bluuebunny/crossref_metadata_2025_split huggingface dataset:
Method for Studying High Temperature Aqueous Electrochemical Systems: A Self Pressurized Autoclave
Authors: Holm Thomas , Dahlstrøm Per Kristian , Sunde Svein , Harrington David A. , Seland Frode 
Published: February 2020

Understanding oxidation kinetics and reaction mechanism at elevated temperatures is paramount to making efficient fuel cells that can run at temperatures higher than 100oC. We describe a method that allows for studies of aqueous electrochemistry at temperatures above the normal boiling point of water, and this system is used to study potential fuels for direct fuel fed fuel cells. Two alcohols with very different partial pressures at temperatures above 100oC are used in this study: methanol and glycerol. A self-pressurized glass autoclave heated in an oil bath is used for this purpose, and a model of the autoclave is shown in Fig. 1a. Slow ramping of the temperature allows for efficient data acquisition by using cyclic voltammetry up to 140oC, exemplified by Fig. 1b, and kinetic parameters such as onset potentials, Tafel slopes and activation energies are found and discussed for the relevant fuels. For methanol oxidation, dissociative water adsorption plays a key limiting role in the total reaction of methanol to CO2 at all temperatures. For glycerol oxidation, some partial oxidation products do not require an oxygen donor in the form of adsorbed water for their formation. This is deemed to play a fundamental role giving a large drop in overpotential at temperatures above 110oC, and making glycerol a potential fuel cell candidate at these temperatures. Therefore, a partial oxidation of glycerol in a fuel cell offers a potential method for a combined fuel cell and value-adding process for abundant glycerol.

Figure 1
Phase Stability and Electrochemical Characterization of Solid Oxide Fuel Cell Cathodes Containing K2NiF4 Structured Oxides
Authors: Cetin Deniz , Poizeau Sophie , Gopalan Srikanth 
Published: February 2020

K2NiF4 -structured oxides, e.g. La2NiO4, exhibit facile kinetics for oxygen surface exchange and comparable electrical conductivity to perovskite-type oxides. Even though they exhibit great potential for replacing the perovskite-type alternatives in SOFC cathodes due to their superior oxygen exchange kinetics, K2NiF4 type-oxides suffer from phase stability issue when in contact with doped-cerias, commonly used as the ionic conducting component in many composite cathode materials.
In this study, we reveal a very effective methodology to stabilize the chemical composition of composite cathodes containing K2NiF4 -structured oxides containing doped-ceria. Phase stability studies were conducted to verify the retention of the K2NiF4 -structured oxides after high temperature processing of the electrode. Electrical conductivity measurements, dilatometry analysis, and X-ray diffractometry as functions of temperature, oxygen partial pressure were conducted over wide compositional windows of interest to identify new high performance cathode compositions.
Button cells featuring the compositions identified through these studies were prepared via tape casting and sintering. The electrochemical performance of these button cells were analyzed through polarization modelling and impedance spectroscopy in the temperature range 700 to 900°C and cathode side oxygen partial pressures between 5x10-2 and 1 atm. The effect of cathode microstructure and thickness on the cell performance is also discussed.
Long-Term Stability of Anode-Supported Solid Oxide Fuel Cells with a Co-Sintered Cathode Backbone and Infiltrated La0.95Co0.4Ni0.6O3 (LCN) Electro-Catalyst
Authors: Küngas Rainer , Veltzé Sune , Ovtar Simona , Xu Yu , Simonsen Søren Bredmose , Kwok Kawai , Frandsen Henrik Lund , Samson Alfred , Zielke Philipp , Kiebach Wolff-Ragnar 
Published: February 2020

