborations with researchers at 3M Company, including Dr. Ang Xiao, Dr. Bill Lamanna and Dr. Kiah Smith have been vital for this work. The authors acknowledge Dr. Jing Li of BASF for supply of many of the electrolyte solvents and additives used in these studies. Dr. Yong-Shou Lin and Dr. David Wang of ATL Battery Co. are acknowledged for the supply of some of the dry pouch cells used in these studies. The authors thank the Natural Sciences and Engineering Research Council of Canada and 3M Canada Company for funding of this work.
Three-Dimensional Flower-Shaped Activated Porous Carbon /Sulfur Composites As Cathode Materials for Lithium-Sulfur Batteries
Authors: Zhou Lan , Yu Aishui 
Published: February 2020

Lithium sulfur battery, which use sulfur as a cathode and Li as an anode, have taken more and more attention for its high theoretical speciﬁc capacity of 1675 mA h g−1 and high theoretical speciﬁc energy of 2600 Wh kg−1. Despite these particular advantages, several troublesome issues associated with the sulfur cathode severely limits the practical use of sulfur in an electrode, such as, the highly electrical insulating nature of sulfur, the redox shuttle of dissolved polysulfide ions and the volume expansion of sulfur cathode materials.
In our work, three-dimensional ﬂower-shaped activated porous carbon/sulfur composites (FA-PC/S) are fabricated for the first time via a simple method utilizing ﬂower-shaped ZnO as a template and pitch as the carbon precursor, followed by carbonization-activation and thermal treatment. A typical flower-shaped FA-PC spherical structure is composed of many nanopetals intersecting with one another. Because of the unique three-dimensional ﬂower-shaped porous spherical structure, FA-PC has high reactivity, high electrical conductivity and a short transport length for the Li ion. Furthermore, the rich micropores of the FA-PC offer enough space to accommodate the volume expansion that occurs during the discharge process of the encapsulated sulfur as well as confine the electrochemical reaction products of the sulfur cathode within the micropores. The composites are also characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM), Brunauer–Emmett–Teller (BET) analysis, Raman spectroscopy, X-ray powder diffraction (XRD), and thermogravimetric (TG) measurements. The results show that sulfur is well dispersed and encapsulated homogeneously in the micropores of the ﬂower-shaped activated porous carbon (FA-PC) with excellent electrical conductivity, high surface area and large pore volume. The electrochemical tests show that the FA-PC/S composites with 60 wt. % S have a high initial discharge capacity of 1388 mA h g-1 at 100 mA g-1, a good cycling stability (reversible discharging capacity of approximately 600 mA h g-1 at 1600 mA g-1) and excellent rate capability.
Characteristics of Nitrogen and Boron Co-Doped Graphene Nanosheets Synthesized By Simple Microwave-Hydrothermal Method
Authors: Kim Il To , Song Myeong Jun , Kim Young Bok , Shin Moo Whan 
Published: February 2020

Graphene nanosheets have received much attention in electrochemical energy research areas because of its remarkable properties such as high specific surface area and electrical conductivity. The properties satisfy various requirements for electrochemical device’s electrode. In that application, the enhancement of the oxygen reduction reaction (ORR) activity has been considered as one of the important issues. For enhancing ORR activity, various precious metal catalysts have been investigated in spite of their high prices. In recent years, research efforts have been focused on developing various non-metal catalysts for overcoming the disadvantage of metal catalysts.
Most of carbon-based non-metal catalysts were synthesized via expensive method such as chemical vapor deposition (CVD) method. The method is not suitable for mass production method. In this study, we synthesized nitrogen and boron co-doped graphene nanosheets (BNG) from graphene oxide (GO) by simple microwave-hydrothermal method. The synthesis time can be significantly reduced result from assistance of microwave heating. The synthesis process includes doping and reduction process. The samples were prepared under different reduction temperature conditions. For observing the morphology of samples, we carried out scanning electron microscopy (SEM). From Raman spectra analysis, we confirmed that intensity ratio (ID/IG) increased with reduction temperature. And we investigated chemical composition and bonding configuration of the BNG samples by X-ray photoelectron spectroscopy (XPS). The results of XPS analysis demonstrated that co-doping and reduction process are successfully achieved. Catalytic activities were characterized by three-electrode system. Linear sweep voltammetry (LSV) was measured in 0.1M KOH electrolyte purged oxygen gas over 1 h, with a 1500 rpm electrode rotation speed and a 10 mVs-1 scan rate. The LSV results revealed that co-doped samples show higher ORR activity compared to that of non-doped sample and the activity is enhanced with reduction temperature.

