bluuebunny/crossref_metadata_2025 huggingface dataset:
(Invited) Challenges for Etch Technology and the Integration of New Channel Materials Beyond 7 nm
Authors: Ranjan Alok , Rastogi Vinayak , Ventzek Peter
Published: February 2020

Even with the copious advances in logic device fabrication, integration of new channel materials would represent a significant advance in CMOS technology. [1] Successful integration of new channel materials (III-V’s, Ge and SiGe) pose significant challenges for etch technology. Dry (plasma) etch technology can be used to pattern channel materials after they are deposited using an epitaxial process [2]; alternatively channels maybe inserted into bounded (for example an oxide) recesses (for example silicon) fabricated using etch technologies already developed for FinFET and SAQP applications. Less appealing is the use of wet processes that have troublesome crystallographic orientation dependencies. Dry etch technology for most new channel material candidates is not new. [3] Still, with dry etch technology there is the ever-present worry of damage. [4-6] High precision etch technology commonly referred to as atomic later etching (ALE) is an emerging viable option for new channel material integration. [7-10] Some approaches employ non-mainstream techniques such as neutral beam technology [8] or complex precursors. [10] Recent developments reinforce that conventional plasma etch technologies developed using concurrent engineering methods can meet the requirements for 7 and 5 nm logic fabrication. [7,11] This presentation will show how advanced plasma etch technologies provide a path for logic manufacture beyond 7 nm with a realistic picture of the trade-offs that must be handled for the introduction of III-Vs, Ge or SiGe. All in all, etch technologies if successfully implemented for new channel material integration relies of leveraging surface chemistry mechanisms. The presentation will be rounded out with a discussion of how first-principles methods (e.g., DFT methods) can be used to gain insight into important plasma –surface interaction mechanisms.

S. Takagi et al., Japanese Journal of Applied Physics 54, 06FA01 (2015)

Chen et al,. Nanoscale Research Letters, 7, 431 (2012)

Plasma Etching of III–V Nitrides,” by R. Shul, in Processing of Wide Band Gap Semiconductors: Growth, Processing and Applications, 250 (2000), ed., S.J. Pearton

F.D. Auret et al., Physica B, 407, 1497 (2012)

Kasumandari et al., Appl. Phys. Lett., 103, 033511 (2013)

“Dry Etching of Semiconductors at the Nano-and Micro-Scale” by S.J. Pearton in Vistas in Nanofabrication, (2012)

A. Ranjan et al., J. Vac. Sci. Technol. A 34, 031304 (2016)

S.D. Park et al., Appl. Phys. Lett. 91, 013110 (2007);

C. T. Carver et al., ECS J. Sol. St. Sci. Tech., 4 N5005-N5009 (2015)

 S. M. George, Chem. Rev., 110, 111 (2010)

 S.D. Sherpa et al., J. Vac. Sci. Technol. A 35, 01A102 (2017)
Fabrication and Characterization of CdTe Schottky Barrier Solar Cell
Authors: Zhang Xiaoyue , Stickney John Lewellen
Published: February 2020

In this work, thin films of CdTe were electrodeposited onto Au substrates at room temperature from aqueous precursor. Different methods of deposition were used to form the high quality films, including co-deposition, electrochemical atomic layer deposition (E-ALD) and rectangular potential pulse electrodeposition. The pulse mode parameters were varied and the effect on the ratio of Cd/Te and crystallinity was observed. XRD patterns of the films show a sharp peak corresponding to single crystalline cubic CdTe (111). The photoelectric behavior of CdTe films was also studied using a photo electrochemical cell (PEC). A CdTe Schottky Barrier Solar Cell with Ag as a Schottky Barrier (SB) contact and Au as Ohmic contact was also fabricated and characterized. Preliminary results on the formation and characteristics will be discussed from all the respects that mentioned above.
(Invited) Semiconductor-Based Biosensing Technology for Clinical Diagnosis
Authors: Sakata Toshiya
Published: February 2020

We are studying and developing biosensing techniques in order to analyze and monitor simply and easily biological phenomena such as DNA recognition events, antigen-antibody reaction and cell functions in vitro by use of functionalities of materials such as semiconductor. Particularly, we focus on a direct detection of ions or ionized molecules with charges, because most of biological phenomena are closely related to ionic or ionized molecular behaviors such as sodium or potassium ions through ion channel at cell membrane which are based on cell-cell communication for example, and DNA molecules also have intrinsic molecular charges based on phosphate groups. In order to detect directly ion or molecular charges, we would like to propose semiconductor-based biosensing devices based on the principle of field effect. In this talk, I will introduce some biosensing methods such as tear glucose sensing, cellular function sensing and so on with the semiconductor devices. In particular, I will point out the importance of three elements for biosensing such as detection device, signal transduction interface and biological target, as shown in image.

Figure 1
Monolithic Integration of 2D Piezoelectric Semiconductors on Printed Electrodes for Stretchable Smart Skin
Authors: Wang Ruoxing , Wu Wenzhuo
Published: February 2020

The seamless and adaptive interactions between functional devices and their environment (e.g. the human body) are critical for advancing emerging technologies, e.g. wearable devices, consumer electronics, and healthcare. Although non-electrical signals such as mechanical stimuli are inherent in these applications, electrical control of device operation dominates existing technologies. This scheme of operation not only requires a complex integration of heterogeneous components but also lacks a direct interface between the (opto)electronics and the working environment. Moreover, all existing technologies require a power source, which complicates the system design and limits operation schemes.

