bluuebunny/crossref_metadata_2025 huggingface dataset:
Mechanistic Insights into Enzymatic Nitric Oxide Reduction Revealed By Surface-Enhanced Infrared Absorption Spectroscopy
Authors: Kato Masaru , Masuda Yuya , Nakagawa Shogo , Tosha Takehiko , Yagi Ichizo
Published: February 2020

Biological nitric oxide reduction occurs in certain bacteria containing nitric oxide reductases (NORs). The NOR is a transmembrane metalloenzyme and selectively catalyzes the reduction of nitric oxide (NO) to nitrous oxide (N2O) in the microbial denitrification process. The enzymatic NO reduction is catalyzed at a binuclear active center of the non-heme FeB and the heme b
3.[1] The molecular mechanism of the enzymatic NO reduction has been extensively studied using physicochemical techniques including protein film electrochemistry.[2] However, the molecular mechanism still remains under debate.

Herein, we report electrochemical and spectroscopic studies on protein film electrochemistry and surface-enhanced infrared absorption (SEIRA) spectroscopy of NOR-modified gold electrodes. The NOR was isolated from P. aeruginosa and then immobilized on SEIRA-active gold electrodes via a self-assembled monolayer of alkyl thiols. The NOR-modified gold electrode showed electrocatalytic NO reduction currents with an onset potential of ca. –0.4 V vs. SHE. Potential-dependent SEIRA spectra of the NOR-modified electrode under CO, which was used as a vibrational probe to identify the electrochemical reduction of iron cofactors, showed a characteristic band at 1972 cm–2 at –0.4 V vs. SHE. This band was associated with the CO binding to heme b
3. Thus, these results suggest that the heme b
3 should be involved in the enzymatic NO reduction.[3] SEIRA spectra of the NOR-modified electrode in the presence of NO are underway to understand the binding mode of NO to iron cofactors in the electrocatalytic condition.

References

[1] T. Hino, Y. Matsumoto, S. Nagano, H. Sugimoto, Y. Fukumori, T. Murata, S. Iwata, Y. Shiro, Science, 330, 1666–1670 (2010).

[2] C. M. Cordas, A. G. Duarte, J. J. G. Moura, I. Moura, Biochim. Biophys. Acta, 1827, 233–238 (2013).

[3] M. Kato, S. Nakagawa, T. Tosha, Y. Shiro, Y. Masuda, K. Nakata, I. Yagi, J. Phys. Chem. Lett., 9, 5196–5200 (2018).
Stress-Induced Interface Instability during Ion Intercalation in Battery Compounds
Authors: Zhang Youtian , Tang Ming
Published: February 2020

Misfit stress generated by lattice mismatch between the lithiated and delithiated phases upon ion (de)intercalation plays a key role in cycling-induced mechanical degradation and capacity fading of battery electrodes. As a general phenomenon, misfit stress also leads to interface instability. A well-known example is the stress-induced island growth or the Stranski-Krastanov growth mode of epitaxial thin films, where the misfit strain between thin film and substrate destabilizes the uniform film growth. In this work, we predict that similar phenomenon can also occur during the ion (de)intercalation process in battery compounds, in which the misfit stress triggers the morphological instability of the moving phase boundary. This phenomenon results in non-uniform (de)intercalation, leading to capacity under-utilization and battery degradation and even failure due to stress concentration, and therefore needs to be carefully mitigated to improve battery performance.

In our theoretical analysis, we consider the kinetic evolution of a sinusoidal perturbation applied to an initially flat interface between the lithium-rich and lithium-poor phases upon (de)lithiation under constant overpotential or flux conditions. The perturbation growth rate is calculated from the linear stability analysis. For interface-limited phase boundary movement, there exists a critical wavelength above which perturbation will growth. On the other hand, two critical wavelengths are identified for diffusion-limited phase transformation, and only perturbations with wavelengths between them will grow with time. The growth exponents predicted by the linear stability theory agree well with phase-field simulations. Based on the analysis, a stability diagram for lithium (de)intercalation is constructed in the space of particle size, applied overpotential (or intercalation flux) and interface location, as shown in Figure 1. Such diagram provides guidance on the conditions at which stress-induced Li intercalation instability can be avoided.

A useful insight from our study is that the interface is most susceptible to instability when it is near the electrode particle surface, i.e. at the beginning of (dis)charge process. Accordingly, we propose a (dis)charging strategy to suppress the instability, in which a high Li flux pulse is applied at the initial (de)lithiation stage to stabilize the interface until it moves into the particles. We compare interface evolution in this (dis)charging protocol against during galvanostatic cycling in phase-field simulations. It shows that the proposed strategy can effectively prevent interface instability, which results in an increase in the (dis)charge capacity and reduction in localized stress hotspots.

Figure 1
Origin of Fast Ion Conduction in Li10GeP2S12, a Superionic Conductor
Authors: Bhandari Arihant , Bhattacharya Jishnu
Published: February 2020

The discovery of additional sites in Li10GeP2S12 (LGPS) has suggested the possibility of cross channel diffusion pathways. Here we present a first principles density functional theory based study of ion migration in LGPS. We find that energy barrier for ion migration depends significantly on the c channel population, local Li environment and the hopping mechanism. A novel mechanism of correlated diffusion between the c channel and ab plane is found with a significantly lower energy barrier. The novel mechanism of Li diffusion can work even if some channels gets blocked after repeated cycling, thereby, providing alternate pathways for Li diffusion. We calculate the overall energy barrier by taking a grand canonical ensemble average of the energy barriers. The computed energy barrier of 239 meV is in remarkable agreement with the experimentally observed energy barrier of 240 meV. The study explains the overall diffusion mechanism in LGPS and is relevant for other solid electrolytes as well.

