bluuebunny/crossref_metadata_2025 huggingface dataset:
Watching Electrochemical Topography Change with Fast, High-Resolution Scanning Probe Microscopy
Authors: Kirchhofer Nathan D. , Proksch Roger , Revenko Irene
Published: February 2020

Due to its exceptional sensitivity, scanning probe microscopy (SPM) enables detailed interrogation of surfaces and interfaces. However, when correlating spatial information to additional surface measurements (such as current, redox activity, force, electrical potential or conductivity, impedance, thermal mapping, viscoelastic parameters, and more), spatial resolution is often limited. Here, we present the development and demonstrate the utility of an Electrochemical (EC) Cell comprised of a sample stage, liquid cup, and cantilever holder that is housed in an environmentally-controlled sample chamber and may be interfaced with an external potentiostat. This EC Cell is employed on a high-resolution, fast scanning Cypher ES atomic force microscope (AFM) in different measurement modes, and enables detailed characterization of localized, electrochemically-controlled morphologies without sacrifices to spatial resolution (atomic resolution is routinely achieved). These EC-AFM measurements are presented and have bearing on the continued development of more-advanced metrologies such as electrochemical scanning tunneling microscopy (EC-STM), scanning electrochemical microscopy (SECM), electrochemical strain microscopy (ESM), and more.

Figure 1. The EC Cell and sample data. (A) Exploded view of the EC Cell. Top: cantilever holder. Middle: sample chamber. Bottom: liquid cup and sample stage. (B) Zoom view of the bottom of the cantilever holder showing the cantilever, clip, and "dipping" architecture. (C) Zoomed, exploded view of the liquid cup and sample stage assembly, including counter electrode. (D) Calcite atomic lattice, imaged in water with the EC Cell (5 nm scan). (E) Example temperature-modulated cyclic voltammetry study conducted with the EC Cell. (F) Example scan-rate-modulated cyclic voltammetry conducted with the EC Cell. (G) Time series of images collected through the Cypher ES top view optics showing deposition of copper on a gold surface during electrochemical reduction. (H) Cyclic voltammogram of copper deposition/stripping on gold, and series of AFM images (2 μm scan) of a copper crystal during stripping.

Figure 1
(Invited) Probing Local Electrochemical Functionalities at Solid-Liquid Interfaces
Authors: Kalinin Sergei V.
Published: February 2020

Energy technologies of the 21st century require understanding and precise control over ion transport and electrochemistry at all length scales – from single atoms to macroscopic devices. Particularly of interest are electrochemical phenomena at solid-liquid interfaces, as a key element of classical and flow batteries, supercapacitors, sensors, and biological systems. At the same time, voltage modulated scanning probe microscopy techniques that have found broad applicability for probing reversible and irreversible electrochemistry and transport phenomena in solids cannot be directly applied in liquids, due to a non-trivial role of liquid electrolytes. In this presentation, I will illustrate several recent applications of SPM for liquid electrochemical imaging, ranging from Electrochemical Force microscopy, SPM – based dilatometry, and direct measurement of liquid layering in active devices.

This research was sponsored by the Division of Materials Sciences and Engineering, BES, DOE, and was conducted at the Center for Nanophase Materials Sciences, sponsored at Oak Ridge National Laboratory by the Scientific User Facilities Division.
(Invited) Probing the Energetics and Kinetics at the Semiconductor Water Interface for Solar Water Splitting
Authors: Wang Dunwei
Published: February 2020

Photocatalysis utilizes the energy delivered by light and enables chemical reactions that otherwise cannot take place. When used to power thermodynamically uphill reactions, photocatalysis offers a solution to large-scale solar energy storage. Despite over four decades of intense research, however, photocatalysis remains either too expensive or too inefficient or both. Poor understanding of the mechanisms behind the low performance is a key reason that limits the progress of this important field. To address this critical challenge, and to complement existing efforts focused on discovering new materials for photocatalysis, we present here a series of experiments designed to elucidate the working principles of photocatalysis. First, we carried out measurements of the system under quasi-equilibrium conditions, and the goal was to understand how the charge separation capability is influenced by the surface treatments of the photocatalyst. Next, we conducted intensity modulated photocurrent spectroscopy and established a quantitative correlation between surface treatment and charge transfer kinetics. Afterward, we compared two co-catalyst systems, one heterogeneous and one homogeneous and found that they improve the performance of the photocatalyst by fundamentally different mechanisms. Lastly, we employed synchrotron X-ray spectroscopy to provide a complete picture of surface energy evolution as a function of water splitting history. The key value generated by this body of research lies in the fundamental understanding of the thermodynamics and kinetics of the photocatalyst/electrolyte interface, which is expected to serve as a foundation for future research on photocatalysis.
Process of Formation of Porous Layers in n-InP
Authors: Quill Nathan , Clancy Ian , Nakahara Shohei , Belochapkine Serguei , O'Dwyer Colm , Buckley D. Noel , Lynch Robert P.
Published: February 2020

The anodic formation of porosity in semiconductors has received considerable attention, due to the fundamental insight it offers into semiconductor etching properties and its wide range of possible applications [1]. Although a number of models have been proposed to explain the formation of porosity in semiconductors [2-5], none as yet can explain the complete range of structures which have been formed in different semiconductor-electrolyte systems.

