bluuebunny/crossref_metadata_2025 huggingface dataset:
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
Measurement of Chemical Potential in Bcy Electrolyte with Varying Thickness and Configuration Using Embedded Reference Electrodes
Authors: Bae Seon Yeong , Lim Hyung-Tae
Published: February 2020

The correlation between internal chemical potential, and durability of anode-supported BCY (yttria-doped barium cerate) electrolyte cells, was investigated as a function of electrolyte thickness and configuration. Internal hydrogen and oxygen chemical potentials were measured using embedded Pt probes. As the electrolyte thickness decreased, the internal chemical potential became dominated by the gases surrounding the cathode, indicating that the thin BCY cell may be vulnerable to water vapor produced at the cathode during operation. BCY cells with BZY (yttria-doped barium zirconate) protecting at the cathode side (bi-layer cells) showed a small chemical potential variation through the electrolyte region close to the electrode side, indicating significant electronic conduction.Constant-current tests were conducted on thin (~ 10 µm) and thick (~ 35 µm) BCY single layer cells, and also on BCY-BZY bi-layer cells, especially under negative voltage conditions. Consistent with the results of the internal chemical-potential measurements, the thin BCY single layer cell showed a significant rate of degradation due to changes in BCY composition in the electrolyte and cathode, while the thick BCY single layer cell showed much better durability, regardless of the sign of cell voltage. The bi-layer cell was stably operated under any severe operating conditions, because of the BZY protecting layer against water vapor’s attack and its significant electronic conduction close to the cathode/electrolyte interface. Thus, the present work shows the effect of BCY electrolyte thickness and configuration on the durability of BCY based cells, in terms of their internal chemical potential.
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
-
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
-
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
-
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
(Invited) Characterization of Thermally and Cathodic Polarization Induced LSM Electrode/YSZ Electrolyte Interface of Solid Oxide Fuel Cells By Combined FIB-STEM Techniques
Authors: Jiang San Ping , Li Na , He Shuai , Chen Kongfa , Cheng Yi , Dodd Aaron , Saunders Martin
Published: February 2020

In high temperature solid oxide fuel cells (SOFCs), electrode/electrolyte interfaces play an ultimate role in the electrocatalytic activity and durability of the cells. In this study, thermally and electrochemically induced electrode/electrolyte interfaces were investigated on pre-sintered and in situ assembled La0.8Sr0.2MnO3 (LSM) electrode on Y2O3-ZrO2 (YSZ) electrolyte, using focus ion beam and high resolution scanning transmission electron microscopy (FIB-STEM). The results indicate that thermally induced interface is characterized by convex contact rings with depth of 100-400 nm and diameter in agreement with the particle size of pre-sintered LSM electrodes, while the cathodic polarization induced interfaces on in situ assembled electrodes are characterized by particle-shaped contact marks (20-50 nm in diameter). The results show that the electrochemical activity of the cathodic polarization induced electrode/electrolyte interface is comparable to the thermally induced one for the O2 reduction reaction under SOFC operation conditions. The FIB-STEM analysis clearly shows that along the rim of the contact rings of pre-sintered LSM electrode, there is formation of a thin layer of La and Sr on the YSZ electrolyte surface, while Mn diffuses into YSZ and the distribution of Mn inside YSZ electrolyte follows closely the profile of the contact rings. The preliminary results provide direct evidences that Mn cation inter-diffusion plays a critical role in the formation of LSM/YSZ interface of SOFCs.
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.
Utilization of Solar Fuels By Implementation of Nife-LDH and Fe-N-C As Bifunctional Catalyst for the Oxygen Reduction Reaction and the Oxygen Evolution Reaction
Authors: Dresp Sören , Luo Fang , Schmack Roman , Kühl Stefanie , Gliech Manuel , Strasser Peter
Published: February 2020