Acknowledgement

This research was supported by the MSIP(Ministry of Science, ICT and Future Planning), Korea, under the “IT Consilience Creative Program” (NIPA-2014-H0201-14-1002) supervised by the NIPA(National IT Industry Promotion Agency)
Fundamental Charge Transfer Processes in Stable Free-Radical Organic Polymer Systems
Authors: Gennett Thomas , Braunecker Wade A. , Hughes Barbara Katherine , Kemper Travis , Bobela David C. , Berry Joseph , Larsen Ross E. 
Published: February 2020

Polymers with stable pendant radical groups are a unique class of redox-active materials emerging as potentially the next generation energy storage breakthrough. These polymers facilitate apparently remarkably rapid, efficient and reversible multi-step charge-transfer processes. The focus of this project is to advance the fundamental understanding of the structure-property relationships associated with the mechanism(s) of electron transfer and ion transport, along with associated interfacial mass-transfer processes that impact the charge-transfer processes of a unique class of organic free-radical polymeric redox active materials.
The project involves an integrated approach of chemical synthesis, electrochemistry, spectroscopy and theoretical modeling of a series of stable organic radical materials. Initially, we have focused on the 2,2,6,6-tetramethylpiperidine-N-oxyl (TEMPO) organic radical moiety incorporated into a complex materials set of poly(4-methacryloyloxy-2,2,6,6-tetramethylpiperidine-N-oxyl) (PTMA). We focused our work to probe, and establish, the charge-transfer mechanisms of a series of the TEMPO-containing macromolecules with varying chain lengths and side-chain compositions. We have investigated the model compound, 4-oxo-2,2,6,6-tetramethylpiperidine-N-oxyl (4-oxo-TEMPO), and compared the results to those for non-cross-linked and cross-linked PTMA oligomers and polymers with: (i) various oligomer chain-lengths; and (ii) controlled densities of the TEMPO radical moieties along the chain (i.e. with some TEMPO-methacrylate units replaced by methyl methacrylate). Our presentation will discuss a complete electrochemical analysis of the TEMPO polymeric materials. The discussion will include the correlation of electron-transfer rates and ionic mobility in various electrochemical solvents, and the role that radical content has on both the heterogeneous electron-transfer rate and the self-exchange charge transfer mechanism of the various materials.
Na3V2O2x(PO4)2F3-2x As a High Voltage Cathode Material for Rechargeable Aqueous Sodium-Ion Batteries
Authors: Petla Ramesh Kumar , Jung Young Hwa , Lim Chek Hai , Kim Do Kyung 
Published: February 2020

As an alternative to current lithium ion batteries, sodium-ion batteries (SIBs) are potential energy storage systems due to the high natural abundance and low cost of Na. However, safety issues for SIBs based on flammable organic solvents still hinder the practical applications of SIBs [1]. In this view, rechargeable aqueous SIBs can overcome safety concerns as well as environmental toxicity [2]. Recently, we reported the reversible electrochemical reaction of Na2FeP2O7, which is a promising polyanion compound for SIBs, in a neutral aqueous solution. But, Na2FeP2O7 in aqueous electrolytes exhibits a low energy density due to the low redox potential of Fe2+/3+ [3]. Therefore, we have studied several polyanion compounds in aqueous electrolytes to achieve high energy density SIBs. Here, the electrochemical activity of the Na3V2O2x(PO4)2F3-2x in aqueous electrolytes is reported for the first time. Na3V2O2x(PO4)2F3-2x with multi-walled carbon nanotubes (MWCNTs) exhibits a long-term stability by 1100 cycles in aqueous electrolytes. Two different types of Na-ion full-cells demonstrate the feasibility of the Na3V2O2x(PO4)2F3-2x/MWCNT composite as a cathode for aqueous sodium-ion batteries. A high full-cell voltage of 1.7 V and a high energy density of 84 Wh kg−1were achieved using Zn metal as an anode.
References:
[1] Z. Chang, Y. Yang, M. Li, X. Wang and Y. Wu, J. Mater. Chem. A, 2, 10739 (2014).
[2] H. Kim, J. Hong, K.Y. Park, H. Kim, S.W. Kim and K. Kang, Chem. Rev., 114 11788 (2014)
[3] Y. H. Jung, C. H. Lim, J. H. Kim and D. K. Kim, RSC Adv., 4, 9799 (2014)
Ionic Liquid-Derived N-Doped Carbon/Sulfur Composite Cathodes with Tailored Nanostructure for High-Performance Li/S Batteries
Authors: Schneider Artur , Sommer Heino , Janek Jürgen , Brezesinski Torsten 
Published: February 2020

