bluuebunny/crossref_metadata_2025_split huggingface dataset:
Degradation of SOFCs by Various Impurities: Impedance Spectroscopy and Microstructural Analysis
Authors: Kikuchi Yuhdai , Matsuda Junko , Tachikawa Yuya , Shiratori Yusuke , Taniguchi Shunsuke , Sasaki Kazunari 
Published: February 2020

Introduction

SOFC is considered as a promising power generation system due to high electric efficiency and fuel flexibility. However, coal gas, for example, contains various impurities. In this study, siloxane, poisoning effect of siloxane to Ni-ScSZ cermet anodes is analyzed by applying Electrochemical Impedance Spectroscopy (EIS). Spectroscopy data are analyzed by the distribution of relaxation times (DRT) method[1] to investigate details of electrode resistance. Furthermore, microstructural analysis was made by electron microscopy.

Experimental

Electrolyte-supported cells with ScSZ (10 mol% Sc2O3
- 1 mol% CeO2-89 mol% ZrO2) plate (20 mmφ×0.2 mmt) were used in this study. Mixture of 56 wt.% NiO and 44 wt.% ScSZ was used for the anode and was sintered at 1300 oC for 3 h. Mixture of (La0.8Sr0.2)0.98MnO3 (LSM) and ScSZ with a weight ratio of 1:1 was used for the cathode. Electrode area was 8×8 mm2 and Pt mesh was used as the current collector. Figures 1 and 2 describe the experimental setup. Siloxane (decamethylcyclopentasiloxane) was supplied to the fuel cell using the bubbler setup. The fuel consisted of 97% H2 and 3% H2O. Cell temperature was 800oC. Table 1 shows the EIS conditions. EIS data analyzed by DRT enable the identification of electrode processes. FESEM-EDX was applied to investigate changes in the anode microstructure and composition after the cell performance tests.

Results and discussion

Figure 3 shows EIS spectra measured after 0h and 100h. Figure 4 shows the DRT result of the Fig. 3 data. Impedance semicircles, especially at the lower frequency, DRT peaks became larger with time. The DRT peak with relaxation time around 102~103 sec at 0h became wider, but the DRT peak around the 10-1~100 sec did not change. DRT peak around 10-1~100 sec may originate from the diffusion of H2 gas, that around 102~103 sec for charge transfer reaction and ionic transport[2][3]. Figure 5 shows EDX mapping of zirconium, silicon and oxygen. Ni particle on the anode surface is covered by silica. This reaction is considered as [4]:

[(CH3)2SiO]5+25H2O→5Si(OH)4(g)+10CO+30H2

(1)

Si(OH)4(g)→SiO2(s)+2H2O
(2)

Silica was formed under SOFC operating conditions at high temperature and high water vapour partial pressure. Therefore, cell performance degraded by inhibiting gas diffusion and covering by Ni particles with silica in the siloxane poisoning of Ni-based anodes.

References

[1] A. Leonide et al., Journal of The Electrochemical Society, 155(2008) B36-B41.
[2] T.H. Wan et al., Electrochimica Acta, 184 (2015) 483-499.
[3] V. Sonn et al., Journal of the Electrochemical Society, 155 (2008) B675-B679
[4] K. Haga et al., Journal of the Electrochemical Society, 155 (2008) B1233-B1239.

Figure 1
Synthesis and Characterization of CeO₂ for Use in Solid Oxide Fuel Cells
Authors: Mendoza Muñiz Diego Armando , Grishin Andrey , Cassir Michel , Ringuedé Armelle , Hinojosa Rivera Moisés , Chavez Carvayar José Álvaro 
Published: February 2020