Stretchable electronic devices are particularly desirable for practical applications because of the high mechanical deformability and adaptability enabling their integration with three-dimensional biological systems. In this work, we demonstrate for the first time a monolithic integration of piezoelectric nanogenerator system with 3D printed electrodes as self-powered wearable devices for physiological sensing on human body. The stretchable electrodes were directly printed on soft substrates with designed patterns. Subsequently, two-dimensional ZnO nanosheets were selectively grown on electrodes without any decrease of electrode conductivity. ZnO nanosheets with controlled atomic thickness are more flexible compared with ZnO nanowires, which can generate distinguishable electrical signals under tiny mechanical deformation and sustainably perform non-invasive physiological functions, e.g. pulses detection, by harvesting power from human body. This research is expected to have a positive impact and immediate relevance to many societally pervasive areas, e.g. biomedical monitoring, consumer electronics, and human-machine interface.
(Invited) An Integrated Microbial Desalination Cell-Driven Capacitive Deionization System as an Electrochemical Means for Wastewater Treatment, Electricity Generation and Desalination
Authors: Hou Chia-Hung , Ma Chih-Yu
Published: February 2020

Due to unstainable use of natural water resources, alternative water resources such as brackish water and seawater desalination have been an emerging solution. However, development of desalination capacity is limited due to the high energy requirements for removing salt ions from water. Currently, capacitive deionization technology (CDI), following the working principle of supercapacitors, has attracted considerable attention from academia, industry, and government agency. As compared to conventional desalination technologies, CDI has several advantages including low energy consumption, easy regeneration, high water recovery, and no secondary waste. In CDI, by applying an external electric filed between two parallel of nanoporous carbon electrodes (i.e., carbon aerogel, activated carbons, carbon nanotubes, and graphene), ions can be stored at the electrode/solution interface via electrical double layer (EDL) formation. Additionally, microbial desalination cell (MDC) is a new bioelectrochemical technology for seawater desalination with simultaneous electricity generation and wastewater treatment. Basically, a MDC reactor contains an anode chamber, a desalination chamber, and a cathode chamber. In MDC, microorganisms can oxidize organic waters in wastewater to harvest electric energy, and meanwhile, salt ions can be removed during the electricity generating process. In this study, we propose a hybrid electrochemical desalination system for seawater desalination by coupling CDI device with a MDC reactor. As a result, MDC produced electricity with open circuit voltage of 0.8 V and a current of 3 mA by using bacteria to degrade organic contaminants through anode bacterial oxidation and cathode reduction. In MDC, 91% removal of chemical oxygen demand (COD) in synthetic wastewater can be achieved, and the solution conductivity can be reduced from 17,000 µS/cm to about 200 µS/cm. More importantly, CDI device can be driven by electricity harvesting from the two MDCs in parallel, and as the downstream desalination process to further desalinate salt water. The results of this study can demonstrate the feasibility of the integrated electrochemical MDC-CDI system for simultaneous wastewater treatment, power production, and water desalination.

.
Hydrogen Isotope Separation By Combined Electrolysis Fuel Cell
Authors: Matsushima Hisayoshi , Ogawa Ryota , Ueda Mikito
Published: February 2020

The heavy isotopes of hydrogen, deuterium (D) and tritium (T) are materially important in nuclear energy production. In current heavy-water nuclear fission reactors, D is used as a neutron-moderator. Similarly, in nuclear fusion reactors, which are expected to represent the next generation of nuclear power, the reaction of D and T is responsible for the energy production stage.

Many researchers have studied various isotope-separation methods, including water distillation, chemical exchange, water electrolysis and combined electrolysis catalytic exchange (CECE). The electrolysis method yields the most effective separation but the process consumes enormous amounts of electricity. This has led to a search for other methods that are more energetically efficient.

In an attempt to solve the above problem, we proposed a new concept of hydrogen separation system: the Combined Electrolysis Fuel Cell (CEFC) process [1]. Here, hydrogen and oxygen were produced by electrolysis and used for power generation by fuel cells. Less electricity was consumed by the separation process owing to the implementation of hydrogen energy recycling. More recent works have reported the hydrogen isotope effect in polymer electrolyte fuel cells (PEFCs) [2, 3].

We found that CEFC could reduce 20 % electric energy, comparing with the only electric separation process. Furthermore, CEFC showed the high separation factor (α ≃10) due to the synergistic effect of PEFC and water electrolysis. Here, we will discuss the separation efficiency and the calculation of the total energy consumption by CEFC in several electrolytic and FC conditions.

REFERENCES

[1] H. Matsushima et al., Energy, 30 (2005) 2413.

[2] R. Ogawa et al., Electrochemistry Communications, 70 (2016) 5.