Figure 1
High-Voltage Aqueous Redox Flow Battery Utilizing Metal Coordination Chemistry
Authors: Robb Brian , Marshak Michael P.
Published: February 2020

Aqueous redox flow batteries have been investigated as a solution to the problem of grid-scale energy storage since the 1970s. However, high costs, poor kinetics, low voltages, and hydrogen generation have prevented wide scale adoption of redox flow batteries as an energy storage medium. A promising approach to solving these problems involves using complexing agents with metal ions. This method is attractive as it can permit tuning of redox potential, solubility, and performance. This presentation describes the performance of a new flow battery electrolyte utilizing low-cost coordination complexes that features a maximum power density over 0.5 W cm-2 and a discharge voltage over 1.6 V.
Predicting the Solubility of Potential Redox Flow Battery Materials Using a Quantitative Structure-Property Relationship Models
Authors: Suduwella T. Malsha , Robinson Sophia , Attanayake N. Harsha , Sigman Matthew S , Odom Susan A.
Published: February 2020

Predicting the solubility and stability of redox-active organics across all states of charge is a challenging task. A trained chemist can often predict trends, but when it comes to numerical values, even the best computer software cannot be counted upon. In screening active materials for redox flow batteries (RFBs) – in which both properties are important – we are slave to trial and error, modifying organic molecules in attempt to optimize (increase) solubility and stability without compromising other important properties such as redox potential.1,2We hope to change our approach to materials development by better predicting properties in advance. Using quantitative structure-property relationship (QSPR), we have shown that properties of unknown organic molecules can be predicted when experimental properties of a training set of related compounds is provided.3Here we sought to expand this approach to a different redox core, phenothiazines, which we have evaluated as posolyte candidates for RFBs. We measured the solubility of about a dozen phenothiazine derivatives – in both relevant states of charge (neutral and radical cation) – in a nonaqueous electrolyte. The structure of these derivatives included variations in the number, type, and position of substituents to offer a diverse training set. We used our experimental values and the results of density functional theory calculations to develop a QSPR model for the phenothiazine core, following which we synthesized and measured the solubility of a new set of phenothiazines. Here we will report on the degree of success of our model for solubility prediction.

References

Kowalski, J. A.; Casselman, M. D.; Kaur, A. P.; Milshtein, J. D.; Elliott, C. F.; Modekrutti, S.; Attanayake, N. H.; Zhang, N.; Parkin, S. R.; Risko, C.; Brushett, F. R.; Odom, S. A., “A Stable Two-Electron-Donating Phenothiazine for Application in Nonaqueous Redox Flow Batteries.” J. Mater. Chem. A
2017,
5, 24371.

Milshtein, J. D.; Kaur, A. P.; Casselman, M. D.; Kowalski, J. A.; Modekrutti, S.; Zhang, P. L.; Attanayake, N. H.; Elliott, C. F.; Parkin, S. R.; Risko, C.; Brushett, F. R.; Odom, S. A., “High Current Density, Long Duration Cycling of Soluble Organic Active Species for Non-Aqueous Redox Flow Batteries.” Energy Environ. Sci.
2016,
9, 3531.

Sevov, C. S.; Hickey, D. P.; Cook, M. E.; Robinson, S. G.; Barnett, S.; Minteer, S. D.*; Sigman, M. S.; Sanford, M. S. "Physical Organic Approach to Persistent, Cyclable, Low-Potential Electrolytes for Flow Battery Applications." J. Am. Chem. Soc. 2017, 139, 2924.
(Invited) Molecular Dynamics Simulations of the Ionic Conductivity: From Aqueous Electrolytes to Polymer Electrolytes
Authors: Zhang Chao , Shao Yunqi , Gudla Harish , Yllö Are , Brandell Daniel
Published: February 2020

Lithium batteries are electrochemical devices which involve multiple time-scale and length-scale to achieve its optimal performance and safety requirement. In terms of the electrolyte which serves as the ionic conductor, a molecular-level understanding of the corresponding transport phenomenon is crucial for the rational design. In this talk, we will report our recent progress on molecular dynamics simulations of ionic conductivities in different types of electrolytes. These include: 1) LiCl solution which is a prototype system for strongly dissociated 1-1 electrolytes; 2) Alkaline electrolyte NaOH where the conduction mechanism involves the interchange of chemical and hydrogen bonds; 3) Polymer electrolytes in which both bond polarity and solvent polarity can play important roles. An outlook on using machine-learning as a multi-scale modelling tool for investigating ion transport and dielectric properties will be also given.
Characterization of Lithium Peroxide Growth Mechanisms at Li-O2 Battery Discharge Conditions Using Ab Initio Computations
Authors: Haskins Justin B , Pham Hieu , Lawson John W
Published: February 2020

