bluuebunny/crossref_metadata_2025 huggingface dataset:
Gas Concentration Measurements Using Photoacoustic Sensors for Industrial Solid Oxide Fuel Cell Process Control
Authors: Lengden Michael , Bauer Ralf , Johnstone Walter
Published: February 2020

Tunable diode laser spectroscopy (TDLS) has proven to be a suitable optical sensing system for the measurement of methane and water vapour concentrations in Solid Oxide Fuel Cells (SOFCs).  The unique advantages of TDLS include the ability to measure gases, including water vapour, in-situ and in real time, providing an ideal measurement system for large-scale fuel cell research and process control on an industrial scale.  In this paper we present a technique similar to TDLS, known as photo-acoustic spectroscopy (PAS), which is capable of achieving much higher concentration measurement sensitivities with reduced sensor dimensions, enabling the possible integration of remotely controllable sensors within the SOFC enclosure.  In order to achieve even greater sensor sensitivities, mid-infrared optical sources are required due to the higher probability of optical absorption.  Here we present our recent work on miniaturised 3D printed PAS trace gas sensors (see figure), which includes the use of a mid-infrared quantum cascade laser as optical source. The 3D printed sensors have outside dimensions of approximately 25x15x10mm, with the optical interrogation coupled to the sensor through optical glass fibres or direct free-space coupling.  The potential for PAS as a process control strategy for measuring SO2 concentration during the desulphurisation of a natural gas SOFC fuel source is presented.  Results are also shown for PAS measurements of CH4 and CO2 concentrations in the mid-infrared and the near-infrared respectively, showing the capability of using PAS as a replacement for a GC in fuel cell research and process control.

Figure 1
Optimization of Tensile Strength Measurements on Glass-Ceramic Sealant Used for SOFC Stacks
Authors: Gross-Barsnick Sonja-Michaela , Babelot Carole , Federmann Dirk , Pabst Ulrich
Published: February 2020

Glass-ceramic sealants are commonly used as joining materials for planar Solid Oxide Fuel Cell (SOFC) stacks. Several requirements need to be fulfilled by these materials: besides electrical insulation and adequate thermal expansion, a good adhesion on the ceramic and metallic components of a SOFC stack is necessary to form a gas-tight joint [1]. A key requirement is the mechanical strength of the sealant to maintain the integrity of the stacks under operation conditions [2]. Due to the lack of standardized methods, tensile tests were developed in-house. Preliminary measurements achieved reproducible results with extremely low tensile strength values for circular butt joints made of the iron-chromium alloy Crofer22APU and a composite sealant based on a glass matrix of the system of BaO-CaO-SiO2 reinforced with yttria-stabilized zirconia fibers [3, 4]. These results have been used for a qualitative ranking of different sealant materials.

The goal of our recent studies is to improve the characterization methods of mechanical strength in order to obtain quantitative results and to achieve the understanding needed to design more robust SOFC stacks. For this purpose, computer simulations using finite element analyses (FEA) have been performed. By modelling different joint configurations, it was possible to homogenize the stress distribution along the sealing layer and to optimize the geometries of the components. It was shown that bending of the metallic components as well as residual thermal stresses had a strong effect on the initial sample setup with thin cylinders. An optimized design for the tensile components allows a more uniform distribution of tensile stresses within the sample. Different joining conditions were investigated and the calculations were verified by experiments. Scanning electron microscopic analyses were carried out on cross sections and broken samples, which allow to evaluate the microstructure of the composite and its interfacial reactions. The mechanical strength values obtained by the improved characterization method represent a tenfold increase compared to the values published in [3].

[1] Gross et al., Fuel Cell Bulletin 9 (2006) 12-15

[2] Blum et al., J. Pow. Sources 196 (2011) 7175-7181

[3] Gross et al., J. Pow. Sources 196 (2011) 7338-7342

[4] Cela Greven et al., Fuel Cells 13, No.4 (2013) 565-57
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).
Surface Modification of La0.6Sr0.4Co0.2Fe0.8O3-δ Cathode by Atomic Layer Deposition of La0.6Sr0.4CoO3-δ for High-Performance Solid Oxide Fuel Cells
Authors: Choi Hyung Jong , Bae Kiho , Jang Dong Young , Park Suk Won , Han Gwon Deok , Shim Joon Hyung
Published: February 2020