The anodic etching of n-type semiconductors in the dark is limited by hole supply at the semiconductor surface. It is generally accepted that this limited hole supply is what causes the initiation and propagation of porous etching, with hole supply being enhanced (and hence, porous etching initiated) at defect sites at the surface [6]. The newly formed pore tips then act as sites for the continuous preferential supply of holes [5]. However, the variation in feature size, as well as the morphology observed, as experimental conditions are varied cannot be so readily explained.

We have developed a mechanism [7], based on our results for pore formation in n-InP in KOH, in which the variations in pore morphology are due to the competition in kinetics between hole supply, carrier diffusion at the semiconductor surface and the electrochemical reaction. The mechanism is represented schematically in Fig. 1. The mechanism can be used to explain the characteristic width of the pore structures, and their directional preference.

In this presentation we will review our recent results and show that they are in support of the mechanism [8-10]. We will also present the results from numerical modelling of pore formation in InP based on the aforementioned pore growth mechanism.

References

1. H. Foll, J. Cartensen, S. Frey, J. Nanomater. 1 (2006)

2. M.I.J. Beale, J.D. Benjamin, M.J. Uren, N.G. Chew, A.G. Cullis, J. Cryst. Growth
73, 622 (1985)

3. R.L. Smith, S.D. Collins, J. Appl. Phys.
71, R1 (1992)

4. V. Lehmann, H. Foll, J. Electrochem. Soc.
137, 653 (1990)

5. X.G. Zhang, J. Electrochem. Soc.
151, C69 (2004)

6. P. Schmuki, U. Schlierf, T. Herrmann, G. Champion, Electrochim. Acta
48, 1301 (2003)

7. R.P. Lynch, N. Quill, C. O'Dwyer, S. Nakahara and D.N. Buckley, Phys. Chem. Chem. Phys.
15, 15135 (2013)

8. C. O'Dwyer, D.N. Buckley, D. Sutton, S.B. Newcomb, J. Electrochem. Soc.
153, G1039 (2006)

9. R.P. Lynch, C. O'Dwyer, D. Sutton, S.B. Newcomb, D.N. Buckley, ECS Trans.
6, 355 (2007)

10. R.P. Lynch, C. O’Dwyer, N. Quill, S. Nakahara, S.B. Newcomb, D.N. Buckley, J. Electrochem. Soc. 160, D260 (2013)

Figure 1
(Invited) Electrodeposition of Germanene
Authors: Stickney John Lewellen , Bui Nhi , Jung Jin , Reber Theodore James
Published: February 2020

Germanene is the Ge analogue Silicene or Graphene. A number of ab-initio calculations in the literature suggest that Germanene sheets should exist. Those reports suggest that the material would have a buckled structure, where half the atoms are about 0.07 nm higher than the other half. Micro Raman, electrochemistry and in-situ scanning tunneling microscopy (EC-STM) have been used to better understand the electrochemical growth of Ge from aqueous solutions, from the first atomic layers on Au(111). Our initial studies of the electrodeposition of Ge resulted in some interesting, though not clearly understood results, such as why only about 2-3 ML of Ge could be formed by direct electrodeposition on Au, depending on the pH. Some reports in the literature indicate that thicker deposits of Ge can be formed by electrodeposition on electrode surfaces other than Au. It is not yet clear why Au would be different. In-situ STM studies of the first atomic layers of Ge have shown a number of processes which indicate that nanoscopic atomically flat layers are forming on the surface, which demonstrate that Germanene is being formed. Micro Raman has also demonstrated the presences of Germanene grown on Au(111), which displays a Raman band near 295 cm-1. These results will be described.

References

Liang, et al., Langmuir, 26(4) (2010) 2877-2884

Xuehai Liang and John L. Stickney, Chemistry of Materials, 23(7)(2011)1742-1752

Xuehai Liang, et al., J. Am. Chem. Soc., 133(2011)8199-8204

M. A. Ledina, et al., ECS Transactions, 66 (6) 129-140 (2015)
Resistive Switching Characteristics of Hydrogen Peroxide Surface Oxidized ZnO-Based Transparent Resistive Memory Devices
Authors: Simanjuntak Firman Mangasa , Pattanayak Bhaskar , Lin Chun-Chieh , Tseng Tseung-Yuen
Published: February 2020

Transparent resistive memory technology has gained a huge interest in these recent years not only due to its potential application for future non-volatile memory but also due to its potential as an embedded device in wearable electronics.1 The impact of hydrogen peroxide treatment on the surface of ZnO film used for transparent resistive memory device application has been investigated. The surface oxidation was conducted by immersing the ZnO film into hydrogen peroxide solution. Switching characteristics of as-deposited and surface treated devices were initiated by double forming programming. Based on our previous result, superior memory performance can be achieved when the bipolar forming process is initiated to activate the switching behavior.2 However, in this experiment, such bipolar forming process cannot be performed on the as-deposited device (Fig 1a). Interestingly, after hydrogen peroxide surface treatment, the device is able to perform successful bipolar forming, thus, shows obvious switching characteristic (Fig 1b). Consequently, memory performance of surface treated device exhibits good endurance as compared to the as-deposited device (Fig 1c). The surface treated device demonstrates a stable switching with memory window (ON/OFF ratio) of about 7 times. This indicates that the thin oxidized layer at top electrode/ZnO interface plays a significant role in the device reliability. The defects concentration in the switching layer and the arrangement of the ionic conduction path may govern the formation and rupture of the conducting filament.3 Therefore, materials characterization and electrical conduction mechanism were conducted to explain the phenomena. This study offers a novel and simple method to enhance switching performance of the transparent resistive memory devices.