Increasing the capacity of Li-O2 batteries requires a detailed understanding of the growth mechanism of the primary discharge product, lithium peroxide. Growth of lithium peroxide via direct reduction and chemical disproportionation pathways is investigated using an advanced electrochemical interface model. The electrochemical interface model is based on density functional theory (DFT) calculations that account for electrolyte solvation and surface potential effects. The solvation effects are incorporated using an implicit solvent described by the linearized Poisson-Boltzmann model, while the surface potential is set by adjusting the Fermi level through electron population. Growth through direct reduction is found to have a low overpotential that agrees with experimental measurements. Growth through chemical disproportionation is found to be favorable near the equilibrium potential. Both mechanisms, then, are favorable during battery discharge. These findings are shown to corroborate the recent experimental observation that electrolyte donor number mediates conformal and solution-based growth of Li2O2 and offer a possible means of improving the capacity of Li-O2 batteries.
Electron Density Topological Analysis of Adsorbates on Pt and Pt Alloy Fuel Cell Catalytic Layers
Authors: Smotkin Eugene S. , Dimakis Nicholas
Published: February 2020

Phenomenological models based on adsorbate orbital occupation have shortcomings. Orbital charges, obtained by integration of densities-of-states (DOS) spectra, do not always correlate to bond strengths. Bader and co-workers have developed the quantum theory of atoms in molecules (QTAIM), which is based on the topology of electron densities, gradients and Laplacians of those densities to describe atoms and bonds of chemical systems. The advantage of QTAIM analyses is that they are basis set and method independent, as long as a minimally adequate basis set is used. We apply both QTAIM and adsorbate orbital approaches to the study of co-adsorption of water and carbon monoxide on Pt and Pt alloy catalytic surfaces relevant to polymer electrolyte fuel cell anodes, and show how the use of both approaches are complementary.
Electrostatics to Electrodynamics Via an Additional Frame of Reference
Authors: Kennell Glyn , Evitts Richard
Published: February 2020

There are many different methods for modeling the electric field coupled with electrolytic transport. Many mechanistic methods are based on Maxwell's equations and Gauss' law of electrostatics with added simplifications and/or assumptions. One common simplification is that the accumulation of charge density may be neglected and electroneutrality may be assumed. Another method might allow for the accumulation of charge density which may then be used as in independent variable in Poisson's equation to calculate the electric field, where Poisson's equation is developed from Gauss' law of electrostatics. One such common example is the Nernst-Planck-Poisson equation set.

This research presents a method to go from electrostatics to electrodynamics using an additional frame of reference and also invoking Newton's third law, allowing the incorporation of Ohm's law into Maxwell's equations. This approach allows for the derivation of electrodynamics that may be used to model the electric field coupled with electrolytic transport. In addition, this research presents a model and results where an electrolyte transport equation is coupled with an electrodynamic equation for the electric field. This model is used to simulate a variety of phenomena including liquid-junctions and electric current distributions. Results are compared with experimental and numerical results of others. The overall model is also tested for multi-dimensional multi-component transport and electric current distributions. This model is also applied to the more complex situation of a multi-scale lithium-ion battery with different sized electrodes undergoing charging.
(Keynote) Cathodic Electrocatalysis Mediated By Polyoxometalates: Reduction of Carbon Dioxide and Reductive Activation of Molecular Oxygen for Hydrocarbon Oxidation
Authors: Neumann Ronny
Published: February 2020

The talk will report on recent developments in our laboratory in electrochemical reactions catalyzed by polyoxometalates. First, combining a specifically designed di-Re(I) catalyst with H3PW12O40 in a hybrid compound, we show that upon electrochemical reduction of the polyoxometalate at a relatively low negative potential of 1.3 V versus Ag/AgNO3, photoexcitation of the polyoxometalate with visible light is enabled through excitation of the intravalence charge transfer band. This leads to electron transfer to the Re(I) catalyst for the overall photoelectrochemical reduction of CO2 to CO. Conceptually this means that such a polyoxometalate can be an electron “shuttle” between a water oxidation reaction on the one hand that produces electrons/protons and O2 and a CO2 photoreduction catalyst. Second, tri-transition metal substituted polyoxometalates such as b-[SiW9O37(CuIIH2O)3]10– are shown to be outstanding electrocatalysts for the selective reduction of CO2 to CO with a turnover frequency by foot-of the wave analysis of nearly 3000 sec–1 without addition of an acid. Very high stability in electrolytic reactions was observed with stable currents for a period of 24h. at a potential of 2.5 V versus Fc/Fc+ and a Faradaic efficiency of >90%. Step-wise reduction of the catalyst followed by UV-vis and EPR spectroscopy indicates that the active species is a likely a four-electron reduced polyoxometalate. Additionally, similar compounds such as b-[SiW9O37(FeIII
2NiIIH2O)3]10– are shown to be functional models of CO hydrogenase/CO2 dehydrogenase enzymes that also have Fe-Ni active sites. As in the enzyme, the CO oxidation is one order of magnitude faster than the CO2 reduction.

