bluuebunny/crossref_metadata_2025_split huggingface dataset:
Relating Microstructure to Surface Exchange Kinetics Using in Situ Optical Absorption Relaxation
Authors: Chen Ting , Sasaki Kazunari , Perry Nicola H. 
Published: February 2020

Reversible solid oxide cells (R-SOCs) are promising devices, which could directly convert chemical fuels to electrical power (Solid Oxide Fuel Cells, SOFCs) and store energy as chemical fuels (Solid Oxide Electrolysis Cells, SOECs). Nonetheless, the polarization resistance of the oxygen electrode, often originating in sluggish surface oxygen incorporation/ excorporation kinetics, causes large efficiency losses. Seeking to understand and ultimately improve surface exchange kinetics, many previous studies have focused on controlling the bulk defect chemistry (oxygen vacancy and/or electron content) or electronic structure through tailoring chemistry or strain. Fewer studies have focused on understanding the role of microstructural features in controlling both the surface exchange coefficient, k, and its deterioration over time (aging), especially for mixed ionic-electronic conductor (MIEC) electrode materials. SrTi0.65Fe0.35O3-δ (STF35) is a mixed conductor with fast k, which serves as a model system in our studies, to study the impact of microstructure (particularly crystallinity) on k and the aging behavior.
In this work, a series of STF35 thin films were grown by Pulsed Laser Deposition (PLD) using different growth parameters (temperature, time) to vary structural aspects such as crystallinity in a well-defined and controlled manner. Structural characterization of the films’ thickness, orientation, crystal quality, and grain size was performed using X-ray reflectivity and diffraction (coupled scans, rocking curves) plus atomic force microscopy. The surface exchange kinetics (k) of the series of STF35 thin films were measured in situ and continuously using a novel optical transmission relaxation approach, to investigate the impact of the aforementioned structural features on the performance. The approach takes advantage of the different optical absorption signatures of Fe in different valence states. Both XRD and AFM results showed that the STF35 thin films grown on yttria-stabilized zirconia at temperatures up to 400 ºC are amorphous, while the films become crystalline and oriented around 500-550 °C, with larger grains at higher temperatures. There is no obvious optical response to changing gas content for the as-grown amorphous films below 500 °C; however, upon heating these films at 500-550 °C, where they begin to crystallize, rapid oxygen exchange could be observed optically in the same films. Subsequently, the films optically demonstrated an ability to exchange oxygen at temperatures as low as 350 °C. The results indicate that crystalline thin films showed faster oxygen exchange kinetics compared to the amorphous thin films. The aging of STF thin films’ surface exchange kinetics was also studied optically as a function of microstructure, which in every case demonstrated a rapid decline in k during the initial 50 hours of measurement. Implications for electrode design will be discussed.
Electrochemically Fabricated Binary Alloy Catalysts for CO2-C1 Fuel Inter-Conversion
Authors: Hwang Eunkyoung , Kim Hoyoung , Park Hyanjoo , Ahn Sang Hyun , Kim Soo-Kil 
Published: February 2020

