bluuebunny/crossref_metadata_2025 huggingface dataset:
Lithium Dendrite Suppression through Controlled Mass Transfer
Authors: Ryan Emily , Tan Jinwang
Published: February 2020

Lithium dendrite formation is a critical challenge that limits the lifetime of lithium (Li) metal batteries including lithium oxygen, and lithium sulfur systems. Dendrite growth occurs at the interface between the electrolyte and the Li metal anode. The formation of dendrites affects the local transport properties, the scale of the critical physics of the anode, leads to increased Joule heating and eventual breakage of the dendrites, which can cause short circuits leading to overheating and possible fires. Dendrite formation also decreases the Li available for the electrochemical reactions of the battery, which causes a decrease in cell capacity. In addition to Li metal batteries, dendrite growth is also a problem for other battery chemistries, such as Li-ion, NaS and NiCd. Among previous experimental studies, it has been shown that the dendrites in Li batteries can form one of two structures depending on the operating conditions. Under high current conditions, dendrite formation is typically dense and considered mossy or bush-like in structure; while under low current conditions dendrites form dense needle-like structures. In addition to charging current, many other factors are reported to influence dendrite growth. A close relation between Li ion mass transfer and dendrite growth rate have been shown; while other groups have found a strong influence between convection effects and the morphology of the dendritic structure.

Measuring dendrite growth in situ is challenging, and examining the dendrites post mortem is difficult as they can fall apart during disassembly. To better understand dendrite growth and morphology, computational modeling can be used to investigate the electrode-electrolyte interface and how operating conditions and battery design effect dendrite growth and morphology. In this work, we use a Lagrangian particle based method known as smoothed particle hydrodynamics (SPH) to simulate the reactive transport in the interfacial region to understand Li ion transport effects on dendrite growth. This includes investigation of material properties and battery design, including the use of hybrid electrolytes and separators to restrict Li ion transport. Further studies are conducted to consider how operation and charging rates effect growth.

Results of these computational studies show that restricted Li ion transport can suppress dendrite growth without sacrificing battery performance. This can be accomplished by changing the materials of electrolyte or using hybrid electrolyte designs. Additionally the charging profile can also be used to effectively suppress dendrites.
Preparation and Characterization of Palladium Supported on Reduced Graphene Oxide for the Electrooxidation of Formate in the Alkaline Medium
Authors: Galvan Vicente , Glass Dean , Prakash G. K. Surya
Published: February 2020

The development of alkaline anion exchange membranes (AEM) has allowed for a myriad of new liquid fuels to be used in fuel cell applications that are not effectively oxidized in PEM fuel cells. Moreover, many of these fuels are readily electrooxidized by nonplatinum catalysts. One such fuel cell that has recently gained a lot of interest is the direct formate fuel cell (DFFC). Herein, palladium supported on reduced graphene oxide (Pd/rGO) was synthesized and its catalytic activity towards formate oxidation reaction (FOR) in alkaline medium was tested. The reduction of GO to rGO and synthesis of Pd nanoparticles were confirmed using XRD, Raman and XPS. The surface morphology was evaluated by SEM and TEM. Half-cell studies demonstrated superior electrocatalytic activity and stability towards FOR for Pd/rGO than commercial Pd/C catalysts. A single cell AEM DFFC was constructed with a Pd/rGO anode catalyst displaying an increase in maximum power density of 20% at 60 °C when compared to commercial Pd/C catalyst.
Neutron Tomographic Investigation of the Effect of Hydrophobicity Gradients within MPL and MEA on the Spatial Distribution and Transport of Liquid Water in Pemfcs
Authors: Kartouzian Dena , Mohseninia Arezou , Markötter Henning , Scholta Joachim , Manke Ingo
Published: February 2020

Neutron tomography is used to visualize the effect of hydrophobicity variations within the micro porous layer (MPL) and membrane electrode assembly (MEA) of a low-temperature polymer electrolyte fuel cell (PEMFC) on the detailed distribution of water in an operating cell. MEAs and MPLs manufactured in-house with different degrees of wettability are implemented in miniature fuel cells featuring an active area of 8 cm², which are specifically designed for neutron imaging experiments. The tomographies are obtained with a pixel size of 13 µm while maintaining the same operating conditions for all cells for comparability.

The quantitative analysis of the water content in two of these cells next to the lands and the channels of the flow field is shown in Figure 1. It can be clearly observed that the implementation of a hydrophobic MEA significantly changes the overall water distribution within the cell. In contrast to the reference MEA, where more water is found in the catalyst layers compared to the membrane, the hydrophobic MEA has a higher water content inside its membrane.

Implementing a GDL with a more hydrophobic MPL on the cathode side shows a higher water content inside the GDL substrate under the lands compared to the channels. This information can significantly help the optimization of material designs and can also provide valuable data for modeling and simulations of water distributions inside PEMFCs. We will show a detailed analysis of hydrophobicity changes on the water distribution inside the cell components, characterization results of various MPLs and MEAs regarding wettability and porosity analysis as well as performance results at different operating conditions

Figure 1
Metal Phosphides As Electrocatalyst and Supports for PEM Fuel Cells
Authors: Parra Puerto Andres , Fahy Kieran F. , Goode Angela E , Ryan Mary P , Kucernak Anthony R. J. , NG Kai Ling
Published: February 2020