An iron-tungsten oxide inorganic molecular catalyst, a Keplerate polyoxometalate with a capsular structure, with a short-hand notation, {Fe30W72}, was used for the cathodic oxidation of simple hydrocarbons such as ethane to acetic acid, ethylene to formaldehyde and benzene to phenol in water. The {Fe30W72} capsule is stabilized in the core by sulfate/bisulfate anions providing a protic environment where three iron atoms are located at each of the twenty pores of the capsule leading to a unique and potent active site for the aerobic hydrocarbon oxidation. This is the first example of the reductive electrochemical activation of O2 that functionally mimics the reactivity of iron-based monooxygenase enzymes. Turnover frequencies based of 300-600 min1– were obtained based on the surface area of the cathode. With a graphitic carbon fiber cathode and Pt anode Faradaic efficiencies of ~60% at a cell potential of 1.8 V were typically obtained where the uncoupled reduction of O2 to water was minimized. Extensive mechanistic research using EPR spectroscopy, kinetic isotope effect measurements as well as reactions of model compounds such a 1,4-difluorbenzene, indicate the intermediacy of a highly active high spin iron-oxo species as the oxygenating species.
(Keynote) Tuning the Activity and Selectivity of CO2 Electroreduction Catalysts through Nanostructuring and Controlled Oxidation
Authors: Roldan Cuenya Beatriz
Published: February 2020

CO2 electroreduction (CO2RR) into useful chemicals and fuels is a promising technology that might be utilized to minimize the impact that the increasing industrial CO2 emissions are having on the environment. In this talk I will discuss the use of O2-plasma treatments and pulsed potential CO2 electrolysis for the activation of nanostructured metallic surfaces and the re-generation of surface oxides.

Although plasma-oxidized silver surfaces were found to display a considerably decreased overpotential for the production of CO, the hydrogen evolution reaction (HER), a competing reaction against CO2 reduction, was found to increase over time. More stable and C1-product selective SnOx/AgOx catalysts will be presented. Additionally, a direct correlation between the presence of Cu2O on well-defined single crystal and nanostructured Cu surfaces and the enhanced production of C2+ products will be illustrated.

Electrochemical tests combined with ex situ SEM/TEM-EDS, quasi
in situ XPS, operando EC-AFM and XAFS data will be used to extract correlations between the activity, selectivity and stability of CO2RR catalysts and their morphology, structure, composition, and chemical state.
(Keynote) Electroreduction of CO2 on Pb and Bi Nanoneedles
Authors: Guay Daniel , Fan Mengyang , Garbarino Sebastien , Tavares Ana C , Prabhudev Sagar , Botton Gianluigi A.
Published: February 2020

The rise in atmospheric CO2 concentration since the beginning of the Industrial Age has raised concerns on its potential effect on global temperatures. While several factors such as natural climate changes, variations in solar activity, and volcanic eruptions may also contribute to observed variations in CO2 concentrations, it has been well established that anthropogenic emissions contribute to the annual emission of over 30 billion tonnes of CO2, only about half of which is recycled through natural pathways.

CO2 conversion into value-added products is an avenue explored to mitigate environmental issues. Conversion methods appear promising, as they offer the potential to produce liquid and gaseous fuels for use either in the aeronautics industry, or as a chemical storage method for the intermittent energy produced by windmills and photovoltaic panels. Fuel synthesis may be achieved via either the production of a syngas mixture (H2 and CO) through the water gas shift reaction and subsequent conversion into hydrocarbon fuel through processes such as Fisher-Tropsch, or by direct electrochemical reduction of CO2. While all methods may result in similar conversion yields, depending on the catalyst used, direct electrochemical conversion of CO2 into value-added products is a low-temperature process, with the further advantage of requiring relatively simple equipment.

Formic acid, or formate salts, are used in a variety of chemical processes such as electrowinning, leather tanning, and aircraft de-icing. Alternatively, formic acid and formate salts may be considered a hydrogen storage medium. Direct formic acid, and more recently, direct formate fuel cells, have been investigated in the literature as they demonstrate significant benefits over methanol fuel cells, including higher open circuit voltage and lower crossover.

Among earth-abundant CO2 electrocatalysts, Sn, Pb and Bi are known to be highly selective for formate production, with faradic efficiency (FE) > 90%. However, several challenges need to be addressed for these materials to become viable alternatives for industrial applications based on an ERC process to become economically viable. In particular, issues related with large overpotential and low current densities need to be addressed, along with the long term stability of electrodes.

In this study, we compared the activity and stability for CO2 electroreduction of high surface area metallic Bi and Pb nanoneedles (see Figure 1). In both cases, the materials films were prepared through a direct electrodeposition (potentiostatic method). Both types of films were extensively characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HR-TEM) and x-ray diffraction (XRD), while electrochemical activities were characterized by cyclic voltammetry (CV), linear sweep voltammetry (LSV), and potentiostatic measurements.

Figure 1
(Keynote) Use of Conducting Metal Oxides to Modulate Charge Density Gradients in Ionic Liquids
Authors: Ma Ke , Jarosova Romana , Swain Greg M , Blanchard Gary J.
Published: February 2020

The ability to store charge in a medium such as a super-capacitor requires a material that is capable of maintaining charge separation. Typical electrolytes perform this task based on their dielectric response, whereas ionic liquids facilitate charge separation and high capacitance based on their ability to create high charge density gradients over a range of length scales. Recent work has shown that ionic liquids are capable of supporting a charge density gradient over macroscopic length scales, with the geometry of the storage cell and its electrical configuration playing a key role in determining the details of the charge density gradient. This work has shown that charge density gradients can be induced in room temperature ionic liquids over distances of ca. 100 micrometers. In this talk we will discuss that physical and chemical basis for the existence of a charge density gradient over such macroscopic distances and we will consider the role that conducting metal oxide surfaces play in mediating the formation of the charge density gradient. We will also consider the chemical effects which can serve to limit the spatial extent of the gradient.
Nano Architectured Binder-Free Metal Oxide Electrodes for High Voltage Supercapacitor
Authors: Sambath Kumar Kowsik , Cherusseri Jayesh , Thomas Jayan
Published: February 2020