Due to the problems with greenhouse gas emission, fossil fuels consumption and air pollution, solid oxide fuel cells (SOFC) are a promising power generation technology, because of its good efficiency and low emissions. The key challenge is to achieve a competitive balance between cost, efficiency and durability. The aim of this work is to develop capabilities in order to acquire state-of-the-art knowledge on the chemical compatibility between stainless steel AISI 316 that was used as a substrate and CeO₂ as interconnector coating, as well as exploring the relationship between the electrolyte and the interconnector. The aim of this work was to synthesize and characterize materials by different techniques in order to have more information about of microstructure and electrochemical properties that may eventually lead to performance improvements.
In this work we report the synthesis and characterization of CeO₂ and Yttrium oxide (Y2O3) the materials were obtained by chemical bath deposition (CBD) and atomic layer deposition (ALD) techniques. The crystalline structures were analyzed by X-ray diffraction, the elemental composition of these materials was obtained by Energy-dispersive X-ray spectroscopy, and the microstructure was analyzed by scanning electron microscope (SEM) we also performed the study of the electrochemical properties by impedance measurements over a wide temperature range of 200-900°C. A mud-cracking pattern was observed in the samples obtained by chemical bath deposition whereas this pattern was not present in the ALD samples.
Numerical Analysis of Ammonia-Fueled Planar Solid Oxide Fuel Cells
Authors: Kishimoto Masashi , Kume Tatsuya , Iwai Hiroshi , Yoshida Hideo 
Published: February 2020

Ammonia is receiving attention as a hydrogen carrier because of a number of advantages over other hydrogen carriers, such as greater hydrogen content, easy liquefaction and no carbon emission. Mass production process of ammonia has also been established and well-known as the Haber-Bosch process. Among the energy systems operated with hydrogen and hydrogen-containing fuels, solid oxide fuel cells (SOFCs) are one of the candidates that can be operated with ammonia-based fuels because they can decompose ammonia on their Ni-based anodes and produce hydrogen inside the systems; this can simplify the whole system configuration and realize cost reduction. In addition, the excess heat generation from the electrochemical reaction can be effectively utilized for the ammonia decomposition reaction.
Because the ammonia decomposition reaction is endothermic, temperature distribution on the cells is likely to be altered compared with the hydrogen-fueled SOFCs. Also, charge-transfer current distribution will be affected by the temperature distribution. To understand unique characteristics of ammonia-fueled SOFCs and to propose their appropriate operation conditions, numerical analysis is indispensable because of the difficulty in the direct measurement of physicochemical properties inside the cells. However, there are not many studies found in open literature where the characteristics of ammonia-fueled SOFCs are analyzed in detail by numerical analysis.
In this study, a numerical model of ammonia-fueled planar SOFCs has been developed. The model consists of a planar SOFC cell and fuel/air supply channels. Mass, momentum, energy and charge conservation equations are considered and coupled with the electrochemical reaction of hydrogen and the ammonia decomposition reaction. The ammonia decomposition rate per unit Ni-pore contact area in the Ni-YSZ anodes was developed in the authors’ group and implemented in the numerical model.
Distributions of the physicochemical properties, such as gas concentration, temperature and charge-transfer current, are analyzed and compared between the ammonia-fueled SOFCs and the hydrogen-fueled SOFCs. It was found that in the ammonia-fueled SOFCs the cell temperature first decreased in the upstream region by the endothermic decomposition reaction and then gradually increased towards the downstream, whereas in the hydrogen-fueled SOFCs the cell temperature monotonically increased in the flow direction. Also the peak in the charge-transfer current distribution was shifted towards the downstream in the ammonia-fueled SOFCs because of the altered temperature distribution.
Group IVA Oxide Surface Modification of LSCF Cathode Powders by Atomic Layer Deposition
Authors: Roeder Jeffrey F , Golalikhani Maryam , Zeberoff Anthony F , Van Buskirk Peter C , Torabi Alireza , Barton Joseph , Willman Carl , Ghezel-Ayagh Hossein , Wen Yeting , Huang Kevin 
Published: February 2020

La0.6Sr0.4Co0.2Fe0.8O3-δ (LSCF) powders have been modified by atomic layer deposition (ALD) with Group IVA based oxides, including zirconia, hafnia, and cobalt doped compositions. Amide (tetrakis(dimethylamido)zirconium and hafnium) and amidinate (bis-(N,N-disopropylacetamidinato)cobalt) precursors were used to treat 0.3 mm nominal diameter LSCF powders at 240°C using water as a co-reactant. The effect of the number of ALD cycles and level of Co additions have been examined up to 30% Co. The morphology and physical properties of sintered samples were similar to untreated powders with a modest shift to lower porosity and pore volume, but well within the desired range of microstructural properties. Cobalt additions lowered overall polarization in symmetrical electrochemical cells for zirconia based compositions. Hafnia based compositions also had significantly improved electrochemical performance.
Evaluation of the Influence of Gadolinium Doped Ceria Particle Size on the Electrochemical Performance and Microstructure of Nickel-Gadolinium Doped Ceria Anodes
Authors: Miyahara Kazuki , Sciazko Anna , Shimura Takaaki , Jiao Zhenjun , Shikazono Naoki 
Published: February 2020