References

1. Simanjuntak, F. M., Panda, D., Wei, K. & Tseng, T. Status and Prospects of ZnO-Based Resistive Switching Memory Devices. Nanoscale Res. Lett.
11, 368 (2016).

2. Simanjuntak, F. M. et al. Enhanced switching uniformity in AZO/ZnO1−x/ITO transparent resistive memory devices by bipolar double forming. Appl. Phys. Lett.
107, 33505 (2015).

3. Simanjuntak, F. M. et al. Impacts of Co doping on ZnO transparent switching memory device characteristics. Appl. Phys. Lett.
108, 183506 (2016).

Figure 1
(Invited) Discovering Wide Band Gap Oxide Semiconductors By Engineering Strong Electron Correlations
Authors: Ramanathan Shriram
Published: February 2020

Wide gap semiconductors are often designed based on energy separation of the cation and oxygen orbitals. In strongly correlated semiconductors, however interacting electrons create effective transport gaps based on the occupancy of orbitals. I will discuss some recent examples from our laboratory on discovery of new electronic phases that have gaps of the order of 3eV that have been designed by electron doping of perovskite nickelates. In the un-doped case, these systems possess small gaps of the order of 0.1eV, and adding electrons to the partially filled d-orbitals, enhances the gap to 3eV taking advantage of strong correlations in the eg orbitals of Ni sites. This new strategy allows us to create wide gaps in semiconductors that are nominally metallic or nearly-metallic like in the pristine state and could be expanded to a broader range of materials systems. Besides the gap opening that in itself is fascinating, there are several opportunities to tune these materials to achieve multiple resistance states, continuous tuning of resistance by anion-site disorder and create multi-functionality. I will then give some examples of their applications in neural science and engineering, photonics and evolutionary biology.
High Performance Radiation-Grafted Anion Conducting Polymer Electrolytes for Energy Applications
Authors: Ponce Gonzalez Julia , Wang Lianqin , Santiago Elisabete , Bance-Soualhi Rachida , Whelligan Daniel , Biancolli Ana-Laura , Varcoe John
Published: February 2020

This presentation will describe the latest research at the University of Surrey and the development of radiation-grafted anion-exchange membranes (RG-AEM) and ionomer powders (AEI) for use in devices such as alkali membrane fuel cells.

The presentation will provide an overview of the following recent achievements:

Synthesis of RG-AEMs with heterocyclic chemistries that are more stable to alkali that the those containing the benzyltrimethylammonium benchmark;

Synthesis protocols that require reduced radiation doses, reduced amounts of monomer and the use of water rather than organic solvents;

Synthesis of thinner RG-AEMs;

The ability to produce RG-AEMs based on low density polyethylene (LDPE) rather than partially fluorinated ETFE;

Synthesis of an interesting class of solid-state AEI powders;

AEMs with high hydroxide conductivities and high performances in H2/O2 fuel cells.

For example, the graph show the beginning-of-life 60°C H2/O2 fuel cell performances achieved with Pt-based catalysts and RG-AEMs made from 25 μm ETFE (red) and 13 μm ETFE (green) with no gas back-pressurization applied.

References:

Ponce-Gonzalez et al., Energy Environ. Sci., 2016, 9, 3724-3735

Wang et al., Green Chem., 2016, Advanced Article DOI: 10.1039/C6GC02526A.

Figure 1
Unraveling Fundamental Descriptors for the Structural and Morphological Degradation of Pt Nanoparticles on Indium Tin Oxide Using in Situ Techniques
Authors: Schmies Henrike , Bergmann Arno , Wang Guanxiong , Drnec Jakub , Kühl Stefanie , Sandbeck Daniel , Mayrhofer Karl , Ramani Vijay K , Cherevko Serhiy , Strasser Peter
Published: February 2020

Enhancing stability of cathode catalysts for PEMFC applications under operating conditions is of great importance because state-of-art supports for nanoparticular Pt electrocatalysts suffer from carbon corrosion especially during start-stop procedure. Metal oxides have been proven to be viable alternatives because of their corrosion resistance and observed strong metal support interaction which is thought to enhance activity as well as stability of the catalyst [1-3]. Tin-based oxides excel by their thermal stability as well as high conductivity and are therefore promising candidates as alternative fuel cell support materials [4]. But the structural evolution of Pt-based nanoparticles under electrochemical conditions on oxides is still unknown. On high surface area carbon it has been shown by using in-situ SAXS studies that Pt nanoparticles grow due to Ostwald ripening and a dissolution/redeposition mechanism decreasing the electrochemical active surface area (ECSA) [5].

Here, we report on metal oxide supported Pt nanoparticles focussing on the structural evolution under electrochemical potential cycling applied to mimic fuel cell operating conditions. The Pt nanoparticles were synthesized using a solvothermal route and deposited on Indium Tin Oxide (ITO) resulting in homogenously distributed particles with well defined size. The electrocatalysts were extensively tested with respect to long-term electrochemical stability in order to investigate its potential as alternative carbon-free support material. We determined the evolution of crystal structure, composition, crystallite size and particle size distribution of the oxide support and the Pt nanoparticles by using in situ XRD and ASAXS. Additionally, we were able to follow the dissolution of the catalyst components during the electrochemical protocol using SFC ICP-MS setup. We can show that in case of ITO the size of Pt nanoparticles increases only slightly, whereas the mass-based catalytic activity decreases primarily due to changes of the support. Furthermore, our results show that we are able to unravel fundamental aspects of morphological degradation of Pt nanoparticles on non-carbon supports under electrochemical conditions. These results will help to understand stability determining properties of oxide supports leading to enhanced cathode electrocatalysts for a PEMFC.