Supercapacitor as an energy storage device is gaining attention as its energy density is almost nearing the batteries. As the supercapacitor already has exceptional properties such as safety, high power density and long cycle stability, the main drawback of low energy density must be tackled by the scientific community. The energy density of the supercapacitor device is largely determined by the factors such as specific capacitance and working voltage of the supercapacitor device as it is directly proportional to them. The high specific capacitance can be achieved from transition metal oxides with excellent electrochemical properties such as manganese oxide and molybdenum oxide and assembling them in asymmetric combination would deliver a high working voltage of the device. Working voltage window is also dependent on the work function difference between the anode and cathode. The prime focus of this work involved selecting the right metal oxide material as anode and cathode with high work function difference providing a higher voltage (> 2V), thus delivering a high energy density. Also, nanostructuring the metal oxides is done to obtain a very high specific surface area. The electrodes are synthesized by a facile, direct growth electrodeposition process eliminating the need for dead binders used typically. The electrodes synthesized are characterized by X-ray diffraction, scanning electron microscopy and Raman spectroscopy. Asymmetric supercapacitor is fabricated and tested by electrochemical impedance spectroscopy, cyclic voltammetry, and galvanostatic charge-discharge measurements.
Chemically Regenerative Redox Fuel Cell As Alternative to Conventional Proton Exchange Membrane Fuel Cell
Authors: Blanchard Pierre-Yves , Donzel Nicolas , Dupont Marc , Rozière Jacques , Jones Deborah J.
Published: February 2020

Here we present the development of a non-conventional fuel cell with a liquid redox cathode. The originality of the project comes from the regeneration of a redox mediator in an additional tank outside of the cell. Instead of oxygen classically used at the cathode, a liquid catalyst is reduced and a fuel (H2) is oxidized at the anode. This system is called a chemically regenerative redox flow cell (CRRFC). This technology allows to answer both issues i.e. price (Platinum free cathode) and chemical stability (absence of ROS at the interface electrode/membrane).

Few examples of chemically regenerative redox fuel cell have been described in the literature[1] with different redox couples (NO3-/NO2-,[2] polyoxometalate[3]). The best performances have been obtained with polyoxometalate derivatives developed and commercialized recently by the ACAL-energy company.[4] The Flowcath® technology is based on a polyoxometalate (POM) solution as catholyte. Their technology has been able to provide energy during more than 10,000 hours. The major issues arising from their technology are the crossover of the polyoxometalate and the efficiency during regeneration process.

In this study, we first synthesize and characterize molecules as redox mediator to carry electron between the regenerator and the electrode. The redox molecule belongs to the family of polyoxometalate containing vanadium moiety. These molecules are a key element of the device and needs to answer some criteria such as a fast electron transfer, a redox potential below 1.23 V vs. ESH and a fast chemical oxidation by dioxygen.

A specific cell stand has been developed with an additional tank to oxidize the redox mediator. All the challenge comes from the regenerator chamber in order to not be limited by mass transport of the oxidised species. Polarization curves have been recorded to give access to the cell performances.

[1] Tolmachev, Y. V.; Vorotyntsev, M. A. Russ. J. Electrochem.
2014, 50, 403–411, doi:10.1134/S1023193514020050.

[2] Han, S. B.; Kwak, D. H.; Park, H. S.; Choi, I. A.; Park, J. Y.; Kim, S. J.; Kim, M. C.; Hong, S.; Park, K. W. Angew. Chemie - Int. Ed.
2017, 56, 2893–2897, doi:10.1002/anie.201610738.

[3] (a) Ward, D. B.; Gunn, N. L. O.; Uwigena, N.; Davies, T. J. J. Power Sources
2018, 375, 68–76, doi:10.1016/j.jpowsour.2017.11.035. (b) Ward, D. B.; Davies, T. J. Johnson Matthey Technol. Rev.
2018, 62, 189–203, doi:10.1595/205651318X696800.

[4] Creeth, A. Pt-free PEM cathode technology with fundamental durability benefits: FlowCath®. Fuel Cells Bull.
2011, 2011, 12–15, doi:10.1016/S1464-2859(11)70126-2.
(Keynote) Promoting Electrochemical Oxygen Evolution in Acidic Media: Hydrophobic Stabilization of Earth Abundant Catalysts
Authors: Galan-Mascaros Jose Ramon , Garcés-Pinedaa Felipe , Yua Jiahao
Published: February 2020

The oxygen evolution reaction (OER) is a key process in the general development of sustainable solar fuels, and essential in the progress/growth of an alternative hydrogen economy. This is a very demanding reaction, since a OER catalysts must be fast and efficient, but also stable and robust to high oxidation potentials, water, oxygen, acids or bases, etc. Several earth abundant metal oxides have appeared as excellent OER electrocatalysts in neutral and basic conditions, with multiple examples from different labs.1 However, the situation in acidic media is quite different. Only noble metal oxides are able to exhibit OER activity in acid, where the hydrogen evolution reaction (HER) is easier and faster, and proton exchange membrane can be used to separate the products, allowing to reach high currents. Transition metal oxides are unstable, whose structural integrity is pH dependent.