Infiltration is a fabrication method that is offering potentially significant improvements in cell performance at reduced materials and fabrication costs, especially when combined with co-sintering. However, important questions regarding the long-term performance and microstructural stability of infiltrated electrodes, as well as the mechanical properties of such electrodes have remained unanswered.
Here, we present the results of a three-year project, where large footprint (12 × 12 cm2) anode-supported solid oxide fuel cells with a co-sintered cathode backbone and infiltrated La0.95Co0.4Ni0.6O3 (LCN) cathode active phase were developed and thoroughly characterized. We report the initial and long-term (1500+ hours) performance of infiltrated cathode backbone cells hours running with 40% H2O/H2 as fuel and ambient air as oxidant, coupled with a scanning transmission electron microscopy - energy dispersive X-ray spectroscopy (STEM-EDS) investigation of microstructural changes in the infiltrated electrodes (Fig. 1). Some electrodes were further aged at elevated temperatures (750- 900°C) for periods reaching up to 5000 hours, while following changes in the electrode properties with scanning electron microscopy (SEM), Brunauer-Emmett-Teller (BET) surface area, and van der Pauw in-plane conductivity measurements. Finally, the mechanical properties of co-sintered cathode backbone cells were determined in four-point bending tests carried out both at room temperature and at 800°C in air. To our knowledge, this is the first time infiltrated cells have been characterized in such detail.
The results of the study suggest that significant coarsening of the infiltrated phase takes place upon long-term testing and aging, resulting in decreased active surface area, reduced in-plane electronic conductivity, increased electrode impedance, as well as re-arrangement of the electro-catalyst in the porous backbone. The Weibull strength of the cells at room temperature was 400 MPa with a Weibull modulus of 12. Both the strength and the modulus were found to be lower at elevated temperature.
This study was funded by EUDP (Danish Energy Agency) project 64012-0225 “SOFC Accelerated – Development to Accelerate Field Demonstrations”.

Figure 1. STEM-EDS maps of infiltrated LCN cathodes after infiltration (left) and after (right) 1500-h cell-testing.

Figure 1
Fabrication of Thin Film Layer Between the Cathode and Electrolyte of Solid Oxide Fuel Cell By Using a Spin Coating Method
Authors: Jang Inyoung , Kim Chanho , Kim Sungmin , Jung Yeongil , Yoon Heesung , Paik Ungyu 
Published: February 2020

Solid oxide fuel cell has been considered as a promising future energy generating system due to its high efficiency and zero-emission of pollutants when hydrogen gas was used as a fuel. There have been numerous efforts to increase the amount of generated power of the cell for many years. In this study, thin film layer of Lanthanum, Strontium and Barium doped ceria (La0.75Sr0.2Ba0.05)Ce0.825O2
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δ was fabricated by using a spin coating method to enhance the bonding property between the cathode and electrolyte layer, and it leads to the improvement of the cell property. The fabrication of (La0.75Sr0.2Ba0.05)Ce0.825O2
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δ layer on the gadolinium doped ceria (GDC) electrolyte layer was confirmed by energy dispersive X-ray spectroscopy (EDS) measurement. The thickness of thin film layer was 150nm~300nm and its cross section was checked by scanning electron microscopy(SEM). Power density of the cell was about 540mW/cm2 at 650℃ and its value was almost twice higher than the cell which didn’t have the (La0.75Sr0.2Ba0.05)Ce0.825O2
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δ layer. Impedance spectroscopy of the cell was measured by electrochemical measurement equipment and its ohmic resistance was lower than the cell without thin film layer, as expected.

Figure 1
High Performance Cross-Linked Composite Gel Polymer Electrolyte Using Mesoporous and Reactive SiO2 Nanoparticles for Lithium-Ion Polymer Cells
Authors: Shin Won-Kyung , Park Myunsoo , Kim Dong-Won , Kim Young Rae 
Published: February 2020