Lowering the working temperature of solid oxide fuel cells (SOFCs) is necessary to avoid undesirable reactions between the cells’ elements and to guarantee long-term stability and a short start-up time. At low temperatures (<650°C), the cathode is considered the main resistive factor for global cell performance, because the oxygen surface exchange is a rate-determining step in the oxygen reduction reaction at the cathode. Modifying the cathode surface with catalytic nanoparticles or thin films has been very effective in improving the surface kinetics of the cathode. Among the surface modification techniques, atomic layer deposition (ALD) has many advantages, such as a low deposition temperature (<250°C), precise control of layer thickness, and uniform distribution. In this study, we modified the surface of La0.6Sr0.4Co0.2Fe0.8O3-δ (LSCF) with ALD of La0.6Sr0.4CoO3-δ (LSC). The ALD LSC was added to the surface of the LSCF cathode by pulsed laser deposition in an anode-supported SOFC cell. As a result, at 600°C, the maximum power density of the ALD LSC-treated cell increased to 250 mW/cm2 compared to the 198 mW/cm2 density displayed by the bare cell. We will discuss the performance enhancement of the LSCF surface-treated with ALD LSC layers in terms of electrode kinetics and fuel cell performance.
Multilayered Precoated AISI 441 for Solid Oxide Fuel Cell Interconnects
Authors: Lundberg Mats W , Berger Robert , Westlinder Jörgen , Holmberg Håkan
Published: February 2020

Sandvik Materials Technology develops nanocoatings for SOFC stainless steel interconnects. In this study a multilayered PVD-coating has been investigated. Cyclic oxidation for more than 20,000 hours at 800°C, chromium volatilization and area specific resistance studies has been conducted on three different coatings and compared with the uncoated steel, in this case AISI441 (EN 1.4509). In this work we have shown that pre-coated AISI 441 show very promising results for SOFC interconnectors at 800°C. We have studied and compared state of the art CeCo coating with a new four layered coating that shows slightly higher cumulative chromium volatilization, similar ASR values and reduced mass gain in the cyclic oxidation experiments.

Figure 1
Electrolysis Operating Mode for Reversible Solid Oxide Fuel Cells
Authors: Minh Nguyen , Williams Mark Christopher
Published: February 2020

Reversible solid oxide fuel cells (RSOFCs) have been considered and developed for power generation from a variety of fuels and hydrogen/syngas production from steam/mixtures of steam and carbon dioxide. When the RSOFC is operated in electrolysis mode (referred to as solid oxide electrolysis cell or SOEC mode), it is critical that electrode performance is reversible and system design is configured for efficient operation in both SOFC and SOEC modes. This paper summarizes recent results on electrode reversibility in SOEC mode for planar hydrogen electrode-supported RSOFCs and discusses a preliminary system design for electrolysis operation.
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)
High-Speed Computational Screening Methods to Design Novel Organic Electrolytes for High-Voltage Lithium-Ion Batteries
Authors: Park Min-Sik , Kang Yoon-Sok , Im Dongmin
Published: February 2020

Recent attention to the development of high-voltage lithium-ion batteries has been growing for electric vehicles applications. The electrochemical stability, i.e., redox potentials, of organic compounds is an important property for designing novel electrolytes. However, the redox potentials have not been generally provided in existing large-sized organic compounds databases and therefore the development of novel electrolytes based on them has been restricted. In this study, we suggest fast computational methods for redox potentials to screen out organic electrolytes from the compounds database and to build a redox potentials map on the database. We also show some screening results in cyclic organic molecules and analyze the relation between redox potentials and molecular structures.
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
Electrochemical Sensor for Power Control of a Micro Fuel Cell
Authors: Lundblad Anders Olof , Chavez Varela Camila
Published: February 2020

Micro fuel cells can be used for autonomous energy systems are used for surveillance, wireless communication nodes and other power needs where there is no access to grid electricity. For small power levels (e.g. 10 W) a battery or supercapacitor pack is often used. For long runtimes there is, however, a need for a large battery. The idea of this autonomous system is to reduce the battery/supercap package and instead use a photovoltaic during the day to charge up the batteries. The fuel cell contributes in the event of bad weather conditions when the photovoltaic is unable to deliver enough energy for several days. The energy system comprises a battery package for storage of electrical energy, a photovoltaic module which delivers electricity to the battery pack, a fuel cell for backup delivery of electricity, and a power control electronics unit which transfers the power to the load. The simplified fuel cell system consists of a hydrogen storage tank (pressurized hydrogen or metal hydride), a pressure regulation valve, a control valve, and a fuel cell stack. Thanks to that the battery pack can handle load variations the fuel cell system can be adapted to run at a constant gas flow level. Thereby, the control valve can be reduced to an on-off valve, which means that simplified the fuel cell system can compete with the cost for batteries. This work will analyse how the voltage from an external fuel cell (short circuited over a resitor and fed by the hydrogen exhaust) can be used to control the power draw of the stack. The sensitivity to hydrogen flow variation, start-up and shut-down procedures will be investigated.
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.
Novel Hydrogen Production and Power Generation System Using Ni-Metal Hydride Battery
Authors: Choi Bokkyu , Panthi Dhruba , Nakoji Masateru , Kabutomori Toshiki , Tsutsumi Kaduo , Tsutsumi Atsushi
Published: February 2020

