bluuebunny/crossref_metadata_2025 huggingface dataset:
Iron Oxide As an Oxygen Evolution Catalyst for Zinc-Air Batteries Synthesized Via Atomic Layer Deposition
Authors: Labbe Matthew , Clark Michael Patrick , Cadien Ken , Ivey Douglas G
Published: May 2020

Implementation of renewable energy into the power grid is a necessary step for a more sustainable future. However, this process is strongly dependent on the capacity of practical energy storage technologies available. Zinc-air batteries show great promise for energy storage, boasting high theoretical energy density, inexpensive electrode materials, and excellent safety. Current development of zinc-air batteries is, however, stifled by the sluggish oxygen kinetics occurring both during discharge and charge. While precious metals such as platinum and ruthenium are considered to be good catalysts, more abundant, inexpensive transition metal catalysts have been found to perform just as well and with better cycling stability [1], [2].

This work focuses on the development of transition metal oxide catalysts using atomic layer deposition (ALD). ALD is a gas phase deposition technique that generates conformal thin films through the use of self-terminating surface reactions. In particular, iron oxide catalysts, which promote the oxygen evolution reaction, are synthesized via ALD using an ethylferrocene precursor. Iron oxide growth from this precursor is enabled by an oxygen plasma reactant. Recipe development is showcased, demonstrating saturating behaviour for the growth of iron oxide films.

The synthesized catalytic films are deposited directly onto a porous carbon substrate (gas diffusion layer or GDL), which is used as the air electrode in metal-air batteries. The high surface area GDL takes full advantage of ALD’s conformal nature to maximize the surface area of the deposited catalytic film, optimizing catalytic performance. As well, compared with other deposition techniques, ALD increases the depth of catalytic loading into the pores of the electrode. This increases the three-phase boundary volume consisting of gaseous oxygen, aqueous hydroxide ions, and solid catalytic active sites, thereby improving battery performance [3]. Deposited iron oxide films are tested through various electrochemical techniques to quantify catalytic activity. Iron oxide is combined with other transition metal oxides with the goal of creating a bifunctional catalyst, which is active for both the charge and discharge reactions in a zinc-air battery.

[1] M. Xiong, M. P. Clark, M. Labbe, and D. G. Ivey, “A horizontal zinc-air battery with physically decoupled oxygen evolution/reduction reaction electrodes,” J. Power Sources, vol. 393, pp. 108–118, 2018.

[2] D. Aasen, M. Clark, and D. G. Ivey, “A Gas Diffusion Layer Impregnated with Mn3O4 -Decorated N-Doped Carbon Nanotubes for the Oxygen Reduction Reaction in Zinc-Air Batteries,” Batter. Supercaps, vol. 2, pp. 1–13, 2019.

[3] Y. Li and H. Dai, “Recent advances in Zinc-air batteries,” Chem. Soc. Rev., vol. 43, no. 15, pp. 5257–5275, 2014.
Metal Chelate Flow Battery Chemistry
Authors: Robb Brian H. , Waters Scott E. , Marshak Michael P.
Published: May 2020

Long-duration energy storage is increasingly recognized as the principal limitation that is preventing the widespread use of renewables on the grid. This talk will present new flow battery electrolytes that use of metal ions coordinated to organic ligands called chelates. One particular class of chelates, called polyaminocarboxylates are known to bind metal ions very strongly and are used for a wide variety of industrial applications including textiles, water treatment, paper pulping, agriculture, consumer products, and medicine. We found that a chelate called PDTA, differing from EDTA by just one additional carbon atom, was better suited for coordination to chromium. By tightly coordinating to the chromium ion, the chelate prevents the electrons stored on the metal from reacting with the water in the electrolyte. This approach has allowed us to create some of the highest voltage aqueous flow batteries and allows them to be operated near neutral pH. In particular, we have demonstrated a chelated iron-chromium flow battery operating at pH 9 with 1.62 V equilibrium potential, stable cycling over 160 hours at 100 mA/cm2.
Battery Durability and Reliability Under Electric Utility Grid Operations
Authors: Baure George , Devie Arnaud , Dubarry Matthieu
Published: May 2020

Battery Energy Storage Systems (BESSs) show promise to help renewable energy sources integration onto the grid. These systems are expected to last for a decade or more, but the actual battery degradation under different real-world conditions is still largely unknown.

In this work we analyzed different types of usage for batteries similar to deployed 1MW and 2MW BESS in the Hawaiian archipelago. These batteries are used for a mix of different applications such as voltage smoothing, curtailment, reserve and frequency regulation. With different usages come different battery degradation. A new protocol encompassing all those applications was designed to be able to test the cells and assess their durability in the field. We investigated the impact of frequency regulation duty cycles with different SOC ranges, depth of discharge and temperatures. We also investigated cells with varying duty cycles and temperatures to decipher whether the degradation can be predicted from a laboratory experiment.