The rapidly expanding use of rechargeable lithium-ion batteries has led to intensive research on electrolyte systems with high electrochemical performance. However, current lithium-ion batteries have risks associated with leakage and fire hazards due to the high flammability of the organic solvents. In addition, the polyolefin separators used in lithium-ion batteries may shrink and even melt at elevated temperatures, which may cause a short circuit between the two electrodes in cases where unusually high heat is generated. Therefore, there is a pressing need for safer and more reliable electrolyte systems. In this work, a cross-linked composite gel polymer electrolyte was prepared and applied to lithium-ion polymer cells as a safer and more reliable electrolyte. Mesoporous SiO2 nanoparticles containing reactive methacrylate groups as cross-linking sites were synthesized and dispersed into the fibrous polyacrylonitrile membrane. They directly reacted with gel electrolyte precursors containing tri(ethylene glycol) diacrylate, resulting in the formation of a cross-linked composite gel polymer electrolyte with high ionic conductivity and favorable interfacial characteristics. The mesoporous SiO2 particles also served as HF scavengers to reduce the HF content in the electrolyte at high temperature. As a result, the cycling performance of the lithium-ion polymer cells with cross-linked composite gel polymer electrolytes employing methacrylate-functionalized mesoporous SiO2 nanoparticles was remarkably improved at elevated temperatures as well as ambient temperature.
Surface Structure Engineering of Cu Thin Films for Electrochemical CO2 Reduction
Authors: Hahn Christopher , Hatsukade Toru , Vailionis Arturas , Higgins Drew Christopher , Nitopi Stephanie Anne , Feaster Jeremy T , Jongerius Anna L , Jaramillo Thomas F 
Published: February 2020

Global dependence on fossil fuels as energy sources and the alarming increase of greenhouse gas emissions has necessitated the development of carbon-free and carbon-neutral renewable energy sources for the future. The sequestration of CO2 emissions along with subsequent electrochemical reduction into fuel products, forms a carbon-neutral synthetic fuel cycle which could potentially be streamlined into existing fuel infrastructures. To date, only Cu has displayed any propensity as a catalyst to electrochemically reduce CO2 into longer chain hydrocarbons. Previous studies on Cu single crystals have shown large facet sensitivities for electrochemical CO2reduction product selectivity. The aim of our research is to utilize these surface structure motifs to design active and selective catalysts that are amenable to device integration.
To this end, we use physical vapor deposition to synthesize Cu thin films in both low and high Miller index orientations for electrochemical CO2 reduction. X-ray pole figures demonstrate that Cu thin films can be epitaxially grown in the <100>, <111>, and <751> orientations by utilizing the orientation of the single crystal substrate. The different Cu thin film orientations were tested for their CO2 reduction activity and selectivity using electrochemical measurements in tandem with gas phase (gas chromatography) and liquid phase (nuclear magnetic resonance) product detection methods. Here, we will demonstrate how surface structure engineering can guide selectivity for C-C coupling and oxygenate formation during electrochemical CO2 reduction.
(Invited) Electrosynthesis of Ammonia Using Intermediate Temperature Solid Electrolyte Membranes
Authors: Garzon Fernando H , Benavidez Angelica D , Tsui Lok-kun , Kreller Cortney R , Kim Yu Seung , Mukundan Rangachary , Balagopal Shekar 
Published: February 2020

The industrial synthesis of ammonia from N2 and H2 via the Haber-Bosch process represented a transformational change in chemical production for humanity. It serves as fertilizer and a feedstock for nitric acid, amine and explosives synthesis. Ammonia also show promise as a carbon free fuel with a high energy density >4 kW/l and a modest liquefaction pressure. Unfortunately, the conventional production of ammonia is very energy intensive process using approximately 1.4% of the world’s energy production. It would be highly desirable to produce NH3 from renewable resources such as wind and solar. The Haber-Bosch process today uses natural gas as the hydrogen source, emitting large amounts of green house gases with 1.8kg of CO2 per kg of NH3. The process economics dictate very large reactors and separation systems, consequently the technology does not downscale well to small-sized plants, nor does it work well with interruptible energy supplies.
The electrosynthesis of ammonia is highly attractive for small plant scaling and high theoretical energy efficiency. Many scientific challenges exist today towards achieving efficient electrochemical ammonia production. The dinitrogen bond is one of the most stable (946kJ/mole) diatomic bonds in nature. Efficient bond breaking via associative or dissociative mechanisms is a major challenge. Parasitic energy losses due to dihydrogen evolution have to be minimized by appropriate catalyst design. The keys to successful implementation of a new ammonia electrosynthesis process are to develop and optimize new intermediate temperature materials for electrolytes and electrocatalysts, and to demonstrate improved efficiency of scalable ammonia electrosynthesis concepts.
Past research eforts have focused primarily on the use of proton conducting electrolytes at typically high temperatures, >600°C, or molten salt systems were protonation of nitrogen occurs via the formation of nitride ions [1]. We are pursuing intermediate temperature, 150-300°C, electrochemical processes for efficient storage of electrons in N-H bonds in a DOE-EERE-ARPA-e sponsored program. We are developing ceramic and composite ceramic polymer electrolytes and novel electrocatalysts with low hydrogen evolution rates for electrochemical ammonia synthesis. Specially tailored tin pyrophosphate-polyphosphate-polymer membranes appear to be well suited for the application.
References:

C. J. van der Ham, M. T. Koper , D. G. Hetterscheid , Chem. Soc. Rev., 2014, 43, 5183
Electrochemical Impedance Spectroscopy on Industrially-Relevant Solid Oxide Electrolyzer Cell Stacks: A Powerful Tool for in-Situ Investigations of Degradation Mechanisms
Authors: Zielke Philipp , Høgh Jens Valdemar Thorvald , Chen Ming , Kiebach Ragnar , Küngas Rainer , Blennow Peter , Hjelm Johan , Hendriksen Peter Vang 
Published: February 2020

In the current efforts of moving energy production to renewable sources, wind and solar energy are widely considered as the key technologies to cover our growing demands. However, the fluctuating nature of these sources requires a flexible energy system and storage technologies to ensure that energy services can be covered in a stable and affordable manner. One promising solution is the synthetic fuel production by solid oxide electrolyzers. Electricity can be stored in a power-to-gas process during times of excess electricity production and then further converted to liquid fuels for e.g. transportation, or at high demands converted back to electricity by either conventional power plants or fuel cells.
One of today’s biggest hurdles for a successful commercialization of solid oxide electrolyzers is the stack’s lifetime with current industry targets in the order of five to ten years. To identify and quantify the different degradation mechanisms sensitive in-situ analysis tools are needed. On single cell level, electrochemical impedance spectroscopy (EIS) is a well-established diagnostics tool. On stack level EIS has been shown to be more difficult because of geometrical restrictions of the stack design and significantly lower resistances due to the larger active cell area. Nevertheless, it is becoming a more and more important technique for stack diagnostics.
Here we present impedance spectroscopy results of two solid oxide stacks provided by Haldor Topsoe A/S. The first stack was a 14-cell stack (Delta design) specifically optimized for EIS measurements, while the other stack was an 8-cell stack (TSP-1 design), where impedance measurements were carried out without major modifications to the stack. The individual cell voltages were monitored simultaneously by EIS during up to 2000 hours in electrolysis within the ForskEL project 2015-1-12276 “Towards Solid Oxide Electrolysis Plants in 2020”, funded by Danish Energet.dk. The analysis provides valuable insight into the degradation processes which could not have been obtained by current-voltage-data alone.
(Invited) Reversible Operation of Solid Oxide Cells for Sustainable Fuel Production and Solar/Wind Load-Balancing
Authors: Graves Christopher , Villarreal Diego , Myrdal Jon S. G. , Jensen Søren Højgaard , Chen Ming , Hendriksen Peter Vang , Mogensen Mogens Bjerg 
Published: February 2020