[3] S. Shibuya et al., Journal of The Electrochemical Society, 163 (2016) F704
(Invited) Interaction of Ni Anode with Gd-Doped CeO2 Studied By Adsorbed Species with Infrared Spectroscopy
Authors: Kubota Jun
Published: February 2020

The interaction between Ni anode and Gd-doped CeO2 (GDC) has been studied by adsorbed CO as probe molecules using infrared spectroscopy. Ni/GDC cermet anodes are frequently used in solid oxide fuel cells (SOFC). The properties of Ni anode, such as carbon deposition with the use of fuel of methane, is known to be strongly affected by oxide electrolytes. The Ni and GDC particles are considered to be in micrometer scale each other, however the GDC particles interact to most reaction sites of Ni surfaces. The structure of Ni/GDC is first examined by Auger micro-analysis. It was found that the Ni particles in micrometer scale is mostly covered with GDC thin layer after the treatment of H2 reduction. Therefore, broadly and thinly migrated GDC on the Ni surfaces was proposed to be the essence of the interaction. Infrared spectra of CO adsorbed on Ni sites are known to reflect the nature of Ni sites. The adsorbed CO on Ni sites of Ni/GDC was found to have obvious low-frequency shift from those of Ni/Y:ZrO2 and Ni/Al2O3, indicating that GDC species were strongly interacted with the most Ni sites. The properties of interaction between Ni anode and GDC after carbon deposition will be discussed.

Figure 1
Assessing Doping Effects on Surface Chemical Stability By in Situ AP-Xps in Barium Perovskites, BaCexZr0.9-XY0.1O2.95 (x = 0.9 ; 0.2 ; 0)
Authors: Jarry Angelique , Ricote Sandrine , Geller Aaron , Zhang Xiaohang , Pellegrinelli Christopher , Takeuchi Ichiro , Wachsman Eric D. , Eichhorn Bryan W. , Crumlin Ethan J
Published: February 2020

The two major proton-conducting solid oxide fuel cell (PCFC) performance limitations are the long-term stability as well as the concentration and mobility of proton defects in the electrolyte. The main electrolyte candidates are perovskite type, in particular, yttrium doped barium Ba(Zr/Ce/Y)O3-s materials. However the poor grain boundary conductivity of BaZr0.9Y0.1O2.95 (BZY) and the lack of chemical stability of BaCe0.9Y0.1O2.95 (BCY) impede their application. The first issue can be addressed by the development of grain boundary-free thin films which exhibit conductivity level up to three orders of magnitude higher than standard sintered pellets.[1] A solid solution of BZY and BCY, BaCe0.2Zr0.7Y0.1O2.95 (BCZY), demonstrates further optimized conductivity levels and chemical stability.[2, 3] However, due to the low concentration of protons and surface gas sensitivity of these materials, detailed knowledge on the chemical interaction between elements from oxide host lattice and fuel cell environment is still lacking, hindering PCFC development.

In this work, we developed BaCexZr0.9-xY0.1O2.95 epitaxial thin films and characterized their performance with electrochemical impedance spectroscopy. We investigated the doping effect on surface chemistry by using Ambient Pressure X-ray Photoelectron Spectroscopy (AP-XPS) in fuel cell environments (100 mtorr of H2O, H2, O2 or CO2) at operating temperature (>400°C). Upon applying water partial pressure, changes in the O 1s and Y 3d core level spectra were observed with a clear dopant dependency. These results indicate the formation of degradation products at the surface. The correlation between surface activity, composition, chemical stability, and conductivity level as well as associated new insights into the dopant effect on hydration and degradation mechanisms will be discussed.

References

[1] D. Pergolesi, E. Fabbri, A. D’Epifanio, E. Di Bartolomeo, A. Tebano, S. Sanna, S. Licoccia, G. Balestrino, E. Traversa, Nat Mater
9 (2010) (10) 846.

[2] S. Ricote, N. Bonanos, A. Manerbino, N.P. Sullivan, W.G. Coors, Journal of Materials Chemistry A
2 (2014) (38) 16107.t

[3] S. Ricote, N. Bonanos, H.J. Wang, R. Haugsrud, Solid State Ionics
185 (2011) (1) 11.

Acknowledgement

This work was supported by the Office of Naval Research (ONR) and The Advanced Light Source (ALS) funded by the U.S. Department of Energy, Office of Science, and Office of Basic Energy Sciences under award DESC0001160 and Contract No. DE-AC02-05CH11231 repectively.
Correlating Cathode/Electrolyte Interface Characteristics to SOFC Performance
Authors: Szász Julian , Wankmüller Florian , Joos Jochen , Wilde Virginia , Störmer Heike , Gerthsen Dagmar , Ivers-Tiffée Ellen
Published: February 2020

Correlating chemical composition and microstructure characteristics of both electrode/electrolyte interfaces to the performance of a solid oxide fuel cell (SOFC) is of fundamental importance for further improvement [1]. Focused ion beam / scanning electron microscopy (FIB/SEM) reconstruction is one of the most advanced techniques for the quantitative assessment of microstructure characteristics of primary material phases. Progress was recently made in approaching also the local distribution of secondary phases and impurities by combining FIB/SEM with TEM/EDXS elemental analysis (transmission electron microscopy / energy dispersive x-ray spectroscopy) [2]. Applying this method to the cathode/electrolyte interface; LSCF cathode (La1-xSrxCo1-yFeyO3-
δ) / GDC barrier layer (Gd-doped Ceria) / YSZ electrolyte (Y2O3 stabilized ZrO2) reveals important findings:

Formation of the secondary phase SrZrO3 (SZO) dominates interface resistance and cell performance, depending on volume and local distribution (Fig. 1 and 2) [2,3]. This is confirmed by in-situ impedance and performance measurements of symmetrical and full cells (Fig. 1). A model is introduced, which simulates the locally resolved contribution of a secondary phase like SZO to the charge transfer reaction and GDC/YSZ interdiffusion (ID) to the ion diffusion at a heterogeneous cathode/electrolyte interface. It will be demonstrated, that the barrier layer functionality is determined by the applied sintering temperature. Functionality is achieved by a custom-tailored thick ID layer at high sintering temperatures. In contrast are low GDC sintering temperatures; then functionality fails, and a continuous SZO layer forms (Fig. 2 (a)) which increases the cathode overpotential over two orders of magnitude.

