bluuebunny/crossref_metadata_2025 huggingface dataset:
Fabrication of Piezoelectric Platforms for Studying Strain in Electrocatalysis
Authors: Counihan Michael John , Simpson Burton H , Rodriguez-Lopez Joaquin
Published: February 2020

The fabrication of piezoelectric supports for straining thin film electrodes using standard photolithography, sputter coating, and atomic layer deposition is detailed. An interdigitated array on the back of single crystal lithium niobate piezoelectric substrates allows large electric fields to be applied to strain thin films on the front of the device. A thin metal oxide insulating layer prevents electronic communication between the electrode of interest and the underlying piezoelectric. Platinum thin films (<10 nm) can be sputtered and annealed to produce quality electrodes. Microelectrode arrays can be patterned on the electrode via another oxide layer or insulating resist. The various challenges of fabricating and testing these devices as well as future prospects are discussed.
Probing the Impact of Interfacial Electric Fields and Hydrogen-Bonding Interactions on the Electroreduction of CO to Ethylene
Authors: Waegele Matthias
Published: February 2020

The electrochemical reduction of carbon dioxide to hydrocarbons on Cu electrodes could potentially provide sustainable pathways to renewable fuels and valuable commodity chemicals, such as ethylene. However, the poor product selectivity of this process hinders the adoption of this promising technology. It is well-known that the electrolyte can profoundly impact the selectivity of electrocatalytic carbon dioxide reduction. However, the molecular-level origins of this dependence are still poorly understood. A better understanding of how surface intermediates interact with their liquid reaction environment is essential for improving the product selectivity of this process. Herein, we employed differential electrochemical mass spectrometry (DEMS) and surface-enhanced infrared absorption spectroscopy (SEIRAS) to dissect how the interfacial properties of the Cu/electrolyte contact impact the catalytic selectivity of the reduction of surface-adsorbed CO, a key intermediate in the reduction of carbon dioxide to ethylene. Specifically, we employed a series of four quaternary alkyl ammonium cations (methyl4N+, ethyl4N+, propyl4N+, and butyl4N+) to systematically tune the properties of the electrochemical double layer. Using DEMS, we found that ethylene is only produced in the presence of methyl4N+ and ethyl4N+. However, ethylene is not formed in the presence of propyl4N+ and butyl4N+. Using SEIRAS, we characterized the Cu/electrolyte interface in the presence of the different cations. We found that, irrespective of the cation of the electrolyte, approximately the same CO surface-coverage is reached, suggesting that the cations do not block CO-adsorption sites. Further, we extracted the electrochemical Stark tuning rates from the dependence of the CO stretch frequency on applied potential. Based on these rates, we have derived the interfacial electric field strengths in the presence of the four different cations. The electric fields are on the order of 0.1 V Å-1. A simple electrostatic model reveals that these electric fields make a negligible electrostatic contribution to the CO adsorption energy. Analysis of the O-H stretch spectrum of interfacial water reveals that the hydrogen bond between surface-adsorbed CO and interfacial water is disrupted in the presence of propyl4N+ and butyl4N+. Our observation suggests that this hydrogen bond is essential for the formation of ethylene during the reduction of CO on Cu. These insights are expected to guide the design of electrocatalytic interfaces with high selectivity for ethylene.
Focal Point Sequestration for Operando Raman Confocal Micro-Spectroscopy of Fuel Cell Catalytic Layers
Authors: Smotkin Eugene S.
Published: February 2020

Intense laser powers used in confocal Raman micro-spectroscopy can photoablate thermally sensitive samples. This has precluded study of polymer electrolyte fuel cell catalytic layers. We now describe how thermal damage is mitigated by lifting the focal point above a transversely homogeneous sample surface. This results in a circular conical illumination volume below the focal point. The geometric probability of photons generated in this volume, having pathways to the detector pinhole, is at least two orders of magnitude lower than those emerging from a focal point. However, excellent signal to noise is recovered by sequestering the laser focal point in an isotropic medium that has no interfering Raman bands.
A Novel Electrochemical-Electron Paramagnetic Resonance Spectroscopic Technique for in-Situ Radical Formation and Detection on Graphite Pencil Electrode.
Authors: Morsy Mohamed A. , Kawde Abdelnasser M. , Bui Liliya M.
Published: February 2020