The solid oxide electrochemical cell (SOC) is a promising candidate for large-scale energy storage. In electrolysis mode it stores renewable electricity as chemical energy in the form of fuels like hydrogen and hydrocarbons, and the same cell can be operated in the reverse direction to produce electricity from fuels – either previously stored fuels or from an external supply e.g. natural gas or biogas. This reversibility combined with fuel-flexibility is unique among energy storage technologies like closed-system batteries and single-direction electrolyzers. However, few studies have been conducted with focus on fundamentals or applications of bi-directional operation. This presentation will highlight our recent developments in applying reversible SOCs (RSOCs) for renewable energy storage with respect to cell and stack testing, cell and system design, and techno-economic analysis.
At the cell level, long-term testing has shown that improved stability can be achieved by reversible operation compared with steady-state electrolysis operation. Further, we have developed novel Ni-free fuel-electrodes that both outperform conventional Ni-based electrodes and do not catalyze carbon deposition, which opens the door to advanced applications of RSOCs that utilize carbonaceous fuels.
At the stack level, we have demonstrated operation that follows real-world time-series electricity supply and demand data, considering a 100% renewable energy scenario where wind power is the only power supply. When the wind power supply exceeds demand, the RSOC stack produces syngas via co-electrolysis of CO2 and H2O. Part of the syngas is converted to methanol downstream in the system to meet the demand of transportation vehicles, and the rest is stored for electrical load balancing by conversion back to electricity in fuel cell mode when electricity demand exceeds the wind power supply.
At the system level, techno-economic analyses and system designs for different scales and applications have been realized. A simulation of an RSOC system that uses real-world time-series market prices for electricity and natural gas in Denmark to decide when to operate in electrolysis mode (buying electricity and selling methane) or fuel-cell mode (buying gas and selling electricity) shows the advantage of a reversible system and the changing operating profile as the fraction of wind power supply grows. Finally, we discuss the potential for systems with novel chemistries and components to compete with state-of-the-art rechargeable batteries with respect to cost and round-trip efficiency.
Physically Based Impedance Modelling of Ni/8YSZ-Cermet Anodes
Authors: Dierickx Sebastian , Weber André , Ivers-Tiffée Ellen 
Published: February 2020

Electrochemical impedance spectroscopy (EIS) is an indispensable tool to investigate the polarization processes in complex electrochemical systems such as Solid Oxide Cells (SOC), which can be operated in both fuel cell and electrolysis mode. We have introduced a methodology to analyze the measured impedance spectra by the distribution of relaxation times [1] and a subsequent Complex Non-linear Square (CNLS) approximation to an equivalent circuit model (ECM) [2] in order to identify and quantify the individual contribution of different loss mechanisms. It has been demonstrated, that electrochemical properties of SOCs operated in fuel cell mode and electrolysis mode can be described by the same ECM [3].
The complex anode electrochemistry is one major loss mechanism that highly affects the performance and durability of SOCs. Porous Ni/8YSZ anodes provide a large number of electrochemically active triple phase boundary (TPB) points, where the electrooxidation of hydrogen couples the electronic, the ionic and the gaseous transport paths. A basic equivalent circuit element designed to describe this configuration is the transmission line model (TLM) [4]. The corresponding TLM deconvolutes the contribution of (i) the ionic transport through the 8YSZ-matrix ,
(ii) the electronic transport through the Ni-matrix and (iii) the charge transfer reaction at the TPB z (fig. 1).
In this study the established ECM [2] for anode supported cells (ASC) is extended by a physically meaningful TLM in order to describe the anode electrochemistry. The required model parameters are obtained from EIS measurements on patterned model anodes [5], 4-point DC conductivity measurements on electrolyte bulks and microstructure properties extracted from FIB-tomography [6] (fig. 1). Using this approach the number of free fitting parameters can be reduced to one. The model has been validated by EIS measurements for a broad range of operation conditions such as temperature and gas composition.
We will present a detailed study on the development and parameterization of the TLM model, as well as the temporal evolution of the abovementioned processes (i) to (iii) during durability tests.

References

[1] H. Schichlein, et. al., J. Appl.
Electrochem., vol. 32 (8), 875-882 (2002).
[2] A. Leonide, et. al., ECS Trans., vol. 19 (20), 81-109 (2009).
[3] J.-C. Njodzefon, et. al., J. Electrochem. Soc., vol. 160 (4), F313-F323 (2013).
[4] V. Sonn, et. al., J. Electrochem. Soc., vol. 155 (7), B675-B679 (2008).
[5] A. Utz, et. al., J. Electrochem. Soc., vol. 157 (6), B920-B930 (2010).
[6] J. Joos, et. al., Proc. 10th EU SOFC Forum, A1006 (2012).

Figure 1