bluuebunny/crossref_metadata_2025 huggingface dataset:
Blue Emission Stimulation in Mixture of ZnO and Carbon Nanocrystals at Mechanical Processing
Authors: Torchynska Tetyana V. , Perez Millan Brenda , Velazquez Lozada Erick , Kakazey Mukola , Vlasova Marina
Published: February 2020

The photoluminescence (PL) and X ray diffraction (XRD) of the mixture of ZnO + xC nanoparticles have been studied before and after intensive mechanical processing (MP) with the aim to identify the native defects in ZnO nanocrystals (NCs). Three types of the ZnO + xC mixtures with the x equal to 0.1, 1.0 and 3.0 %wt have been investigated. The study reflects the diversity of physical and chemical processes occurring in samples during MP: the destruction of primary ZnO nanoparticle aggregates, crushing individual ZnO nanoparticles from the size of 250nm down to 14 nm, the development of pulse and accumulative thermal processes, the interaction of carbon atoms with oxygen in the treatment chamber and with the surface of ZnO nanoparticles etc. The new PL band peaked at 2.82-2.88 eV has been revealed in PL spectra after 9 min of MP. The origin of this emission in ZnO has not been conclusively established and a number of hypotheses have been proposed. Using carbon content variation in the studded ZnO + xC mixture the new PL band at 2.82-2.88 eV has been studded and its nature has been discussed.
Effect of Rare-Earth Doping on Structural and Luminescent Properties of Screen-Printed ZnO Films
Authors: Khomenkova L. , Kushnirenko V.I. , Osipyonok N.M. , Singaevsky A.F. , Pekar G.S. , Avramenko K. , Strelchuk V.V. , Borkovska L.V.
Published: February 2020

Over the past decades, zinc oxide has attracted considerable attention for its possible application in optoelectronics due to simultaneous observation of intense ultraviolet and visible emission offering the development of white light-emitting devices. However, in the most cases the native defects responsible for visible emission are not stable upon materials processing. Moreover, for white phosphors, efficient and controllable emission in specific spectral range is often required. This can be achieved in particular via materials doping with rare-earth (RE) ions.

In the present study the results on effect of doping of screen-printed ZnO films with Sm3+ and/or Ho3+ions are presented. Photoluminescence (PL) and Raman scattering spectra as well as the X-ray diffraction patterns of undoped and doped films are examined in details versus sintering conditions and doping level.

In the PL spectra of undoped ZnO films sintered at 400−700°C, the excitonic emission was observed only, whereas sintering at higher temperatures (up to 1200°C) resulted in the appearance of visible defect-related PL bands peaked at 540−600 nm. The most intensive defect-related emission was found in the films sintered at 1000°C and these latter were doped with rare-earth ions of different concentration in the range of 1·1019− 4·1020 cm-3.

In the PL spectra of the RE-doped films, the corresponding RE emission was observed at low temperatures, but not at room temperature. Since the defect-related PL band caused by intrinsic defects in ZnO overlapped essentially with corresponding Ho and Sm PL bands, the PL bands peaked at about 700 nm due to 4G5/2→6H11/2
transitions in Sm3+ ions were observed only. At the same time, simultaneous codoping with both Sm3+ and Ho3+ ions produced significant decrease in the intensity of the UV and visible defect-related PL bands as well as the increase in the intensity of Sm3+ and Ho3+ PL components. In the PL excitation spectra of the PL band peaked at about 720 nm in addition to excitation caused by ZnO band-to-band absorption and absorption involving intrinsic defects of zinc oxide, a new characteristic absorption band at about 410 nm appeared. The effect of RE doping on the PL and PL excitation spectra is discussed in terms of the formation of RE ions complexes as well as energy transfer from ZnO host to RE ions.
(Invited) Critical Metrics and Fundamental Challenges for Hydrogen and Fuel Cell Technologies
Authors: Randolph Katie , Peterson David , Sutherland Erika , Rustagi Neha , Studer Sarah , Stetson Ned T , Miller Eric Lars
Published: February 2020

Research and development investments by the US Department of Energy’s (DOE) Fuel Cell Technologies Office have contributed to significant technological advancements leading to the cost reductions witnessed in hydrogen and fuel cell technologies over the past decade.  The long-anticipated rollouts of fuel-cell electric vehicles (FCEVs) by major automotive manufacturers over the next several years provide clear evidence of this progress.  At this tipping point when FCEVs are just entering the market, continued cost reductions sustained by ongoing scientific advances remain critical. Consumer acceptance will hinge not only on affordable cars, but also on the widespread availability of low-cost hydrogen. In the near term, hydrogen demand for early FCEV markets can be supplied through standard reforming of natural gas and biomass feedstocks.  Emerging commercial technologies based on water electrolysis can also contribute.  In the DOE’s longer term vision, a significant penetration of FCEVs into transportation markets coupled with an industrial-scale supply of renewable hydrogen could help the U.S. achieve its clean-energy and environmental goals.  The continued development of enabling technologies for the widespread and affordable production, delivery, storage and utilization of renewable hydrogen is essential.  Materials costs as well as system-level performance and durability issues all contribute to the cost barriers in these technologies. Quantifying these barriers and tying them to specific scientific and engineering metrics provides a powerful tool toward achieving needed performance enhancements and cost reductions.  In the hydrogen and fuel cell space, DOE utilizes technoeconomic analyses to quantify key materials- and system-level cost drivers over a broad technology portfolio including fuel cells, hydrogen storage and compression, and hydrogen production by electrolytic, solar-thermochemical and photoelectrochemical water splitting, among others. In these technologies, the ultimate technical and economic viability can be linked to capital and operations costs, which are in turn impacted by fundamental materials properties, including thermodynamic and kinetic limitations. As discussed in this talk, technoeconomic sensitivity studies are invaluable in linking technology-dependent cost reduction targets with specific scientific and engineering metrics and goals. They also provide vital information for establishing research priorities for addressing the key cost drivers across all hydrogen and fuel cell technologies. Opportunities to exploit research synergies among these technologies in cross-cutting functionalities such as catalysis and separations will also be discussed.
(Invited) Benchmarking Transformational Energy Technologies
Authors: James Brian David , Colella Whitney G. , Moton Jennie M.
Published: February 2020