One of the main bottle neck for the complete introduction of the fuel cells technology in the market, is their dependency on precious metals as catalyst. Focusing on the electrochemical reactions involved, the most sluggish is the Oxygen Reduction Reaction (ORR). Many techniques and research were done to reach the high optimization for the amount of the precious metal used, keeping the same activity. In the other hand, many investigations were carried on to find non-precious metal catalyst with the same performance for the different reactions (ORR, HER, OER and HOR)[1]. One of those candidates are the metal phosphides [2], however, this catalysts nowadays only are active for ORR, HER, OER and they have very poor activity related to HOR [3]. Here we present the work done related to the really simple synthesis of CoP catalyst with a very interesting ORR catalytic behaviour and peroxide generation under acid and alkaline conditions. Some TEM characterization was done to understand the changes in the morphology before and after the ORR reaction. Another application of these materials is to use thezzm as support, due to their chemical resistance and low cost. As well, depositing platinum on them gives the possibility to obtain an interesting synergistically effect improving the activity with lower loadings of Pt deposited [4].

[1] M. S. Faber and S. Jin, “Earth-abundant inorganic electrocatalysts and their nanostructures for energy conversion applications,” Energy Environ. Sci., vol. 7, no. 11, pp. 3519–3542, Oct. 2014.

[2] A.-M. Alexander et al., “Alternative catalytic materials: carbides, nitrides, phosphides and amorphous boron alloys,” Chem. Soc. Rev., vol. 39, no. 11, p. 4388, Oct. 2010.

[3] R. Prins and M. E. Bussell, “Metal Phosphides: Preparation, Characterization and Catalytic Reactivity,” Catal. Letters, vol. 142, no. 12, pp. 1413–1436, Dec. 2012.

[4] H.-Y. Park et al., “Pd nanocrystals on WC as a synergistic electrocatalyst for hydrogen oxidation reactions.,” Phys. Chem. Chem. Phys., vol. 15, no. 6, pp. 2125–30, 2013.
In-Situ Electrochemical Characterization of Proton Exchange Membranes for Water Electrolysis
Authors: Hohenadel Amelia , Lee Hsu-Feng , Khoza Thulile , Barnett Alejandro Oyarce , Holdcroft Steven
Published: February 2020

Proton exchange membrane water electrolysis (PEM-WE) is a clean method for hydrogen production and an important piece in the adoption of a hydrogen fuel economy. Proton exchange membranes require specific chemical and physical properties for efficient use in the PEM-WE system, and development of these membranes still presents a major challenge. Current industry standards such as Nafion®, developed by DuPont, are costly, show high gas permeability, and are limited to operation below 90 °C.1 Performance of a novel sulfonated poly(arylene ether) membrane, SA8, is investigated in this research. SA8 has shown a significantly higher glass transition temperature than Nafion, better mechanical properties, higher proton conductivity, and better chemical stability from various ex-situ tests and in-situ fuel testing. The multiphenylated backbone creates free volume around the sulfonic acid sites, which allows for greater water uptake with minimal swelling.2 The presence of water is not only necessary for proton conductivity but is of particular importance in the water electrolyzer where the cell is fed liquid water, rather than operated at various humidities as in a fuel cell. In this research SA8 is found to successfully operate in a water electrolysis system at a temperature of 90 °C for over 120 hours. Polarization curves taken at 60 °C show operation of a 25 μm membrane at 1.8 V reaching a current density of 4 A cm-2.

Ito, H., Maeda, T., Nakano, A. & Takenaka, H. International Journal of Hydrogen Energy (2011)

Lee, H. F., Huang, Y.C., Wang, P.H., Lee, C.C., Hung, Y.S., Gopal, R., Holdcroft, S., Huang, W.Y. Mater. Today Commun.
3, 114–121 (2015).
Bimetallic Nano Electrocatalyst for HER in Alkaline Polymer Electrolysis
Authors: Faid Alaa Y , Manikandan Maidhily , Seland Frode , Barnett Alejandro Oyarce , Sunde Svein
Published: February 2020

Recent developments in alkaline membrane technology have led to the possibility of using anion-exchange membranes containing alkaline ions in water electrolysis. This technology has the potential of combining the advantage of non-precious catalysts of alkaline process, with the advantages of PEM electrolysis, e.g. fast power-up/power-down rates, low parasitic energy losses and low energy consumption, in other words consolidating the best of both technologies.

Although the HER is a well-studied reaction, it continues to attract the attention of researchers for both practical applications and fundamental understanding. Ni and alloys of Ni (with Fe,Co,Mo) still represent the most suitable electrodes for HER un alkaline media , the differences in the kinetic rates for the HER on various electrode materials in alkaline environments have linked to variations in the hydrogen adsorption energy. Although this supposition is Kinetically viable, it is still puzzling as to why the HER activity on Pt and other catalysts shows a hundred-fold decrease in activity or why the reaction is more sensitive to the catalysts’ surface structure in alkaline media than in acids.

In this study, bimetallic nano particles of NiFe and NiCo were fabricated by oleylamine polyol and co precipitation process , The process of oleylamine involves synthesis of metal-containing compounds in oleylamine. The oleylamine acts as both the solvent and reducing agent. While co precipitation method involves precipitation agent like NaoH to precipitate the metal based nitrates, Different synthesis conditions in terms of concentration, time and heating rate were studied. Structural characterization of produced nanoparticles was carried out using X-ray diffraction, transmission electron microscopy, Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. Electrochemical behavior of nanoparticles investigated using rotating disk electrode. the electrochemical characterization investigated the effect of catalyst composition on electrochemical behavior of the catalyst.