Recently, we have demonstrated how Co-containing polyoxometalates (POMs), molecular metal oxide fragments,2 are active OER catalysts in acidic conditions.3 Our strategy consists of incorporating water-insoluble salts of these POMs into a hydrophobic composite electrode, yielding very good stability and, remarkably, competitive electrocatalytic performance when compared with noble metals. We also disclosed that this strategy is also useful with bulk metal oxides of abundant transition metals, becoming a general approach for the development of cost-effective OER catalysts. In this communication we will present our latest results regarding acidic OER catalysis with POMs and bulk metal oxides, shedding some light into the origin of the hydrophobic-catalytic synergy for this electrochemical process.

[1] J. R: Galan-Mascaros, ChemElectroChem, 2015, 2, 37.

[2] H. Lv, Y. V. Geletii, C. Zhao, J. W. Vickers, G. Zhu, Z. Luo, J. Song, T. Lian, D. G. Musaev, C. L. Hill, Chem. Soc. Rev, 2012, 41, 7572.

[3] M. Blasco-Ahicart, J. Soriano-Lopez, J. J. Carbó, J. M. Poblet, J. R. Galan-Mascaros, Nat.
Chem.
2018, 10, 24.
Vanadium Oxide Nanoflower – Carbon Nanofiber Composite Electrodes Derived from Poly(acrylonitrile-co-itaconic acid)
Authors: Wunch Melissa , Mahmood Samsuddin , Balkus Kenneth J. , Ferraris John P. , Yang Duck Joo
Published: February 2020

Composite electrodes composed of vanadium pentoxide nanoflowers (VNFs) and carbon nanofibers (CNFs) were prepared by co-electrospinning method. Co-polymer poly(acrylonitrile-co-itaconic acid) was used to provide the carbon backbone. Presence of the itaconic acid allows for in situ activation. Morphological analysis shows that upon carbonization the resulting composite fibers have a fiber diameter of 60nm ±15nm at a 15wt% V2O5 concentration in the electrospinning solution. This composite was applied towards a two-electrode asymmetric supercapacitor device. Presence of redox active vanadium oxide composited with high surface area CNFs can help to enhance the electrochemical performance of the device. Different loadings of V2O5 were tested in order to observe how increasing loading effects the performance of the device. Results have shown specific capacitance of 150 Fg-1 at a 15wt% V2O5 loading using ionic liquid electrolyte. Ionic liquid electrolyte allows for the voltage window to be expanded, which can help to enhance the energy density. These composite electrodes have shown results comparable to ones reported using aqueous electrolytes.

Figure 1
Nanocrystalline Electro-Chemo-Mechanical Actuator Operating at Room Temperature
Authors: Makagon Evgeniy , Mishuk Eran , Cohen Sidney , Wachtel Ellen , Lubomirsky Igor
Published: February 2020

Chemical expansion of a solid refers to dimensional change due to change in stoichiometry. Dimensional change due to charged defect redistribution in an electric field has been termed the electro-chemo-mechanical (ECM) effect. Such instability is clearly deleterious for batteries or fuel cells, but, as recently suggested, has potential for use in actuation[
1
]. A typical ECM actuator includes: electrode1\WB1\solid-electrolyte(SE)\WB2\electrode2, where WB denotes working-body solids with a large chemical expansion coefficient. The main advantage of ECM is that it can simultaneously deliver large strain and large stress, which is difficult to achieve with other actuation mechanisms. We have constructed a room temperature ECM nanocrystalline membrane actuator (2mm diameter and »2µm thick) with Gd-doped ceria as SE. We tested two alternatives for the WB’s: (1) metal/(metal oxide) or (2) ceria/metal nanocrystalline composite. Electrical and electromechanical measurements demonstrated that the actuator response with metal/metal oxide WB’s is limited by the rate of oxygen diffusion from the solid electrolyte to the metal surface. Actuators with ceria/metal composite WB’s provide shorter response time (»20sec) and larger vertical displacement (>3.5µm). Our findings suggest that ECM may become a viable actuation mechanism.

[1] J. G. Swallow, J. J. Kim, J. M. Maloney, D. Chen, J. F. Smith, S. R. Bishop, H. L. Tuller, K. J. Van Vliet, Nat. Mater. 2017, 16, 749.

Figure 1
(Invited) Sensing, Measuring and Imaging Surface Charge with Nanoscale Pipettes
Authors: Baker Lane Allen
Published: February 2020

Charge is a fundamental interfacial property that governs physical and chemical interactions at surfaces. The workings of catalysts, sensors, separation devices, biological interfaces, and colloidal systems, are well known to be strongly influenced by surface charge, typically present in the form of protonated or deprotonated chemical moieties. Directly measuring and sensing charge in situ, especially for small (micro/nanoscale), heterogeneous charge distributions presents an interesting and important challenge for electroanalytical chemistry. Here, recent studies in mapping interfacial charge with scanning ion conductance microscopy (SICM) and the influence of electrolyte concentration on the charge sensing mechanism will be described. We have validated a SICM method that utilizes current‐voltage relationships that can be intuitively understood for surface charge detection. The effect of electrical doublelayer (EDL) thickness on signal generation on chemically modified surfaces will be demonstrated. The differential measurement approach used here allows visualization of individual domains of surface charge. EDL effects are modeled with finite element simulations, and extension of our studies to sensing at biological samples and mineral samples will be demonstrated.
Characterization of Arsenic Adsorption on Metal Oxide Nanoparticles By Nanoimpact Electrochemistry
Authors: Hosseini Narouei Farideh , Andreescu Silvana , Andreescu Daniel
Published: February 2020