The increasing demand for solar fuels and hydrogen as most promising energy carrier requires new materials for electro-catalytic splitting of water or the back-transformation of hydrogen into electricity. Especially, the oxygen electrode caused by sluggish kinetics is hampering progress for cheap hydrogen made by electrolysis. Moreover the low abundance and the high costs of current highly active noble metal catalysts require new developments for novel cheap and abundant materials. Therefore we have developed a new two-component catalyst system consisting of Nickel-Iron layered double hydroxide (NiFe-LDH) and Fe-N doped carbon material (Fe-N-C) as non noble bifunctional catalyst for the oxygen electrode in alkaline unitized reversible fuel cells/electrolyzers (URFC). The combination of NiFe-LDH known as most active non-noble catalyst for the oxygen evolution reaction (OER) in alkaline media and Fe-N-C known as highly active catalyst for the oxygen reduction reaction (ORR) resulted in a combined overpotential with their respective advantages. NiFe-LDH was prepared by a simple and time-saving microwave assisted solvothermal synthesis route. The crystallinity was confirmed by X-ray diffraction (XRD) spectroscopy and Transmission electron microscopy (TEM) verified morphological characteristics. Rotating Ring disk (RRDE) measurement revealed high selectivity for the multi-component catalyst. We further investigated the behaviour in a membrane based reversible electrolyzer using an anion exchange membrane (AEM, Tokuyama A201). Compared to noble catalyst systems such as Iridium and Platinum the membrane electrode assembly (MEA) measurements proved the ability to compete and supported the initial high activities.
(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) Elevated Temperature CO2 Adsorption Separation and Electrochemical Conversion：Reaction Mechanism and Technology Development
Authors: Shi Xiang Yi , Luo Yu , Cai Ningsheng
Published: February 2020

Coal gasification is a clean way to utilize coal. Carbon dioxide is a significant emission in coal chemical plants. Before the fuel gas produced from coal chemical plants is utilized, CO2 mixed in the fuel gas has to be separated. A technical route combining elevated temperature CO2 adsorption separation, high temperature CO2 electrolysis and curtailed renewable energy can achieve high-efficiency carbon dioxide separation and utilization in a coal chemical plant. Elevated temperature CO2 adsorption separation (250-350oC) greatly match the temperature of the produced gas from coal chemical plants and thereby purifies the fuel gas in an efficient way. Further, high temperature CO2 electrolysis by solid oxide electrolysis cell (SOEC, operated at 600-1000oC) can fully utilize the curtailed renewable energy, like solar power, wind power and hydropower, to convert CO2/H2O into syngas again. In this study, the effort on these two key technologies, the elevated temperature CO2 adsorption separation and CO2 electrolysis by SOEC, were focused from the perspective of micro scale to macro scale. In the micro scale, the heterogeneous reaction mechanism of CO2 adsorption and electrolysis at an elevated temperature was discussed. In the unit level, the reactor was developed coupling the reaction mechanism and multi-physics (including fluid flow, diffusion, heat transfer and charge transfer). Facing with unstable renewable energy, the dynamic behavior of CO2 electrolysis become a new study focus. In the macro scale, system integration and technology development in the future were analyzed. This technical route is a potential way to simultaneously relieve such a great amount of renewable energy curtailment and carbon dioxide emission.
(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
Energy Generation from CO2 Capture Associated RED Power Generation System
Authors: Kim Han-Ki , Kim Young-Eun , Yoon Yeo-Il , Hwang Kyo-Sik , Han Ji-Hyung , Jeong Nam-Jo , Kim Chan-Soo
Published: February 2020

Today, global warming induced by green house gas (GHG) has been critical environmental issues. Among the direct GHGs, CO2 is the major gas which largely contributes to global warming. It is an issue of great concern to develop the cost effective carbon dioxide capture technology. However, current CO2 capture processes are becoming limited because these processes could not reached regeneration energy of 2.0 GJ/tCO2. Recently, it is reported that salinity gradient energy is one of most novel candidates for energy harvesting from CO2 (Hamelers et al., Environ. Sci. Technol., 1, 31, 2014). Reverse electrodialysis (RED) salinity gradient energy is the renewable energy which using concentration gradient between two different sources. And the energy potential of CO2 is larger than seawater in RED system. Therefore, we suggested the CO2 capture associated RED power generation system (CO2RED) to dramatically reduce the regeneration energy. This CO2 capture associated RED power generation technology is suggested for the first time. This proposed CO2RED system is possible to ensure the efficient power generation and economical CO2 capture performance using the concentration difference between the CO2 rich/lean solutions. We have make the lab-scale CO2 associated RED system. The RED stack comprised of five cell pairs. Each cell pair contained an anion and cation exchange membranes, spacers, and gaskets. In this study, we introduced the CO2 saturated absorbent to the RED system instead of seawater. As the results, CO2RED system achieved the power density of 0.8 W/m2. It was corresponded with 300 kJ/ton CO2 absorbent. Furthermore, pH of CO2 absorbent was changed from pH 7.9 to pH 8.4. It means that absorbed CO2 was transported through anion exchange membranes and the RED system can help to regenerate CO2 absorbent during the power generation. From this research, we have succeeded to obtain the core technology of CO2 associated RED power generation system and confirmed the possibility of this suggested CO2RED system for power generation technology.
(Invited) Deionization and Energy Recovery in Capacitive Systems with Inverted Operation Characteristics
Authors: Omosebi Ayokunle , Li Zhiao , Gao Xin , Holubowitch Nicolas , Landon James , Cramer Aaron M , Liu Kunlei
Published: February 2020