Based on the BESS representative usage profiles, we designed cycle-aging and calendar-aging experiments to test the degradation in a controlled fashion. The frequency regulation duty cycle was extracted from a 3 years usage analysis of a previous generation lithium titanate BESS in operation in Hawai'i since 2012. Laboratory testing was used to investigate the degradation in detail to improve remaining useful life predictions. The degradation mechanisms, and their path dependency, were analyzed using incremental capacity analysis and mechanistic modeling. It was found that despite the fact that most of the cells did less than 0.5% capacity after more than 400 days of testing, they actually degraded significantly. Cell temperature had the strongest impact on the loss of lithium inventory whereas duty cycle had a big impact on the loss of positive electrode material. Interestingly, the impact of SOC in the calendar aging experiments, was found to be counter-intuitive as batteries lost capacity faster at low SOCs than at high.
(Invited) Surface Acoustic Wave Sensors for Refrigerant Leak Detection
Authors: Thallapally Praveen K
Published: May 2020

Advanced sensors for detection of gases and vapors are required for energy and environmental monitoring. For example, detection of refrigerant leaks from HVAC equipment specifically difluoromethane at low concentrations in air is required. When a refrigerant leak occurs from a HVAC system, there are several consequences, i) reduction in cooling efficiency and ii) higher greenhouse gas emissions to the atmosphere. Sensing refrigerant leaks requires sorbents with high affinity at low partial pressures. Having a highly effective sorbent sensitive to fluorocarbon refrigerant vapors provides a means to develop a sensing device for leak detection. In this regard, Pacific Northwest National Laboratory is exploring novel classes of materials including metal organic frameworks (MOFs), covalent organic frameworks and porous organic cages as a thin film on surface acoustic wave sensor for detection of refrigerant leaks. The structure and selectivity of these materials can be tailored by the selection of various organic bridging ligands used in the synthesis. Further these materials shown to have high surface area and shown to have high gas mobility higher than many other sorbent materials. These characteristics are highly favorable for development sorptive materials for sensing refrigerant molecules from air. Our work in this area suggest these materials reflect a range of sorbent properties from high uptake capacity (over 170 wt%) at high vapor pressures to very high sorption affinities at very low vapor pressures. I will discuss methods to use these materials as a thin film on surface acoustic wave sensor for detection of refrigerant molecules
Synthetic Melanin Coated Carbon Fiber Micro-Electrodes for Selective Detection of Peroxynitrite
Authors: Kalil Haitham , Thompson Mitchell , Pignataro Gina , Al-Mahmoud Ousama , Maher Shaimaa , Ibrahim Magdy , Bayachou Mekki
Published: May 2020

Melanin is a natural pigment produced by melanocytes and has many physiological functions. Recent studies have suggested that melanin can behave like a free radical scavenging antioxidant. In biological systems, free radicals can damage a wide array of the essential components in the human body, such as cells/tissues, DNA, proteins, and lipids. Peroxynitrite (PON) has emerged as a combination of two free radicals and it can yield secondary free radicals per homolytic decomposition. PON is a biological oxidant that has been linked with oxidative damage and disruption of redox control systems. The short lifespan and fast reactivity of PON add more challenge to measure its concentration under physiologic conditions.

Carbon fiber electrodes (CFEs) have the advantage of providing a minimally invasive and a non-toxic platform when compared to other metal-based electrodes. In this research study, synthetic melanin-coated CFEs were prepared using electro-deposition of 5,6-dihydroxyindole monomer. Surface characterizations including scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS) were utilized to confirm the melanin deposition and to examine the morphological differences between the modified CFEs before and after exposure to PON. Cyclic voltammetry, differential pulse voltammetry, and amperometry were used to test the performance of CFEs modified with synthetic melanin in terms of detection and quantification of PON. Our preliminary findings have shown that synthetic melanin modified CFEs have greater sensitivity when compared to glassy carbon electrodes and other macro-electrodes. In addition, melanin-coated CFEs exhibit high selectivity when they tested for PON detection in the presence of biological interferents. The present results indicate the possibility of using melanin-coated CFEs as a sensitive and selective sensing platforms for peroxynitrite detection in the nanomolar range at physiologic conditions.
Local Hypoxia System As a Sensing Interface of Cellular Responses
Authors: Wong Joseph Jo Yin , Varga Balazs , Karadottir Ragnhildur Thora , Hall Elizabeth Anne Howlett
Published: May 2020

Oxygen concentration is one of the critical factors tightly controlled in each part of an organism to regulate the cells’ role and function. Yet, changes in tissue oxygenation often occur in small focal areas with aging or as a result of an injury. Despite the serious health implications of focal hypoxia, no methodologies exist that can model oxygen supply system accordingly in animal models or in vitro models. Therefore, we designed a novel local hypoxia system as a sensing interface for in vitro cell culture. The oxygen removal efficiencies measured by Clark electrodes showed that O2 concentration can be reduced from 20.9% / 140mmHg or 5% / 35mmHg and maintained at hypoxia (< 1.5% / 10mmHg) in 15 or 8 minutes respectively. The induced hypoxia stimulated localized time-dependent HIF-1α transcription factor nuclear accumulation at the region of interest on human neural progenitor cells. This is the first system capable of robustly generating normoxia and hypoxia side-by-side on the same culture dish for comparative study. The new culture system provides the opportunity to decipher the pathophysiology of hypoxia-related diseases including stroke, dementia and cardiovascular complications.
Electrochemical Release of His-Tagged Proteins By Destruction of NTA-Cu(II)-Protein Complex
Authors: Bellare Madhura , Kadambar Vasantha Krishna , Bollella Paolo , Gamella Maria , Melman Artem , Katz Evgeny
Published: May 2020