Last years, composite anodes consisted of nickel-gadolinium doped ceria (Ni-GDC) cermet gained a lot of attention as they have potential to be a beneficial solution for the intermediate temperature solid oxide fuel cells. In the range of temperatures below 700oC, a GDC cermet is characterized by a higher ionic conductivity compared to conventionally used yttria-stabilized zirconia (YSZ) cermet. Moreover, with the use of GDC as the mixed ionic-electronic conductivities (MIEC) material, electrochemical reaction sites are not restricted to triple phase boundaries (TPBs), but also extended to the double phase boundaries (DPBs) which consist of GDC/pore interfaces. Therefore, microstructure of electrodes has the crucial effect for the performance of the SOFCs and the evaluation of its changes are required to predict the deterioration of cell performances. Moreover, the precise mechanism behind observed microstructural reaction kinetics has not been fully revealed yet. For the further understanding of the electrochemical reaction kinetics, evaluation of the influence of TPB and DPB reaction for the overall electrochemical performance of MIEC anodes is required.
In this paper, the influence of the initial microstructure of Ni-GDC anode on the electrochemical performance and its deterioration after 100-h operation are investigated using electrolyte supported cells. The initial microstructure of anode is determined by the different aspect ratios and sizes of GDC powder used in the fabrication of cells. Four types of SOFC anodes were fabricated with the initial composition of NiO:GDC=60:40vol%.
The microstructural parameters of the fabricated anodes have been investigated by the focused-ion-bean – scanning electron microscopy tomography and 3D reconstruction of the representative structures. The parameters such as TPB length, surface area, porosity, tortuosity factor and connectivity have been quantitatively evaluated. From the observed microstructural changes and cell performances, contribution of the Ni-GDC microstructure and electrochemical reaction kinetics on anode performance are discussed.
Operando Vibrational Studies of Ni Electrode Degradation and Restoration in SOFCs Operating with Steam Reformed Methane
Authors: Walker Robert A , Owrutsky Jeffrey C. , Eigenbrodt Bryan C. 
Published: February 2020

Two primary mechanisms responsible for Ni-based anode degradation in SOFCs are carbon accumulation (or coking) and reduction/oxidation cycling. Numerous strategies have been developed to suppress carbon formation on SOFC anodes including steam reforming and doping the anodes themselves with materials intended to prevent carbon growth. Once coking begins, however, removing carbon can cause even more anode degradation due to partial oxidation of the Ni anode itself. In experiments described below, operando Raman spectroscopy coupled with EIS and voltammetry measurements examine the propensity of carbon deposits to form from both methane and steam reformed methane in electrolyte supported SOFCs operating at temperatures between 700˚C and 800˚C. Vibrational spectra acquired from functioning cells shows that steam reformed methane limits but does not eliminate carbon accumulation. Changes in the mid- and low-frequency EIS data correlate closely with the spectroscopic observations and suggest that carbon accumulation affects both fuel oxidation activation energies as well as mass transport through the anode. Removing carbon electrochemically also induces Ni oxidation as reported directly in vibrational Raman experiments. Subsequent ex-situ experiments show a heterogeneous distribution of species throughout the anode and evidence of irreversible material degradation at the electrolyte/anode boundary. Steam by itself, however, proves to be remarkably effective at removing carbon while leaving the Ni anode largely intact. The ability of steam to remove carbon, presumably through solid carbon gasification, while allowing the Ni to remain in its elemental state shows microscopic reversibility of Ni oxidation and Ni reduction by H2O/H2 strongly favors reduction. Taken together these studies present a clear roadmap for restoring Ni-based SOFC anodes to their original operational state without forcing repetitive redox cycling that ultimately results in cell failure.
Modified LSCF Anode for Direct Conversion of Propane to Propylene in Proton Conducting Fuel Cell
Authors: Xu Yunjie 
Published: February 2020