Electrochemical reduction of carbon dioxide to useful chemical has been studied as a promising method to utilize CO2. This method can selectively produce a variety of useful chemicals (e.g. carbon monoxide, formic acid, methane, and other hydrocarbons) according as reaction condition such as types of electro-catalysts, electrolytes, operation voltage, and so on [1,2]. In this study, we selected formate as a target product because it has various advantages as a feed stock chemical. Formate is produced by the electrochemical reduction of the CO2 and the formate, after treatment to form formic acid, will be used as fuel for Direct Formic Acid Fuel Cell. Particularly in the case of CO2-based unitized re-generative fuel cell, the inter-conversion reaction between CO2-C1 fuels is important. Therefore, we develop a catalyst that can be used in both sides reaction; the electrochemical conversion of CO2 to formate and the oxidation of formic acid [3]. In this case, it is most important to develop bi-functional catalysts that have activities for both reactions. In addition, high selectivity and activity to CO2 reduction as well as reduced amounts of noble metal loading for the formic acid oxidation reaction are also desired.
The catalysts were made by co-electrodeposition of noble metal and post-transition metal to form binary alloy catalysts. Electrodeposition was performed at a constant deposition potential in a 3-electrode cell containing metal precursors, supporting electrolyte, and complexing agent. For some cases, thermal annealing was performed to enhance the characteristics of the fabricated catalysts. The alloy catalysts were characterized with EDS, SEM and XRD. The electrochemical reduction of carbon dioxide was performed and the produced amounts of formate were measured with HPLC. Formic acid oxidation was also performed with CV using the same catalysts. The activities to both reactions were characterized according to the alloy composition, morphologies, and other physic-chemical properties. In conclusion, certain composition of the alloy catalysts exhibited the significant activities to both reactions simultaneously.
References
1. Journal of The Electrochemical Society, 137 (6) 1772-1777 (1990)
2. Journal of The Electrochemical Society, 159 (7) F353-F359 (2012)
3. Catalysis Today, 244 58-62 (2014)
High Temperature and Pressure Alkaline Electrochemical Reactor for Conversion of Power to Chemicals
Authors: Chatzichristodoulou Christodoulos 
Published: February 2020

Moving away from fossil fuels requires harvesting more and more intermittent renewable energy resources and establishing a sustainable system for the production of chemicals. This brings forward the need for efficient large scale energy storage technologies 1-3 and technologies for the conversion of renewable electricity to chemicals. Electrochemical reactors can play a crucial role in this endeavor, since they can efficiently and reversibly transform electricity to high-value chemicals, and thus serve as energy storage and recovery devices for balancing the grid, while offering a means for the sustainable production of chemicals 4-6.
A novel type of alkaline electrochemical cell that can operate at elevated temperature and pressure has been developed that relies on corrosion resistant high temperature diaphragms, based on mesoporous ceramic membranes where aqueous KOH is immobilized by capillary forces. Raising the operating temperature offers a means to boost performance, as both ionic transport and reaction kinetics are exponentially activated with temperature. Indeed, we have demonstrated alkaline electrolysis cells operating at 200-250 °C and 20-50 bar at very high efficiencies and power densities.
This work will provide an overview of our efforts to develop components of such high temperature alkaline electrochemical reactors for different applications. Low-cost large-scale production methods have been successfully employed for the production of ceramic diaphragms and full cells. The influence of composition and microstructure on the long-term chemical stability and mechanical durability of the mesoporous ceramic membranes has been explored. Instrumentation for electrochemical testing at elevated pressures (up to 99 bar) and temperatures (up to 300 °C) with in-line chemical analysis has been established enabling experiments with gaseous or liquids reactants/products at cell sizes of up to 25 cm2. Efforts are currently directed towards the investigation of the intrinsic activity of mixed oxides for the oxygen evolution reaction at elevated temperatures and pressures, and of the intrinsic activity, selectivity and stability of supported metal catalysts towards the electrocatalytic conversion of biomass derivatives to high-value chemicals. Finally, the use of selected electrocatalysts for the production of high performance electrodes will be reported.

References

1. Barton, J. & Gammon, R. J. Power Sources
195, 8222-8235 (2010).
2. Evans, A., Strezov, V. & Evans, T. J. Renew. Sust. Energ. Rev.
16, 4141-4147 (2012).
3. Mansilla, C., Louyrette, J., Albou, S., Bourasseau, C. & Dautremont, S. Energy
55, 996-1001 (2013).
4. Jensen, S. H., Larsen, P. H. & Mogensen, M. Int J Hydrogen Energy
32, 3253-3257 (2007).
5. Zhan, Z. et al. Energy Fuels
23, 3089-3096 (2009).
6. Lebæk, J., Bøgild Hansen, J. & Mogensen, M. GreenSynFuels final project report. (2011).
Characterisation of a Planar Solid Oxide Cell Stack Operated at Elevated Pressure
Authors: Jensen Søren Højgaard , Graves Christopher , Chen Ming , Sun Xiufu , Hansen John Bøgild 
Published: February 2020