Capacitive deionization (CDI) continues to emerge as a viable option for the treatment of saline streams with up to brackish levels of ionic contaminants. CDI functions similar to a capacitor, storing ions from a liquid stream onto highly porous electrodes with the aid of an applied electric field. When the pores become saturated, the electric field can be reduced or reversed to discharge the previously stored ions and form a concentrate stream [1]. At the same time, the electronic energy input to the cell during ion storage can be recovered to power auxiliary devices or coupled CDI units. The coupling of CDI cells offers not only the ability to lower the energy requirements for cell operation, but also the possibility of semi-continuous CDI operation. With much effort devoted to materials development and performance enhancements, there have been few reports on energy recovery in CDI literature. Of these, discharging a charged CDI cell over a resistive load, direct connection of CDI cells, and the use of buck-boost DC-DC converters have been demonstrated. In this work, parallel CDI cells are integrated with a DC-DC converter based on a Ćuk topology (Figure 1) to show active energy recovery from a discharging cell and subsequent deionization with a secondary cell using energy stored in the initial charged cell. Unlike buck-boost, the Ćuk topology incorporates a power supply that compensates for energy losses during the electron transfer process, thereby allowing the system to simultaneously transfer energy and meet its desalination goals.

Inverted capacitive deionization (iCDI) was recently demonstrated where deionization was accomplished by a polarity difference between chemical surface charges on electrode pairs that facilitates adsorption of ions from solution [2]. Conversely to classical CDI, cell discharge is accomplished by applying an external electric field. We have improved upon the iCDI cell architecture by incorporating ion-selective membranes to form a new inverted membrane capacitive deionization cell (iMCDI). We will demonstrate energy recovery results for both the iCDI and iMCDI cells, and explore the influence of converter operation and cell architecture on energy recovery.

References

[1] M.A. Anderson, A.L. Cudero, J. Palma, Electrochim. Acta 55 (2010) 3845.

[2] X. Gao, A. Omosebi, J. Landon, K. Liu, Energy & Environmental Science 8 (2015) 897.

Acknowledgements

These authors are grateful to the U.S.-China Clean Energy Research Center, U.S. Department of Energy (DE-PI0000017) for project funding.

Figure 1
(Invited) Fabrication and Characterization of Transparent Fluorescence Nanocomposite Film Containing Inorganic Phosphor Nanoparticles
Authors: Iso Yoshiki , Isobe Tetsuhiko
Published: February 2020

Nano-sized inorganic phosphors possess good photostability and thermal stability as compared with organic dyes and metal complexes. They exhibit high transparency due to low light scattering intensity in the visible region. A transparent fluorescence film of phosphor nanoparticles with a function of conversion from near UV light to visible light are therefore suitable candidates for applications to spectral down-shifters in white LEDs and photovoltaic devices. To fabricate the transparent nanocomposite film, the phosphor nanoparticles must be well-dispersed without their aggregation because light scattering intensity is proportional to the sixth power of a particle diameter according to Rayleigh’s theory. Nanoparticles aggregate easily in a solution due to their high surface energy. To solve this problem, we use electrostatic repulsion between charged nanoparticle surfaces. In this presentation, we discuss fabrication and characterization of transparent fluorescence nanocomposite films containing phosphor nanoparticles in a matrix.
Creation of 4fn-4fn-15d1 Transition Energy Diagram of Trivalent Lanthanide Ions in Fluorides Based on First-Principles Calculations
Authors: Ogasawara Kazuyoshi
Published: February 2020

The theoretical prediction of the 4fn-4fn-15d1 transition energies of lanthanides in crystals is an important issue in the development of novel luminescent materials such as solid-state lasers or phosphors. In our previous work, the first-principles calculations of the entire multiplet structures of lanthanide (Ln) ions in LiYF4 (YLF) corresponding to 4fn and 4fn-15d1 configurations were performed using the relativistic discrete variational multi-electron (DVME) method [1]. However, the lowest 4fn-4fn-15d1transition energy was overestimated for light lanthanides while it was underestimated for heavy lanthanides. In this work, in order to improve the accuracy of the theoretical transition energy, a correction based on the molecular orbital (MO) calculation in the Slater’s transition state was introduced.