Discussion of emerging energy conversion technologies is often made more difficult by conflicting terminology, assumptions, and perspectives of researchers who are often in different scientific specialty areas. Furthermore, researchers tend to describe their work in terms of the physical parameters they are able to measure in the laboratory, whereas policy developers and the general public tend to speak in terms of top-level system performance and economics. Consequently, there is often less than effective communication between researchers in different specialty areas, and between researchers and public policy developers. Development of a common framework to discuss all low-carbon energy conversion technologies would facilitate the transfer of ideas and foster more rapid development.

Strategic Analysis Inc. (SA) has conducted a variety of techno-economic analyses of emerging low-carbon energy conversion technologies for the Department of Energy covering a range of hydrogen production technologies including electrolysis (Alkaline, Proton Exchange Membrane (PEM), Solid Oxide (SO)), photo-electrochemical (PEC) (electrode and slurry based systems), biological, and solar to hydrogen conversion (STCH). Additionally, SA has examined fuel cell systems (PEM, SO) and fuel-cell/electrolyzer regenerative systems.  Examination of these systems grants SA an excellent vantage point to classify the similarities and differences between the systems and their corresponding performance and economic metrics.  For instance, all the solar systems utilize sunlight as the primary input energy source. However, performance is typically specified using the full light spectrum energy for photovoltaic (PV) arrays , using only the photosynthetically active radiation (PAR) spectrum for bio systems, and only the energy of direct light (not diffuse) for concentrating PV arrays. Thus all three systems would report a “% efficiency”, where the performance metrics are not directly comparable.

The objective of this presentation will be to discuss the common performance and economic metrics that apply to most/all low-carbon energy conversion technologies so as to allow easy and appropriate comparisons of the technologies. An effort will be made to chart a direct path between system level performance and economic parameters that policy makers and the general public find most useful, with the laboratory and scientific metrics that researchers typically use to discuss their work. From this, researchers will have a better holistic understanding of how their particular efforts would translate into system-level performance and a heighted awareness of negative factors that might sabotage the overall economics of the system.
(Invited) Needed Research Focus for Achieving Cost-Effective and Reliable Solar-Thermal Water Splitting
Authors: Muhich Christopher , Ehrhart Brian , Alshankiti Ibraheam , Ward Barbara , Musgrave Charles , Weimer Alan
Published: February 2020

Solar thermal water splitting (STWS) is a method for producing renewable hydrogen from water and concentrated sunlight using energy from the entire solar spectrum to directly drive the splitting reactions and, therefore, providing the opportunity for high theoretical solar to hydrogen efficiencies. In two-step STWS, a metal oxide is heated to high temperatures using concentrated sunlight until it reduces, forming a reduced product and O2. In a second step, H2O re-oxidizes the material to its original state, forming H2. Various aspects of the operation of this process have been investigated since the 1970’s including the chemistry of the active redox material which is reducing and oxidizing, the effects of redox operating conditions, and the solarthermal reactors in which the reactions occur. A perspective will be presented for important future research directions that will allow the opportunity to be realized.
(Invited) Performance and Durability of Solid Oxide Cells for Energy Storage
Authors: Barnett Scott A
Published: February 2020

The first part of this talk will discuss the application of reversible solid oxide cells (SOCs) for grid-scale energy storage, focusing on pressurized reduced-temperature cell conditions where co-electrolysis yields methane-rich fuel.  A full analysis of a storage system utilizing low-resistance thin Lanthanum Gallate electrolyte cells and large-scale underground caverns for gas storage indicates that round-trip storage efficiency > 70% can be achieved, along with storage capacity and operating cost values that are comparable or better than pumped hydroelectric storage. 

The second part of the talk will describe results on degradation mechanisms, important for SOC storage technologies to achieve sufficient long-term durability for economic viability. LSM-YSZ and LSCF oxygen electrodes have been studied in both dc electrolysis and reversing-current (alternating between electrolysis and fuel cell operation) modes; similar delamination mechanisms are observed in both cases, although stability is improved by current cycling.  A critical current density and overpotential is observed below which degradation is too slow to measure over ~ 1000 h, but above which degradation rate increases rapidly.  High efficiency storage requires SOCs characterized by low resistance at intermediate temperatures.  This makes it desirable to utilize nano-scale electrodes, but these may be susceptible to degradation by particle coarsening. Accelerated life test results for impregnated oxygen electrode materials are presented and fitted using a combined electrochemical/coarsening model, and the resulting expressions are used to predict long-term performance degradation. Life test results on Ni-based fuel electrodes are also discussed.
(Invited) Efficient Electrochemical Biogas Reforming with Enhanced Carbon Deposition Resistance of Ni/YSZ Electrode Coated with Chromium Oxide in a Solid Oxide Electrolyzer
Authors: Qi Wentao , Xie Kui , Chen Shigang , Wu Yucheng
Published: February 2020