Stimuli responsive release of biomolecules from surfaces such as gold and carbon is gaining importance for past couple of decades due to its application in biomedical field. Electrochemically induced release of biomolecules from the surfaces is one of such techniques. The simplicity of the electrochemical techniques brings-in a wide opportunity for loading and releasing biomolecules from the electrode surfaces. Here-in we report the loading and electrochemical release of His-tagged proteins from the electrode surfaces such as gold and graphite1. Reversible chelation of His-tagged proteins on Ni-NTA surfaces is studied for decades. Competing ligands such as imidazole and EDTA are used for releasing the His-tagged proteins from the Ni-NTA surfaces. However, switching the metal to Cu(II) instead of Ni(II) brings an excellent opportunity for releasing the His-tagged proteins by the reduction of Cu(II). The affinity of Cu(I) towards complexation with NTA and His-tag is substantially lower than Cu(II) which facilitates the release of the protein. Cu-NTA crafted graphite and gold electrodes were used for the coordinative loading of His-tagged proteins and electrochemical reduction of metal ion for the release of the proteins from the surface. In this study a redox mediator coupled model peptide (ferrocene-hexahistidine) and a model recombinant protein (containing His-tag) “Protein A” were used as examples for loading and electrochemical release.

ǂ These authors equally contributed to the work

Reference:

1. Bellare, M.; Kadambar, V. K.; Bollella, P.; Gamella, M.; Katz, E. and Melman, A; Electrochemical release of His-tagged proteins by destruction of NTA-Cu(II)-protein complex; Electroanalysis
2019, accepted manuscript.
Ionic Liquids and Conductive Polymers for Construction of Chemical and Biosensors
Authors: Zeng Xiangqun
Published: May 2020

Chemicals and materials with active ionic species are widely employed in various chemical and electrochemical applications such as solvents, catalysts, sensors, fuel cells, batteries, atomic switches, etc. Ionic liquids (IL) are liquids often composed of bulky organic cations or anions whereas conductive polymers are solids with dopant ions in a rigid organic framework. In this presentation, I will discuss the fundamental research of ionic liquid and conductive polymer interface electrochemistry for sensor applications. Being composed entirely of ions and with a broad structural and functional diversity i.e., bifunctional (organic/inorganic), biphasic (solid/liquid), and biproperty (solvent/electrolyte) materials, ionic liquids have the complementing attributes and the required variability to allow a systematic design process across many components to enhance sensing capability for miniaturized gas sensor system implementation. Being composed with dopant ions in a rigid organic framework, the unique properties of conductive polymers allow ease of functionalization with bio-recognition elements and enable label free electrochemical, optical and mass sensing technologies for study bio-interactions on a single platform. The simplicity of the demonstrated detection principles could yield forward-thinking solutions to many sensors challenges, especially miniaturization and robustness that is essential for their integration with engineering advancements such as portable electronics, networked sensing and next-generation monolithic implementation of autonomous sensors with the performance, cost, power, and operational lifetime characteristics to suit a broad range of applications.
Interfacial Engineering on Electronic States and Gas Sensing Performances of Metal Oxide/Graphene Composites
Authors: Ma Fei , Zhang Lizhai
Published: May 2020

Heterojunctions of two-dimensional materials have been attracting considerable attention because of their outstanding tunable optical and electrical properties. Taking the composites of CeO2/graphene and SnO2/graphene as examples, the interfacial effects on the electronic states and gas sensing properties are studied. For the CeO2/graphene composites, the electron is transferred from graphene onto CeO2 {111} facets showing the Schottky contact, but from CeO2 {100} facets onto graphene resulting in Ohmic contact. Furthermore, since CeO2{100} surface is the polar surface, and NO2 is a polar molecule, the interactions between NO2 and CeO2 with {100} polar facets should be stronger thus promoting adsorption of NO2. The internal electric field near the polar surface promotes charge separation and accelerates charge exchange between NO2 and the composites. As a result, the CeO2 {100}/graphene composites deliver substantially enhanced gas sensing performance to NO2, as compared to CeO2 {111}/graphene composites. It was also found that oxygen vacancies (Ov) have significant influences on the gas sensing performance. According to the first-principle calculations, the tunable electronic states and enhanced gas sensing performances owing to interfacial effects can be well understood.
Deposition of Pt/IrO2 Composite Films By Electroplating and Electrophoresis for Bio-Sensing Applications
Authors: Fan Tzu-Ling , Chou Shih-Cheng , Chan Tzu-Ying , Wu Pu-Wei
Published: May 2020

We demonstrate a facile approach to deposit Pt/IrO2 composite films via a bipolar pulsing deposition technique in which the Pt ions are electrochemically reduced and the IrO2 colloids are electrophoretically deposited. The composite Pt/IrO2 films are subjected to both potential pulse and differential pulse voltammetry to detect the presence of dopamine (DA) and ascorbic acid (AA) for bio-sensing applications. In human’s body, a critical concentration of DA is used as an indicator for onset of Parkinson's disease. Unfortunately, the existence of AA would interfere with the detection of DA due to their similar oxidation potential. By fabricating a composite of Pt and IrO2, a lower detection limit with a minimized interference of DA and AA could be achieved. Electrochemical parameters relevant to the preparation of Pt/IrO2 films are optimized and the resulting morphology and composition are analyzed by SEM and EDS. The oxidation state of Pt and Ir are determined by XPS. The electrical resistance and electrochemical surface area of Pt/IrO2 films are recorded by impedance spectroscopy and electrochemical analysis.
Pristine and Palladium-Doped Bismuth Ferrite Nanostructures for Nitrogen Dioxide Gas Sensor
Authors: Jadhav Vijaykumar
Published: May 2020