The unique capability of electron paramagnetic resonance (EPR) to detect and characterize paramagnetic species has been applied to measure free radical intermediates from any oxidative processes. Recently, sensitive benchtop EPR spectrometers have been used to quantify several radical intermediates of drug and pharmaceutical radio sterilization such as ketoconazole and alanine, respectively. During the earlier days of the EPR (also called, electron spin resonance, ESR), simultaneous EC-EPR techniques were developed and accepted as a highly powerful means for identifying paramagnetic intermediates in EC-reactions by using a variety of EC-EPR cells. However, these cells are either expensive or not easy to use, and the electrodes in these cells are made of platinum or precious silver metals. None of these cells could be utilized for the EC-EPR redox processes on the surface of graphite pencil electrodes (GPE) that produced the highest radical intermediate content (see Figure 1). The present work uses a simple, inexpensive flow electrochemical-electron paramagnetic resonance (FEC-EPR) cell for the determination of redox intermediate of different kind of drugs and their derivatives’ solutions. A well-established method for instantaneous electrochemical and EPR measurements with a new EPR-instrument, called EPR-Lab that is equipped with a FEC-EPR cell, flow pump, and OEM-potentiostat, produces data for both electro-analysis and EPR spectroscopy. The new system permits early radicals’ formation detection and analysis. It will also enable the lifetime analysis of radicals’ formation and decay by alternating the applied potential between ‘ON’ and ‘OFF’ states. The method also supports radical detection at a much lower concentration than other electrochemical or chemical oxidation techniques of similar materials. The new system has been used to elucidate the kinetics of the acidified ketoconazole (KTZ) oxidation in vitro in its real forms; tablet, cream, and shampoo extracts as well as in urine model matrix, that could be linked to its delivery in acidic solutions in vivo.

Figure 1
A Versatile Architecture for Electronically Tunable Electrocatalytic Activity: Graphene-Templated Atomically Thin Pt Supported on Oxygen-Deficient Titania
Authors: Bell Crystal , Lee Dong- Chan , Rouleau Chris , Sasaki Kotaro , Williams Michael , Alamgir Faisal M.
Published: February 2020

Platinum (Pt) is an essential catalyst for many reactions including, but not limited to, oxidation/reduction, hydrogenation, and water gas shift. Despite its common use, the major disadvantages of platinum lies within its high cost due to its low abundance, and propensity for deactivation through poisoning. One way to address this setback is to reduce its loading content in catalyst design. Recently, our group has successfully synthesized a wetted atomic layer- by- layer Pt on carbon-based and noble metal supports via the surface limited redox replacement mechanism. This methodology produced atomically-thin catalyst films on graphene, an architecture that allows for unprecedented through-graphene electronic tuning of the catalyst activity by the support material below. Implementing transition metal oxides as the support with tuned electronic properties (such as work function) can dictate the activity of the surface catalyst atoms through vicinity effects.

The research presented here will review the synthesis and structural characterization of atomically thin-filmed platinum overlayers on top of oxygen deficient titanium oxide supports using imaging and spectroscopic techniques. Oxygen deficient titanium oxides supports (TixOy) were used to alleviate corrosion issues caused by the Vulcan XC-72, a known carbon support that is commonly applied in fuel cells. To implement growth of the atomically thin-filmed Pt monolayers, a single layer of graphene was transferred onto TixOy supports before layer-by-layer Pt deposition. Four-point probe measurements, Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), X-ray absorption spectroscopy (XAS), and ultraviolet photoelectron spectroscopy (UPS) were used to examine the chemical and electrical properties of the TixOy supports. It was revealed that variations in the pulsed laser deposition technique parameters for support synthesis gave rise to Ti2O3- and Ti3O5-like films. The chemical properties of electrochemically deposited Pt on a graphene/TixOy films were found, using XPS, to exist in a metallic state. The functionality of the synthesized catalyst were tested using major (direct methanol) fuel cell reactions including, but not limited to, the oxygen reduction reaction and the methanol oxidation reaction. Overall, varying the stoichiometry of the TixOy supports lead to reaction overpotential tunability.
SLOCKTM- Sleep Sock for Tracking Chronobiology
Authors: Upasham Sayali , Prasad Shalini
Published: February 2020