The LnF8 clusters were constructed based on the crystal structures of YLF and CaF2. The fully-relativistic MO calculations were performed using the relativistic DV-Xα code. The multiplet calculations were performed using the relativistic DVME code. The Slater determinants corresponding to 4fn and 4fn-15d1 configurations were constructed from the four-component relativistic MOs and used as the basis functions to diagonalize the relativistic many-electron Hamiltonian. In order to correct the errors in the transition energy, MO calculations in the Slater’s transition state where a half electron was excited from the Ln 4f level to the Ln 5d level were also performed. A constant correction term was added to the diagonal matrix element of the many-electron Hamiltonian for 4fn-15d1 configuration so that the 4fn -4fn-15d1transition energy is consistent with the 4f-5d transition energy obtained by the MO calculation in the Slater’s transition state.

The diagrams representing the lowest 4fn-4fn-15d1transition energies of trivalent lanthanide ions in YLF calculated with and without the above correction are shown in Fig. 1. The overestimation in the light lanthanides and the underestimation in the heavy lanthanides are significantly reduced by the correction and the theoretical transition energies approached to the experimental values in the literature [2-5].

References

[1] K. Ogasawara, S. Watanabe, H. Toyoshima, M.G. Brik, ”Handbook on Physics and Chemistry of Rare Earths”, 37, Chapter 231 (Elsevier,2007).

[2] A. Meijerink and R.T. Wegh, Mater. Sci. Forum, 315-317, 11 (1999).

[3] L. van Pieterson et al., Phys. Rev. B, 65, 045113 (2002).

[4] L. van Pieterson et al., Phys. Rev. B, 65, 045114 (2002).

[5] M. Kirm et al., Phys. Rev. B, 75, 075111 (2007).

Figure 1
(Invited) Cyborg Insect: Insect Computer Hybrid Robot
Authors: Poon Kee Chun , Tan Desmond Chun Long , Li Yao , Cao Feng , Vo Doan Tat Thang , Sato Hirotaka
Published: February 2020

Insect-computer hybrid robot, often referred as to ‘Cyborg Insect’, is the fusion of living insect and miniature radio-enabled wireless electrical stimulator to control the locomotion of the insect platform in walking and flight. The miniature stimulator is mounted on the back of the living insect and metal thin wires are implanted into neuromuscular sites of our interest to electrically stimulate for eliciting experimentalist’s desired motor actions and behaviors.

Insects exhibit amazing modes of locomotion. They float, swim, crawl, jump, run, fly and they even walk on water. They do this with such efficiency, sophistication and elegance of function across a vast size range that they have mastered locomotion on almost every terrain on the earth. Very recently researchers have started building ultra-small data recording systems for flying insects and tried to stimulate insects (moths, locusts, beetles) to induce desired actions.

The miniature stimulator (~1.3 g in total mass) consisted of a custom PCB (printed circuit board), an off-the-shelf microcontroller, a rechargeable micro battery and thin-wire electrodes. We employed Mecynorhina torquata, a giant flower beetle as the insect platform for the hybrid robot (10 g, 6 cm, 3 g payload capacity in flight). The stimulator assembly was mounted on the beetle’s pronotum and the terminals of wire electrodes were inserted into the optic lobes, brain, basilar flight muscles and dorsal thorax (counter electrode).

Flight initiation was triggered by applying 2 - 4 V, 100 Hz, 20 % duty cycle, biphasic square pulse trains between the two electrodes implanted into the optic lobes, massive neural clusters of compound eyes. Cessation was triggered by a single DC pulse applied to the same sites as the initiation. The wing power was decreased (and thus throttle down) when the same 100 Hz pulse trains were applied to the brain. Turnings were elicited by applying the same pulse trains to either the left or right basilar flight muscle. The beetle turned in opposite direction to stimulated side: left turn was, for example, conducted by the right side stimulation.