This research work reports the chemical spray synthesis and nitrogen dioxide (NO2) and hydrogen (H2) gas sensor applications of bismuth ferrite (BiFeO3, abbreviated as BFO) and tungsten-doped bismuth ferrite (W-BiFeO3, abbreviated as BWFO) nanostructures. The influence of tungsten-doping on the structure, morphology, surface area and the NO2 and H2 gas sensors properties was examined and compared with pristine BFO. W-doping was confirmed by X-ray diffraction, energy-dispersive X-ray and Fourier-transform infrared spectroscopy measurements. Based on the results obtained, a model demonstrating the gas sensing performance difference for the BFO and BWFO nanostructures was also proposed. At dilute concentrations (100 ppm) of NO2 and H2, BWFO displayed enhanced sensitivity (sensor response) compared to BFO, which can be accounted for by a change in morphology, structure and surface area.
Improving Monolayer Chemistries to Achieve Multiday Aptamer-Based Sensing
Authors: Arroyo Curras Netzahualcoyotl
Published: May 2020

Electrochemical aptamer-based (E-AB) sensors are a technology that enables precise measurements of specific molecular targets in the body. They have been demonstrated to support real-time therapeutic drug monitoring and feedback-controlled drug dosing in living animals. However, one drawback of E-AB sensors is the rapid degradation of their sensing interface upon continuous interrogation in biological fluids by, for example, voltammetry. Over time, the faradaic current from their aptamer-attached redox reporter decreases, and the currents from charging the electrical double-layer increase beyond the faradaic current, thus preventing signaling. The latter effect is due to progressive desorption of electrode-passivating alkyl thiol monolayers employed in these sensors. This progressive degradation limits their in-vivo operational life to hours, a period too short for monitoring the vast majority of drugs in humans, which generally have half-lives on the order of days. In response, our laboratory is investigating novel monolayer chemistries that extend the operational life of E-AB sensors without compromising their sensing performance or biocompatibility. In this presentation, I will discuss the effects that different monolayer chemistries have on E-AB sensing performance and how they extend the in-vitro operational life of E-AB sensors for days in undiluted biological fluids.
Monitoring Corona Exchange Dynamics on Single-Walled Carbon Nanotubes Using Multiplexed Fluorophore Quenching
Authors: Yang Darwin , Pinals Rebecca L , Lui Alison , Landry Markita P
Published: May 2020

Single-walled carbon nanotubes (SWCNTs) non-covalently modified with DNA have been widely implemented as probes for near-infrared molecular sensing and imaging in biological systems. However, these constructs show poor stability in biomolecule-rich, in vivo environments leading to attenuation of sensor response. To study the relevant interactions that occur between DNA-SWCNTs in a biological environment, we develop a method to capture real-time binding behavior of fluorophore-labeled biomolecules, utilizing the SWCNT surface as a fluorescence quencher. We apply this assay to monitor corona dynamics of proteins adsorbing on single-stranded DNA (ssDNA) functionalized SWCNT dopamine sensor. We show the proteins albumin and fibrinogen adsorb to varying degrees on the ssDNA-SWCNT surface. Fibrinogen adsorption was 168% greater than that of albumin on a mass basis. Furthermore, fibrinogen induced more DNA desorption than albumin. These results are recapitulated by the respective kinetic rate constants for adsorption and desorption, calculated by fitting experimental adsorption data to a competitive adsorption model. Greater fibrinogen adsorption and induced DNA desorption coincide with a 78.2% reduction in dopamine response compared to 52.2% for albumin. We use this method to further study the passivation of ssDNA-SWCNTs with PEGylated phospholipid, a molecule shown to improve biocompatibility of nanoparticle platforms. The non-covalent interaction causes marginal desorption of DNA but significantly reduces subsequent adsorption of fibrinogen. The mitigated protein adsorption by phospholipid-PEG coincides with a reduction in sensor response attenuation. This methodology presents a generic yet robust protocol to track solution-phase competitive adsorption of multiple chemical species on a nanoparticle surface and to relate these phenomena to sensor efficacy.
Soft Electrochemical/Electronic Devices and Their Applications in Point-of-Care Testing
Authors: Li Fei
Published: May 2020

Using soft materials (e.g., paper, hydrogel) to replace the traditional hard materials (e.g., glass, silicon) as substrates have become a recent trend in developing point-of-care testing (POCT) platforms. And through integration of the soft materials with electrochemical or electric devices can further extend the applications of POCT. In our recent work, we used four kinds of soft materials, including paper, PDMS, hydrogel and liquid marble, as the new soft substrates of POCT platforms and realized their new applications in POCT. For example, by integration of the electrodes and hydrophobic channels on paper through simply writing method using home-made pens, the fabricated paper-based electrochemical devices have been successfully applied to detect glucose in artificial urine and melamine in sample solutions. By fabrication of MWNTs/PDMS fibers as multifunctional sensors and integration them on a glove, the measurement of gesture recognition and temperature have been realized by the “smart” glove. Through injection of liquid metal into the 3D helical structure of hydrogel and combination the hydrogel with electronic sensing device, the temperature, UV sensing and EMG signal detections have been performed by the wearable, multifunctional hydrogel device. By using liquid marble as a separator and small device for isoelectric focusing, the POCT separation and analysis of proteins have been realized. The proposed new soft platforms show wide application potential in POCT.