Figure 1
Mechanical and Structural Degradation of LiNi
x
Mn
y
Co
z
O2 Cathode in Li-Ion Batteries
Authors: Zhao Kejie
Published: February 2020

The structural and mechanical stability of NMC plays a vital role in determining the electrochemical performance of batteries. However, the dynamic mechanical properties of NMC during Li reactions are widely unknown because of the microscopic heterogeneity of composite electrodes as well as the challenge of mechanical measurement for air-sensitive battery materials. We employ instrumented nanoindentation in an inert environment to measure the elastic modulus, hardness, and interfacial fracture strength of NMC of a hierarchical meatball structure as a function of the state of charge and cycle number. The mechanical properties significantly depend on the lithiation state and degrade as the electrochemical cycles proceed. The results are further compared with the properties of bulk NMC pellets. We perform first-principles theoretical modeling to understand the evolution of the elastic property of NMC on the basis of the electronic structure. This work presents the first time systematic mechanical measurement of NMC electrodes which characterizes damage accumulation in battery materials over cycles.
The Potential of Hybrid Micro/Nanoporous Surface for Biomedical Titanium Implant Applications: Surface Characteristic, Biomechanical Behavior and Hemocompatibility
Authors: Yang Tzu-Sen , Chou Hsin-Hua , Ou Keng-Liang , Hou Ping-Jen
Published: February 2020

Micro-arc oxidation (MAO) is one of the most potential methods to generate the hybrid micro/nanostructural surfaces on the Ti dental implant because of its simplicity, high efficiency and low cost. The MAO surface-treated Ti (MST-Ti) implants have also been shown to have good biocompatibility by in vitro and in vivo evaluation of the interfacial behaviors of Ti implants and bone tissue. From a clinical point of view, it would be desirable if the traditional Ti implant could be developed as the high osseointegration accompany with low elastic modulus Ti implant to avoid stress-shielding formation without sacrificing desirable physicochemical and biological properties. Therefore, the purpose of the present study was to investigate the surface characteristic, biomechanical behavior, hemocompatibility and in vivo biocompatibility of the optimal MST-Ti (OMST-Ti) implant with hybrid micro/nanoporous surface. The surface morphology of the OMST-Ti implant was characterized using scanning electron microscope. Hemocompatibility was evaluated by blood dripping and immersion tests. Moreover, biomechanical properties were simulated using finite element model (FEM) analysis. It was found that the hybrid volcano-like micro/nanoporous structure was formed on the surface of the OMST-Ti implant. The OMST-Ti implant with volcano-like micro/nanoporous surface layer showed the well wettability and hemocompatibility. In addition, the FEM analysis results also revealed that the stresses were transferred more uniformly in the implant that presence of micro/nanoporous surface. Therefore, these results demonstrated that the OMST-Ti implant is a promising biomaterial for dental and biomedical applications.
(Invited) ARPA-E Refuel Program: Electrochemical Synthesis and Utilization of Sustainable Fuels
Authors: Soloveichik Grigorii L.
Published: February 2020

The Advanced Research Projects Agency (ARPA-E) funds high risk, high reward transformational research to reduce energy related emissions, reduce imports of energy from foreign sources, improve energy efficiency across all economic sectors, and ensure US technological lead in advanced energy technologies, including electrochemical technologies for energy transformation and storage for distributed, grid scale and automotive applications.

Electrochemical technologies have a great potential for increasing efficiency of synthesis of sustainable fuels and their utilization for power generation for different applications. Switching from gaseous fuels (H2, CH4) as an energy vector to liquid fuels has numerous advantages including higher energy density, available infrastructure and increased safety. Low footprint and cost of storage and transportation of carbon-neutral liquid fuels (CNLFs) enables vehicle electrification (directly or as hydrogen carrier), long-time energy storage and effective long-distance energy transportation. Easily liquefied ammonia (4.25 kWh/L) is one of the most promising CNLFs. It can be used directly in fuel cells or as hydrogen carrier for PEM fuel cells thus enabling the infrastructure of hydrogen fueling stations for public transportation. The Renewable Electricity to Fuels through Utilization of Energy-dense Liquids (REFUEL) program funds the development of transformational technologies to reduce the barriers to widespread adoption of intermittent renewable energy sources by enabling the conversion of energy from these sources, water and air to energy-dense CNLFs, mostly ammonia, (Category 1) and their conversion back to electricity using fuel cells (Category 2). The program objective is to demonstrate delivery of source-to-use electricity (including production, transportation, storage, and conversion) at the cost below $0.30/kWh to be competitive with other carbon-free delivery methods.

Development of novel synthetic methods for CNLFs and regenerative fuel cells for energy storage is also being funded via OPEN program. Possible future ARPA-E program targeting the use of CNLFs for transportation (in hybrids, range extenders, APUs) will be also discussed.
(Invited) Electrochemical Ammonia Synthesis - Facts or Dreams?
Authors: Chorkendorff Ib
Published: February 2020

Producing ammonia from sustainable energy sources is a new and interesting route for decentralized production. Ammonia is an essential chemical for mainly fertilizer production but also an essential compound for the chemical industry. Normally ammonia is produced by large scale production – several thousand tons/day - by the Fritz-Haber process at 150-200 bar and 400 °C. Nature can, however, produce ammonia at ambient conditions using ATP as the energy source. This is done by bacteria living in symbiosis with plants who in exchange of sugar synthesize ammonia by the nitrogenase enzyme. In this presentation, the progress of synthesizing ammonia in a decentralized manner using an electrochemical process shall be discussed and in particular highlight some of the challenges.