Batteries are one of the key technologies in the field of energy storage and conversion. Among the broad range of available cathode active materials, elemental sulfur has the highest theoretical specific capacity (1675 mAh/g) and thus holds great promise as positive electrode material in rechargeable Li-batteries.[1] There are, nevertheless, major safety and performance issues that need to be addressed before commercialization of Li/S batteries can be contemplated. Recently, significant progress has been made by incorporating sulfur into nano-structured carbons. Such carbon/sulfur composites seem to be capable of providing a stable cathode performance by somewhat hindering the lithium polysulfides from leaving the architecture (through specific chemical and/or physical interactions).[2] Furthermore, nanostructured carbons have been shown to have the potential to preserve the electrode integrity by better accomodating the volume changes of sulfur during conversion to lithium sulfide. Here, we report on the use of hierarchically structured N-doped carbon/sulfur composites for long-life and high-performance Li/S batteries.[3] Highly conductive carbon with tailored porosity was fabricated by silica templating followed by sulfur melt infiltration to produce carbon/sulfur nanocomposites. Cathodes with a sulfur content of 60% and sulfur loadings ranging from 1 to 4 mg/cm2 were tested electrochemically both in coin and pouch cells. At a moderate C-rate of C/5, stable specific capacities of approx. 700 mAh/g can be achieved over hundreds of cycles; and cathodes with a sulfur loading of 4 mg/cm2 demonstrate areal capacities approaching 3.0 mAh/cm2. Literature reports on sulfur cathodes providing similar areal capacities are scarce, especially when the electrolyte-to-sulfur mass ratio is <15:1.[4] Overall, we show that our ionic liquid-derived carbon/sulfur composite possesses a beneficial microstructure for Li/S battery applications.
[1] Manthiram, A. Acc. Chem. Res.
2013, 46, 1125–1134.
[2] Ji, X.; Lee, K.T.; Nazar, L. Nature Materials
2009, 8, 500-506
[3] Schneider, A.; Weidmann, C.; Suchomski, C.; Sommer, H.; Janek, J.; Brezesinksi T. Chem.
Mater.
2015, DOI: 10.1021/cm504460p.
[4] Song, J.; Wang, D. Adv. Funct. Mater.
2013, 24, 1243–1250.
Modelling Proton Transport Phenomena in Nanopores of Fuel Cell Catalyst Layers
Authors: Muzaffar Tasleem Ahmad , Eikerling Michael 
Published: February 2020

Proton transport through nanoporous media is an important process in electrochemical energy conversion. Proton density and mobility in porous electrodes determine the proton conductivity as well as the rates of interfacial electrochemical processes. In the case of polymer electrolyte fuel cells (PEFCs), the foremost practical objective is to design porous electrodes or catalyst layers with high performance at markedly reduced platinum loading. Achieving this objective demands an understanding of the impact of composition and porous structure as well as surface structure and charging properties of pore walls on the proton density distribution. In the presented work, we consider simple pore geometries to study the concerted effects of ionomer structure and metal charging properties on proton density and transport in nanopores. The approach employs Poisson-Nernst-Planck theory.
1,2
The basic model system is a cylindrical pore with an ionomer shell. In one variant, we consider a core consisting of a solid metal rod. In another variant, we assume a random porous core that represents Pt/C aggregates. In both variants, the remaining pore space is filled with water. The set of ordinary differential equations for transport and reaction in these model structures is formulated and solved. Solutions are analysed by comparing potential and proton density distributions for varying pore geometries and charging properties at interfaces. The effectiveness factor of catalyst utilization is calculated to evaluate the electrocatalytic performance at the pore level.

References

[1] R.Coalson, and M.Kurnikova, Biological membrane Ion channels, Chap 13, Springer, NewYork (2001)
[2] K.Chan and M. Eikerling, J. Electrochem. Soc. 158(1), (2011), B18-B28.