References

[1] H. Liu, M. X. Li, S. B. Liu, P. P. Jia, X. J. Guo, S. S. Feng, T. J. Lu, H. Y. Yang, F. Li, F. Xu, Spatially Modulated Stiffness on Hydrogel for Soft and Stretchable Integrated Electronics, Material Horizons. 2019, DOI: 10.1039/C9MH01211G.

[2] Z. D. Li, H. Liu, X. C. He, F. Xu, F. Li, Pen-on-Paper Strategies for Point-of-Care Testing of Human Health, Trac-Trends Anal. Chem. 108 (2018) 50-64. doi.org/10.1016/j.trac.2018.08.010

[3] H. Liu, M. X. Li, C. Ouyang, T. J. Lu, F. Li, F. Xu, Bio-friendly, Stretchable, and Reusable Hydrogel Electronics as Wearable Force Sensors, Small. 14 (2018) 1801711. doi: 10.1002/smll.201801711
Tailored Syngas Production Via High Temperature H2o-CO2 Co-Electrolysis
Authors: Marina Olga A. , Coyle Christopher A , Meinhardt Kerry D , Holladay Jamelyn
Published: May 2020

Solid oxide electrolysis cells (SOEC) operating at 600 – 850°C are used to split water using excess renewable or nuclear electrical energy and convert it to chemical energy which is stored in H2 and O2. SOECs can also be used as electrochemical reactors for the co-electrolysis of steam and carbon dioxide. The two reactants, typically waste products in an industrial plant, could be turned into syngas (CO+H2), a valuable and very commonly used reagent in the chemical industry. Syngas is subsequently used to produce synthetic fuels, olefins or other liquid hydrocarbons via Fischer-Tropsch synthesis or for methanol synthesis and hydroformylation.

In this presentation we focus on CO2-H2O co-electrolysis, the simultaneous electrochemical reduction of carbon dioxide and steam, carried out on the porous Ni-based electrodes in high temperature SOECs. Experiments were conducted using multiple button cells. The rate of the electrochemical reactions was measured in the temperature range 700-850oC for varied reactant compositions: 10-98% CO2 and 5-50% H2O, also in the presence of some H2 and CO. Kinetics of electrochemical CO2 reduction were evaluated for different CO2/H2O ratios and compared to steam electrolysis. Product analysis was completed using gas chromatography. Long term electrochemical performance of multiple cells was recorded simultaneously for over 500 hours of continuous testing with occasional interruptions to obtain current-voltage characteristics and collect the impedance spectra. The ability to control H2 :CO ratios in generated syngas by varying the inlet H2O/CO2 ratios and cell potential was demonstrated. Thus, precise control of the H2 to CO ratios, a unique feature of electrochemical conversion can be used to optimize selectivity of the desired byproduct.
Advanced Electrochemical System for Energy Storage through CO2 conversion
Authors: Zhang Jiawei , Li Wenping , Zhang Bowen , Gao Minrui , Xu Chenyu , Duan Nanqi , Luo Jing-Li
Published: May 2020

The extensive usage of fossil fuel as energy source has led to the increased atmospheric concentration of CO2, which is mainly responsible for the negatively intensified greenhouse effect upon our living habitat. Various pathways have been studied in order to alleviate the negative effects of CO2 emission; electrochemical reduction of CO2 is considered as one of the promising method to effectively reduce CO2 emission. The process involves the conversion of CO2 to useful chemicals and fuels using high temperature solid oxide electrolysis cells (SOECs), these devices can run in the opposite direction in solid oxide fuel cells but utilize similar concepts, and involve materials challenges and operating conditions to achieve ‘Power to Fuels’. It is well known that CO2 molecules are very stable so that high energy input is required for cathodic reaction to proceed. The cathodic reaction, therefore, plays a vital role in the overall cell performance and so far, extensive investigations have been conducted to develop the advanced cathode materials with high catalytic activity and stability.

Among various types of catalysts for SOECs, perovskite-based materials have attracted world wide research efforts as the mixed ionic and electronic conductors through introducing proper doping elements into perovskite lattice during synthesis process. Nonetheless, the cathodic material thus developed still suffer from relatively lower catalytic activity compared to conventional nickel-based cermets. In this work, three strategies are adopted to improve their performance of CO2 electrochemical reduction. It has been demonstrated that the perovskites with exsolved nanoparticles anchored on the surface of matrix exhibit excellent catalytic activity in comparison with the conventional ones. As a facile in-situ process, exsolution can significantly increase the number of reaction sites by forming uniformly dispersed active nanoparticles and at the same time, can efficiently impede agglomeration of nanoparticles under high temperature. Therefore, the perovskite with exsolved nanoparticles is a promising cathode material that can enhance the overall performance of CO2 reduction in an electrochemical cell.
(Invited) Oxygen Vacancy Mobility in Praseodymium Doped Ceria over Wide Temperature Limits
Authors: Kalaev Dmitri , Defferriere Thomas , Nicollet Clément , Kadosh Tamar , Tuller Harry L.
Published: May 2020