[1] A. Kumar, V. Ramani, J. Electrochem. Soc.
2013, 160, F1207-F15.

[2] A. Lewera, L. Timperman, A. Roguska, N. Alonso-Vante, J. Phys. Chem. C
2011, 115, 20153-59.

[3] T.T.H. Van, C.J. Pan, J. Rick, W.N. Su, B.J. Hwang, J. Am. Chem. Soc.
2011, 133, 11716-24.

[4] H.-S. Oh, H.N. Nong, P. Strasser, Adv. Funct. Mater.
2015, 25, 1074-81.

[5] X. Tuaev, S. Rudi, V. Petkov, A. Hoell, P. Strasser, Acs Nano
2013, 7, 5666-74.
(Invited) Electrochemical Characterization of Complete La0.6Sr0.4Co1-XFeXO3-δ Composition Phase Space By Microelectrode Impedance Spectroscopy
Authors: Kucharczyk Christopher J , Liang Yangang , Choi Sihyuk , Zhang Xiaohang , Takeuchi Ichiro , Haile Sossina M
Published: February 2020

Solid oxide fuel cells are a promising clean energy technology due to their high efficiency and fuel flexibility, but current commercialization efforts are limited by expensive components needed to withstand high operating temperatures [1]. Attempts to decrease operating temperature have been stymied in large part by cathode materials with high polarization resistance [2], and efforts to improve performance through composite electrode morphologies [3] lead to complex geometries that prevent rigorous comparisons between different materials. We present a case study employing a novel methodology [4] for electrode characterization that enables fundamental property determination of multiple electrode compositions and allows for rigorous performance comparisons.

In this work, the entire composition phase space of a state-of-the-art ion- and electron-conducting solid oxide fuel cell cathode material (La0.6Sr0.4Co1-xFexO3-δ) is examined with unprecedented compositional resolution (x=0 to x=1 with Δx=0.05). Gradient pulsed laser deposition was employed to obtain a compositionally graded thin film on a (100)-oriented 8 mol% Y2O3-ZrO2 electrolyte substrate. The film was patterned using photolithography and ion milling to obtain electronically isolated circular microdot electrodes ranging from 80-500 µm in diameter. Microelectrode impedance spectroscopy was performed with a robotic scanning probe in an environmental chamber to obtain relevant electrochemical parameters. The measured impedance spectra are consistent with a two-phase boundary electrochemical pathway including bulk ionic conduction through the oxide. A monotonic increase in electrochemical resistance is observed from La0.6Sr0.4CoO3–δ (LSC) to La0.6Sr0.4FeO3–δ (LSF) along with a decrease in chemical capacitance corresponding to a decrease in reducibility and oxygen vacancy concentration. This case study demonstrates the rich insights that can be gleaned from this high-throughput approach and its promising application toward searching for new high-performance solid oxide fuel cell electrode materials.

1. Yang, Z.G., Recent advances in metallic interconnects for solid oxide fuel cells. International Materials Reviews, 2008. 53(1): p. 39-54.

2. Kuklja, M.M., et al., Combined theoretical and experimental analysis of processes determining cathode performance in solid oxide fuel cells. Physical Chemistry Chemical Physics, 2013. 15(15): p. 5443-5471.

3. Sun, C.W., R. Hui, and J. Roller, Cathode materials for solid oxide fuel cells: a review. Journal of Solid State Electrochemistry, 2010. 14(7): p. 1125-1144.

4. Usiskin, R.E., et al., Probing the reaction pathway in (La0.8Sr0.2)(0.95)MnO3+delta using libraries of thin film microelectrodes. Journal of Materials Chemistry A, 2015. 3(38): p. 19330-19345.
(Invited) From Fundamentals to PEMFC Systems
Authors: Lv Haifeng , Li Dongguo , Lopes Pietro Papa , Strmcnik Dusan , Wang Rongyue , Markovic Nenad M , Stamenkovic Vojislav
Published: February 2020

Search for active and durable, but cost effective catalysts that can be employed in fuel cells remains one of the main challenges for broad application of this technology. This presentation intends to provide an overview of progress that has been made in design of Pt-based electrocatalysts that are currently used in low temperature fuel cells. The main focus will be placed on necessity to resolve current limitations at molecular scale, which can ultimately lead towards design of electrocatalysts with advanced properties.

A major challenge lies in the insufficient activity and durability of materials that are currently employed as cathode catalysts for electrochemical reduction of oxygen. These limitations inevitably lead to a lower operating efficiency of the devices, which highlights the need for development of more active and durable oxygen reduction reaction catalysts. Consequently, the majority of research efforts are placed on the catalyst design and synthesis aiming to improve their efficiency. It has been found that properties such as surface structure, surface and subsurface composition associated with electronic properties have distinguished roles in determining functional properties of electrocatalysts. In addition to the catalyst materials it is of paramount importance to emphasize the role of liquid phase which is influencing on the overall properties of an electrified interface. Molecular species from employed electrolyte and the nature of their interaction with catalyst surfaces can be used in tuning the PEMFC performance.
(Invited) Tortuosity and Effective Transport Properties for Porous Materials in Electrochemical System
Authors: Fuller Thomas F , Star Andrew G.
Published: February 2020

Modeling has become an instrumental tool is the design and development of electrochemical systems. Multiple length and time scales are treated, but perhaps the most import and well developed models are macrohomogeneous physical models. These are typified by the porous electrode models advanced by Newman and others. These porous electrode models have been applied with great success to a variety of batteries, fuel cells, and double layer capacitors. The detailed geometry isn’t used, but instead effective transport properties account for the reduction in the magnitudes of diffusivities and conductivities. These effective transport properties are measured experimentally or often estimated using the Bruggeman relationship.