Metal oxide nanoparticles (MNP) such as titania (TiO2), Ceria (CeO2) and Iron Oxide (Fe3O4) are heavily used in consumer products and discarded in the environment with little regulation. Although these NPs are found to be relatively non-toxic, when released in the environment they can undergo transformation and interact with existing contaminants such as heavy metals which can drastically change their properties and toxicity profile. This presentation will discuss electrochemical studies to investigate the interaction of MNPs with inorganic arsenic species and characterize surface processes (e.g. oxidation, adsorption) at the level of individual particles. Examples of NP systems and studies to assess the effect of particle type, surface coatings and environmental composition will be provided along with the parameters controlling adsorption/desorption of toxicants, using electrochemical methods and a suite of spectroscopic procedures. We demonstrate the use of electrochemistry as a powerful tool to quantifying heavy metal adsorption and determining mechanisms that can be used to predict the interaction of NPs in the environment.
Ultrathin Hydrophobic Uhmwpe Membrane for Moisture Sensing and Removal through Water Confinement Effect
Authors: GU Qiao , Xie Liangxu , Li Jin , Huang Xuhui , Gao Ping
Published: February 2020

Water confinement within the hydrophobic nanopores has attracted intensive research interest recently. Extensive research has been conducted to elucidate the water confinement mechanisms. However, direct measurements of water confinement has been extremely challenging except when high external pressure or electric field were applied. Here we report the unique water confinement effect in a hydrophobic ultrathin and nanoporous ultrahigh molecular weight polyethylene (UHMWPE) membrane. The UHMWPE membrane with thicknesses about 50 nm, consisting of highly aligned interpenetrating fibrous nanoribbons, can rapidly adsorb and confine water molecules when exposed to moist atmosphere of different relative humidity levels. The water confinement effects were characterized systematically using FTIR, TGA-MS and electrochemical impedance spectroscopy (EIS), respectively. The maximum water uptake can reach upto 13 wt%，and conductivity of the film is as high as 50% of that of pure water, which is more than one billion times of that of dry UHMWPE. Molecular dynamics simulation shows that water molecules specifically adsorb to the steps of the aligned PE films around the nanopores, and the adsorbed water clusters form conductive water chains when subjected to external electrical field strengths greater than 0.2 V/nm. The high moisture sensitivity and water confinement property of the film will be of broad applications particularly in moisture sensitive electrocatalysts where the presence of minute amount of moisture might be detrimental to the stability of the electrocatalyst.
Development of a Graphene-Nickel Composite Electrode for Hydroxyl Ion Sensing Applications
Authors: Jafari Behnaz , Botte Gerardine G.
Published: February 2020

The control and measurement of hydroxyl ion (OH-) concentration in solution are crucial in numerous industrial applications, namely treatments of natural water and wastewater, and food industries [1]. However, no portable method has been reported to directly measure OH ion concentration[2].

This study aims to develop a portable nickel-based electrochemical sensor which directly detects OH ion. The sensor signal is based on the current produced by the following reaction that happens between the nickel electrode and the hydroxyl ions present in solution [3, 4];

Ni(OH)2(s)+OH−

⇄
NiOOH(s)+H2O(l)+e−

(1)

The analysis of the nickel reactions was evaluated by cyclic voltammetry. Furthermore, chronoamperometry measurements were performed for a nickel electrode in alkaline solutions and the results demonstrated mathematical correlation between the current and OH- concentration.

In order to maximize the sensitivity of the sensor, graphene-nickel composite electrodes were designed and used in the hydroxyl ion sensor. Graphene was synthesized by chemical vapor deposition (CVD) method and its characterization was carried out by Raman spectroscopy. Findings of this work will be presented.

References

Alam, P., et al., Highly Selective Detection of H+ and OHâ€“with a Single-Emissive Iridium (III) Complex: A Mild Approach to Conversion of Non-AIEE to AIEE Complex. Organometallics. 34(18): p. 4480-4490.

Sun, D., et al., A low-cost portable electrical sensor for hydroxyl ions based on amorphous InGaZnO4 thin film at room temperature. Sensors and Actuators B: Chemical. 239: p. 679-687.

Medway, S., et al., In situ studies of the oxidation of nickel electrodes in alkaline solution. Journal of Electroanalytical Chemistry, 2006. 587(1): p. 172-181.

Jafari, B., M. Muthuvel, and G.G. Botte. Development of a Portable Nickel-Based Sensor for Hydroxyl Ion. in Meeting Abstracts: The Electrochemical Society.
Impact of Titanium Content on the Structural Properties and Sensing Performance of Sol-Gel Synthesized CeTixOy Sensing Films
Authors: Wang Chih-Wei , Tan Chia-Ying , Her Jim Long , Pan Tung Ming
Published: February 2020

In this paper, a high performance CeTixOy sensing film was developed by using a simple sol-gel spin-coating method for an electrolyte-insulator-semiconductor (EIS) pH sensor. The crystal structures, surface morphologies, and chemical compositions of the CeTixOy films prepared under different titanium concentrations (0.1, 0.3 and 0.5 M) were explored using a combination of X-ray diffraction, atomic force microscopy, and X-ray photoelectron spectroscopy, respectively. The structural properties of the CeTixOy membranes were associated with the sensing performances of their EIS pH sensors. The CeTixOy sensing film fabricated at the 0.3 M condition exhibited the best sensing characteristics (pH sensitivity, hysteresis voltage and drift rate) among these conditions. We attribute this behavior to the optimal titanium content in the film forming the stoichiometric Ce2TiO5 structure, enhancing the surface roughness CeTixOy film, and increasing the Ce3+/Ce4+ ratio.