The results of this contribution are fundamental for understanding the microstructure characteristics of secondary phases and their correlation to SOFC performance. They convey intuitive knowledge to fabricate high performance cathode/electrolyte interfaces for individual cell concepts.

References

[1] J. Joos, T. Carraro, A. Weber, E. Ivers-Tiffée, J. Power Sources, 196 (17), (2011) 7302-7307.

[2] H. Yokokawa, N. Sakai, T. Horita, K. Yamaji, M. E. Brito, H. Kishimoto, J. Alloys Compd., 452 (1), (2008) 41–47.

[3] J. Szász, F. Wankmüller, V. Wilde, H. Störmer, D. Gerthsen, E. Ivers-Tiffée, ECS Trans., 66 (2), (2015) 79–87.

Figure 1
Effect of Fe-Doping on Oxygen Anion Diffusion in PrBaCo2-xFexO5+δ Double Perovskite Electrodes for Solid Oxide Fuel Cells
Authors: Anjum Uzma , Agarwal Manish , Khan Tuhin Suvra , Haider M Ali
Published: February 2020

The Molecular dynamics simulations on PrBaCo2O5+δ (PBCO) was carried out to calculated the oxygen anion diffusion coefficient in the a-b direction, which was measured to be 3 x 10-8 cm2s-1 at 873 K and the diffusion coefficient was observed to be higher than the c plane (D=8x10-9 cm2s-1 at 873K) as shown in inset of Figure 1a.The electrochemical performance was observed to correlate with the oxygen diffusion coefficient. The diffusivity in PrBa0.5Sr0.5Co1.5Fe0.5O5+δ (PBSCF) (1.18 x 10-7cm2s-1) was calculated to be higher by an order of magnitude as compared to PBCO (3x10-8 cm2s-1 at 873 K, Figure 1a). Dense thin-film of electrodes of PBSCF (2 µm thick) with <500 nm grain sizes measured to give a polarization resistance of 7.21 Ω cm2 at 873 K, (Figure 1b), which was ascribed to the bulk-diffusion in the electrode. In parallel, oxygen vacancy formation in the Gd plane (Eov= 98.4 kJ/mol) of GdBaCo2O5+δ (GBCO) was measured to be lower than that of Ba plane (Eov=266.3 kJ/mol), therefore; vacancies were observed to be concentrated in the Gd plane. The surface energy of the Ba plane was measured to be minimum ϒ =7.2 kJ/mol, which makes it the most exposed surface, while it is least diffusive for oxygen anions. Therefore, larger size bulk microstructures of GBCO were measured to give lesser than expected oxygen anion diffusivity (D=6.04x10-10cm2s-1). GBCO particles of reduced size are expected to expose higher energetic Gd plane, which may enhance diffusivity. The particle size of GBCO was reduced to 20 nm using a bio-milling approach, wherein the chemically synthesized particles were subjected to fungus Saccharomyces Cerevisiae, for 72 hrs of fermentation (Figure 1c). The electrochemical performance of the bio-milled nanoparticles electrode was improved by 20% as compared to bulk electrode of GBCO particles (Figure 1c). MD simulation on a GBCO nanoparticle showed, the diffusion in nanoparticles to represent two distinct regimes; one corresponding to the surface and other the bulk. The stability of nanoparticles were validated by calculating the root mean square deviation (RMSD) of atomic positions in MD simulations. The thickness (20A0) of diffusive surface shell regime was observed to be particle size independent, while the thickness of the diffusive core regime varies with the size of nanoparticle as shown Figure 1d. The diffusivity of the shell regime (D=3.61x10-9 cm2 s-1) was calculated higher than of the core (D=5.07x10-10 cm2 s-1 at 1073K). Thus, nanoparticles showed improved electrochemical performance as compared to the bulk electrode.

Figure 1
(Invited) H. Russell Kunz: A Perspective on His Early Career
Authors: Kunz Roderick
Published: February 2020

Fuel cell research at the Power Systems Group at Pratt & Whitney Aircraft rapidly expanded in 1962 when NASA awarded a contract to produce the fuel cells for the Apollo space program. At the time, Russ Kunz had already been at Pratt & Whitney for nine years, having been hired in 1953 straight out of college. Upon joining Pratt & Whitney, Russ was assigned to a team that had before his arrival been working to develop an advanced axial-flow turbojet engine, an activity with national security implications. This engine was to be used in two aircraft of strategic importance, an eight-engine long-range bomber and the world's first supersonic interceptor. The engine received the Air Force designation J57 and became the power plant used in both the B-52 Stratofortress bomber and the F-100 Super Sabre fighter, the latter of which became the first jet-powered aircraft able to sustain supersonic speed at low altitude and which set performance records that held for 10+ years. During his first nine years at Pratt & Whitney, Russ made significant contributions to the J57 that enabled subsequent versions to increasingly provide greater performance.