It has been well documented that the Bruggeman relationship is far from universal. These limitations are not unexpected considering the basis for the relationship between porosity and tortuosity. It should be clear that a simple relationship is not adequate. Consider, for instance shape changes in the electrode of battery undergoing cycling. The porosity may be unchanged, but effective transport properties vary. The Bruggeman relationship cannot explain this behavior.

Although the community generally agrees upon the concept of tortuosity, the ratio of effective path length to thickness of material through which transport occurs, multiple mathematical definitions exist. These descriptions are explored here. From the detailed geometry, the reverse problem can be solved, namely calculate and effective transport property and then calculate tortuosity from .

More recently, computation tools and methods to image electrode have improved dramatically. There are still many challenges, but more and more detailed geometries of electrodes are becoming available. Focused-ion-beam techniques combined with scanning electron microscopy (FIB/SEM) is such an example. Resolution on the order of tens of nanometers is routine. These developments allow us to begin to answer questions such as how to bridge length-scales between molecular dynamic and macroscopic models? Can we calculate a property of the porous media akin to a tortuosity that is both well-defined and relevant to the effective transport properties that we seek for the macroscopic models? These questions are explored through an example of the corrosion of the cathode of a PEM fuel cell.
(Invited) Materials By Design for Energy Applications: Incorporating Metastability
Authors: Tumas William
Published: February 2020

Meeting our future global energy needs in an environmentally responsible way is perhaps the greatest challenge facing the world in the twenty first century. The discovery of new functional materials is critical to developing the needed disruptive technologies for energy conversion, delivery, storage, and use. Remarkable advances in theory and high-throughput materials synthesis and characterization are enabling a new approach to new materials discovery where theory can directly guide experimental materials discovery and development.

This talk will present recent results from a number of research groups within the Next Generation for Materials by Design (CNGMD) Energy Frontier Research Center (EFRC), a multi-institution funded by DOE. Our overall goal is to design, discover and synthesize new energy-relevant functional materials, including non-equilibrium structures, with targeted functionalities by integrating theory, high-throughput computation, synthesis, and characterization. Our focus is on semiconductor materials for renewable energy and energy efficiency applications including solar energy conversion, solid-state lighting, solar fuel production and piezoelectrics. A primary goal is to incorporate functional metastable materials into materials by design and establish ranges for materials metastability as a function of the chemistry, energetics, and structure. We are examining three classes of metastable systems: defects, polymorphs, and solid solutions (alloys). We are also trying to develop a systematic theory-driven approach to guide the synthesis of new materials—including metastable systems—by coupling theory and state-of-the-art in-situ characterization to probe materials growth pathways. Highlights from our research will be presented including: Pnictide Search where we are exploring new metal nitrides to discover new functional semiconductor materials; Polymorphs and Synthesizability where we are understanding energy landscapes and identifying synthetic pathways for specific polymorphs focusing on Mn and Ti oxides; Chalcogenide Alloys where we predict and guide the synthesis of new functional semiconductor alloy materials; and Perovskite-Inspired Materials Search which designs new materials based on the electronic features of defect tolerance and long carrier lifetimes observed in hybrid organic-inorganic halide perovskites.
(Invited) Crosscutting Research in the Critical Materials Institute
Authors: Schwegler Eric
Published: February 2020

The Critical Materials Institute (CMI) is an Energy Innovation Hub that is led by the U.S. Department of Energy's Ames Laboratory. CMI is focused on the research and development of technologies that can diversify the sources of critical materials; provide substitutes for materials that are in short supply; or improve the utilization of existing resources through enhanced efficiency in manufacturing and improved recycling. Within CMI, the Crosscutting Research Focus Area has been working to accelerate the development of these new technologies by ensuring that CMI research teams have ready access to key tools and capabilities, such as advanced electronic structure approaches for identifying new magnets and phosphors with reduced rare earth element content, and unique experimental techniques for high-throughput synthesis and characterization of alloy materials. Much of our work in this area is being carried out with the Materials Genome Initiative (MGI) framework where computational, experimental, and data informatics tools are tightly coupled in a materials innovation infrastructure. In this talk, I will review several recent examples where CMI has used the MGI approach to achieve significant speedups in the development of technologies that address materials criticality issues. Prepared by LLNL under Contract DE-AC52-07NA27344.
(Invited) Water Splitting Catalyst Performance Benchmarking in the Joint Center for Artificial Photosynthesis
Authors: Houle Frances A , McCrory Charles C L
Published: February 2020

The design of efficient and durable photoelectrochemical water splitting devices requires that each component incorporated have optimized properties. Electrolytes with extreme pH minimize resistances, but catalyst stability at operating potentials under these conditions is not assured. The literature offers many options for catalysts, however their characteristics are typically reported under conditions selected according to the interests of the research team, and are difficult to compare to each other. JCAP has developed a protocol for heterogeneous oxygen and hydrogen evolution catalysts that enables rigorous comparisons of performance at pH 0 and pH 14, and has also evaluated several elements for standardized photoelectrochemical benchmarking. The methodology and findings will be described, and areas where advances are needed in methodology and in materials discovery will be discussed.
Organic Electrochemistry at Abbvie: Expanding the API Synthetic Toolbox
Authors: Graaf Matthew D.
Published: February 2020