There is a substantial very recent body of literature claiming ammonia synthesis by electrochemical routes and some of these data and their validity shall be critically reviewed. Often the ammonia is detected by the indo-phenol method which is an extremely sensitive method allowing for detection down to the ppb level. It is therefore mandatory that the amount of ammonia reported is quantified both in terms of turn over frequencies, but also in measured concentrations since contamination on the ppm level easily occurs leading to erroneous conclusions. Therefore, the experiments must also be followed up by proving that the nitrogen is coming from N2 and not by activation of some nitrogen compounds being present either in the catalysts or in the electrolyte. This is extremely important since the most difficult step in this process is the activation of the nitrogen molecule that is the second most stable molecule in nature. It shall be demonstrated that this can convincingly be done by using isotopically labelled 15N2. The ammonia synthesized can then subsequently be quantified using mass-spectroscopy, NMR or IR spectroscopy to prove that the source was indeed molecular nitrogen and not some other erroneous source of activated nitrogen. The advantage of using NMR or mass-spectroscopy shall be discussed and some of the tricks for measuring small amounts of ammonia in the presence of water shall be demonstrated. Examples of ammonia synthesis or lack of same for a number of catalysts tested shall be demonstrated.
(Invited) Atmospheric Ammonia Synthesis – Mechanism, Materials and Processes
Authors: Liu Bin
Published: February 2020

Ammonia is a critical chemical that sustains the global food chain by feeding approximately 40% of world’s population. Ammonia can also be utilized as a clean fuel or energy carrier to power efficient energy conversion devices. However, ammonia production based on Haber-Bosch process is increasingly challenged by scalability and energy intensity (consuming almost 2% of the world’s energy). Ideally, feasible ammonia synthesis processes enabling intermittent operations at milder conditions and smaller scale, as well as the integration with renewable energy sources, will bring the technological breakthrough in order to better suit current societal needs.

In this talk, theoretical density functional theory (DFT) will be used to evaluate a class of novel alternative materials for N2 activation, ammonia formation and decomposition. Specifically, our recent work on transition metal or alloy-based nitrides (TMNs) will be discussed to show that the knowledge of molecular mechanism from theory is necessary and can lead to the formulation of guidelines to help identify appropriate materials and their optimizations. TMNs have been successfully demonstrated in stepwise, atmospheric ammonia synthesis in a nitridation cycle. Recent studies have also suggested that TMNs are also promising materials to catalyze N2, via electroreduction, to ammonia under ambient conditions. By following a Mars-van Krevelan mechanism, we identified that the nitride formation thermodynamics and nitrogen species diffusion kinetics under relevant process condition are both the key and will invoke the consideration of both aspects simultaneously in the nitridation-reduction cycle. To improve the TMN performance, the simple strategy to modify the electronic structures of TMN by alloying with other transition metals, targeting both bond formation and nitrogen transport within TMN, will be presented. Derived from our computational findings, bifunctional materials that are capable of efficient N2 activation and ammonia synthesis in synergy may hold the ultimate solution. Potential candidate materials that can be deployed for electrochemical or thermal ammonia production will be presented.
(Invited) Partially Reduced Metal Oxide Supported Ni-Fe Electrocatalyst for N2 Reduction to NH3 at Ambient Conditions
Authors: Xin Le , Qiu Yang , Gu Shuang , Li Wenzhen
Published: February 2020

Haber-Bosch ammonia synthesis is a mature industrial process, via which >150 million tons ammonia per year was produced for the fertilizer industry to support the large global population growth over a century. However, this process consumes about 1~2% of all global energy and emits 2~3% of all global greenhouse gas CO2 emissions. Synthesis of ammonia directly from air and water, driven by renewable electricity, has been envisioned as an alternative and green process, as the global energy supply is shifting from fossil fuel based sources to renewable energy sources. The major technical challenges associated with nitrogen reduction reaction (NRR) using water as proton source are the low rate and very low selectivity (e.g. current efficiency or faradaic efficiency), in which most protons and current are used to produce H2. Intensive research efforts on the development of efficient and robust electrocatalysts and electrocatalytic process are highly desirable. Guided by the qualitative model laid out by Norskov group (ACS Catal. 2017, 7, 706−709), our rational design of NRR catalytic materials is based on the combination of the transition metals (e.g. Ni and Fe) that were predicted to be optimal for N adsorption (Phys. Chem. Chem. Phys., 2013, 15, 7785-7795) and to support them on different composite metal oxide substrate. Despite of the low surface area of the metal oxide support (ca. 35 m2/g) versus carbon black (XC-72, ca. 254 m2/g), the strong interaction between Ni-Fe and metal oxide after partial reduction in the flow of forming gas significantly improves the NRR activity tested in an H-type cell filled with 0.1 M KOH at ambient conditions (25°C and 100kPa). Comparing the NRR selectivity (in term of faradaic efficiency to ammonia production) and activity (in term of NRR rate), it clearly shows that at an optimized potential, the faradic efficiency of NRR over NiFeOx/C, partially reduced-NiFeOx/C and partially reduced NiFeOx/metal oxide is 0.54%, 3.97%, 15.27%, respectively, and the NH3 production rate also follows the order of NiFeOx/C << partially reduced-NiFeOx/C < partially reduced NiFeOx/metal oxide. The fundamental study of the NRR mechanisms on these composite catalysts based on the advanced physical characterizations and primary theoretical calculations, as well as our latest technology development of efficient alkaline electrolyzers for ammonia synthesis will be presented.
Detection of the Bacterial Warfare Toxin, Pyocyanin, Using Transparent Carbon Utlramicroelectrode Arrays
Authors: Stevenson Keith J , Simoska Olja , Shear Jason
Published: February 2020