This work investigates the Ni/YSZ and chromium oxide (Cr2O3) coated Ni/YSZ cathodes as electrodes of solid oxide electrolysers for biogas reforming. XRD, TEM, SEM and XPS confirm the formation of NiCr2O4 on Ni surface for the coated samples while it is in-situ reduced to a core-shell structure with Ni metal coated with Cr2O3. The electrical properties of Ni/YSZ and Cr2O3-coated Ni/YSZ are investigated and correlated to their electrochemical performances. The Rp of the symmetric cell with Cr2O3-coated Ni/YSZ is smaller than the Rp with Ni/YSZ in methane atmosphere. Carbon fibers is observed in the Ni/YSZ electrode, rather than in the Cr2O3 loaded Ni/YSZ electrode after exposing in CH4-CO2 (1:1) atmosphere at 800 °C for 1 h. Electrochemical reforming of dry CH4-CO2 (1:1) mixture is successfully achieved in oxide-ion-conducting electrolysers with Ni/YSZ and Cr2O3-coated Ni/YSZ cathodes, respectively. Moreover, it is found that the coating of Cr2O3 on Ni further improves CH4-CO2 conversion. The higher methane and carbon dioxide conversions has demonstrated the superiority of direct electrochemical reforming compared with the low conversions under open circuit condition in oxide-ion-conducting solid oxide electrolysers.
Electrochemical Methanation of Carbon Dioxide with Highly Dispersed Copper Nanocatalysts
Authors: Manthiram Karthish , Beberwyck Brandon J. , Alivisatos A. Paul
Published: February 2020

Although the vast majority of fuels and hydrocarbon products are presently derived from petroleum, there is immense interest in the development of alternate routes for synthesizing these products by hydrogenating carbon oxygenates. Electrochemical methods of reducing carbon dioxide could serve as a method of storing electrical energy derived from intermittent sources like solar and wind if efficient catalysts with high hydrocarbon selectivity are developed. Although metals in the form of foils are increasingly well-characterized as electrocatalysts for carbon dioxide reduction, the activity and stability of their nanoscale counterparts remain poorly understood. We present an understanding of the electrochemical conditions and catalyst architectures that afford control over the selectivity of copper nanoparticles for electrochemical methanation. Highly dispersed copper nanoparticles supported on glassy carbon exhibit enhanced Faradaic efficiencies for methanation compared to copper foils. The improved hydrocarbon selectivity for the copper nanoparticles is due to an underlying difference in the mechanism by which electrochemical carbon dioxide reduction proceeds on the nanoparticle surface. Our understanding of highly dispersed copper nanoparticles for electrochemical methanation is a first step towards their incorporation into membrane-electrode assemblies in practical electrolyzers.
Manganese Doped Lanthanum-Strontium Chromite Fuel Electrode for Solid Oxide Fuel Cell and Oxygen Transport Membrane Systems
Authors: Gupta Sapna , Singh Prabhakar
Published: February 2020

La0.75Sr0.25Cr1-xMnxO3 perovskite family, a mixed ionic electronic conductor has promising attributes to function as fuel electrode and electrolyte membrane in high temperature electrochemical devices including solid oxide fuel cell as well as oxygen transport membrane systems. In this study, role of oxygen partial pressure on the sintering behavior of (La0.75Sr0.25)0.95Cr0.7Mn0.3O3 is investigated at 1400°C (simulating device fabrication condition). Unlike conventional chromite, results show a decrease in the density during exposure to reducing atmospheres. Chronology of microstructural development is presented along with mechanisms for the role of exposure conditions on the compound formation. Electrochemical impedance spectroscopy is performed on LSCM73+8YSZ//8YSZ//LSCM73+8YSZ symmetrical cells under constant bias for 80h at ~950°C (simulating device operating condition) in both oxidizing (air) and reducing atmosphere (Ar-3%H2-3%H2O). Stable and higher performance is obtained in oxidizing atmosphere when compared to reducing atmosphere. Sr-segregation on the LSCM73 surface is attributed to the lower performance in reducing gas atmosphere. Bulk, surface and the electrode/electrolyte interfaces are examined during post-test characterization of the tested cells. No electrode delamination as well as no interface layer or compound formation is identified in the bulk and/or interface in both oxidizing and reducing atmosphere.
(Industrial Electrochemistry & Electrochemical Engineering Division Student Achievement Award) Anhydrous High-Proton Conductor Based on Ionic Nanopeapods
Authors: Hasani-Sadrabadi Mohammad Mahdi , Dashtimoghadam Erfan , Bahlakeh Ghasem , Jacob Karl I
Published: February 2020