Russ' involvement with the jet engine program ended when, in 1964, Pratt & Whitney moved its Power Systems Group from East Hartford, CT twelve miles north to a smaller facility in South Windsor, CT and Russ moved with it. It was at this facility where the fuel cells for every Apollo mission from 1966 to 1972 were produced. Work there continued with the transition to the Space Shuttle program from 1981 to 2011. During this period, Russ played a leading technical role.

Although the fuel cell community may now remember Russ' for his more recent contributions, it was his earlier work on high-performance jet engines and power systems for the space program that embodied the technical challenges of a time when the future of aerospace technology was still being defined. This presentation will provide a brief overview of the contributions Russ made in his early career, within the context of the times, and the influence this work had on his family.
(Invited) Hydroxide Exchange Membrane Fuel Cells
Authors: Yan Yushan
Published: February 2020

Hydroxide exchange membrane fuel cells (HEMFCs) allow the use of PGM-free catalysts and are thus potentially economically viable. In this presentation I will provde brief overview of the history, the present state as well as the future challenges of the technology
(Invited) High-Performance PGM-Free Electrocatalysts for the Polymer Electrolyte Fuel Cell Cathode
Authors: Yin Xi , Chung Hoon T , Lin Ling , Purdy Geraldine M , Martinez Ulises , Zelenay Piotr
Published: February 2020

The activity of oxygen reduction reaction (ORR) catalysts often determine performance of polymer electrolyte fuel cells (PEFCs) as measured by their power output, open circuit voltage, and fuel conversion efficiency. Currently, Pt-nanoparticle catalysts, either supported on high surface-area carbons or prepared in a form of contiguous thin layer on conductive or non-conductive supports, represent the state of the art in ORR electrocatalysis at the PEFC cathode. However, the high and variable price and scarceness of Pt have limited its widespread implementation in the -temperature fuel cells to date, especially in automotive transportation. Under these circumstances, platinum group metal-free (PGM-free) ORR catalysts have received growing attention in recent years as a possible replacement for Pt-based formulations. The progress achieved since the development of the first nature-inspired electrocatalysts of oxygen reduction in the seminal work by Jasinski in the 1960s (Nature 201, 1212, 1964), which mostly happened through the broad implementation of the high-temperature synthesis approach, makes replacement of Pt in ORR electrocatalysts with earth-abundant elements, such as Fe, Co, N, and C, a realistic possibility.

In this this presentation, we will summarize recent progress in research targeting development of high-performance PGM-free catalysts for oxygen reduction reaction (ORR) at Los Alamos National Laboratory. Two approaches will be discussed in a greater detail: (i) the approach involving fine-tuning of the catalyst porosity and surface area using pore-forming compounds and (ii) the method specifically focusing on the development of atomically dispersed transition metal moieties and avoiding the formation of transition metal-rich nanoparticles during the heat treatment of catalyst precursors. We will demonstrate the impact that porosity/surface area optimization, through the use of either pore formers (cyanamide, ZnCl2) precursor templating (metal organic frameworks) or both, can have on the fuel cell performance of PGM-free catalysts. We will also show how modifications to the electrode structure through the change in the ionomer content and ionomer equivalent weight can lead to substantial improvements in the fuel cell performance at both low- and high current densities (aerial power density of more than 0.50 W/cm2 in H2-air testing at 80°C).

Finally, we will recapitulate the challenges still facing PGM-free research that, in spite of all the progress achieved in recent years, is yet to produce materials capable of competing with the incumbent Pt-based catalysts in terms of oxygen reduction activity, performance durability, and cost (specifically, when extended to the overall cost of a fuel cell stack).

Acknowledgement

Financial support for this research by DOE-EERE through Fuel Cell Technologies Office is gratefully acknowledged.
(Invited) Understanding Fuel Cell Materials Degradation through the Use of Advanced Microscopy Methods
Authors: More Karren L.
Published: February 2020

Polymer electrolyte membrane fuel cell (PEMFC) performance and materials degradation, particularly associated with the cathode catalyst layer, can be directly attributed to the stability and durability, as well as the uniformity/homogeneity, of the individual material constituents comprising the membrane electrode assemblies (MEAs) e.g., electrocatalyst, catalyst support, and ionomer films, and the interfaces formed between these constituents. The structural and chemical homogeneity of the constituent materials and their interfaces within catalyst layers can be quantified via advanced electron microscopy methods. Ultimately, this microstructural evidence can be directly correlated with materials-specific degradation mechanisms that contribute to PEMFC performance loss, and can be used to identify potential processing variables that will improve the microstructure and compositional homogeneity within the electrode structure and enhance MEA durability and stability during operation. Research efforts at Oak Ridge National Laboratory are focused on the high-resolution microstructural and microchemical characterization of MEAs fabricated using different electocatalysts (Pt-based) and catalyst loadings, carbon-based support materials, and ionomer solutions, as well as the same MEAs subjected to accelerated stress tests (ASTs) designed to degrade specific MEA components. High-resolution analytical microscopy methods are used to directly image and map the distribution and chemistry of the various phases within catalyst layers, both on the micrometer-scale for assessing electrode through-thickness homogeneity and at the sub-Å-level to interrogate the individual constituents and the various interfaces formed. This presentation will focus on the application of advanced microscopy methods used to evaluate cathode catalyst layers before and after ASTs and how such methods can provide insight towards improved electrode design, durability, and performance.