Pyocyanin is a virulence factor exclusively secreted as a secondary metabolite by the opportunistic human pathogen Pseudomonas aeruginosa. Fast and direct detection of pyocyanin is of importance as it could provide fundamental insights regarding P. aeruginosa’s virulence mechanisms. Here, we demonstrate an electrochemical-sensing platform that is able to quantitatively determine the bio-synthesis and release of redox-active pyocyanin in real time using transparent carbon ultramicroelectrode arrays (T-CUAs). We quantified pyocyanin concentrations on various types of T-CUA electrodes using square-wave voltammetry to determine limits of detection (LODs) and linear dynamic ranges (LDRs). LODs and LDRs fall within the micromolar range for a variety of in vitro and in vivo cellular environments and offer promise of the application of T-CUAs as sensing devices for the quantitative study of biotoxins, bacterial group behavior phenotypes, and pathogenesis. We also demonstrate successful use of T-CUAs for electrochemical detection of pyocyanin secreted from P. aeruginosa strains while optically imaging the cells through the transparent electrodes. Secreted pyocyanin levels from two virulent bacterial strains, clinical PA11 and wild-type PA14, were measured. Finally, we present real-time electrochemical monitoring of pyocyanin using T-CUAs while optically and fluorescently analyzing aggregate formation of various clinical and laboratory bacterial strains.
Electrosynthesis of Bio-Based Dicarboxylic Acids
Authors: Rauen Anna Lisa , Waldvogel Siegfried R.
Published: February 2020

Currently, oil and gas are dominating feedstocks for bulk and fine chemicals. However, limited fossil resources and growing awareness for the environment requires sustainable alternatives [1]. One potential source for renewable raw materials is wood. In the pulping process of wood to cellulose, large amounts of lignin and also turpentine accumulate as a by-product. With the holistic use of waste streams in mind, lignin and the components of the turpentine fraction represent promising sources for carbon building blocks.

α-Pinene, the major compound of the turpentine fraction, can be oxidized to a biogenic dicarboxylic acid which finds a potential application as a hardener in bio-based thermosets. For a fully sustainable application, the necessity for renewable resources goes hand in hand with the demand for green chemical processes, such as electrosynthesis [2].

The key step of a possible oxidation sequence of α-pinene to bio-based dicarboxylic acids is successfully performed by electrocatalytical conversion of pinanediol to pinonic acid. To establish this transformation as a green method, we developed a simple, high-yielding protocol for the anodic oxidation of pinanediol, while maintaining of the intrinsic stereogenic information, at nickel oxidehydroxide anodes in water, the least hazardous of all solvents.

[1] C. Brandt,
Chem. Unserer Zeit
2002, 36, 214–224.

[2] A. Frontana-Uribe, R. D. Little, J. G. Ibanez, A. Palma, R. Vasquez-Medrano, Green Chem. 2010, 12, 2099–2199.

Figure 1
Electrosynthesis of 2,1-Benzisoxazole from o-Nitrobenzaldehyde
Authors: Hosseini Seyyedamirhossein , Peters Dennis G
Published: February 2020

Chemical synthesis of organic compounds is often a complex process that requires toxic catalysts, long reaction times, and many reagents. One example is the conventional synthesis of 2,1-benzisoxazole (BNZ). This compound has great importance for both pharmaceutical applications and as a starting material in the total synthesis of natural products.1 Chemical synthesis of this compound requires use of ruthenium and palladium catalysts, high pressure of carbon monoxide, and long reaction times.2 Also, the yield for the conventional chemical reaction is low, and there are no reports of yields higher than 50%.3

On the other hand, electrochemistry offers a clean and fast method for the synthesis of organic compounds. However, the electrosynthesis of BNZ has previously involved the use of a mercury pool cathode over a long reaction time, which makes the synthesis unfavorable.4 In the present work, the electrochemical behavior of o-nitrobenzaldehyde was studied in different solvent systems with the aid of cyclic voltammetry. Subsequently, the electrosynthesis of BNZ was accomplished with bulk electrolysis at a carbon cathode. Upon optimization, the yield of the BNZ reached 80% within a 1-hour electrolysis without any catalyst to facilitate the process.

References

Wiȩcław, M.; Bobin, M.; Kwast, A.; Bujok, R.; Wróbel, Z.; Wojciechowski, K. Mol. Divers.
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Figure 1
Electrochemical Functionalization of Methylarenes Initiated By Hydrogen Atom Transfer and Comparison to Electron-Transfer-Initiated Functionalization
Authors: Rafiee Mohammad , Stahl Shannon S.
Published: February 2020

Aerobic oxidations catalyzed by N-hydroxyphthalimide (NHPI) are commonly utilized for the oxygenation of activated C–H bonds (allylic, benzylic, adjacent to heteroatoms).[i] NHPI undergoes proton-coupled oxidation to afford phthalimido-N-oxyl (PINO), which then mediates HAT from weak C–H bonds. In 1983, prior to the development of aerobic methods to generate PINO, Masui and co-workers demonstrated the ability to access PINO from NHPI under electrochemical conditions [ii] and site-selective oxygenation of the electrochemically generated radical using O2 as radical trap.[iii] Electrochemical PINO generation was utilized recently for scalable oxidation of terpenes[iv] and benzylic oxygenation of heterocyclic compounds.[v] In the latter reactions, metal-free electrochemical oxygenation overcomes the challenges encountered with chelating substrates that inhibit Co/NHPI-catalyzed aerobic oxidation reactions. Electrochemical oxidation of NHPI to PINO additionally presents the opportunity to trap organic radicals with reagents other than O-atom sources. This presentation will describe the first example of this concept, showing that iodine (I2) is an effective radical trap for electrochemical NHPI-mediated oxidation of methyl­arenes to benzyl iodides.