Here we describe, significant improvement in electrochemical performance of proton exchange membrane fuel cells (PEMFCs) via incorporation of superacid-filled single wall carbon nanotubes (CNTs), called ionic nanopeapod. It has been shown that capillary filling of carbon nanotubes is an effective method to alter their physical characteristics. Here and for the first time, we describe that there is a lot of room for development through modification of the interior space of CNT by tuning its ionic nature to boost the proton transport inside the CNT with or without the presence of water molecules. High-resolution transmission electron microscopy (HRTEM) images confirm the successful modification of the interior space of CNTs. The molecular dynamic simulations revealed that anisotropic alignment of ions/water molecules inside the carbon nanotubes makes wire-like proton chains that can facilitate ionic conductivitions with very low humidity dependency. The experimental results confirm these simulation observations by showing a very high-proton conductivity (>0.2 S.cm-1) at low humidifies. The proton conductivity behavior of the membranes based on Nafion and these ionic nanopeapods is investigated in broad ranges of temperature (25-140°C) and humidity (20-100 RH%). Water and proton self-diffusion coefficients are measured using a DOTY Z-gradient probe by the NMR pulse gradient spin–echo technique (NMR-PGSE), using the Hahn spin–echo pulse sequence to confirm the proton dynamic inside the CNTs in the presence of superacids. Arrhenius plot of NMR-based diffusion coefficients, as well as ionic conductivities (based on the electrochemical impedance spectroscopy), are used to evaluate the ease of proton transportat inside the CNTs. The fabricated nanohybrid nanocomposite membranes showed outstanding characteristics including fourfold increase in the maximum power density. These newly designed ionic nanosystems have great potentials to impact high-performance PEMFC applications.
(Invited) Engineering the Microstructure and Atomic Arrangement of Pt-Based ORR Catalyst for High Activity and Durability
Authors: Yang Jun , Xu Chunchuan , Gath Kerrie , Pietrisz Patrick , Soltis Richard , Pence Benjamin , Jagnar Mark , Sun Kai , Meng Guangnan , Sohm Evan , Jia Qingying , Mukerjee Sanjeev
Published: February 2020

Polymer Electrolyte Membrane Fuel Cells (PEMFC) have been developed for passenger vehicle applications for several decades. The durability and activity of the Oxygen Reduction Reaction (ORR) catalysts is one of the main obstacles to be overcome to make PEMFC vehicle commercially viable. Efforts have been focused on: 1) Developing non-precious metal catalysts. 2)  Reducing the Pt loading and modifying the d-band structure of Pt by forming  nano-sized core-shell structures on various cores  including metallic materials, oxides, carbides and borides,  and/or alloying Pt with transition metals (Cr, Ni, Co, Mn, etc.). 3) Stabilizing the Pt nano-particles by growing them larger and making the particle size more uniform.  4) Atomically engineering the Pt environment by using hybrid support of conductive metal oxide and carbon.  Worldwide efforts have greatly improved the durability of the ORR catalysts, extending the life time of PEM fuel cell vehicles to about 2000 hours, which is still less than half of the required commercialization target of more than 5000 hours.

Pt-based ORR catalysts still dominate in PEMFC. The main requirements for an effective ORR catalyst are low Pt loading, high activity and durability. We used a PVD based method to engineer the microstructure and atomic arrangement of Pt into a 2-D connected network on worm-shaped islands of conductive metal oxides, which are deposited on graphitic carbon. A model catalyst was first developed on flat surface graphene, and it showed  much improved  activity and durability. Later, this desired Pt 2-D structure and morphology was replicated onto graphitic carbon powders. In this talk, we will discuss the catalyst, its development, and structural and electrochemical characterization using RDE and in-situ single cell experiments.  A  mechanistic understanding  for the  improvement in both activity and durability will be discussed.
Preparation and Performance Study of an Unsupported Pt Catalyst for Proton Exchange Membrane Fuel Cell
Authors: Ye Licheng , Zheng Junsheng , Tian Tian , Gao Yuan , Li Ping
Published: February 2020

As the key material of proton exchange membrane fuel cell (PEMFC), the carbon supported Pt nanoparticles are the most widely used catalyst for cathode and anode of PEMFC1. Unfortunately, the corrosion of the carbon support can lead to a decrease of catalyst performance, stability and lifetime. And then, the research on unsupported Pt catalyst is very important for the commercialization of PEMFC.

We firstly prepared PtO2 colloidal solution and an unsupported Pt catalyst was obtained by the reduction of PtO2 colloidal solution. The microstructure and morphology of samples were characterized transmission electron microscopy(TEM). The electrocatalytic performances were measured by cyclic voltammetry(CV), linear sweep voltammetry(LSV) techniques. Reaction time, temperature and pH value have significant influence on catalyst performance. The results were compared with Pt/C-JM.TEM results show that average particle size of this catalyst is 2.46 nm. After treatment at 50 oC for 1h in H2 andN2 mixture (VN2:VH2=9:1), the ECA increased to 43.15 m2·g-1. It has high oxygen reduction reaction (ORR) onset reduction potential (0.98 V). 

Acknowledgments

The authors acknowledge the support from the National Natural Science Foundation of China (21006073), the Scholarship Council and the Fundamental Research Funds for the Central Universities at Tongji University.

Reference

J.S. Zheng, X.Z. Wang, Fu R, D.J. Yang, P. Li, H. Lv, J.X. Ma. Int J Hydrogen Energy 37(2012) 4639.

J.S. Zheng, X.Z. Wang, Fu R, D.J. Yang, P. Li, H. Lv, J.X. New Carbon Materials 4 (2011) 262.

Figure 1
Effects on Wetting Agents in Cationic Contamination and Mitigation in PEFCs
Authors: Park Jaehyung , Uddin Md. Aman , Ganesan Selvarani , Pasaogullari Ugur , Bonville Leonard J.
Published: February 2020

Effects of cationic impurities on performance loss are investigated by incorporation of foreign cation into the MEA in a form of salt solution. The hydrophobic property of the gas diffusion layer (GDL) acts as a barrier for transport of aqueous contaminant solution to reach the catalyst-coated membrane (CCM). In our previous work, the role of the GDL in cationic contamination and mitigation has been studied with isopropanol (IPA) as a wetting agent of the GDL [1]. Here, we present the effect of the added 15% IPA in the cationic solution to the overall fuel cell performance by an ex-situ soak method and an in-situ injection.