Circadian rhythm is the natural rhythm associated with the sleep-wake cycle present in the body, it is an indication of the functioning of Hypothalamic-pituitary (HPA) axis. This rhythm can be tracked using biomarkers such as cortisol. Circadian rhythm is often disrupted in people that are shift workers, frequent travelers, suffering from sleep disorders, depression or adrenal disorders. An estimate of 50-70 million Americans suffer from chronic sleep disorders (NHLBI, 2003) which hinders routine functioning and have deleterious health implications including elevated cortisol levels, increased risk of hypertension, diabetes, depression, cardiac conditions and stroke. Currently available technologies for monitoring the circadian rhythm include techniques like Polysomnography (Ambulatory monitoring of nocturnal sleep), Actigraphy (Multiday ambulatory assessment), cortisol assays, core body temperature monitoring and cardiovascular activity monitoring. However, these technologies do not provide an accurate estimation of the extent of circadian disruption, as they are superficial. Biomarker estimation using cortisol helps us analyze the severity of the disease. Assays for cortisol usually rely on the use of blood or serum and take about 3-4 hours for the test results which proves to be an ineffective solution, from the point of view of developing a circadian profile for the user.

This project is aimed at developing a wearable, circadian rhythm self-monitoring platform which is non-invasive, label free and cost- effective solution to track the sleep-wake cycle in the body. The platform is a flexible porous electrochemical sensor integrated into a sock that is ideally used to capture the rise and fall of circadian biomarkers like cortisol during the sleep-wake cycle in order to track the HPA axis functioning in the user. This sensor is calibrated using Electrochemical Impedance Spectroscopy (EIS) and the Impedance changes are recorded as a function of cortisol concentration, depicted in Fig. 1. Limit of detection of the sensor is 1 ng/ml and it operates over the relevant physiological range for cortisol in sweat i.e. 8-141 ng/ml.

Figure
1
: Calibrated dose response curve for cortisol plotted as impedance vales against cortisol concentration.

Figure 1
Introduction of New Iron Sulfate Cathode Material for Na-Ion Batteries with Great Power-Capability and out Standing Cyclability
Authors: Ko Wonseok , Park Hyunyoung , Lee Yongseok , Kim Jongsoon
Published: February 2020

In this work, a novel cathode material for Na-ion batteries, Na0.97KFe(SO4)2, was successfully prepared via slow evaporation and a low-temperature process, and its outstanding electrochemical performance was demonstrated. Based on the structural information of KFe(SO4)2 obtained from Rietveld refinement of X-ray diffraction data, the possible atomic sites for Na ions entering the structure were verified using bond-valence sum energy maps. Electrochemical measurements and X-ray absorption near-edge structure analyses revealed that ~0.97 mol Na ions can be reversibly (de)intercalated into the structure via the Fe3+/Fe2+ redox reaction. The average redox potential of Na0.97KFe(SO4)2 was shown to be ~3.27 V (vs. Na+/Na), which is higher than that of other Fe-based phosphates owing to the inductive effect of (SO4)2-. It was verified that the specific capacity of Na0.97KFe(SO4)2 at C/10 was ~85 mA h g-1. At 10C (full charge/discharge in 12 min), ~53% of its capacity measured at C/10 was retained. In addition, up to ~99% of its initial capacity was retained over 200 cycles at 1C with a high coulombic efficiency of 99.3097%, which was attributed to the negligible volume change (~1.8%) during charge/discharge.

Figure 1
Plasma Enhanced Formation of Lithium Nitride As Artificial SEI Layer for Lithium Metal Batteries
Authors: Chen Ke , Pathak Rajesh , Qiao Qiquan , Zhou Yue
Published: February 2020

Lithium (Li) metal has been considered as one of the most promising anode materials to replace conventional graphite for Li ion battery. However, it still faces some problems such as unstable solid electrolyte interphase (SEI) and uncontrolled Li dendrites growth. Although plenty of efforts have been devoted to stabilize the interphase by employing a protective layer on the surface of Li metal and to suppress the dendrite growth, those materials usually suffer unstable chemical contact with Li metal electrode as well as low Li ion conductivity. Moreover, the fabrication procedures are quite complicated with long processing time or high cost.