Figure 1
Internal Reforming Methanol Fuel Cell Development
Authors: Bandlamudi George C , Steffen Michael , Meijer Tobias , Heinzel Angelika 
Published: February 2020

Methanol is a liquid fuel which could also be produced from renewable energy sources and has appreciably high energy density. It has a high H : C ratio of 4 : 1 without any C-C bond. It is easier to reform when compared to CH4 to produce H2 rich gas that could be fed into a high temperature polymer electrolyte membrane fuel cell or HT-PEMFC. A typical IRMFC module consists of a HT-PEMFC thermally integrated with a methanol evaporator and reformer in a closed thermal loop. Simulations show that the total heat demand of the evaporator and the methanol steam reformer would require only 20% of the heat generated by the HT-PEMFC where the geometrical area of the HT-PEMFC is almost equal to that of the geometrical area of the reforming catalyst.
In the current work a novel IRMFC which is operated in the 210-220°C range is presented. Operating an IRMFC at these high temperatures would mean novel materials and components to be employed within the HT-PEMFC as well as within the methanol reformer unit. The high temperature stable membrane electrode assemblies were developed by Advent technologies in Greece. The high temperature stable bipolar plates were developed by ZBT in Germany within the scope of a current EU funded project. When operated at 220°C on 350 mA/cm² of load current, the novel HT-PEMFC could deliver 210 mW/cm² at 0.6 V. As for the methanol reforming unit operated at 220°C, when fed with methanol-water mixture with a steam to carbon ratio of 1.5, the methanol conversion rate was around 90%. The performance analyses of the IRMFC single unit as well as that of the 5 cell unit demonstrate the potential to developing a compact light weight power generating unit offering double the gravimetric and volumetric energy densities offered by the current direct methanol fuel cell based units.
Oxygen Functionalised Carbon Surfaces - a Suitable Electrode Material for Vanadium (V) Reduction in Redox Flow Cell Applications
Authors: Taylor Susan Margaret , Patru Alexandra , Schmidt Thomas J. 
Published: February 2020

Carbon based materials have been found to be one of the most suitable electrode materials for the vanadium (V) reduction reaction at the cathode side of redox flow cell systems. Carbon electrodes modified with oxygen functional groups show a significant improvement in activity and reversibility of the vanadium (V) reduction reaction compared to non-functionalized carbon. The trend in the literature is to use different types of carbon materials modified by different surface functionalisation techniques (1, 2, 3), opening up a number of possibilities for different electrode materials for this application. Since not all these studies are in agreement (4), there appears to be a lack of clear understanding of the surface functionalisation-activity correlation. In order to better understand the role of surface functional groups on the electrochemical properties of vanadium (V) reduction, we present here a systematic study using glassy carbon as a model electrode system.
The glassy carbon surface is functionalised by different treatment methods including: i) thermal treatment in oxygen, ii) electrochemical oxidation and iii)acid treatment. The identification and quantification of the different functional groups is evaluated using X-ray photon spectroscopy (XPS) and Fourier transform infrared spectroscopy (FT-IR) techniques. The activity and reversibility of the vanadium (V) reduction reaction is related to the extent of functionalisation i.e. type and amount of functional groups, in order to find the optimum surface termination. Furthermore, the wettability of the carbon surface is investigated. Wettability is inherently related to the presence of surface functional groups, with the surface becoming more hydrophilic in the presence of oxygen containing surface terminations. Finally, the correlation between the relative contributions of surface wettability and surface functional groups towards the overall activity is determined.
References
1. Li, W. et al. 2011. Multi-walled carbon nanotubes used as an electrode reaction catalyst for /VO2+ for a vanadium redox flow battery. Carbon, 49(11), pp.3463–3470.
2. Maruyama, J. et al. 2013. Mechanism of Dioxovanadium Ion Reduction on Oxygen-Enriched Carbon Surface. Journal of the Electrochemical Society, 160(8), pp.A1293–A1298.
3. Kim, K. et al. 2014. A new strategy for integrating oxygen fucntional groups into carbon felt electrode for vanadium redox flow batteries, Scientific Reports, 4, Article Number: 6906.
4. Melke, J. et al. 2014. Carbon materials for the positive electrode in all-vanadium redox flow batteries. Carbon, 78, pp.220–230.