As shown in Figure 1(a), MEAs were disassembled from cell and exposed to further soaking test after preconditioning process for 24 hours. Two MEAs with same configurations have been subjected to ex-situ contamination with wetting agent (cell #1) and wetting agent alone itself (cell #2). The continuous voltage drop was observed in the case of cell #1, while there was no additional performance loss during the cell operation in the cell #2. Distributed Ca2+ ion in the membrane cross section after the soaking in the 15% IPA added cationic solution was gradually moved and accumulated in the cathode side due to migration under the potential gradients, resulting in performance degradation. Figure 1(b) shows the performance loss about 80mV by the only 15% IPA solution injection in both cases of the 400mA/cm2current density and at the OCV condition due to parasitic current of IPA oxidation in the cathode leading to a mixed potential.

To analyze the effect of IPA soaking on irrecoverable performance loss during soaking, the ion exchange capacitance (IEC) values are measured for fresh CCMs, IPA soaked CCM and re-protonated CCM. In Figure 2, the IECs of reinforced membranes show remarkably different behavior in compared to non-reinforced Nafion membranes. The IEC results reveal the IPA led to a strong impact on the proton conductivity of the membrane and catalyst layers that provides an irrecoverable performance in the fuel cell.

Acknowledg
e
ments

Financial support from the Department of Energy (DOE)-EERE, DE-EE00000467 (University of Hawaii, prime contractor, Jean St-Pierre, PI) is greatly acknowledged. 

References

 [1] M. Uddin, J. Park, X. Wang, J. Qi, U. Pasaogullari, L. Bonville and T. Molter, ECS Transactions, 64 (3) 537-544 (2014)

Figure 1
Novel Gas Diffusion Layers with Separate Gas and Water Pathways for Pemfcs
Authors: He Qianran , Li Jie , Li Ling , Shaw Leon
Published: February 2020

Proton exchange membrane fuel cells (PEMFCs) as one of the low temperature fuel cells have the advantages of high energy conversion efficiency, high energy density, and environmental friendly emission.The water management on the cathode side ofPEMFCs is a main factor for the fuel cell performance, because too little water will lead to dryness of the membrane with huge ohmic loss, while too much water will block the gas channels and result in flooding. Herein, we have designed a novel gas diffusion layer (GDL) with separate gas and water pathways enabled by3D printing of PTFE in the desired locations and patterns fully controlled by a computer. With this engineered GDL the water generated in the catalyst layer can be extracted out through hydrophilic channels and brought away by the flowing air, whereas oxygen can go through the hydrophobic channels and reach the catalytic sites for the cathodic reaction without being blocked by water.This novel concept is demonstrated using different solid loadings of PTFE in slurries for 3D printing of the GDL, followed by construction of the printed GDL with the MEA,bipolar plates, and end plates to form a proton exchange membrane fuel cell stack. The electrochemical performance of the PEMFC with the 3D printed GDL is compared with that of the PEMFC without the 3D printed GDL under various gas flow rates and humidity conditions. These results will be discussed in this presentation.
Polarization Induced Changes in LSM Thin Film Electrode Composition Observed by In Operando Raman Spectroscopy and TOF-SIMS
Authors: McIntyre Melissa D. , Traulsen Marie Lund , Norrman Kion , Sanna Simone , Walker Robert A
Published: February 2020

For decades strontium doped lanthanum manganite (LSM) electrodes have been the material of choice for cathodes in high temperature solid oxide fuel cells (SOFCs). LSM has relatively high electrical conductivity at high temperatures and has mechanical properties that are well matched to yttria stabilized zirconia (YSZ), a common electrolyte material.  Recently, LSM electrodes have been employed in lower temperature (300-500 °C) electrochemical gas purification applications. Several studies have attributed the electrochemical activation of LSM electrodes to changes in the surface stoichiometry under an applied potential.1-3  The presented work explores the polarisation induced changes in LSM electrode composition by utilizing in operando Raman spectroscopy and post mortem ToF-SIMS depth profiling on LSM thin film model electrodes fabricated by pulsed laser deposition on YSZ substrates with a thin (200 nm) CGO barrier layer. Experiments were conducted on cells with 200 nm thick (La0.85Sr0.15)0.9MnO3
±δ  electrodes in 10% O2 at 500°C and 700°C under various electrical polarisations (-0.5V, ±1V and -2.5V). Raman spectra recorded continuously during polarisation showed evidence of shifts in band intensities that were both reversible and dependent on the direction of the applied potential (Figure 1).  The spectral changes were assigned to changes in the LSM electronic structure and specifically to changes in the relative oxide concentration in LSM’s near surface region.

Ex situ ToF-SIMS depth profiles were recorded through the LSM thin film electrodes and revealed distinct compositional changes throughout the electrodes (Figure 2). The electrode elements and impurities separated into distinct layers that were more pronounced for the stronger applied polarisations. The mechanism behind this separation into “layers” in the LSM electrode poses interesting questions about mass transfer and ion migration in conducting materials subject to electrical polarisation.

Figure 1. Representative Raman spectra collected on an LSM electrode at 700 °C with the cell open at circuit voltage (OCV) and polarised at (a) -1 V and (b) +1 V.  The peaks at 440 and 600 cm-1 are signatures from the CGO and YSZ electrolyte, respectively. 

Figure 2. ToF-SIMS depth profile of LSM electrode polarised at -1V at 700 °C for 2 h. Stapled lines mark layers enriched in different species.