Solid state mixed ionic-electronic conductors in which ionic transport is commonly accompanied by predominant electronic conductivity, underpin key technologies and require universal characterization methods for monitoring transport at the nanoscale, at both high and near ambient temperatures, the latter being especially challenging. In this study, a novel dynamic current-voltage analysis technique is utilized to decouple ionic and electronic transport properties from each other. The versatility of the method is demonstrated by enabling measurement of the oxygen vacancy mobility in Pr0.1Ce0.9O2-δ
thin films, across an unusually wide temperature range, from 35 to 500 °C. Despite the presence of predominant electronic conduction, the oxygen vacancy mobility in Pr0.1Ce0.9O2-δ
was measured, being 6.8×10-6 cm2V-1s-1 at 500 °C, decreasing by seven orders of magnitude down to 35 °C, and following a single thermal activation energy of 0.82 ± 0.02 eV. A comparison with previous reports on oxygen vacancy transport and with the one derived in this study from impedance spectroscopy, interpreted with the Jamnik-Maier model, further confirms the dynamic current-voltage analysis results. This method can more generally be applied to other types of mixed ionic-electronic conductors, thereby enabling deeper insights into mobile ionic defect transport and accompanying thermodynamic properties.
Introduction of Disruptive Gas Flow Via Fluidic Oscillation to Improve Solid Oxide Cell Performance
Authors: Rothman Rachael H , Call Ann V , Holmes Thomas D , Desai Pratik D , Zimmerman William B
Published: May 2020

An increased focus on renewable technologies is necessary to meet the level of carbon emission reduction required to achieve the 2°C scenario (2DS). Carbon containing materials are at the root of most industrial value chains and currently 90% of organic chemicals are made from fossil fuels and 5-10% of global crude oil demand is for the manufacture of chemicals. By providing a process to convert waste CO2 into high value CO we can take steps towards the goal of reducing emissions and provide an important link between various sectors to turn waste materials into new products, improving resource efficiencies, and reducing negative environmental factors. This presents a significant opportunity to leverage CO2 as a feedstock while supporting global goals in green energy, manufacturing, etc.

Solid oxide cells (SOCs) provide an effective mode of simultaneously reducing CO2 and separating O2, however, over 80% of the cost to co-electrolyse CO2 and H2O comes from electrical input necessary to drive a SOEC. While changes in cell geometry and composition have been used to improve performance, energy inputs need to be reduced to increase overall device efficiency for widespread commercialisation to be realised.

In this work we focus on the use of oscillating the gas flow into an SOC to create a highly efficient energy conversion device to facilitate the reduction of CO2 to CO. Fluidic oscillation is known to cause disruptive flow which promotes turbulence in small flow fields, thereby increasing the overall efficiency – key to furthering their commercialisation.

Fluidic oscillators are one of a variety of fluidic switching devices developed in the field of microfluidics. A single gas supply inlet guides an incoming gas flow into a destabilising microfluidic feature, generating the necessary disruption that results in jet diversion between two identical channels. This switching results in a pulsed flow in each of the outlet channels, alternating between full forward flow, and very slight backflow. The flow in the forward regime bears similarity to laminar flow, whereas the slight backflow regime more closely resembles turbulence. This effect can be observed even in extremely small channel diameters and causes a disruptive effect which interrupts the formation of a boundary layer of stagnant gas flow along flow field chamber walls. While conventional oscillators require high flow rates on the order of 50-80 L/min, for this particular work we are utilising a novel fluidic oscillator capable of producing an oscillatory flow at low onset flow rates of as low as 50 ml/min, which is necessary for operation with lab scale SOCs.

Experimental results show improved performance with the addition of oscillating gas flow and no other changes to cell geometry, materials composition, or gas composition. The magnitude of improvement in polarization resistance was dependent on operating conditions, the reasons for which will be discussed in the paper.
Development of Protonic Ceramic Fuel Cells Using Yb-Doped BaZrO3 Electrolytes
Authors: Kuroha Tomohiro
Published: May 2020

In recent years, protonic ceramic fuel cells (PCFCs) have been widely studied and are expected to be used as intermediate temperature solid oxide fuel cells (SOFCs) [1]. PCFCs’ power generation efficiency will likely be higher and operating temperature lower than those of SOFCs using yttrium stabilized zirconia as an electrolyte [2]. However, PCFCs are at the research and development phase and many issues such as durability must be overcome for practical use. Therefore, we fabricated single-cells and evaluated their power generation performance and durability from a practical perspective.

Acceptor-doped barium zirconate was used as the electrolyte material because it has CO2 stability. Previous studies have shown that yttrium-doped barium zirconate (BZY) has the highest proton conductivity. However, cells using BZY crack in the conventional ceramic tape-casting and firing process used to fabricate laminated ceramic electronic devices. This is because the NiO used for the anode reacts with BZY to form BaY2NiO5.