Figure 1
An Electrochemical Approach for Development of Novel Magnetic Multicomponent Alloy Thin Films for Sensor Applications
Authors: Pavithra Chokkakula Leela Pydi , Siri Kiran Janardhana Reddy Kunda , Ummethala Govind , Murapaka Chandrasekhar , Malladi Sairam Krishna , Dey Suhash Ranjan
Published: February 2020

Magnetic multi-component alloys (MCAs) are the new class of multicomponent alloys where, combination of magnetic properties can be tuned with the composition. Due to their significant performance, MCAs have been proposed as the most appropriate choice of materials for several magnetic based sensor applications such as magnetoresistive sensors, etc. At times, for each application, multilayers with specific combination of magnetic properties or morphology throughout the material is required. In such cases, composition of alloying elements plays a significant role in the magnetic behaviour. Electrochemical approach in aqueous media is the most cost-effective method and favours better control over the composition with the help of pulse parameters. Therefore, major focus of the present work is to replace the non-aqueous/organic electrolytes with aqueous electrolytes for synthesizing the MCAs with five and/or six elements through electrodeposition. To the best of our knowledge, there haven’t been any reports on deposition of five principle alloying elements by an electrochemical approach in a single step using an aqueous media. The present study reveals the details on electrochemical deposition of multicomponent alloy thin films (Fe, Co, Ni, X, Y) for magnetic sensor applications. Firstly, a single step approach to develop nanocrystalline Fe-Co-Ni-X-Y (X, Y: Transition elements) MCA thin films is presented. Subsequently, the control over composition of MCA thin films and preliminary studies on their magnetic behaviour will be discussed. Finally, tuning of the magnetic properties of MCAs, such as saturation magnetization, magnetic permeability, and coercivity with respect to composition will be discussed. Based on the performance, these MCA thin films will be categorized for specific sensor applications. As it is important to understand the microstructure and composition of these MCA thin films, preliminary characterisation has been carried out using X-ray diffraction, scanning electron microscopy. For transmission electron microscopy (TEM), specimens have been prepared using focused ion beam (FIB) and analytical scanning/transmission electron microscopy including energy dispersive spectroscopy and electron energy loss spectroscopy have been carried out. The magnetization reversal curves for the MCA thin films were acquired initially using Kerr microscopy and detailed magnetic characterization will be carried out using physical property measurement system (PPMS) with a vibrating sample magnetometer. All the comprehensive details of this study will be discussed during the presentation.
Electrochemical Determination of Copper(II) Ions in Soil of Cultivation of Vegetables with Use of Bordeaux Syrup
Authors: Sussuchi Eliana Midori , Silva Jonatas O. S. , Lima Jéssica B. S. , Carvalho Sanny W. M. M. , Farias Ravir R. , Victor Maurício M.
Published: February 2020

Organic agriculture is growing and among the inputs produced are vegetables. Bordeaux syrup, prepared from lime and copper(II) sulphate, is able to protect them from the most common insects and diseases. Copper is responsible for important functions in the development of plants and is strongly related to the process of respiration and photosynthesis, for example. However, it can increase Cu2+ levels in vegetables and copper ions in high concentration in the soil can lead to problems for distribution of other ions important for the development of the plant and can cause diseases in the human body [1]. The development of modified carbon paste electrodes comes as a sensible, low-cost, and easy-to-move alternative for detection of this species [2-3]. In this study, a modified electrode with the organic ligand 1,3-bis(4-butyl-1H-1,2,3-triazol-1-yl)propan-2-ol, which was able to detect Cu2+ in soil samples of vegetables cultivation with use of bordeaux syrup through interactions involved in the formation of the metal-L complex.

The optimization of parameters resulted in better analytical signals in B-R buffer solution at pH 5.00 as the electrolyte, potential of - 0.4 V for 900 s for preconcentration, scan rate of 10 mV s-1 and amount of modifier of 5%. The electroanalytical method obtained linear behavior in the range of 1.00 10-8 to 1.30 10-7 mol L-1, linear coefficient equal to 0.994 for determination of copper with LQ = 5.05 10-9 mol L-1 and LD = 1.67 10-9 mol L-1 (Figure 1). The electrode is successfully applied for the determination of copper(II) in samples of soil.

Acknowledgements: FAPITEC, CNPq, CAPES, Corrosion and Nanotechnology Laboratory – NUPEG and CLQM (Center of Chemistry Laboratories Multi-users) from Federal University of Sergipe for the analysis support.

[1] J. Liu, J. Wang, S. Lee, R. Wen. Plos One. 13 (2018) 1-12.

[2] A. Nezhadali, S. Sadeghzadeh. Sens. Actuators, B. 224 (2016) 134-142.

[3] J. C. Santos, C.R.S. Matos, G.B.S. Pereira, T.B.S. Santana, H.O. Souza, L.P. Costa, E. M. Sussuchi, A.M.G.P. Souza, I.F. Gimenez. Microporous Mesoporous Mater. 221 (2016) 48-57.

Figure 1