References

1 M. Backhaus-Ricoult, K. Adib, T. St.Clair, B. Luerssen, L. Gregoratti and A. Barinov, Solid State Ionics, 2008, 179, 891.

2 M. A. Haider and S. McIntosh, J. Electrochem. Soc., 2009, 156, B1369.

3 S. P. Jiang and J. G. Love, Solid State Ionics, 2003, 158, 45.

Figure 1
(Invited) Accurate Measurement of the Water Content of Proton-Exchange Membrane Fuel Cells Using Neutron Radiography
Authors: Hussey Daniel S , Jacobson David L
Published: February 2020

The water sorption of proton-exchange membranes (PEMs) was measured in situ using high-resolution neutron imaging in small-scale fuel cell test sections. A detailed characterization of the measurement uncertainties and corrections associated with the technique is presented. With high-resolution neutron-imaging detectors, the water distributions across N1140 and N117 Nafion membranes are resolved in vapor-sorption experiments and during fuel cell and hydrogen-pump operation and measurements are in reasonable agreement with a 1-D macrohomogeneous model. The measured in situ water content of a restricted membrane at 80 °C is shown to agree with ex situ gravimetric measurements of free-swelling membranes over a water activity range of 0.5 to 1.0 including at liquid equilibration.  Schroeder’s paradox was verified by in situ water-content measurements which go from a high value at supersaturated or liquid conditions to a lower one with fully saturated vapor.  At open circuit and during fuel cell operation, the measured water content indicates that the membrane is operating between the vapor- and liquid-equilibrated states.
Electrocatalytic Aziridination of Alkenes in an Undivided Cell Mediated By Iodide
Authors: Zeng Chengchu , Chen Jie
Published: February 2020

Abstract

Efficient synthesis of aziridines is of significant importance due to their various biological activities and potential application in organic synthesis. The most popular approach to construct aziridine ring is the reaction of alkene with nitrene or its precursors. To this end, a variety of chemical protocols have been developed using chloramine-T or N-aminoheterocycles as nitrogen source in the presence of chemical oxidant. On the other hand, an electrochemical process for aziridination of alkenes with PhthNH2 was also reported in a divided cell at a controlled potential using Pt as a working electrode.

Based on our previous work, we hypothesized that the electrochemically generated oxidative state of halide species may also apply to the catalytic aziridination reaction of alkene and PhthNH2. Herein, we reported an electrochemical approach for the efficient catalytic aziridination of alkenes using iodine ion as a redox catalyst. The process is conveniently carried out at constant current in an undivided cell.
Molecules on Semiconductors: From Chromogenic Interactions to Information Processing Devices
Authors: Szacilowski Konrad , Kwolek Przemyslaw , Mech Justyna , Pilarczyk Kacper , Oszajca Marek
Published: February 2020

Rapid development of electronic technologies requires new semiconducting and dielectric materials of superior quality. Recently new applications (like LCD and OLED displays) initiated the employment of various organic materials (pentacene, oligothiophenes) as semiconductors for thin layer field effect transistors. Micro- and nanoelectronics also search for new materials of unusual properties. One of the recent examples is a memristor - a memory resistor. This fourth fundamental passive element (like resistor, capacitor and inductor) was predicted theoretically in early seventies  and demonstrated experimentally 37 years later. Memristors have opened new fields of electronics and enabled fabrication of circuits with synaptic properties  and learning abilities. Not surprisingly the prototype of this amazing device was based on very popular wide band gap semiconductor: titanium dioxide. This material is widely used as photocatalyst and in dye-sensitized solar cells, but its applications in electronic elements are relatively rare. However, TiO2 is the first material for which the photoelectrochemical photocurrent switching effect was described, which further resulted in new materials for unconventional logic devices. Other metal oxides, especially binary ones (e.g. PbMoO4, BiVO4) exhibit similar semiconducting properties (the same n-type conductivity, similar band gap values), but their properties as active materials in micro/nanoelectronic devices are almost not recognized. The role of these oxide semiconductors may be two-fold. Firstly, they can provide a solid substrate and a scaffold for self-assembly of molecular layers. Transition metal oxides should provide self-assembly template for organic molecules. Secondly, due to their non-innocent interactions with organic ligands may substantially modify properties of organic materials. These interactions may be strong enough to generate new (emergent) optical and electronic features which are not present in parent compounds. Photoinduced electron transfer (PET), optical electron transfer (OET) and photoelectrochemical photocurrent switching effect (PEPS) are such phenomena.

            This contribution presents the nature of chromogenic interactions from the quantum-chemical point of view on the example of aromatic hydrocarbons anchored to various d
0 ions in the coordination environment present in semiconducting oxide phases. The consequences of these interactions are related to the functional properties which are shown from experimental perspective in the second part. Optoelectronic switches, logic gates, binary computing circuits and artificial synaptic devices will be discussed in detail.
Simple Strategies Towards Lowering the Activation Potential of Electrochromic Devices. Case Study on TiO2-Viologen Based Displays
Authors: Manceriu Laura , Danine Abdelaadim , Da Rocha Mathias , Rougier Aline
Published: February 2020

The purpose of this study is to demonstrate the easy tuning of the activation potential of electrochromic devices (ECDs) by varying the nature of the electrolyte and counter electrode. For this purpose ECDs with a simplified configuration were fabricated (i) by using TiO2-viologen deposited on Transparent Conducting Oxide (TCO) as electrochromic active layer (EC1) and (ii) by replacing the counter electrode consisting of an electrochromic material and a conductive one (EC2/TCO) in a traditional 5-layers battery type ECD (TCO/EC1/electrolyte/EC2/TCO) by a metal electrode.