________________________________________________________________________

Research sponsored by (1) the Fuel Cell Technologies Office, Office of Energy Efficiency and Renewable Energy, U.S. Department of Energy and (2) Oak Ridge National Laboratory’s Center for Nanophase Materials Sciences (CNMS), which is a U.S. Department of Energy, Office of Science User Facility.
(Invited) Measuring Transport in Polymer Electrolyte Membranes
Authors: Mittelsteadt Cortney K
Published: February 2020

It is commonly agreed upon that the transport properties of PEMs have a great effect on fuel cell performance. These include proton conductivity, ion mobility, reactive and inert gas solubility and diffusivity, water transport due to concentration and pressure gradients, and electroosmotic drag. Despite this there are widely different methods used to obtain these properties, and even greater differences in reported numbers.

Much of the difficulty in reaching agreement on transport numbers lies in the difficulty of defining the polymers themselves. Small changes in temperature or relative humidity can lead to large changes in transport properties, especially conductivity and water transport. The membranes water content is also a strong function of these conditions, and therefore the dimension of the polymer is also changing. Compounding difficulties is the fact that the thermal and hygral history greatly affect structure on the nano scale, and also have a strong impact on these properties.

This talk looks at the different transport phenomena in PEMs, there relative influence on fuel cell performance, methods that have been used to measure them, and common errors that are made. It also focuses on some unsolved questions, or areas of open debate in the fuel cell community, such as does diffusivity differ when a membrane is hydrating and expanding, compared to when it is dehydrating or contracting? Can the electroosmotic drag coefficient decrease below unity? Is transport greatly affected by ionomer thickness?
(Invited) Duramat - a Systems Driven Approach to Improving Module Material Durability in the Energy Materials Network
Authors: Barnes Teresa M. , Olson Dana , Gordon Margaret , Ginley David , Toney Michael F , Jain Anubhav , Schunk Randy , Kurtz Sarah
Published: February 2020

The Durable Module Materials Consortium, or DuraMat, is a consortium led by the National Renewable Energy Laboratory (NREL), in partnership with Sandia National Laboratories, Lawrence Berkeley National Laboratory, and SLAC National Accelerator Laboratory, that is intended to accelerate the development of module materials for photovoltaics (PV) and lower the cost of electricity generated by solar power.

The overarching goal of DuraMat is to discover, develop, de-risk, and enable the rapid commercialization of new materials and designs for photovoltaic (PV) modules that can improve performance and lifetime with the goal of enabling a solar levelized cost of electricity (LCOE) of less than $0.03 per kilowatt hour. As part of the Energy Materials Network (EMN), DuraMat brings together the best of the national lab and university research infrastructure in active collaboration with the PV and supply-chain industries to achieve this goal. DuraMat provides a unique opportunity to employ the Materials Genome Initiative methodology in the EMN framework in order to accelerate advances in materials and module designs and increase US competitiveness.
(Invited) Synthetic Screening of Electrolytes for Li-Air Batteries
Authors: Jones Reese E , Gittleson Forrest S , Foster Michael E. , Ward Donald K
Published: February 2020

There is increasing interest in designing and manufacturing high-performance batteries for a wide variety of applications;however, finding the best electro-chemical system and configuration is a challenging task given all the possibilities.In particular, choosing an electrolyte optimal for a given battery configuration and chemistry is a daunting and crucial task in and of itself. We propose a computational approach to electrolyte screening and selection for a Li-air battery.Li-air batteries are particularly attractive for mobile and transportation applications given their high theoretical volumetric and gravimetric energy densities, which in part is due to using environmental oxygen.Through a combination of techniques, starting with \abinitio calculations to provide fundamental parameters, to molecular dynamics which, in turn, provides transport coefficients to a full-scale model battery, we can predict battery performance.Predictions using these techniques spanning many spatio-temporal scales are compared with a limited set of cyclic voltammetry experiments for validation before applying the process to a wide range of solvent, salt and other permutations to select the best candidates for intensive development.The concept of computational screening for battery development is not novel, eg the work the Ceder group, but here we focus on identifying ideal electrolytes for Li-air batteries where the diffusion of dissolved Li ions and molecular oxygen have been identified as power performance metrics.
(Invited) Benchmarking and Round Robin Testing for Polymer Electrolyte Membrane Water Electrolysis
Authors: Carmo Marcelo , Bender Guido , Smolinka Tom , Gago Aldo Saul , Danilovic Nemanja , Müller Martin , Ganci Fabrizio , Alia Shaun M , Fallisch Arne , Lettenmeier Philipp , Friedrich K. Andreas , Ayers Katherine E , Pivovar Bryan S , Mergel Jürgen , Stolten Detlef
Published: February 2020

The development of water electrolysis based on polymer electrolyte membrane (PEM) technology is of high importance for the advancement of hydrogen based energy solutions. To facilitate rapid improvement in material performance and durability, domestic and international collaboration is essential. A successful exchange however requires a meaningful comparison of data across laboratories. The establishment of such a meaningful comparison is a challenging undertaking that requires attention to detail with respect to operating conditions, protocols, test hardware, and instrument calibration. Members of the Annex 30 Electrolysis working group (The IEA Technology Collaboration Programme on Advanced Fuel Cells), focusing on the progress of water electrolysis and the alignment of test procedures on an international basis, have recently started an effort to address these challenges for PEM water electrolysis cells.