In order to develop a facile and controllable method to fabricate a stable and low cost Li metal anode, in this work, we report for the first time to fabricate Li3N film in situ on the Li metal surface by using N2 plasma activation technology. A unique flower-shape Li3N layer with [001] crystal orientation was obtained after N2 plasma activation. With a high Young’s modulus and high ionic conductivity, the Li3N layer enabled a fast Li ion transport channel between Li metal and liquid electrolyte. This Li3N protective layer can also blocked the direct contact between Li metal and liquid electrolyte, physically suppressing the growth of Li dendrites. As a result, the cycling life of Li symmetric cell was improved dramatically compared with the untreated bare Li metal. In the full cell configuration, the plasma activated Li3N electrode also demonstrated an enhanced capacity retention.
Understanding the Roles of Mass Transport in Electrochemical Plating Process of Lithium
Authors: Tian Yang , Wu Bingbin , Lochala Joshua Andrew , Xiao Jie
Published: February 2020

Lithium metal anodes have the lowest potential (-3.04 V vs. SHE) and highest specific capacity of 3860 mAh g-1 of any metal anodes. [1] However, they still face critical problems, such as lithium dendrites, which may cause internal short circuit, and lithium pulverization. [2] Lithium pulverization increases the surface area of the whole lithium metal anode, which consumes increased amount of electrolytes, forming a solid electrolyte interphase (SEI) which covers these newly exposed Li surfaces. The end result is the depletion of electrolyte and formation of “dead” lithium. [3] The accumulation of the SEI significantly increases the cell impedance and a sudden voltage polarization is seen at the end of Li metal cycling. [4] Fundamentally, the uneven Li deposition is related to the diffusion process of Li+ in the electrolyte. An electrochemical tool has been developed by using lab-made micro-electrodes to measure critical kinetic parameters such as diffusion coefficients, limited current densities, and the onset voltages of the diffusion-controlled region in different electrolytes. The morphologies of electrochemically plated Li, on the surface of these micro-electrodes, in various electrolytes, are also compared and correlated to the measured kinetic parameters. An effective electrochemical method has been built to quickly screen compatible electrolytes providing new insights for understanding the mass-transport controlled Li plating process.

Reference:

1) Xu, W., Wang, J., Ding, F., Chen, X., Nasybulin, E., Zhang, Y. and Zhang, J.G., 2014. Lithium metal anodes for rechargeable batteries. Energy & Environmental Science, 7(2), pp.513-537.

2) Wu, B., Lochala, J., Taverne, T. and Xiao, J., 2017. The interplay between solid electrolyte interface (SEI) and dendritic lithium growth. Nano Energy, 40, pp.34-41.

3) Zhang, S.S., 2018. Problem, status, and possible solutions for lithium metal anode of rechargeable batteries. ACS Applied Energy Materials, 1(3), pp.910-920.

4) Lu, D., Shao, Y., Lozano, T., Bennett, W.D., Graff, G.L., Polzin, B., Zhang, J., Engelhard, M.H., Saenz, N.T., Henderson, W.A. and Bhattacharya, P., 2015. Failure mechanism for fast‐charged lithium metal batteries with liquid electrolytes. Advanced Energy Materials, 5(3), p.1400993.
Understanding the Electrochemical Deposition Process of Silver Metal
Authors: Martin Witness Atutala , Lochala Joshua Andrew , Wu Bingbin , Xiao Jie
Published: February 2020

While lithium metal anode has been intensively studied in recent years, the unavoidable formation of solid electrolyte interphase (SEI) layers on Li surface implicates the fundamental understanding of the origin of uneven Li deposition driven by over potentials 1. Unlike Li, Ag has a very clean surface in contacting with the liquid electrolyte2 providing a good platform to study the mass transport process of metal cations in the solution phase and how they affect the final morphologies of Ag deposited. The effects of current density, and concentration of cation species on silver metal deposition firstly investigated and correlated to the various crystalline structures of Ag plated. Then different anions are added in the electrolyte to further understand how the coordination environments of Ag+ change in the presence of different anions and their impacts on the nucleation and growth process of Ag particles. A microelectrode was applied to measure the kinetic parameters such as diffusion coefficient and limited current density in different electrolytes. The kinetic and thermodynamic mechanisms governing the observed morphological changes in the deposited silver material will provide new insights for understanding the more complicated system such as Li deposition and inspire new solutions to fundamentally control the cation transport to realize the final morphology control of the electrochemically deposited metals.