We proposed a novel electrochemical system for hydrogen production and power generation based on a fuel cell/battery system. The reactions (hydrogen evolution and oxidation) in the system occur at solid/liquid and solid/gas two-phase boundaries. From a theoretical analysis of the energy efficiency, we found that this novel electrochemical reactor has high energy efficiency for both hydrogen production and power generation. Following the theoretical analysis, electrochemical charge/discharge performance characteristics were studied at various current densities by fabricating an experimental cell, which was composed of negative and positive electrodes with a 1:3 capacity ratio. From the experimental results, we found that hydrogen gas was produced in a linear manner during the charge process and it was completely consumed during the discharge process. The energy conversion efficiency of the hydrogen production and the round-trip efficiency of hydrogen production and power generation at a current density of 37.0 A/m2 were 98.3% and 79.6%, respectively. These results indicated that the present system is highly efficient compared with the conventional water electrolysis and/or power generation systems.
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.
A Simple Synthesis of an Excellent Oxygen Reduction Catalyst: Nitrogen-Doped, Sharply-Mesoporous Carbon from Magnesium Salts
Authors: Eisenberg D. , Yan Ning , Rothenberg Gadi , Mabayoje Oluwaniyi , Mullins Charles Buddie
Published: February 2020

Any new oxygen reduction catalysts for practical low-temperature fuel cell applications must compete with the commercial platinum catalysts on efficiency and cost. Mesoporous nitrogen-doped carbon (N:C) has emerged as a leading alternative, mostly due to its high surface area, and the promise for low-cost production. While the best mesoporous N:C catalysts in the literature can operate on par with commercial platinum/carbon composites,1 their synthesis is complex and difficult – increasing their cost and rendering them impractical.

We present a particularly simple synthesis of N-doped carbon, starting from magnesium salts of nitrogen-containing ligands. Pyrolysis of the salts proceeds by the little-researched mechanism of self-templating – formation of similarly sized MgO nanoparticle cores, which are then washed out with dilute acid, leaving behind a narrow pore size distribution.

These carbons have high surface areas (>1400 m2/gr), nitrogen doping levels topping what is required for catalysis (>4%), and most interestingly, a very narrow pore size distribution (ranging from 10 to 20 nm for different carbons). Tested in alkaline ORR catalysis, these carbons compete successfully with commercial platinum-based electrodes, so they are efficient, cheap, and simple to prepare.

(1) W. Wei, H. Liang, K. Parvez, X. Zhuang, X. Feng, K. Müllen, Angew. Chem.
2014, 126, 1596.
Development of Energy-Efficient Thermal Management System for Proton Exchange Membrane Fuel Cell and Reformer
Authors: Sundar Pethaiah Sethu , Subiantoro Alison
Published: February 2020

The rising energy cost and limited supply of fossil fuel make it important for an alternative renewable energy source. Of all the alternatives, proton exchange membrane (PEM) fuel cell is very promising due to its high efficiency and zero emission characteristics. A fuel cell converts chemical energy to electricity by combining hydrogen with air. However, hydrogen storage poses a lot of practical challenges. Hence, alcohol based steam reforming systems are widely used for on-site hydrogen generation instead. During operation, a fuel reformer needs heating to maintain its temperature. At the same time, the fuel cell stack needs cooling to maintain its temperature. Currently, separate heating and cooling systems are used, resulting in an inefficient thermal management system.