The reactivity between the acceptor-doped barium zirconate and NiO was examined at the 1500 °C firing temperature. Ytterbium-doped barium zirconate (BZYb) did not form the complex oxide with NiO. Using BZYb revealed no problems such as cell cracking. In the cell using BZYb, the maximum power density at 700 °C and 600 °C were 0.70 Wcm-2 and 0.49 Wcm-2, respectively. Electrochemical impedance spectroscopy of the cell showed that the ohmic resistance was 0.28 Wcm2, approximately three times larger than the resistance value calculated using the bulk conductivity of BZYb and electrolyte thickness. It seems to be due to the solid solution of Ni in the electrolyte. To improve performance, techniques to prevent Ni solid solution diffusion are necessary.

References

[1] C. Duan, R. O’Hayre, Nature 557 (2018) 217–222.

[2] Y. Matsuzaki, K. Sasaki, Scientific Reports 5 (2015) 12640.
(Invited) Equivalent Circuit Analysis of Mass Transport of Proton- Oxide Ion- Electron Mixed Conductors for Fuel Cells and Electrolysis Cells
Authors: Yashiro Keiji , Okuyama Kotaro , Kawada Tatsuya
Published: May 2020

Recently proton conducting ceramics have been intensively developed for proton ceramic cells (PCCs) for fuel cell and electrolyzer. There are potentially three conduction carriers (proton, oxide-ion, electron hole) in a proton conducting electrolyte, whose partial conductivities vary drastically with change in chemical potential and temperature. Therefore the complicated mass transport phenomena in proton conducting electrolyte must be fully understood to develop the fuel cell and electrolysis cell. While a couple of papers have reported the analysis results of behavior of proton, oxide-ion, and electron hole in the electrolyte [1, 2], the cell behavior including electrode materials are not yet fully understood. In this paper, we analyze complex impedance response of PCCs under the operation conditions of fuel cell and electrolysis cell by equivalent circuit analysis using universal circuit simulator.

[1] H. Zhu, R. J. Kee, Int. J. Hydrogen Energy, 41 (2016) 2931.

[2] D. Poetzsch, R. Merkle, J. Maier, Adv. Func. Mater., 25 (2015) 1542.
Electrochemical Analysis of Anode Supported Pcfc with Pseudo Symmetrical Cell
Authors: Yamauchi Kosuke , Kuroha Tomohiro , Goto Takehito , Terayama Takeshi , Mikami Yuichi , Asano Hiroshi , Tsuji Yoichiro , Shiraishi Seigo , Okuyama Yuji
Published: May 2020

Protonic Ceramic Fuel Cell (PCFC) is expected to be the next-generation fuel cell for its higher energy conversion efficiency and lower operation temperature. BaZrO3 based oxide are potential materials as PCFC electrolyte because they have a high chemical stability under CO2 condition and high proton conduction. [1] Recently, we have developed PCFC using BaZr0.8Yb0.2O3-δ (BZYb) as the electrolyte. The proton conductivity of the BZYb pellet was 1.1×10-2 S/cm at 600℃ and did not form the complex oxide with NiO. The power density of the developed cell (Ni-BaZr0.8Yb0.2O3-δ|BaZr0.8Yb0.2O3-δ|La0.6Sr0.4CoO3-δ) achieved 0.49 W/cm2 at 600℃.To improve the performance of anode supported PCFC, anode supported pseudo symmetrical cell:

Ni-BaZr0.8Yb0.2O3-δ|BaZr0.8Yb0.2O3-δ|Ni

was manufactured and analyzed by impedance spectroscopy under the various conditions and temperatures (Figure).The thickness dependence of the ohmic resistance was measured for three types of electrolyte (thickness: 8 μm, 16 μm and 25 μm) under 48%H2-49%N2-3%H2O gas condition at 300-700℃. The conductivity was calculated from the relation between electrolyte thickness and the ohmic resistance, which was 0.35×10-2 S/cm at 600℃. The degradation of proton conductivity occurs due to Ni dissolution. The performance of anode supported PCFC might be improved further if the Ni dissolution to electrolyte can be inhibited.

Reference

[1] K. D. Kreuer, Proton-conducting oxides, Annu. Rev. Mater. Res., 33 (2003) 333–359.

Figure 1
Electronic Transport within Proton-Conducting Ceramics and Its Effect on Faradaic Efficiency of High-Temperature Water Electrolysis for Hydrogen Production
Authors: Regalado Vera Clarita Yosune , Ding Hanping , Zhou Meng , Ding Dong
Published: May 2020

Proton conducting ceramics are used as electrolyte materials for protonic ceramic electrolysis cells to produce hydrogen through water electrolysis at high or intermediate temperatures. The widely applied barium-cerium-yttrium-zirconium oxides have been well studied as proton conductors for fuel cell applications, which present a promise in commercialization. In water electrolysis operating conditions electronic leakage within electrolyte can be observed, which reduces the Faradaic efficiency (FE) of hydrogen production. To address this electronic leakage problem, the intrinsic mechanism behind it should be understood. In this work, the defect chemistry in barium cerate and barium zirconate doped with yttrium is comparatively studied in terms of proton, electron and hole defect concentration/conductivity, and respective distribution profile within electrolyte, where electronic and protonic current density are calculated under electrolysis working conditions such as steam concentration, oxygen partial pressure, and over-potential. In addition, the conduction behaviors of three typical proton-conducting ceramics: BaCe0.7Zr0.1Y0.1Yb0.1O3-δ, BaCe0.4Zr0.4Y0.1Yb0.1O3-δ and BaZr0.8Y0.2O3-δ are experimentally investigated under different oxygen partial pressures and temperatures to validate with the prior defect equation derivation. The results indicated that high FE can be achieved under optimized conditions with reduced temperatures, implying numerous research opportunities in materials R&D of protonic ceramic electrochemical cells (PCECs) as well as the feasibility for widespread market adoption.
(Invited) A Full Carbon Balance Analysis on High Current Density Electrochemical CO2 Reduction Reactors with Cu Catalysts
Authors: Seger Brian , Ma Ming , Clark Ezra L , Therkildsen Kasper , Chorkendorff Ib
Published: May 2020