The method provides the basis for direct (in situ) or sequential benzylation of diverse nucleophiles using methylarenes as the alkylating agent. Voltammetric studies demonstrate that this mediated HAT mechanism for C–H iodination allows C–H oxidation to proceed with minimal dependence on the substrate electronic properties, contrasting benzylic C–H functionalization methods that proceed via direct electron transfer. The operating potential of the NPHI-mediated process is 0.5 – 1.2 V lower than that of direct electrochemical C–H oxidation.

[i]. Recupero, F.; Punta, C. Chem. Rev.
2007, 107, 3800.

[ii]. Masui, M; Hara, S.; Ueshima, T.; Kawaguchi, T.; Ozaki, S. Chem. Pharm. Bull. 1983, 31, 4209.

[iii]. Masui, M.; Hosomi, K.; Tsuchida, K.; Ozaki, S. Chem. Pharm. Bull.
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33, 4798.

[iv]. Horn, E. J.; Rosen, B. R.; Chen, Y.; Tang, J.; Chen, K.; Eastgate, M. D.; Baran, P. S. Nature
2016, 533, 77.

[v]. Hruszkewycz, D. P.; Miles, K. C.; Thiel, O. R.; Stahl, S. S. Chem. Sci. 2017, 8, 1282.

Figure 1
Umpolung Diels-Alder Reactions By Electrocatalysis
Authors: Okada Yohei , Ozaki Atsushi , Yamaguchi Yusuke , Chiba Kazuhiro
Published: February 2020

Although the Diels–Alder reaction is a classic reaction, it is still at the forefront of the carbon–carbon bond formation toolbox in synthetic chemistry. In particular, the mechanism of the reaction has been well studied, and the scope has been expanded to a wide variety of diene/dienophile combinations. However, electronic matching needs to be considered; more specifically, that one reaction partners should be electron-rich and the other electron-deficient. To overcome this hurdle, "umpolung" strategy has been proven to be powerful approach. In this context, single electron transfer (SET) would be the most simple and straightforward process. For example, electron-deficient radical cation species can be produced from electron-rich reactant via SET oxidation. A typical example of the umpolung Diels-Alder reactions is the reaction between an electron-rich diene and a dienophile. These combinations are electronically mismatched, however, SET oxidation can produce a radical cation of one component, which is then able to be trapped by the other component.

In addition to the use of chemical redox agents, photocatalysis and electrocatalysis are currently recognized as effective approaches to induce SET processes. Umpolung Diels-Alder reactions have also been extensively studied for almost half a century, however, scope of the reactions has been limited. In many cases, the reactions were triggered by SET oxidation of diene components, generating the radical cation species, and which were then trapped by dienophiles. In 2011, Yoon elegantly demonstrated the opposite version, namely, the reaction triggered by SET oxidation of dienophile components using photocatalysis.

We have been developing carbon-carbon bond formations by electrocatalysis in lithium perchlorate (LiClO4)/nitromethane (CH3NO2) electrolyte solution.1 In most cases, the use of LiClO4/CH3NO2 electrolyte solution is critical, which exhibits remarkable property as a Lewis acid to facilitate the reactions of carbon-centered radical cations with carbon nucleophiles. We also have shown that the electrocatalysis in LiClO4/CH3NO2 electrolyte solution is effective to induce umpolung Diels-Alder reactions.2 In this talk, recent advancement of the umpolung Diels-Alder reactions by electrocatalysis will be discussed in details.

(1) Imada, Y.; Yamaguchi, Y.; Shida, N.; Okada, Y.; Chiba, K. Chem. Commun.
2017, 53, 3960–3963.

(2) (a) Ozaki, A.; Yamaguchi, Y.; Okada, Y.; Chiba, K. ChemElectroChem
2017, 4, 1852–1855. (b) Okada, Y.; Yamaguchi, Y.; Ozaki, A.; Chiba, K. Chem. Sci.
2016, 7, 6387–6393.