References

Zhang, S. S. Problem, Status, and Possible Solutions for Lithium Metal Anode of Rechargeable Batteries. ACS Appl. Energy Mater.
1, 910–920 (2018).

Suo, L. et al. “Water-in-salt” electrolyte enables high-voltage aqueous lithium-ion chemistries. Science
350, 938 (2015).
Influence of the Formulation on the Microstructure and Thus Performance of Li-Ion Batteries
Authors: Rynne Olivier , Dubarry Matthieu , Molson Corentin , Lepage David , Ayme-Perrot David , Prébé Arnaud , Rochefort Dominic , Dollé Mickael
Published: February 2020

The research in the field of Li-ion batteries is stronger than ever, with a common aim of increasing the energy and power density. More and more studies pinpoint the limitation of power-related performance for Li-ion batteries to the microstructure of each electrode. This random arrangement of the active material and carbon filling particles bound by the binder is typically characterized through physical values such as tortuosity, porosity and MacMullin Number.

To investigate the relationship between microstructure and performance in details, we used a design of experiment to evaluate close to seventy different formulations with LiFePO4 and Li4Ti5O12 as the active materials (AM), carbon black (CB) and carbon nanofibers (CNF) as the conductive fillers, and two different binders: polyvinylidene fluoride and a thermoplastic elastomer. By keeping the loading and porosity constant throughout the study, all formulations are homogenously dispersed in a regular tetrahedron of coordinates (AM, CB, CNF, Binder). First, the microstructure was characterized in order to extract data related to the tortuosity, porosity and electrical conductivity. Then, galvanostatic measurements, in charge and discharge, from C/25 to 30C allowed to gather information such as the low- and high-rate capacity, energy and power and the Peukert constant for intermediate rates. The statistical analysis of all these results showed some clear correlation between the formulation and the microstructure and performance of the cells. Thus, it was made possible to draw the optimal formulation to get the best compromise depending on the application requirements (energy, rate or power). Finally, trends between the physical properties and performance were deciphered. This could be used to fine-tune the best possible electrode.

Figure 1
Electrode Design for Improving Fast Charging Performance without Loss of Energy Density in Lithium Ion Batteries
Authors: Kim Don-Won , Yoo Ji-Beom , Kim Young-Jun
Published: February 2020

The technical developments of lithium-ion batteries for electric vehicles have been focused on higher energy densities for increased mileage. On the other hand, as the supply of electric vehicles increases, the demand for fast charging is also increasing. Conceptually, lithium ion and electron conduction resistance should be kept as small as possible in order for smooth fast charging without undesirable side reactions. To solve these problems, researches mainly on materials having the larger specific surface area and better electronic conductivity have been conducted, but commercialization of these kinds of researches has not been achieved due to high manufacturing cost, loss of energy density and electrochemical instabilities. For this reason, herein, we have investigated the design of electrodes for fast charging that minimizes material changes without loss of energy density. In an electrode having a high current density, the lithium ion and the electron conduction mentioned above need to be optimized for improvement of fast charging performance, but the conduction directions are opposite to each other. In order to reduce the conduction resistance of lithium ions, it is necessary to supply a sufficient electrolyte around the active materials, so it is necessary to secure open pores in the electrode for the smooth movement of the electrolyte. Whereas, in order to reduce the electronic conduction resistance, it is needed to have a compact electrode structure to achieve close physical contact between materials. In this study, we investigated the effect of various design parameters such as current density, electrode density and types of conducting agent on the fast charging performances. During the CC-CV charging process, the ratio to the reaction capacity in the CC region was measured while varying the C-rate for various design factors. In addition, electrical conductivity and porosity were analyzed to identify the root causes of the electrochemical performance and cyclic voltammetry was performed using the Randles-Sevcik equation for the analysis of lithium ion migration characteristics. Details of the research will be presented through the presentation materials.
Anion Exchange Membranes with Low Hydration Conditions from an Ab Initio Molecular Dynamics Perspective
Authors: Zelovich Tamar , Vogt Leslie , Dekel Dario R. , Hickner Michael , Bae Chulsung , Paddison Stephen J. , Tuckerman Mark E.
Published: February 2020