Using impregnation method to modified anode material LSCF(LaSrCrFe) to make it has PDH(propane dehydrogenation) catalytic activity and it can direct cogenerate electricity and propylene in proton conducting fuel cell.
LSCF is highly modified and has high surface area. And using PtGa and PtCo solution to treat anode material provides LSCF highly catalytic activity. Under Miro-reactor test, it shows that modified LSCF has very high propane conversion and propylene selectivity and it also has very promising stability and can keep catalyst stable more than 10 hours without steam treat. Different characterization methods are used. From TEM-EDX, it shows that PtGa nanoparticle cover on surface of LSCF and particle size is less than 10nm, and from EDX, it shows that even in nano-sclale, each element of LSCF is uniform distribution. And it shows in XRD pattern that LSCF doesn’t have any other phase. This modified material and method to treat anode material can highly improve anode material performance and give a promising future of directly convert fuel to electric.
Electrochemcial Performances of La-Doped SrTiO3 Anode Materials for Intermediate Temperature-Solid Oxide Fuel Cells
Authors: Jo Suyeon , Yang Jayoon , Park Jun-Young 
Published: February 2020

Anode plays a very important role in the performance of solid oxide fuel cells (SOFCs) [1, 2]. In order to improve the cell performance proper anode materials should be selectd with suitable cell fabrication techniques. La-doped SrTiO3 (La0.4Sr0.6TiO3, LST) has received many attentions as an alternative anode material to state-of-art Ni-cermets anode for solid oxide fuel cells (SOFCs), because of its high redox stability, good electrical conductivity, and similar thermal expansion properties of yttria-stablized zirconia (YSZ) elecrolytes [3, 4]. Nowdays, decreasing the operating temperature of SOFCs down to intermediate temperature (IT) range (less than 800) is required to improve long-term durability and operational stability with economical advantages [5]. Hence, in this work, LST anode materials are fabricated with the highly conductive Nd0.1Ce0.9O2 (NDC) electrolytes and characterized to investigate the feasibility of SOFCs at the IT. In addition, LST is composited with the NDC to improve the ionic conductivity and decrease the thermal expansion mismatch of anode materails to the electrolyte. The Electrochmical impedance spectra (EIS) analysis shows that the polarization resistance of LST-NDC composite anode decreases with increasing of NDC concentrations, and 60:40 (LST:NDC in weight fraction) exhibits the lowest polarization resistance value at 650. The maximum power density of LST-NDC composite anode-cell is 143 mW cm-2 at 650, and thus we confirm the possbilty of LST as an anode material for the application of IT-SOFCs.

References

[1] S. Park, J.M. Vohs, R.J. Gorte, Nature 404 (2000) 265.
[2] S. Tao, J.T.S. Irvine, Nat. Mater. 2 (2003) 320.
[3] Ahmed D. Aljaberi and John T. S. Irvine. J. Mater. Chem. A. 1 (2013) 5868.
[4] Azra Yaqub, Cristian Savaniu, Naveed K. Janjuab and John T. S. Irvine, J. Mater. Chem. A, 1 (2013) 14189
[5] K.T. Lee, E.D. Wachsman, Science 334 (2011) 935.

Keywords:
anode-supported solid oxide fuel cells, Ni-free anode material, redox stability, La-doped SrTiO3, Nd0.1Ce0.9O2 electrolyte.

*
Corresponding author: Tel.: +82-2-3408-3848; Fax: +82-2-3408-4342
E-mail address: jyoung@sejong.ac.kr (J.-Y. Park)
Influence of Operating Parameters and System Design on Efficiency of Biomass and Biogas Based SOFC Systems
Authors: Herrmann Stephan , Hauck Maximilian , Geis Michael , Fendt Sebastian , Gaderer Matthias , Spliethoff Hartmut 
Published: February 2020