Figure 1
Cycloaddition Reaction Assisted By Photoinduced Electron Transfer in a Lithium Perchlorate-Nitromethane System
Authors: Nagahara Shingo , Wakamatsu Hiroki , Okada Yohei , Chiba Kazuhiro
Published: February 2020

Photochemical and electrochemical processes both have proven to be powerful tools that enable unique bond formations to construct various carbon skeletons. In this context, we have been developing electrochemical reactions in lithium perchlorate/nitromethane (LiClO4/MeNO2) electrolyte solution. This solvent system possibly stabilizes the anodically-generated cation species and acts as a Lewis acid catalyst. The feature of the LiClO4/MeNO2 allows effective syntheses of various compounds, such as dihydrobenzofuran derivatives formed via phenoxonium cation intermediates [1] and azanucleoside derivatives formed via iminium cation intermediates.[2] Furthermore, it is also demonstrated that the LiClO4/MeNO2 is effective for several [2+2] cycloaddition reactions between enol ethers and unactivated olefins,[3] affording cyclobutane products, and electrocatalytic Diels-Alder reactions[4]. In this way, our reaction development is governed by the use of a high concentration LiClO4/MeNO2 electrolyte solution. Recent 7Li NMR and calorimetric studies showed that Li+ is weakly coordinated in the solution to exhibit Lewis acidity, which we termed entropic effect.[5]

During such reaction developments, we serendipitously found the [2+2] cycloaddition reactions in LiClO4/MeNO2 also proceed under UV (365 nm) irradiation without any other reagents such as photo-catalyst. UV-Vis spectra study suggested that MeNO2 would absorb UV light and drive the reaction. This could be reasonably understood based on energy transfer mechanism, namely, irradiation of the MeNO2 with UV light produces the excited state, which then generates the excited state of the enol ether that undergoes the reaction. Molecular oxygen must also be involved in the overall process, since Ar bubbling had a negative impact on the reaction. . The reaction was also dramatically suppressed in other solvent systems Furthermore, we found this photo-induced reaction in LiClO4/MeNO2 system also can be applied to [4+2] and [3+2] cycloadditions. Details of reaction mechanism and scope & limitation would be discussed in the presentation.

Reference

[1] Kim, S.; Hirose, K.; Uematsu, J.; Mikami, Y.; Chiba., K. Chem.
Eur.
J.,
2012, 18, 6284–6288.

[2] Shoji, T.; Kim, S.; Chiba, K. Angew. Chem. Int. Ed., 2017, 56, 4011-4014.

[3] Okada, Y.; Nishimoto, A.; Akaba, R.; Chiba, K. J. Org. Chem., 2011, 76, 3470-3476.

[4] Okada, Y.; Yamaguchi, Y.; Ozaki, A.; Chiba, K. Chem. Sci., 2016, 7, 6387-6393.

[5] Imada, Y.; Yamaguchi, Y.; Shida, N.; Okada, Y.; Chiba, K. Chem. Comm., 2017, 53, 3960-3963.
Electrochemical Analysis of Circulating Nucleic Acids for Liquid Biopsy
Authors: Kelley Shana , Das Jagotamoy
Published: February 2020

To put disease-related biomarkers to work in the clinic, new high-performance technologies are needed to enable rapid and sensitive analysis of clinical specimens. Electrochemical methods providing low cost and direct biomarker readout have attracted a great deal of attention for this application. We exploit controlled nanostructuring of electrode surfaces to enhance biomolecular capture rates and efficiencies to solve this long-standing problem, and showed that the nanoscale morphologies of electrode surfaces control their sensitivities. An electrocatalytic reporter system that leverages a pair of redox reagents is used to readout the presence of specific nucleic acids and other analytes bound to electrode surfaces. Recently, we have developed assays that are able to detect nucleic acids, proteins and small molecules, with universally high sensitivity levels. This presentation will highlight how electrodeposited metals can be used to create high performance sensors that can be applied to the analysis of circulating tumor DNA (Das et al, JACS (2016)) and RNA (Das et al, Nature Chemistry (2015) for the realization of liquid biopsy as an alternative to invasive methods.
Electrochemical Activation of the Tetrazine Ligation for Surface Modification
Authors: Devaraj Neal
Published: February 2020

Our lab has been interested in developing conjugation reactions that can be triggered by electrochemical potential. Such reactions could have application in the functionalization of independently addressable electrode arrays. These include past effortsusing the electrochemistry to locally generate copper+1 to trigger the well-known copper catalyzed azide alkyne cycloaddition. Our lab has been interested in an alternative bioorthogonal reaction, the tetrazzini ligation, as a versatile coupling tool. Unlike “click” chemistry, the tetrazine ligation does not have a redox active catalyst. However, one of the reactive components (the tetrazine) is redox active and can be reduced to a dihydrotetrazine, preventing cycloaddition. Through this manner, bioconjugation can be controlled electrochemically. I will summarize our findings in this area and discuss applications.
Non – Linear Electrochemical Impedance Spectroscopic Analysis of Instabilities in Electrochemical Systems
Authors: Pachimatla Rajesh , Srinivasan Ramanathan
Published: February 2020

Electrochemical impedance spectroscopy (EIS) is one of the principle technique which is capable of in situ analysis of electrode – electrolyte interface and of probing electrochemical reaction mechanism. Typically, small amplitude perturbations are employed and the response is analyzed assuming that the system behavior is linear and stable [1, 2]. If large amplitude perturbations are employed, the resulting current will have significant higher harmonic signals, which can provide more information about the system examined [3]. This is often referred to as nonlinear EIS (NLEIS).

In this work, we present NLEIS analysis of an unstable system, where potential drifts and concentration changes are introduced. The classical Fe2+/Fe3+ redox couple is chosen for experimental and numerical analyses. A setup comprising of three instruments (Potentiostat, Lock-in amplifier and signal analyzer from Stanford Research System) to acquire the NLEIS data with the help of an in-house developed software was established. The applied perturbation frequency was varied from 100 kHz to 125 mHz and the amplitude was varied from 20 mV to 100 mV. The current magnitude and phase at fundamental and higher harmonics were measured using FFT analyzer. Instabilities were introduced by continuously changing the dc potential or the active species concentrations, during the NLEIS measurements. All the solution contained 100 mM Na2SO4 as supporting electrolyte. The initial concentration of Fe2+/Fe3+ species was 5 mM each. Figure 1 shows the experimental results with fixed as well as changing concentrations. In case of experiments denoted as ‘changing concentration’, the active species concentrations at any time ‘t’, min, were given by C = (200+ 3 t)-1 M. The governing equations were solved without linearization, using numerical methods. Both mass transfer and reaction kinetics effects were taken into consideration and the experimental results were compared with the numerical solutions.