On the other hand, toward a self-powering unit for the insect-computer hybrid robot, we have proposed a miniature biofuel cell implantable into living insect to generate electrical energy by consuming energy source, for example, saccharide. For that we have developed nanoparticle catalysts for oxygen reduction reaction such as P or B doped Pd, denoted by Pd-P or Pd-B. By doping these non-metal elements into Pd, the catalytic activity of Pd was drastivally enhanced. These Pd-P and Pd-B catalysts were facilely synthesized by a electroless deposition process using hypophosphate and DMAB (dimethylaminoborane) as reducing agent, respectively.

In the presentation, we will show the demonstration of insect locomotion control and the experimental data and discussion on the enhanced catalytic activities of the Pd nanoparticle catalysts.

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In Operando neutron Imaging of Enzymatic Electrochemical Cells
Authors: Longchamps Ryan , van Zandt Zachary , Bilheux Hassina , Dhiman Indu , Santodonato Louis , Ulyanova Yevgenia , Singhal Sameer , Nelson George J.
Published: February 2020

Enzymatic electrochemical cells (EECs) convert sugars, alcohols, and other fuels into electrical energy through electrochemical reactions catalyzed by naturally occurring enzymes. These devices typically consist of porous carbon electrodes, which may be separated by a polymer membrane. The porous electrodes in EECs are typically saturated with aqueous solutions to support electrochemical activity. The anode contains fuel within the liquid solution, while EECs often incorporate an air-breathing cathode. This work focuses on the characterization of the active anode assembled in a prototype three electrode cell developed to support investigation of the effects of varying environmental conditions on EEC performance. The aluminum three electrode cell reactor was designed and fabricated for in operando neutron imaging. This reactor consisted of two compartments for housing the working and counter electrodes. These halves of the reactor were separated by a Teflon gasket and filter paper. A three electrode cell arrangement was completed by embedding a silver reference electrode in the filter paper. Utilizing neutron tomography the active regions of the three electrode cell were mapped in the absence of the aqueous fuel solution. The reactor was then opened and wetted with a solution of 0.1 M glucose and 0.01 M hydroquinone in an aqueous sodium phosphate buffer. Cyclic voltammetry (CV) was performed to ensure proper function of the cell. Following CV in operando imaging was performed to generate radiographic representations of the anodic components prior to, during, and after discharge. Simultaneous chronoamperometry was performed to provide a connection between the dynamics of the aqueous fuel and buffer solutions and cell performance. Following discharge, tomographic scans were performed to allow for the observation of changes in the active regions of the half-cell. Following the initial measurements the three electrode cell was opened and flushed with fuel solution. The CV, in operando imaging, and tomographic measurements were then repeated. Increased aqueous solution content was found to improve the overall response of the system, yielding higher current in CV and a more consistent discharge behavior during chronoamperometry. Solution content is quantified based on tomographic scans and the related effects on performance are addressed. In general, the studies presented demonstrate a means of controlling test cell geometry to permit the study of EECs using neutron imaging techniques.
(Keynote) Utilizing Bioengineering for Fabricating Catalytic Cascade Bioanodes
Authors: Minteer Shelley D.
Published: February 2020

Over the last decade, there have been major developments in materials engineering for bioelectrodes (i.e. bioanodes and biocathodes in biofuel cells and biosensors), including the engineering of nanomaterials and nanostructured electrodes for increasing electrochemically active surface areas and increasing the rate of direct electron transfer. However, materials engineering does not solve all problems in bioelectrocatalysis. This paper will detail the use of bioengineering to improve the performance (current density, power density and/or efficiency) of bioelectrodes. Enzymes have evolved to function in a particular environment in a living cell, but operating at the biointerface in a bioelectrode is a very different microenvironment. This paper will include a discussion of the use of recombinant enzymes that can be tailored to the bioelectrode application and their microenvironment. The paper will also discuss the use of these recombinant enzymes in the formation of minimal catalytic cascades for deep or complete oxidation of biofuels and substrates/analytes. This paper will also discuss the use of bioscaffolding for improving the performance of these catalytic cascades through controlling the proximity of sequential catalytic active sites.
Quantitative Assessment of Channeling Mechanisms in Nanoscale Catalytic Architectures
Authors: Earl Erica , Calabrese Barton Scott
Published: February 2020