With the recent COP 21 declaration many countries have dedicated themselves to a clear path towards decarbonization. This requires major installation of wind and solar power. However, these only provide intermittent electricity. Thus, balance power has to be provided, ideally from renewable resources. Currently only biomass seems to be available in large enough quantity to provide significant balancing power. A wide range of biomass feedstocks can be made available for power generation for example via anaerobic digestion or thermo-chemical gasification. However, resources are still limited. Hence, in order to maximize its potential the biomass has to be used at the highest possible efficiency. Electrochemical conversion, especially in SOFC, in general offers very high efficiency. However, also in SOFC systems the choice of the optimal system design and operating parameters can make a big difference.
The presented work investigates utilization of biogas and syngas from biomass gasification in different system designs. This is done using a thermodynamic SOFC model built in Aspen Plus, which has been validated against literature data. A comparison to cell and stack performance of the well known manufacturers Fuel Cell Energy and Forschungszentrum Jülich is presented. It is shown that at identical operating conditions the model shows slightly worse performance than the real stacks.
With the model, the influence of different fuel pre-treatment and pre-reforming options are compared at a fixed stack size. Furthermore the effect of anode offgas recirculation, as well as the choice of fuel utilization, oxidant, operating temperature and pressure are investigated. During the analysis operating conditions prone to the risk of carbon deposition are excluded. Also the impact on the balance of plant is taken into account. Results show, that depending on the fuel, system design and parameters the electrical efficiency of the fuel cell alone can vary between 35 and 71%. From this, depending on the system parasitic consumption and losses of up to 8% points have to be subtracted. Thus, net AC efficiencies reach 30 to 63%.
Finally a new system design and operating regime is proposed, which can significantly raise the DC efficiency while reducing the parasitic consumption by adjusting the gas treatment and operating parameters. Modelling results of new design show net AC system efficiencies of up to 72%.
High Energy Rechargeable Metal Free Na-Ion Seawater Batteries: Phosphorus/Carbon Composite As a Promising Anode Material
Authors: Kim Yongil , Hwang Soo Min , Yu Hyein , Kim Youngsik 
Published: February 2020

A new energy conversion and storage system, named ‘seawater battery’, has recently been introduced in electrochemical academia. The recently introduced seawater battery concept is an eco-friendly energy storage system that offers appealing electrochemical performance. Its radically innovative design, compared to conventional lithium-ion batteries, makes use of seawater as an almost infinite sodium reservoir for the positive electrode (catholyte) and, thereby, avoids the use of expensive, scarce, and toxic elements like nickel and cobalt.
Herein, we report a phosphorus/carbon composite anode material which was successfully employed as the anode in seawater batteries, showing good cycling stability with high reversible capacities exceeding 920 mAh g-1
composite with coulombic efficiencies over 92% for 80 cycles and good rate capabilities. These results show that the seawater battery system would be a new way to overcome the limitations caused by the use of high-capacity alloying reaction-based anodes in existing batteries with a closed system. The full cell system configuration problem caused by low coulombic efficiencies using alloying reaction anode materials were solved through the seawater batteries by supplying unlimited Na-ions. Therefore, these results represent an important step toward practical application of the sodium-based seawater battery technology.
Coupled Electrochemistry and Mechanics in Mesoscale Simulation of NMC Cathodes
Authors: Ferraro Mark E. , Trembacki Bradley L. , Brunini Victor E. , Noble David R. , Roberts Scott A. 
Published: February 2020

Analysis of lithium-ion battery performance and degradation presents many multi-physics challenges as we look to understand the plethora of coupled mechanisms occurring within a single electrode. Electrochemical reactions in the active material introduce mechanical stresses as cathode particles swell upon lithium intercalation. Over numerous charge-discharge cycles, this behavior can lead to mechanical degradation, and thus, capacity fade. The presence of a secondary conductive binder phase additionally complicates these mechanisms, altering ionic and electronic conduction pathways, masking available surface area for reaction, and buffering mechanical contacts. As these mechanisms are largely governed by effects at the mesoscale (structures of 100s of active material particles joined by binder), we focus our computational efforts on resolved cathode mesostructures.
In this talk, we will present a variety of different simulations which study half-cell performance at constant current discharge. The Conformal Decomposition Finite Element Method (CDFEM) algorithm is used to generate conformal mesoscale meshes of particle, conductive binder, and electrolyte phases, derived directly from 3D computed tomography data of NMC333 cathodes. This mesoscale approach for coupled electrochemical and mechanical simulations allows exploration of phenomena at the particle scale, while also providing insight on macroscale effective properties. Here, we will discuss the manifestation of local stresses from lithiation-induced swelling, as well as the impact of concentration gradients and local mesostructure on half-cell discharge curves and other macroscopic behavior. Additionally, we will investigate the influence of manufacturing processes on cell performance by studying a range of calendering pressures and binder loading fractions.
Sandia National Laboratories is a multi-mission laboratory managed and operated by National Technology and Engineering Solutions of Sandia, LLC., a wholly owned subsidiary of Honeywell International, Inc., for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-NA0003525.