Keywords: nonlinear EIS, system instabilities, potential drift, mass transfer effect

References

[1]. Orazem, M., Tribollet, B., Electrochemical Impedance Spectroscopy, John Wiley & Sons, NJ, (2008)

[2]. Wilson, J. R., Sase, M., Kawada, T. Adler , S.B., Electrochem. Solid-state Lett. 10 (5) (2007) B81-B86.

[3]. Fathima Fasmin and Ramanathan Srinivasan, J Electrochem. Soc., 164 (7) H443-H455 (2017)

Figure 1
Fluorescent Readouts of Spectroscopically-Silent Reactions on Single Metal Nanoparticle Electrodes
Authors: Willets Katherine
Published: February 2020

The ability to measure electrochemical reactions on single nanoparticle electrodes reveals how local structural and surface heterogeneity impacts electrochemical performance. However, integrating traditional electrochemical techniques with single nanoparticle measurements remains an experimental challenge and typically does not allow many individual nanoparticles to be interrogated simultaneously. Optical readouts of electrochemical reactions provide a solution to this challenge, allowing reactions on many nanoparticles to be followed in parallel, while providing single nanoparticle sensitivity. However, optical readouts are traditionally limited to a specific subset of redox-active probes that show a change in their optical signature upon a change in their redox state, limiting the scope and applicability of the approach. This talk will discuss using pH sensitive probes to follow spectroscopically-silent redox reactions such as hydrogen production on single nanoparticle electrodes.
Optical Direction of Morphological Complexity of Periodic Semiconductor Nanoarchitectures Deposited Via Templateless Photeolectrodeposition
Authors: Carim Azhar I , Batara Nicolas A. , Thompson Jonathan R , Atwater Harry A , Lewis Nathan S
Published: February 2020

Electrodeposition of Se-Te alloy films under illumination spontaneously generates nanopatterned films with significant periodic order. The feature sizes, periodicities, anisotropies, and orientations of the nanoscale pattern are a function of the exact nature of the optical excitation. Isotropic morphologies consisting of ordered arrays of nanopores were generated using unpolarized illumination whereas linearly polarized light resulted in highly-anisotropic lamellar morphologies with the long axes of the patterns aligned along the E-field vector. The pattern periodicity was encoded by the illumination spectral profile. A single periodicity in single spatial direction was only generated even with the use of broadband and multimodal spectral profiles and multiple polarization inputs and the periodicity was found to be sensitive to all investigated tuning of such profiles. Structures with nonequal periodicities in the two orthogonal in-plane directions could also be generated and both periodicities could be independently controlled. Additoinally, the anisotropies, subwavelength feature size and periodic nature of the deposits enables the fabrication of optical elements with significant wavelength and polarization discrimination.

The nanopatterning process occurred without the use of any type of physical or chemical templating agents: no photomask, patterned substrate nor surfactants/ligands were used to influence the morphology. Modeling of the growth using a combination of full-wave electromagnetic simulations of light absorption and scattering coupled with Monte Carlo simulations of mass addition successfully reproduced the experimentally observed morphologies and indicated that morphology development was a consequence of the fundamental light-matter interactions during growth.
Methane Pulse and in-Situ Raman Study of Impregnated Ni/CGO As Anodes of SOFC
Authors: Ouyang Mengzheng , Boldrin Paul , Maher Robert C. , Brandon Nigel P.
Published: February 2020

Nickel/gadolinium doped ceria (Ni/CGO) has been a popular SOFC anode material for decades for its superior mix conductivity and excellent oxygen storage capacity. However, the study of Ni/CGO in a realistic working condition is still lacking. Also, not much research has linked the chemical properties of CGO with the carbon resistance which is essential when using hydrocarbon as fuels.

In this research, Ni/CGO powder was prepared via impregnation-calcination method. A novel pulse experiment has been conducted on impregnated powder. We did certain pulses of a fixed amount of methane into the sample at 600℃.The outlet gas was monitored by a quadrupole mass spectrometer.

The product gas was composed of several species including hydrogen, steam, carbon monoxide, carbon dioxide, and methane that was not participated to the reaction.

The major reaction was the partial oxidation of methane.

With the increase of pulsing number, the product and shape of product peak changed a lot. Also, we observed a “tail” after each carbon monoxide production peak which was deduced to be the self-oxidation of carbon by the bulk migrated oxygen.

After detailed quantitative analysis of the shape and intensity of the peaks and tails. We came up with a model in which the mechanism of methane partial oxidation was confirmed and so was the relation between carbon self-oxidation rate, surface oxygen and bulk oxygen migration rate of CGO.

In-situ Raman spectroscopy was performed during the pulse experiment to monitor the change of CGO surface oxygen stoichiometry and deposited carbon. Thus we can confirm the conclusion deduced by pulse experiments and directly relate the carbon self-oxidation rate with bulk oxygen migration of CGO.

The results would provide an insight into the design and modification of SOFC anode materials.