This presentation will focus on the challenges encountered and solutions found when developing benchmarking procedures and performing round robin testing across laboratories. The effort targets to harmonize testing procedures and enable benchmarking of PEM water electrolysis performance via in-situ performance testing using single cells.
(Invited) Best Practices for Building Robust and Usable Materials Datastores
Authors: Gunter Dan
Published: February 2020

For many years, but accelerated by the Materials Genome Initiative in 2011, there has been increasing awareness across the materials science community of the importance of the confluence of computational tools, experimental tools, and digital data. Algorithms and supercomputers have become capable of computing characteristics that can predict real-world materials performance; networks and storage can interface with high-performance computing to sift through petabytes of information from experimental instruments. Some call his confluence of computer science and materials science knowledge "materials informatics". One of the central challenges of this confluence of computer science and materials science knowledge, often called "materials informatics", is building datastores that can ingest, organize, curate, archive, disseminate, and help share and analyze materials data. Due to the nearly universal use of computing, this is arguably the most cross-cutting activity in materials science research today. Yet this activity occurs largely in the shadows. There is very little visibility of existing practices and available infrastructure from established projects such as the Materials Project or the Center for Hierarchical Materials Design, as well as little guidance for the materials science community, or sub-communities, on how to navigate the bewildering array of database products and connect these to websites or analysis environments. Despite the existence of many independent efforts, there has been little discussion on how data can be exchanged or validated between them, or scientists' lives made easier by the invention of common access patterns. The Energy Materials Network, as a cross-cutting effort, represents a significant opportunity to address some of these core social and technological challenges and bring the materials informatics efforts "into the light" of the more general scientific software community. This talk will focus on four aspects, with the overall goal being to provoke thought and discussion: (1) how to approach the scoping and design of databases, so you can solve the right problem for the right community, (2) a highly selective tour of some key technologies and design decisions in existing materials databases, and (3) considerations and best practices for the overall data lifecycle, and (4) thoughts on how the open-source development model may apply to materials data hubs. These points will draw on the speaker's long experience creating software for scientific projects in fields including high-energy physics, bioinformatics, process engineering, and materials science.
(Keynote) Electroreduction of Nitrocyclopropanes and Nitrophenyl Cyclopropanes: Mechanism of Cleavage of the Radical Anion
Authors: Lessard Jean , Fry Albert J.
Published: February 2020

There are three possible mechanisms of cleavage of a nitrocyclopropane radical anion 1•‾, mechanisms A (homolytic cleavage to a cyclopropyl radical 2• and a nitrite anion), B (homolytic cleavage to a distonic radical anion 3•‾ ), and C (heterolytic cleavage to a distonic radical anion 4•‾ [1]. With the models synthesized so far (Y = Z= alkyl, H = COOCH3), only products of mechanism A have been observed [1]. On the other hand, only two cleavage mechanisms are possible for a nitrophenyl cyclopropane radical anion 5•‾, mechanisms D (homolytic cleavage to the distonic radical anion 6•‾ ) and E (heterolytic cleavage to the distonic radical anion 7•‾ ) [1]. The isolation and characterization of the products resulting from the cleavage of the nitrophenyl radical anion 5•‾ do not allow to distinguish between the two cleavage mechanisms D (homolytic cleavage) and E (heterolytic cleavage) leading to the distonic radical anions 6•‾ and 7•‾ respectively.

To shed light on the mechanisms of cleavage of those radical anions, density functional (DFT) quantum chemical calculations were carried out on species 1-3 (B3LYP 6-31+G(d), including solvation energies in acetonitrile computed using the polarizable continuum method. The results clearly favor mechanism B and species 3 over mechanisms A and C for the decomposition of anion radicals 1•‾ whenZ = Y = alkyl and X = H.

[1] F. Couture-Martin, A. Sardashti, C. Cristea, J.M. Chapuzet, J. Lessard, ECS Transactions, 2008, 13, 13-19.

Figure 1
Chemical Modification of Surfaces By the Diazonium Chemistry
Authors: Bélanger Daniel
Published: February 2020

Modification of surfaces is currently a very active field of research. Modification by using organic molecules as precursor is attractive due to the large variety of available compounds. Although the electrochemistry of diazonium salts has been studied for more than 50 years, it was not until the early 1990s, that the formation of a film resulting from the electrochemical reduction of such salts have been demonstrated. Since then, many fundamental studies have led to a better understanding of the various processes involved in the grafting reaction. In the presentation, a brief summary of some important findings on the subject made by our group will be made. Also the presentation will show the new approaches currently developed in our laboratory for the chemical and electrochemical modification of surfaces.
Molecular Au25(SR)18 Nanoclusters: Lifetime of Electrogenerated Species and Dielectric Properties of the Protecting Monolayer
Authors: Antonello Sabrina , Dainese Tiziano , Maran Flavio
Published: February 2020