CO2 emissions are significantly contributing to anthropogenic climate change, but at the same time the costs of sustainably based electricity has greatly been reduced in the last decade. This has provided a perfect economic and societal opportunity for electrochemical CO2 reduction into chemicals. However, this field is not technologically mature yet, and there are many engineering details that needs to be investigated. This talk will focus on understanding the complete carbon balance on low temperature electrochemical CO2 reduction reactors operating at industrial relevant current densities (100-500 mA/cm2). The focus will be primarily be on using a gas diffusion approach with a liquid catholyte using sputtered Cu as a catalyst.

By employing a post-reactor volumetric flow rate to measure outlet flow rates, highly accurate faradaic efficiency measurements were achieved. Furthermore, these results show that if one instead assumes inlet gas flowrates, this can overestimate faradaic efficiencies of gas products by up to 25%. By careful analysis of both gas and liquid products we show a near 100% faradaic efficiency as well as completely accounting for all the carbon in our reactor. Our liquid analysis showed glycoaldehyde and ethylene glycol, two products never seen before in high current density electrochemical CO2 reduction reactors

Using an anion exchange membrane, we show significant crossover to the anode of anionic species such as acetate, and formate, as well as carbonate crossover and subsequent CO2 evolution on the anode. We show that the ratio of CO2 to oxygen evolution on the anode is 2:1 throughout a current density range of 100-300 mA/cm2, however the time it takes to equilibrate at this ratio is both current dependent and dependent upon the catholyte and anolyte reservoirs. This talk will also discuss variations in pH at both the anode and cathode as a function of operating parameters and give insight into the potential advantages and pitfalls of various reactor designs.

This work was funded by the ECOEthylene project from Innovation Fund Denmark (Grant # 8057-00018B)
Microkinetic Modeling of the Oxygen Evolution Reaction (OER) on Hydrous Iridium Oxide during Dynamic Operation
Authors: Geppert Janis , Kubannek Fabian , Krewer Ulrike
Published: May 2020

In an energy system which is based on intermittent renewable sources, efficient energy storage and conversion technologies are needed. Proton exchange membrane (PEM) electrolysis is a promising technology for the storage of electrical energy in the form of hydrogen. In PEM electrolyzers, the oxygen evolution reaction (OER) is seen as the bottleneck due to its high overpotential. To enhance the overall performance, highly active but stable OER catalysts are essential. Oxidized iridium shows good activity for the OER and is more stable compared to other materials such as ruthenium oxide[1]. It has been shown that electrochemically grown hydrous iridium oxide is particularly favorable[2]. A better understanding of the changes of its complex surface structure and chemistry during dynamic operations is crucial for practical applications and for obtaining deep insights in factors that affect its activity and stability.

In the present work we investigate the surface states of hydrous iridium during the OER. For this purpose, we implement a dynamic physical model to simulate the formation of different types of intermediate states. A complete set of microkinetic equations is derived, solved and validated with cyclovoltammetric data (see figure 1). By solving the surface species balances dynamically, the phenomena that are observable in cyclovoltammetric, chronoamperometric and impedance spectroscopic experiments can be interpreted quantitatively[3].

Applying this method onto hydrous iridium oxide we are able to study the degree of oxidation of the iridium atoms at the surface at various electrode potentials. In a wide potential region from 0.4 V vs RHE up to the OER potential range, the simulation predicts the amount of adsorbed -OH, -O, -OOH and -OO species, which determine the overall oxidation state of the iridium. The characteristic peaks and shoulders in the cyclovoltammogram are assigned to the single reaction steps. By comparing different mechanisms, a deep understanding of the predominant reaction pathway is gained. Furthermore, the quantification of microkinetic rate constants allows us to define rate determining reaction steps during the dynamic operation. With this study we confirm that the mechanism in figure 1, in which two parallel reaction pathways are present, can describe the experimental cyclovoltammogram quantitatively.

[1] S. Cherevko et al., Oxygen and hydrogen evolution reactions on Ru, RuO

2

, Ir, and IrO

2

thin film electrodes in acidic and alkaline electrolytes: A comparative study on activity and stability, Catalysis Today 262 (2016) 170–180

[2] S. Cherevko et al., Oxygen evolution activity and stability of iridium in acidic media. Part 2. –Electrochemically grown hydrous iridium oxide, Journal of Electroanalytical Chemistry 774 (2016) 102–110

[3] U. Krewer et al., Impedance spectroscopic analysis of the electrochemical methanol oxidation kinetics, Journal of Electroanalytical Chemistry, 589 (2006) 148–159

Figure 1