As the global and local energy production becomes more dependent on intermittent renewable sources like wind and solar, efficient and reversible conversion of electricity to storable fuels becomes increasingly important. Solid oxide cells (SOCs) are interesting in this context since they can be operated either as electrolysers (SOEC) to convert electricity to fuels such as hydrogen or methane, and as fuel cells (SOFC) to convert fuels to electricity. Both productivity and conversion efficiency can be improved if the SOC operation pressure can be increased from ambient pressure to 10-30 bar.
Here we characterize an SOC stack operated at pressures from ambient pressure to 10 bar without fluctuations in the steam supply. The pressure dependency of stack temperature, cell area specific resistance (ASR), current-voltage (iV) curves, stack impedance spectra and pressure drop across the stack and heat exchangers is analyzed and the expected impact of pressurization on the hydrogen production cost is evaluated.

Figure 1
Investigation of Manganese-Cobalt Oxide Nanoparticles As Electrocatalysts for the Oxygen-Evolution Reaction: Influence of Synthesis Conditions on Structure and Activity
Authors: Gliech Manuel , Klingenhof Malte , Spoeri Camillo , Bergmann Arno , Strasser Peter 
Published: February 2020

The storage of electric energy has become one of the main challenges in infrastructure development. The development of scalable, cost-efficient and robust synthetic routes toward well-defined solid state structures is a major objective in this field.
Electrocatalytic water splitting is a promising way of chemical energy storage wherein the anodic oxygen evolution reaction (OER) is the determining factor. Manganese based oxides have attracted particular attention as non-noble metal catalysts for the OER. Due to their abundance, low price and ecological harmlessness, those materials are promising candidates for a commercial application. Therefore insights into the relations between synthesis conditions, composition, structure and activity as well as stability are of fundamental interest. 1,2

Here, we present the comparison of different synthesis routes for Mixed Oxide Nanoparticles (NPs) of Manganese and Cobalt to yield Mn3-xCoxOy-NPs in a range from X=0 to 3. The well characterized (TEM, EDX, XRD) catalysts were tested with respect to the relation of crystal structure to electrocatalytic activity and stability for the OER in alkaline media using Rotating Disk Electrode (RDE) measurements.
We report a significant impact of the Cobalt fraction on the morphology, while the crystal structure remains unchanged. Further we found a non-linear relation between composition and activity.

References

(1) Bergmann, A.; Martinez-Moreno, E.; Teschner, D.; Chernev, P.; Gliech, M.; de Araujo, J. F.; Reier, T.; Dau, H.; Strasser, P. Nat Commun
2015, 6.
(2) Gliech, M.; Bergmann, A.; Spöri, C.; Strasser, P. Journal of Energy Chemistry
2016.
Potential Generation Using Salinity Gradients
Authors: Chandran Aishwarya , Khandelwal Ashwini , Amaravati Sivakumar , Chittur Krishnaswamy Subramaniam 
Published: February 2020

Salinity gradient power (SGP) is the energy that can be generated from reversible mixing of two kinds of water with different salt contents. A process for generating potential from salinity concentration gradient produced in single cell (25 cm2) and multi-cell assembly is presented. The salinity gradient is created using a fuel cell type cell with a micro-porous ion exchange membrane, both anionic (AEM) and cationic (CEM). The study was performed for various gradients. Salt : Fresh, from 100 : 0 to 16000 : 0 was established using NaCl solution, in the electrode chambers. A potential of about 25 mV/cm can be realized at ambient temperatures and pressures for a bipolar AEM/CEM cell. The achievable potential is still below theoretical value. The performance was optimized for various static and dynamic flow rates of the saline and fresh water. For this purpose the cell flow field was simulated using ANSYS and the flow field design was optimized for maximum coverage of the cell area. The cell performance can further be optimized for various Membrane Electrode System (MES) structure. The thermodynamic, electrochemical and electrical efficiency was discussed for various gradients and flow rates. The higher the salinity gradient the larger is the potential generated. This is limited by the membrane characteristics. There exists a monotonic relation between the number of valence electron/ion/unit time and the potential generated up to about 16000 concentrations. The membrane characteristics have been studied for optimal ion crossover for various gradients and flow.
Hydrogen Production through a Multi-Ion Exchange Membrane Based Electrolysis System
Authors: Nazemi Mohammadreza , Padgett James , Hatzell Marta C. 
Published: February 2020