Regardless of the initial hydration level, a typical Anion Exchange Membranes (AEMs) fuel cell device would operate ultimately under extremely low hydration values. It is therefore vital to fully explore the hydroxide diffusion in AEMs under such conditions. In this work, we present fully atomistic ab initio molecular dynamics (AIMD) simulations to obtain a molecular-level understanding of the hydroxide solvation complexes and diffusion mechanism in low hydration AEMs. By changing the polymer electrolyte cation spacing and the hydration values we create three different AEMs models. We find that under extreme low hydration conditions, the water molecules attain a non-uniform distribution. We further see that the unique water distribution results in distinct hydroxide diffusion mechanisms varies from a stationary behavior, a vehicular diffusion, and a mixture of structural and vehicular diffusion, depending on the existence of a water oxygen at the hydroxide second solvation shell. Therefore, we find the water density to be a better descriptor than hydration values when exploring AEM under low hydration condition. Furthermore, as the hydroxide transport is essentially different compared to bulk solution, we provide an idealized hydroxide diffusion mechanism for the three diffusion categories. We believe the results presented in this study enable us to define the terms required for achieving high hydroxide conductivity in high-performance AEM fuel cell devices under extremely low hydration conditions.
(Invited) Mechanical Forces Around the Diffuse Double Layer
Authors: Monroe Charles W
Published: February 2020

Our group has recently fleshed out a general theoretical framework applicable to problems where electricity induces mechanical responses within electrolytic media. We take a continuum approach, rooted in classical thermodynamics and irreversible thermodynamics, which extends Newman's concentrated-solution theory by accounting for mechanical dynamics via a coupled momentum balance.

This talk will focus on an application of coupled electrochemical/mechanical transport theory to ideal parallel-plate electrolytic capacitors. A classical Poisson-Boltzmann model of the diffuse double layer within the electrolytic separator is augmented to include space charging within the conductive capacitor plates, which are modelled as Sommerfeld-Fermi electron gases. When accounted for in this way, the electrodes are found to contribute significantly towards the double-layer capacitance, as well as exerting a substantial compressive force on the electrolyte's boundary.

This toy problem may help to clarify modelling approaches to piezoelectric materials with substantial electrochemical activity. Both nonlinear and linear versions of the theory will be explored, the former around a single plate and the latter for the entire capacitor. The linear model holds when the electrolyte's Debye length far exceeds the plate separation, allowing the mechanical forces to be studied in the well-understood limit where the separator is an ideal dielectric.
(Keynote) Water-Oxidation By Polyoxometalate-Complexed Manganese-Oxide Nanocrystals: Visible-Light Driven Photoelectrocatalysis through Hierarchical Assembly
Authors: Weinstock Ira A.
Published: February 2020

Building on our use of polyoxometalate (POM) cluster-anions as ligands for gold-nanoparticle catalysts and building blocks [1], we show how POMs can serve as covalently attached ligands for reactive metal-oxide nanocrystals, providing soluble and isolable assemblies uniquely positioned between molecular macroanions and traditional colloids. For example, covalently coordinated redox-active POMs, serving as ligands for individual anatase titanium-dioxide nanocrystals [2], control hydrogen formation by rationally tuning rates of visible-light driven electron injection into the TiO2 cores, while soluble POM complexes of alpha-Fe2O3 (see Figure) serve as oxidatively and hydrolytically stable catalysts for visible-light driven water oxidation [3]. We now report the synthesis and characterization of POM complexed 3-nm manganese oxide nanocrystals that serve as building blocks for the assembly of water-soluble 200-nm cubic nanostructures. Notably, the hierarchical assembly of these cubic structures, each comprised of more than 50,000 of the manganese-oxide-core POM complexes, induces a shift of UV-vis absorbance into the visible. This results in enhanced visible-light semiconductor properties, whose utility is demonstrated through photoelectrocatalytic water-oxidation.