AbbVie R&D has expanded its synthetic capabilities to include organic electrochemistry in active pharmaceutical ingredient (API) and metabolite synthesis. Elimination of hazardous reagents and waste is an important benefit in addition to the technology’s versatility and selectivity. Recent advancements made by AbbVie and collaborative academic chemists are discussed herein.
One-Pot Anodic Thiocyanation and Isothiocyanation of Alkenes
Authors: Becker James Y. , Levy Avishai
Published: February 2020

Previously we studied the anodic thiocyanation of aromatic compounds [1, 2]. The one-pot anodic thiocyanation and isothiocyanation of alkenes in both acidic two-phase (water-dichloromethane) and homogeneous one-phase (water-acetonitrile) media will be described [3]. A selected example of type of products obtained is illustrated in the scheme below:

References

[1] A. Gitkis, J.Y. Becker, J. Electroanal. Chem., 593 (2006) 29-33.

[2] A. Gitkis, J.Y. Becker, Electrochim. Acta, 55 (2010) 5854-5859.

[3] A. Levy, J.Y. Becker, Electrochim. Acta, 178 (2015) 294–302.

Figure 1
Organic Electrochemistry Goes to Work: Genotoxicity Sensor Arrays
Authors: Rusling James F , Kadimisetty Karteek , Malla Spundana , Bist Itti
Published: February 2020

This paper focuses on fundamental concepts derived from the technical evolution of organic electrochemistry that have helped us to develop sensors for the chemistry of genotoxicity, which is essentially the damage of DNA by chemicals and their metabolites. This research is driven by the need to screen for the possibility of genotoxicity of new environmental chemicals and drug candidates, about 30% of which have toxicity issues that do not manifest until clinical trials on humans. A major issue is metabolic chemistry driven mainly by cytochrome (cyt) P450s and other metabolic enzymes. Metabolic chemistry involves catalysis of organic reactions, oxidations in the case of cyt P450s. We found ways to inject electrons into cyt P450s in thin films via their native reductase electron-transfer partners to catalyze metabolic reactions electrochemically via mechanisms that are the same as in our livers. This is organic electrochemistry.

For the sensors, we needed a way to detect the resulting metabolite-related DNA damage in sensors combining thin LbL films of metabolic enzymes and DNA in which the metabolites are generated and react with DNA. We found that guanines in DNA chains can react in an electrocatalytic process involving a Ru metallopolymer (RuPVP) and provide a strong visible light output via electrochemiluminescence (ECL). This electrocatalytic process oxidizes RuII in the polymer to RuIII to oxidize guanine moieties in the DNA, and a complex redox reaction sequence produces the light. The catalytic oxidation current can also be measured. Organic electro-oxidations are responsible for these outputs. Similar approaches can be used to design sensor arrays that monitor DNA oxidation.

Electrocatalytic Cyt P450 oxidations and ECL generation are combined in our most sophisticated genotoxicity sensor arrays. When DNA is damaged, its double-stranded structure is disrupted and RuIII sites in the film gain better access to guanine moieties to produce more ECL light, or more catalytic current. Examples, including the genotoxic potential of e-cigarettes, will be discussed.
(Keynote) Electrochemical Reduction of Bromobenzenes at Silver Cathodes
Authors: Pence Michael Andrew , Peters Dennis G , Mubarak Mohammad S.
Published: February 2020

In 1959, it was observed that poly-halogenated arenes would undergo a halogen dance under very basic conditions.1 Later, in a study of the electrochemical reduction of halogenated thiophenes at glassy carbon cathodes, an electrochemically induced halogen dance was discovered.2 Halobenzenes were studied shortly after and it was found that 1,2,4,5-tetrabromobenzene would undergo an electrochemically induced halogen dance at glassy carbon in dimethylformamide with 0.10 M tetramethylammonium perchlorate as the supporting electrolyte.3 In the present study, we have investigated a possible halogen dance resulting from the reduction of poly-brominated benzenes at a silver cathode for comparison with known behavior at glassy carbon cathodes. Cyclic voltammograms (CVs) of di-, tri-, and tetrabromobenzenes were recorded at a scan rate of 100 mV/s with a silver cathode in dimethylformamide containing 0.1 M tetramethylammonium perchlorate as a supporting electrolyte. All potentials are reported versus a Cd/Hg amalgam reference electrode with a potential of –0.76 vs SCE. CVs of 2 mM 1,2,4,5-tetrabromobenzene exhibit three peaks, the most positive of which is found at –0.70 V; a small shoulder is also present at –0.65 V. Controlled-potential (bulk) electrolysis of 1,2,4,5-tetrabromobenzene at –0.65 V vs. Cd/Hg yielded 1,2,4- and 1,3,5-tribromobenzene in trace amounts. Products were confirmed by means of GC–MS. The presence of 1,3,5-tribromobenzene among electrolysis products indicates the occurance of a halogen dance following the reduction of the first bromine–carbon bond. Due to similar reduction potentials for multiple carbon–bromine bonds at silver, complete removal of only a single halogen is difficult; to better isolate a single electron-transfer event, other halogenated benzenes were investigated. CVs of 2 mM 1-bromo-2,4,5-trichlorobenzene also exhibited three peaks, with the most positive at –0.50 V, separated by 800 mV from the next reduction peak. This large peak separation allows for more complete electrolysis and quantitation of halogen-dance products, aiding in development of a mechanism for the reduction of halogenated benzenes at a silver cathode.