Firstly a comparison is made between polymer membrane and aqueous gel electrolytes with varying compositions, focusing on the influence of ionic conductivity on the contrast and the switching time. Low toxicity aqueous based gel electrolytes were prepared from gelatin, glycerol, and NaCl/LiCl as ion precursor, whereas the polymer membrane electrolyte consisted of 0.3M LiTFSI in BMITFSI with 40% PMMA. At the end of our study we have investigated the influence of the metal counter electrode nature, more precisely the type of metal and its surface morphology, on the devices response time and optical modulation.

The use of an aqueous gel electrolyte (~10-3/-2 S/cm) instead of a membrane electrolyte (~10-4/5 S/cm) leads to lowering the working potential window; ECDs are colored at -0.5V and bleached at 0V (Fig. 1), turning from blue to white in few seconds. Also, higher contrast (DR) and shorter coloration (tc) and bleaching (tb) times are reached for electrolytes exhibiting higher ionic conductivity (σ). The morphology of the metal electrode influences mainly the coloration kinetics, and the difference is more obvious for the electrolytes with lower ionic conductivity (Fig. 1).

Figure 1
Fibroin Films Doped with Lithium Ions for Application in Electrochromic Devices
Authors: Silva M. M. , Pereira Rui F. P. , de Zea Bermudez V.
Published: February 2020

Silk fibroin is a commonly available natural biopolymer produced in specialized glands of arthropods, with a long history of use in textile production and also in health cares. The exceptional intrinsic properties of these fibers, such as self-assembly, machinability, biocompatibility, biodegradation or non-toxicity, offer a wide range of exciting opportunities [1].

Silk research is mainly devoted regarding the biomaterials field. Although, it has long been recognized that silk is can be a rich source of inspiration for designing new materials with tailored properties, enhanced performance and high added value for targeted applications, opening exciting new prospects in the domain of materials science and related technological fields, including bio-friendly integration, miniaturization and multifunctionalization. Progresses in new technological fields such as optics, photonics and electronics are emerging [2,3]. The incorporation of polymer electrolytes as components of various devices (advanced batteries, smart windows, displays and super-capacitors) offers significant advantages relative to traditional electrolytes, including enhanced reliability and improved safety.

Preliminary tests performed with a prototype electrochromic device (ECD) incorporating the most promising electrolyte composition, silk fibroin films doped with lithium ions (LiTFSI and LiBF4) as electrolyte and WO3as cathodic electrochromic layer, are extremely encouraging.

Acknowledgements:

This work was supported by Fundação para a Ciência e a Tecnologia (FCT) and Feder (contracts PTDC/CTM-BPC/112774/2009, PEst-OE/QUI/UI0616/2014 and PEst-C/QUI/UI0686/2013) and COST Action MP1202 “Rational design of hybrid organic-inorganic interfaces”. R.F.P.P. acknowledges FCT and program POPH/FSE for a grant (SFRH/BPD/87759/2012). COST Action MP1202 “Rational design of hybrid organic-inorganic interfaces”.M. M. Silva acknowledges  CNPq, for the mobility grant provided by this institution.

 

References

[1] L. B. Shi et al.Biomaterials, 2014, 35, 1519-1530

[2] R. F. P. Pereira, M. M. Silva, V. de Zea Bermudez, Macromol.
Mater.
Eng.2014, 299, DOI: 10.1002/mame.201400276

[3] H. Tao, D. L. Kaplan and F. G. Omenetto, Adv. Mater., 2012, 24, 2824-2837
Color e-Paper Technology with Electrochemistry
Authors: Kobayashi Norihisa
Published: February 2020

The demand for global environmental conservation and decrease of CO2 evolution require the development of “new imaging media”, instead of paper.  This is called “electronic paper (e-Paper)”.  Electrochromism (EC) is defined as a reversible color change by electrochemical reaction and has several features such as color variation, memory property and so on.  Electrochromic display (ECD) is therefore a potential candidate to realize full color e-Paper.  EC materials showing color changes from clear to the three primary colors such as RGB or CMY should be required to realize full color e-Paper.

    This paper focuses on novel e-paper technology with electrochemical reaction.  First, we will show our recent results on EC materials and devices which show three primary colors (CMY) in subtractive color mixture system1, 2.   Electrodeposition is also attractive method to create colors3-5.  We will discuss the mechanism of electro-deposition and a wide range of its applications. 

We also demonstrated novel display device with dual reflective and emissive modes.  This is called dual mode display (DMD).  DMD enables both reflective and emissive mode of representation which can be chosen as a situation demand.  We fabricated DMD by combining both electrochromic (EC) and electrochemiluminescence (ECL) materials in a single cell6, 7.  The device functions as an EC cell in the reflective mode, and as an ECL cell in the emissive mode.