Reverse electrodialysis (RED) is a membrane based electrochemical system used for capturing a portion nearly 2.6 TW of power released through the mixing of sea and river water at global estuaries[1]. This technology encompasses a series of alternating anion and cation exchange membranes (AEM and CEM) which actively separate channels with high and low concentration solutions (0.5 M and 0.011 M NaCl). Creating a concentration gradient across each ion selective membrane, generates a Donnan or Membrane potential. Typically, one cell pair (three membranes, and one high and low concentration chamber) produced an open circuit voltage of 120 mV. As more membranes are added to the system, the generated potential increases and drives faradic reactions at electrodes on either end of the membrane stack.
To date, most RED work has focused on utilizing a large numbers of membranes to produce electrical power through a galvanic cell approach. Due to this focus, traditionally low overpotential reactions are preferred rather than the water splitting reaction (oxygen evolution and hydrogen evolution). Here we investigate the potential for using the RED electrochemical platform for hydrogen production through an electrolysis approach[2, 3]. The use of multiple monopolar membranes and multiple chambers, allows a sustained pH gradient to be maintained across the cell, minimizing the whole cell voltage necessary for hydrogen production. When the cell was operated with a pH gradient equal to 10 pH units, the steady state whole cell onset potential decreased by 700 mV when compared to no pH gradient. This represented a 33% decrease in the energy consumption for the water splitting reaction. Additionally, the steady state current density (11.7 mA/cm2) was achieved using an acidic cathode and basic anode, which was 12 x greater than no pH gradient. We also evaluate the potential tradeoffs between added ohmic resistances, decreased onset potential, and increased membrane potentials within this architecture.
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2. Hatzell, M.C., I. Ivanov, R.D. Cusick, X. Zhu, and B.E. Logan. Physical Chemistry Chemical Physics, 2014. 16(4): p. 1632-1638.
3. Hatzell, M.C., X. Zhu, and B.E. Logan. ACS Sustainable Chemistry & Engineering, 2014. 2(9): p. 2211-2216.
Improvement of Reverse Electrodialysis Cells for Generating Electrical Power from Salinity Gradient
Authors: Kang Byeong Dong , Kim Dong-Kwon , Kim Hyun Jung , Yoon Baek , Yoo Jaisuk 
Published: February 2020

Reverse electrodialysis cells can effectively generate electric power form salinity gradient. Howerver, the power generation densities from the reverse electrodialysis cells are low compared to conventional cells for power generation, and various reserach groups incluidng our group have focused on improving the performance of the reverse electrodialysis cells. In this presentation, the technique for improving the performance of the reverse electrodialysis cells, which have been investigated by our group, is introduced.
Solar Generation of Ion Gradients Using Dye-Sensitized Ion-Exchange Membranes
Authors: White William , Sanborn Christopher D. , Reiter Ronald S. , Ramirez Claudia P. , Ardo Shane 
Published: February 2020