References

Wotiz, J.; Huba, F. J. Org. Chem., 1959, 24, 595–598.

Mubarak, M. S.; Peters, D. G. J. Org. Chem., 1996, 61, 8074–8078.

Mubarak, M. S.; Peters, D. G. J. Electroanal. Chem., 1997, 435, 47-53.

Figure 1
Modification on Glassy Carbon Surfaces By Homogeneous Oxidation of Ferrocenecarboxilate in Presence of Ferrocenecarboxylic Acid and 1,4-Benzoquinone As Mediator
Authors: Gamboa-Valero Nadia , González Felipe J
Published: February 2020

The quinone-hydroquinone system is one of the most important and well studied examples of organic redox couple. This system participates as electron and proton carrier in different mechanisms involved in some biological systems. In aqueous as well as in organic solvents, the quinone molecules can be reduced following a 2-electron exchange and due to their high basicity, protonation to yield the respective hydroquinone represent a significant thermodynamic driving force. On the other hand, the oxidation of carboxylates give rise to a transient acyloxy radical whose cleavage afford CO2 and a free radical that can dimerize. This process is also highly favoured from the kinetic and thermodynamic point of view. Therefore, the combination of quinones, carboxylates and the respective carboxylic acid, would be an interesting mixture to promote the spontaneous decarboxylation and hydroquinone formation. This proposal was confirmed in this work through the study of the interaction between 1,4-benzoquinone, ferrocenecarboxylic acid and ferocenecarboxylate in acetonitrile, mainly to promote the formation of an excess of free radicals that modify chemically glassy carbon electrodes with ferrocene groups. The study was performed using cyclic voltammetry, chronoamperometry, 1H-NMR and atomic force microscopy.

Figure 1
Hydrogenation at Metal-Ligand Interfaces in CO2 Electrochemical Reduction
Authors: Fang Yuxin , Cheng Xun , Xu Ye , Flake John
Published: February 2020

CO2 holds the potential to a significant source of renewable carbon. Previous studies have shown that it can be converted to CO, CH4, HCOOH, CH3OH and other higher order hydrocarbons suitable as fuels or chemical intermediates. The electrochemical approach holds the advantage in using renewable electric source (wind, solar and tide). Extensive experimental and theoretical studies have been done on pure metals (such as Au, Ag, Cu, etc.)1, 2 range from bulk to nano scale3, Cu4 appear to be the only catalyst that is capable of perform hydrogenation to yield hydrocarbon liquid products at the expense of single product selectivity and overpotential. Density function theory based simulation suggest the unique binding energies of CO* and COH* are the key for copper to perform the hydrogenation. 5

We took the inspiration from nature’s enzyme chemistry6 which manipulate metal nanoclusters with ligands in photosynthesis, explored the possibility using engineered metal-ligand electrocatalyst to yield the hydrocarbon liquid products. Our previous work has shown that thiolate ligands can facilitate reduction and hydrogenation at neutral to mildly acidic pKa. Suitable ligands can significantly enhance the yield of CO or HCOOH (usually trace on Au) production. We are taking a step further by depositing strong CO binding metal nanoparticles on to salinized semiconductor substrate with proton donor group to create metal-ligand interfaces. We have observed enhanced CH3OH production in such systems. The engineered metal-ligand interface thus appear to be a highly promising method to promote hydrogenation routes in CO2 electrochemical reduction.

Reference:

1. Y. Hori, A. Murata, R. Takahashi and S. Suzuki, Chemistry Letters, 16, 1665 (1987).

2. Y. Hori, in Modern Aspects of Electrochemistry, C. Vayenas, R. White and M. Gamboa-Aldeco Editors, p. 89, Springer New York (2008).

3. D. R. Kauffman, D. Alfonso, C. Matranga, H. Qian and R. Jin, Journal of the American Chemical Society, 134, 10237 (2012).

4. K. Manthiram, B. J. Beberwyck and A. P. Alivisatos, Journal of the American Chemical Society, 136, 13319 (2014).

5. C. Shi, H. A. Hansen, A. C. Lausche and J. K. Norskov, Physical Chemistry Chemical Physics, 16, 4720 (2014).

6. B. El-Zahab, D. Donnelly and P. Wang, Biotechnology and Bioengineering, 99, 508 (2008).
Understanding Electron Transport in Photosynthetic Membranes for Electrochemical Energy Conversion
Authors: Ramasamy Ramaraja P. , Sekar Narendran
Published: February 2020

The light reactions of natural photosynthesis can be manipulated towards electricity generation in photo-bioelectrochemical cell (PBEC) as demonstrated in our earlier work. The photosynthetic reactions occur in the thylakoid membrane and involve a complex set of redox reactions that result in the transfer of electrons between protein complexes. The electrons from the photosynthetic reactions can be channeled towards an external electrode for electricity generation by inhibiting the photosynthetic protein complexes in order to divert the flow of electrons towards to desired electron transport path within the photosynthetic membrane. Investigation using site-specific photosynthesis inhibitors revealed that the electrons generated through water oxidation reaction from photosystem II complex can be diverted to the external electrode for photocurrent generation primarily through the plastoquinone pool. Besides site specific inhibition, other approaches to increase photocurrent generation were investigated. One of those approaches is to engineer photosynthetic organisms such as Synechococcus elongatus PCC7942 with an outer membrane cytochrome (OmcS) derived from dissimilatory metal reducing bacteria which increase the photocurrent generation at an external electrode by two fold. This paper will summarize some of our recent work on multiple different approaches to enhance photocurrent generation through an understanding of electron transport reactions in photosynthetic membranes.
Electrochemical Studies of Zinc/Cysteine Interactions
Authors: Doan Michelle Y , Worosz Matthew A. , Cheek Graham T.
Published: February 2020