References;   1)
Solar Energy Materials and Solar Cells, 92 136 (2008), 2)
Solar Energy Materials and Solar Cells, 104, 140 (2012), 3)
Adv. Mater., 24, OP122 (2012), 4)
Adv. Mater., 25, 3197 (2013), 5)
Chem. Mater, 26, in press (2014). 6)
Chem. Lett., 39, 1309 (2010), 7)
Phys. Chem. Chem. Phys., 13, 19420 (2011).
An All-in-One Electrochromic Device Containing Thermally Cured Dual Functional Viologen
Authors: Kao Sheng-Yuan , Lu Hsin-Che , Chang Ting-Hsiang , Kung Chung-Wei , Ho Kuo-Chuan
Published: February 2020

Viologens are promising electrochromic material due to their high optical contrast when switched between its oxidized/reduced states.1,2 However, the utilization of the viologen in liquid form would lead to leakage problems.3Herein, a thermal-cured electrochromic gel was prepared through the utilization of dual functional vinyl-bearing viologen, which acts as an electrochromic chromophore and at the same time serves as a thermal cross-linker. When this dual functional viologen was injected into an electrochromic device (ECD), followed by the thermal treatment, an uniform electrochromic gel can be obtained. This approach provides an easier fabrication of the all-in-one leakage-free ECD. Moreover, this leakage-free ECD exhibits good compatibility with electrolytes and other chromophores, thus resulting in uniform color change. Significant optical contrast can be achieved in this ECD (as shown in Fig. 1(a)). Ultimately, This ECD reveals reversible coloring and bleaching processes while maintaining high transmittance change (> 55%) at 615 and 570 nm (as shown in Fig 1(b) and Fig. 1(c)).

REFERENCES

(1) Mortimer, R. J. Chem. Soc. Rev.1997, 26, 147.

(2) Mortimer, R. J.; Varley, T. S. Chem. Mat.2011, 23, 4077.

(3) Thakur, V. K.; Ding, G. Q.; Ma, J.; Lee, P. S.; Lu, X. H. Adv. Mater. 2012, 24, 4071.

Figure 1
Spatially Resolved Spectro-Electrochemistry Using Soft X-Ray Scanning Transmission X-Ray Microscopy
Authors: Hitchcock Adam P , Rosendahl Scott M. , Appathurai Narayan
Published: February 2020

We are using soft X-ray scanning transmission X-ray microscopy (STXM) [1] at CLS beamline 10ID1 (SM) and at ALS beamline 5.3.2.2 to investigate Cu deposition onto, and stripping from a Au surface. Electrochemical reduction of Cu(II) under acid conditions is a commonly used process to deposit copper for integrated circuit interconnects. The reduction of Cu(II) to Cu(0) proceeds via a Cu(I) intermediate, which can be detected under neutral or basic conditions. Cu 2p and O 1s spectromicroscopy is used to analyze initial and  final states, follow the process in situ, and search for intermediate species. The apparatus and techniques for spectro-electrochemical-microscopy will be described. Ex situ and in situ deposition & stripping of copper from CuCl2(aq) and CuSO4(aq) electrolytic solutions will be described. Progress towards an in situ  flow electrochemical cell and a faster response time for kinetics measurements will be presented.

STXM performed on BL 10ID1 at CLS  and on BL 5.3.2.2 at ALS. Research supported by NSERC and the Catalyst Research for Polymer Electrolyte Fuel Cells (CaRPE-FC) network.

 [1]   A.P. Hitchcock, Soft X-ray Imaging and Spectromicroscopy in Handbook on Nanoscopy, eds. G. Van Tendeloo, D. Van Dyck and S. J. Pennycook 2012.  (Wiley)

Figure 1
(Invited) High-Performance and Long-Lifetime Oxygen Evolution Catalysts for Proton Exchange Membrane Water Electrolysis
Authors: Rasimick Brian , Alia Shaun M , Pivovar Bryan S , Xu Hui
Published: February 2020

Hydrogen production from proton exchange Hydrogen production from proton exchange membrane (PEM) water electrolysis is attractive due to its simple and clean nature.  However, the technology is still expensive due to high materials cost for the catalysts, membrane, and bipolar plate. In most commercial processes, iridium (Ir) black is used as an oxygen evolution reaction (OER) catalyst at the anode. A high precious group metal (PGM) loading (> 4mg/cm2) has been used due to significant anode activation loss caused by sluggish kinetics of the OER.

Instead of using commercial Ir black, we have developed two types of high-performance OER catalysts for PEM water electrolysis. One is Ir dispersed on some supports with high oxidation resistance; the other is extended continuous nanostructures including Ir nanowires and Ir nanotubes (see Figure 1).   

First, Ir nanoparticles have been dispersed on tungsten-doped titanium oxide (Ir/W-TiO2). Doping of TiO2 with an element W can substantially enhance the electronic conductivity of TiO2 while maintaining its high corrosion resistance at high electrolyzer operating voltages. A series of Ir/ W-TiO2 catalysts with decreasing Ir loading from 70 wt. % to 25 wt. % has been synthesized. TEM images illustrates that Ir nanoparticles vary from 1 nm to 5 nm. The electrochemical surface area (ECSA) has been measured via mercury underpotential deposition (UPD).

In addition to Ir/W-TiO2, Ir nanotubes have been synthesized via a porous alumina template.  The template was coated with an iridium precursor by subliming iridium precursor at an appropriate temperature. The template support was removed via chemical   etchings. The average length of the Ir nanotubes is 5mm and the diameter ranges from 250 – 400 nm with a wall thickness of ≤50 nm. The template pore size and process conditions are being varied to change the dimension of the Ir nanotubes.  

The activity and durability of these catalysts have been evaluated in rotating disk electrodes (RDEs) and electrolyzers. Selected catalysts have reduced PGM loading of electrodes by a factor of 10 while maintaining equivalent electrolyzer performance. These catalysts will help to lower the PEM electrolyzer capital cost making PEM water electrolysis more viable for a variety of applications.

Figure 1