In this study, a more efficient thermal management system is proposed. It incorporates a vapor compression refrigeration (VCR) system to a reformer - PEM fuel cell unit. A VCR system can be seen as a device that transports heat from one place to another with a very high efficiency. In this application, heat is removed from the stack and is transferred to the reformer. This method will save around 38% of energy as compared to the conventional thermal management system.
The Characteristics of New Synthesized Metal-Organic Framework-Based Catalysts for Fuel Cell Systems
Authors: Lei Lin , Lee Eon Soo , Zhuang Shiqiang , Nunna Bharathbabu
Published: February 2020

Metal-organic frameworks (MOFs), such as zeolitic imidazolate framework-8 (ZIF-8), are recently used as carrier for catalysts of fuel cell systems to enhance the performance of catalysts, because of its high porosity structure and good electrical conductivity. Different synthesis methods and doping ways have an impact on the structure and characteristics of MOF doped with catalysts. A new type of MOF-based catalyst, which is synthesized by using an innovative method, high energy wet ball milling with zeolitic imidazolate framework-8 (ZIF-8) and nitrogen doped graphene (N-G) as raw materials, is investigated in this work. The main purpose of this paper is to study the characteristics of the new synthesized catalyst. The physical, chemical and structural characteristics of new MOF-based catalysts are analyzed through XPS, XRD, SEM and STEM-EDS. Moreover, this work is moving forward to find out the reaction mechanism of the new material synthesized by high energy wet ball milling.
Lithium Battery Using High Conducting Emifsi-Doped Solid Polymer Electrolytes Process Under the Electric Field
Authors: Chang Alice Yi-han , Chu Peter Po-jen
Published: February 2020

Lithium-ion battery holds great promises for future energy storage purpose. However, traditional Lithium-ion battery uses liquid organic electrolytes which is flammable and leads to safety problems. In this work, we present a highly ion conducting membrane which is discovered by doping a nonvolatile conducting medium, ionic liquids (ILs) in solid polymer electrolytes (SPEs) prepared under external electric field(EF)  poling. The poling created aligned morphology in PVDF-HFP and PMMA blending system yield the long-range ordered but nearly totally amorphous domains where nonflammable ionic liquids is inter-dispersed to display unusually high Li+ transport with room temperature conductivity reaching over 10-3S/cm. The highest conductivity of 7.53x10-3 S/cm is observed for polymer electrolyte containing PMMA/PVDF-HFP (50/50 wt%, eV8E2L). The alignment by the external electric field not only altered the interaction between polymer components which suppressed PVDF-HPF crystallinity in the SPEs, it also improves mechanical strength of the membrane .The coin cell (R2032) using eV8E2L as the SPEs and LiFePO4 cathode shows fair half-cell performance and durable cycle stability. Under 0.1C-rate the half-cell displayed consistent discharge capacity of 140 mAh/g , without apparent capacity decay.

Figure 1
Self-Assembled LiNi1/3Co1/3Mn1/3O2 Nanosheets Cathodes with Excellent Electrochemical Performances
Authors: Feng Chuanqi
Published: February 2020

LiNi1/3Co1/3Mn1/3O2 nanosheets were prepared via a facile co-precipitation and hydrothermal method. The structure and morphology evolution mechanism was disclosed through temperature and time-dependent experiments. Tested as materials of Li-ion batteries, LiNi1/3Co1/3Mn1/3O2 nanosheets presented attractive electrochemical performances. The capacities were over 193 mAh·g−1 for initial charge, 189 mAh·g−1 after 100 cycles at 0.2C, and 155 mAh·g−1 after 400 cycles at 1C. The 1D nanosheets assembly interior endow this material efficient contact with electrolyte, short Li+ diffusion paths, and sufficient void spaces to accommodate large volume variation. The LiNi1/3Co1/3Mn1/3O2 with rationally designed nanostructures is a promising anode candidate for Li-ion batteries.

Figure 1
Silicon Non-Metal Compounds As New Promising Materials for Lithium Ion Batteries
Authors: Reinhold Romy , Stoeck Ulrich , Ahrens Eike , Eckert Jürgen , Kaskel Stefan , Giebeler Lars
Published: February 2020

Due to an increasing energy demand caused by an expanding global population and the rapid development of new technologies, a high priority to a further development of new battery systems is given. In fact, there is a great interest in Lithium Ion Batteries as they offer a high energy density and a high rate capability [1]. Owing to a high theoretical capacity silicon is a promising anode material to replace commercially used graphite [2]. The electrochemical energy storage originates from an alloying-dealloying mechanism where different lithium-silicon phases like Li12Si7, Li15Si4 or Li22Si5 were formed [2]. This mechanism conducts capacity fading caused by volume expansion during the insertion and extraction of lithium ions. Therefore, nanostructured silicon is expected to meet future criteria defined for new electrochemical energy storage systems.