Introduction

 The amino acid L-cysteine has been studied because of its role in several biochemical pathways (1). Electrochemical studies are possible due to the redox characteristics of the sulfhydryl group, so that the electrochemical characteristics of L-cysteine can be determined by voltammetric methods (2). In this study, the biochemical importance of zinc(II)/cysteine complexes in proteins (“zinc fingers”) has prompted an investigation of the interaction of ZnSO4with L-cysteine in various media.

 Experimental

 L-Cysteine was obtained from Sigma-Aldrich Company, and ZnSO4
.7 H2O was obtained from ThermoFisher Scientific. A Gamry Interface 1000 potentiostat with Gamry Framework software was used to carry out electrochemical experiments. Potentials are referenced against a Ag/AgCl reference electrode. Platinum and glassy carbon electrodes were purchased from BASi. Gold electrodes were obtained from eDAQ.

Results and Discussion

 In a study of the complexation of Zn2+ by L-cysteine in pH 7.4 phosphate buffer, it was found that addition of ZnSO4
. 7 H2O to the buffer solution produced a cloudy appearance due to the low solubility of the resulting Zn3(PO4)2 . Upon addition of L-cysteine, the system was still cloudy at the 1:1 L-cysteine : Zn2+ point; however, at the 2:1 L-cysteine : Zn2+ point, the solution became clear. This behavior evidently occurs because the interaction of Zn2+ with L-cysteine is stronger than is its interaction with phosphate. These results are consistent with Zn(cys)2 complexation reported in the literature (3). The corresponding voltammograms at glassy carbon are shown in Figure 1. For ZnSO4 addition, the scan showed only a very small zinc stripping peak at the negative end of the potential range. At the 1:1 L-cysteine : Zn2+ point, processes are clearly evident for zinc deposition/stripping, and oxidation of complexed L-cysteine is observed at +0.7 V vs Ag/AgCl. This oxidation process is slightly altered compared to that observed for only L-cysteine (no added Zn2+) (2). Similar behavior for the oxidation processes was also observed at gold. Further additions of L-cysteine gave larger currents for the L-cysteine oxidation process. These results support the uptake of zinc ion into the solution as L-cysteine interacts with Zn2+, initially added as ZnSO4
. 7 H2O in pH 7.4 phosphate buffer.

References

C.K. Mathews, K.E. Van Holde, D.R. Appling, and S. J. Anthony-Cahill, Biochemistry, 4th Edition, Pearson Canada, Toronto, 2013.

G. T. Cheek and M. A. Worosz, ECS Transactions, 2016, 72(27), 1-8.

S. Foley and M. Enescu, Vibrational Spectroscopy, 2007, 44, 256-265.

Figure 1. Cyclic voltammograms at glassy carbon (3 mm diameter) in aqueous pH 7.4 phosphate buffer, 100 mV/s scan rate.

[ Dashed red line : ZnSO4 . 7 H2O, 2.1 mM nominal concentration ]

[ Solid black line : Addition of 2.4 mM L-cysteine to previous solution ]

Figure 1
X-Ray Spectroscopic and Electroanalytical Studies on the Bio-Electic Interface of Metal Oxide Semiconductors and Algal Proteins and Biofilms
Authors: Braun Artur
Published: February 2020

Artificial photosynthesis has been the domain of molecular biology and biophysics and is traditionally restricted to the study of modified natural photosynthetic organisms and their components and has not matured yet to a technology. Photovoltaics is the established field of electric power generation with semiconductor solar cells and has made it to technologies with market share and commodity. Photoelectrochemical cells based on the principles of semiconductor photoelectrochemistry are right now about to become a technology and can produce solar fuels. I present a hybrid approach where bio-organic motifs are combined with metal oxide semiconductor substrates so as to enhance the performance of photoelectrodes.

Specifically, we have functionalized the surface of the hematite photoelectrode with the light harvesting antenna protein c-phycocyanin (CPC) and ran it as a bio-hybrid pphotoelectode in strong alkaline and neutral pH buffer saline - and found that the chromophores surpass the denaturation of the proteins and still can be performance enhancing. Further refinement of the assembly by genetic engineering of the algae to obtain a histidine tagged CPC was also investigated, as well as the blending the system with melanin. We carried out impedance studies and synchrotron based resonant valence band photoemission studies to learn abu the cahrge transfer across the bio-metal oxide interface.

Finally we grew an algal biofilm on the photoelectrode and operated it under photoelectrophysiological conditions in an ambient pressure XPS chamber under 150 mTorr water vapor and determined the valence band shift under different electric bias and light/dark influence.

[1] A. Braun, F. Boudoire, D. K. Bora, G. Faccio, Y. Hu, A. Kroll, B. S. Mun, S. T. Wilson, Biological components and bio-electronic interfaces of water splitting photo-electrodes for solar hydrogen production, Chem. Eur. J. 2015, 21(11), 4188-4199.