Highly efficient catalytic cascades are found in nature, where the efficiency of multi-step biochemical pathways is enhanced by substrate channeling, wherein the transport of intermediates from on active site to the next is managed by physical interactions [1]. Modes of substrate channeling include proximity between active sites, confinement [2], electrostatic interactions [3], and surface adsorption. Investigating these natural pathways could lead to the development of innovative designs for catalytic systems. We investigate the efficiency of these pathways through numerical continuum modeling, to identify their limits and the extent to which they can interact. The model considers transport between two active sites and includes both transport and kinetic properties of the system (Figure 1). The effectiveness of this model is quantified by yield of the second reaction and by flux control coefficients (FCCs) [4]. FCCs have traditionally been applied to purely kinetic systems, but will be expanded to incorporate one that includes mass transport. Acknowledgement We gratefully acknowledge support from Army Research Office MURI (#W911NF1410263) via The University of Utah. References 1. I. Wheeldon et al., Nat. Chem., 8, 299–309 (2016) doi:10.1038/nchem.2459. 2. C. C. Hyde, S. a. Ahmed, E. a. Padlan, E. W. Miles, and D. R. Davies, J. Biol. Chem., 263, 17857–71 (1988). 3. A. H. Elcock, M. J. Potter, D. a Matthews, D. R. Knighton, and J. A. McCammon, J. Mol. Biol., 262, 370–374 (1996) doi:10.1006/jmbi.1996.0520. 4. D. A. Fell, Biochem. J., 286, 313–30 (1992).

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Sodium Cobalt Oxide As a Non-Platinum Cathode Catalyst for Microbial Fuel Cells
Authors: Ichihashi Osamu , Hirooka Kayako , Takeguchi Tatsuya , Kusui Takashi
Published: February 2020

Microbial fuel cell is a device that can achieve wastewater treatment and power generation simultaneously. For the practical application of microbial fuel cell, development of alternative cathode catalyst for platinum is necessary. In this study, a kind of sodium cobalt oxide, NaCo2O4was investigated, because estimated cobalt reserve is 100 times higher than platinum, and its price is about one thousandth.

Catalyst ink was prepared by mixing NaCo2O4powder with carbon black powder and Nafion dispersion. Then cathode was fabricated by applying the ink to PTFE treated carbon paper. Cathode with Pt catalyst and that with activated carbon (NORIT SX PLUS) were also prepared for comparison.ORR activity of the cathodes was measured by linear sweep voltammetry (LSV).

Oxygen reduction reaction (ORR) activity of NaCo2O4 cathode increased 15-25 times by the addition of carbon black as conductive assistant material in catalyst ink. Two kinds of carbon black were tested, and a cathode with Ketjen black showed better ORR activity than that with Vulcan XC-72. By increasing coating amount of catalyst ink from 2mg/cm2 (NaCo2O4) to 4mg/cm2, ORR activity increased 1.6 - 1.7 times, which was equivalent to 50-60% of Pt catalyst (Fig) . Gram based ORR activity of this catalyst was higher than that of activated carbon (NORIT SX PLUS) catalyst (Fig). The NaCo2O4 cathode having highest ORR activity was built into a pre-acclimated MFC, and then used for the treatment of synthetic wastewater. The current density was about 3A/m2, which was a little lower than the value during the operation equipped with a Pt cathode (about 4A/m2). However, any problems such as a decrease in electricity generation were not observed in several days of operation. Power density curve of the MFC equipped with the NaCo2O4 cathode was obtained by the LSV measurement , and the maximum current density was 0.58 W/m2, which is about a half of the density achieved by a Pt cathode.

Further research on the preparation condition of the cathode, such as the amount of conductive assistant material, the amount of binder, and the coating amounts of the catalyst ink, would probably contribute to further improve the cathode ORR activity, which would improve electricity generation performance of a MFC.

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(Invited) Photoredox Catalysis: An Easy Access to Versatile Radical Functionalization
Authors: Koike Takashi
Published: February 2020

Photoredox catalysis by well-known ruthenium(II) polypyridine complexes and cyclometalated iridium(III) derivatives is a useful tool for redox reactions in synthetic chemistry, because these materials can effectively catalyze single-electron-transfer (SET) processes by irradiation with visible light (sunlight). This provides a new strategy for efficient and selective radical functionalization. We have developed several photocatalytic radical reactions in which radicals are generated by photoredox catalysis and which also have merits in terms of green and sustainable chemistry.

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