A new promising way to produce silicon nanoparticles is the application of silicon non-metal compounds and their decomposition through an electrochemical in situ conversion mechanism. In addition, the non-metal serves as a Li-containing matrix that buffers the volume expansion during charging and discharging. Moreover, the synthesis of silicon non-metal compounds via planetary ball mill is environmentally benign and easy scalable.

Initial studies show that phase-pure produced silicon diphosphide (SiP2) is electrochemical active over a wide potential range. The first discharge cycle reaches a capacity closely to theory (about 3100 mAh/g). Continuous cycling is stable about 100 cycles. Cyclic voltammetry experiments give an insight into the behavior of the redox properties of materials which is in this case very similar compared to pure silicon. From this observation a similar reaction of silicon diphosphide as known from silicon is indicated. Ex situ XRD results confirm the proposed reaction mechanism and refers to the formation of lithium phosphide which serves as buffering matrix. The production of smaller particles is challenging and the large capacity fading after the first cycle needs to be explained and to be overcome. Both points are taken as prospective tasks.

[1] C.-M. Park, J.-H. Kim, H. Kim, H.-J. Sohn: Li-alloy based anode materials for secondary batteries. In: Chem. Soc. Rev. VI. 39, 2010, S. 3115–3141.

[2] S. Goriparti, E. Miele, F. De Angelis, E. De Fabrizio, R. P. Zaccaria, C. Capiglia: Review on recent progress of nanostructured anode materials for Li-ion batteries. In: J. Power Sources VI. 257, 2014, S. 421–443.
Metal Complex and Organic Compounds Modified Electrode Used As a Mediator for the Redox-Flow Batteries
Authors: Sato Yukari , Narita Ayumi , Kaneko Yuji , Negishi Akira , Nozaki Ken , Kato Tohru
Published: February 2020

Redox-flow batteries, which are using organic compounds, aqueous solution, and new metal complexes, have been actively investigated. Non -metal redox-flow batteries are strongly expected by the increasing in needs for low-cost, safe, and trusted energy storage applications. Both of redox active materials and cell systems of redox-flow batteries have made rapid and great progress in recent years. Redox-flow batteries are investigated frequently, and are now in a transition stage.

 Recently, redox-flow batteries using organic compounds and metal complexes (or inorganic materials) as active materials were investigated. In such cases, redox potentials and efficiencies of electron transfer of each active materials on the electrode surface will be quite important as with the stability of the active materials. If we can control the redox potentials of organic/inorganic active materials flexibly, we will be able to receive suitable systems.  

   The electrode modified with self-assembled monolayers having electrochemical active sites have been often adopted as mediator for controlling the redox reaction of other electro active species in the electrolyte solution. In our previous studies, ferrocene derivatives attached on the gold electrode worked as suitable mediator for the reduction of Fe(III) ion in solution (1). On the other hand, same ferrocene derivatives on the electrode did not work as the mediator of the K4Fe(CN)6 ion at all. Although redox potentials of both Fe(III) and K4Fe(CN)6 were ca. +0.4 V (vs. SCE) in the acidic solution (1M HClO4), ferrocene attached electrode only mediated for Fe(III) oxidation. Electrochemical properties of quinone/ hydroquinone modified electrodes were also reported previously (2) (3). In the case of quinone-modified electrode, the redox potential of quinone species was controlled stably by changing solution pH. We newly investigate suitable mediator attached on the electrode /substrate surfaces for constructing all organic-aqueous redox-flow battery.  

References

(1) Y. Sato, H. Itoigawa and K. Uosaki, "Unidirectional Electron Transfer at Self-Assembled Monolayers of 11-Ferrocenyl-1-undecanethiol on Gold", Bull. Chem. Soc. Jpn., 66, 1032 - 1037 (1993).

(2) Y. Sato, M. Fujita, F. Mizutani, and K. Uosaki, "Electrochemical Properties of 2-Mercaptohydroquinone Monolayer on Gold Electrode. Effect of Solution pH, Adsorption Time and Concentration of Modifying Solution", J. Electroanal. Chem., 409, 145 -154 (1996).

(3) S. Ye, A. Yashiro, Y. Sato, and K. Uosaki, “Electrochemical in situ FT-IRRAS Studies of Self-Assembled Monolayer of 2-(11- Mercaptoundecyl)hydroquinone”, J. Chem. Soc., Faraday Transaction, 92, 3813 - 3821 (1996).