We used a series of molecular Au25(SCnH2n+1)18 clusters (n = 2, 3, 4, 5, 6, 8, 10, 12, 14, 16, 18) to study the effect of n and the presence of electrolytes on their redox potentials. We found that the average dielectric constant of the monolayer, ε
m, depends on n and is the result of contributions from ligands, solvent and electrolyte. When n increases, ε
m decreases until a virtually constant value is attained for sufficiently long ligands. The electrochemically calculated HOMO-LUMO energy gap, on the other hand, does not depend on n and, therefore, ε
m.1 We also studied the effect of n on the lifetime of electrogenerated species. Whereas on the voltammetric timescale the -1, 0, and +1 charge state of Au25 clusters are stable, formation of the -2 and +2 states causes fragmentation of the cluster. Voltammetric analysis indicates that the former entails reactions involving ligands in the Au12(SCnH2n+1)18 protecting shell, whereas the latter is accompanied by a slower but also more substantial fragmentation affecting the integrity of the central Au13 core. 2

References

1. Antonello, S.; Dainese, T.; De Nardi, M.; Perotti, L.; Maran, F. Insights into the Interface Between Electrolytic Solution and Gold Core in Molecular Au25(SR)18 Clusters. ChemElectroChem.
2016, 3, 1237–1244.

2. Antonello, S.; Dainese, T.; Maran, F. Exploring Collective Substituent Effects: Dependence of the Lifetime of Charged States of Au25(SCnH2n+1)18 Nanoclusters on the Length of the Thiolate Ligands. Electroanalysis
2016, 28, 2771-2776.
Developing New Synthetic Methods for the Construction of Complex Molecules and Complex Molecular Surfaces
Authors: Moeller Kevin D
Published: February 2020

Electrochemical methods enable the generation, study, and utilization of reactive intermediates that are derived by reversing the polarity of known functional groups. In this way, they provide a unique method for exploring new reactions that would not otherwise be possible. In the talk to be presented, two such methods will be discussed.

In the first, we have been examining both radical cation and radical intermediates that are generated under net oxidative conditions. The reactions can be used to generate a wide variety of new bonds and ring systems. Recently, we have been focusing on two aspects of the reactions. First, how the reactions can be best incorporated into a synthetic sequence so that either radical cation or radical pathways can be utilized. The key is the development of a rapid means to generate either enol ether or endiol substrates for the electrolysis and then a study of the subsequent reactions (Scheme 1). Second, we have been examining how mechanistic insight into the nature of the reactive intermediates generated can be used to overcome synthetic barriers that have in the past limited use of the reactions.

In the second method to be discussed, electrochemistry and the ability it offers to generate and control new umpolung reactions is being used to conduct the total synthesis of complex molecular surfaces. The reactions range from transformations that convert synthetically optimized surfaces for use on microelectrode arrays into surfaces optimized for subsequence signaling studies (Scheme 2) to methods for the diversification of molecular scaffolds on an array. All of the reactions utilize electrochemical methods to shape the way synthetic challenges are addressed.

In the talk to be given, selected examples from both methods will be used to illustrate how a basic understanding of electrochemical reactions can be used to solve a diverse array of synthetic challenges.

Figure 1
Exploratory Analysis of Bacterial Raman Spectra in Electroactive Biofilms
Authors: Lebedev Nikolai , Strycharz-Glaven Sarah , Tender Leonard M
Published: February 2020

Bacterial electroactive biofilms attract researchers’ attention due to their ability for generation of electric current when electrons travel for very long distance, up to several tens microns in the course of cell metabolic activity. It was demonstrated that this electron transfer (ET) ability correlates with the accumulation in the BF huge amounts of a c-type cytochrome (Cyt), but molecular nature of this Cyt, its spatial localization, interaction with the environment, regulation and the controlling factors are not completely understood. Raman spectro-electrochemical analysis is a very useful tool for nondestructive spatially-resolved in vivo study of ET mechanisms. But utilization and especially interpretation of Raman spectra requires deep understanding of their origin. Traditional approach to interpret Raman spectra is based on an assignment of specific Raman bands to the vibration of individual chemical bonds. Though some interesting results and conclusions were made using this approach, especially for small molecules, it does not allow for mapping Raman spectrum to complex organic and biological molecules like Cyt. Moreover, we and others have shown that most of Raman spectral bands of biomolecules are due to collective oscillation of several chemical bonds that requires another means of spectral description. This problem can be solved by computer simulation of Raman spectra allowing for identification of their structural origin and project/map them to molecular structure at sub molecular spatial resolution. This opens up the possibility of wise analysis of molecular interaction of individual biomolecules and their components. Spectroscopic analysis of more complex multi-structural and multicomponent biological systems, like biological cell and biofilms is often so complex that detection and separation of individual bands is very difficult to achieve. This problem can be solved by Principal Component Analysis (PCA) allowing for data squeezing to smaller number of the main, so called principle, components (PCs). Prescribing these PCs to specific classes of molecule allows for classification and comparative analysis of complex systems. In this presentation we will summarize our results on the application of Exploratory Confocal Raman Spectroscopic Analysis for identification of the main ET components (structure-functional relationship) in bacterial Raman spectra and organization of these ET components in multifunctional and multidimensional bacterial anodic and cathodic electroactive biofilms. We will show how interaction of the cells with inorganic substrates affects their metabolic activity; how cells talk to each other about that; and how electron transfer through an individual bacterial cell can be monitored.