Most solar energy conversion technologies generate power through transport of energized electron particles; however, the physics that describes these technologies only requires that the particles be charged and not specifically that they are electrons. My research group studies solar energy conversion technologies that generate power from sunlight through ion transport. In my presentation I will report on my research group’s recent demonstration of ion transport against concentration gradients driven by solar illumination of dye-sensitized ion-exchange materials. Mechanistically, visible light was used to drive endergonic excited-state proton transfer from a covalent photoacid-functionalized polymer membrane. Photoacid molecules convert the energy in light into a change in the chemical potential of protons via a weakening of protic functional groups on the photoacid, i.e. a drop in its pK
a.
As a model system for ion-channels in polymer-electrolyte ion-exchange membranes, dye-sensitized conical nanopores in poly(ethylene terephthalate) (1 – 108 pores/cm2) were investigated. Remarkably, in a region occupied by ~20 zeptoliters (~2 x 10-20 L) of aqueous electrolyte, electrochemistry was used to determine the number of binding groups of the dyes and the ground-state pK
a of the dyes, and fluorescence microscopy was used to determine the conditions where excited-state proton transfer occurred. These data were consistent with a hypothesis that pK
a values of the photoacids in the ground-state and excited-state were significantly smaller than those measured for dye molecules in solution, likely due to incomplete screening of surface charges in the confined nanopores.
Dye-sensitized Nafion monopolar ion-exchange membranes and bipolar ion-exchange membranes were also investigated. Under sunlight-simulated illumination these materials were found to exhibit photovoltaic action, i.e. generation of a photocurrent and a photovoltage. Bipolar membranes are a class of polymeric ion-exchange materials that consist of a monopolar cation-exchange membrane that is in intimate contact with a monopolar anion-exchange membrane. They are unique among the ion-exchange membranes in that they that separate and maintain pH differences across the membrane even during passage of ionic current. Moreover, the physics of ion equilibration processes within these membranes resembles that which occurs during equilibration of semiconductor pn-junctions.
This body of work represents an underexplored solar energy conversion process that is being pioneered by my research group to operate via a mechanism similar to that in semiconductor pn-junctions. The applicability and practicality of these materials as standalone ionic photoelectrochemical devices will also be presented.
(Invited) Electrical Detection of Biomolecules Using Graphene-Based Devices
Authors: Maehashi Kenzo 
Published: February 2020

Label-free electrical monitoring of biorecognition events provides a promising platform, which is simpler, less expensive and requires less energy. Rapid testing of different proteins is required in various applications, including clinical diagnostics, environmental testing, food analysis, bioterrorism detection technologies, etc.
Graphene, a single honeycomb-like sheet of carbon atoms, have been intensively investigated in most recent owing to its extraordinary high mobility even at room temperature [1]. Since graphene has a perfect two-dimensional structure, electrical characteristics in graphene devices are very sensitive for modulation of surface potentials in graphene channels. In this study, we have demonstrated highly sensitive electrical detection of biological molecules based on graphene devices.
A monolayer graphene was obtained by mechanical cleavage of graphite or CVD-based graphene on SiO2 films. Graphene devices were fabricated by conventional lithography and lift-off method. A silicone rubber was placed on the graphene devices so that the graphene channel was immersed in a buffer solution. An Ag/AgCl reference electrode was used as the top-gated electrode to minimize environmental effects.
Solution-gated graphene devices showed good transfer characteristics in buffer solution [2]. To selectively detect targets, receptors were modified on graphene channels [3-7]. For highly sensitive detection of biomolecules, small receptors such as aptamer or antigen-binding fragment (Fab) were utilized. Atomic force microscopy images revealed that receptors were successfully immobilized on the graphene channel. The receptor-modified graphene devices showed electrical detection of targets with concentration from few hundred pM to several hundred nM. Moreover, for development of highly sensitive influenza-virus sensors, glycan-modified graphene devices were also fabricated.
The biological molecules were detected with high sensitivity based on graphene devices. When a different kind of receptor is functionalized on each graphene channel in the graphene-device array, many kinds of biomolecules can be electrically detected simultaneously. Therefore, the graphene-device array can be useful for the fabrication of multiplex hand-held chemical and biological sensors for home medical care.

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