[1] (a) Zhang, M.; Hao, J.; Neyman, A; Wang, Y.; Weinstock, I. A. Inorg. Chem., 2017, 56, 2400-2408 (Front
cover); (b) Wang, Y.; Raula, M.; Wang, Y.; Zeiri, O.; Chakraborty, S.; Gan-Or, G.; Gadot, E.; Weinstock, I. A. Ang. Chem. Int. Ed.
2017,56, 7083-7087; (c) Wang, Y.; Zeiri, O.; Raula, M.; Le Ouay, B.; Stellacci, F.; Weinstock, I. A. Nature Nanotech.
2017, 12, 170-176.

[2] M. Raula, G. Gan-Or, M. Saganovich, O. Zeiri, Y. Wang, M. R. Chierotti, R. Gobetto, I. A. Weinstock, Angew. Chem.
Int. Ed.
2015, 54, 12416 –12421 (“Hot paper”).

[3] Chakraborty, B.; Gan-Or, G.; Raula, M.; Gadot, E.; Weinstock, I. A., Nature Comm., 2018, 9, 4896.

Figure 1
(Keynote) The Use of Polyoxometallates in Proton Conducting Membranes for Electrochemical Energy Conversion
Authors: Herring Andrew M. , Kuo Mei-Chen
Published: February 2020

Heteropoly acids (HPAs), a subclass of the polyoxometalates, are a class of proton conducting radical activating or decomposing molecules. Several types of HPAs have demonstrated the ability to improve membrane chemical stability and proton conductivity through polymer blends, but they still suffer from migration of the HPA species and only result in marginal gains. A method of covalent bonding HPAs to carbon in the catalyst layer has also shown some improvements in chemical stability, but chemical degradation mitigation within the membrane is needed. Our group has developed two membrane platforms with HPAs covalently attached and immobilized within a polymer membrane, serving as the proton conducting acid. More recently, the outstanding chemical stability of one of these platforms has been demonstrated, however, the stability demonstrated in this study was criticized for using rather thick, 80 µm membranes in sub-scale fuel cells.

In a recent study a 50 cm2 fuel cell was fabricated using a thin, 25 µm membrane with covalently attached silicotungstic acid, which was subjected to an accelerated stress test for chemical degradation and displayed an OCV decay rate of 520 µV h-1. To the authors knowledge, this is the first reported fuel cell of a larger practical area containing a hybrid HPA film and represents a significant step towards demonstrating this technology on a commercially relevant scale. The resulting data was analyzed to show the loss in OCV is mainly due to an electrical short and not increased reactant gas crossover. This study further analyzes the chemical stability observed in these membranes and proposes a mechanism for radical decomposition. A reaction mechanism is proposed utilizing reactions found in literature as well as density functional theory (DFT) calculations. The main conclusion from this work is that covalently attached HPAs could be more efficient radical scavengers with less susceptibility to migration, accumulation, and leaching when compared to the use of Ce(III) cations.

We have recently realized a method for cleaning these membrane materials, removing many of the impurities formed during synthesis and have also begun to cross-link these material to eliminate swelling and achieve a dimensionally stable films. These much-improved materials show even higher performance in fuel cells and could potentially solve many of the issues associated with the PFSA materials. In addition the HPA functionalized films have advantages in selective low area spec resistant membranes for redox flow batteries with a variety of redox couples. We all shoe that these membranes can facilitate redox flow batteries with labile vanadium substituted HPAs.
(Keynote) Perovskite Lanthanum Titanium Oxides for Solar Water Splitting
Authors: Wu Nianqiang
Published: February 2020

Perovskite lanthanum titanium oxides are very stable but have large band gap and poor charge mobility. This talk presents our effort to tune lanthanum titanium oxides to enhance solar water splitting. Anion doping can result band narrowing while cation doping can increase charge mobility. Incorporation of lanthanum titanium oxides with the reduce graphene oxide sheets to significantly improve the charge extraction from the perovskite oxide. Also, transient absorption spectroscopy has been sued to track the charge dynamics.
(Invited) Nanomaterial-Based Electrochemical Sensors for Environmental, Food Quality, and Medical Applications
Authors: Chen Aicheng , Manikandan Venkatesh , Liu Zhonggang
Published: February 2020

Electrochemically based methods offer facile and reliable analytical tools, which are desirable for environment monitoring, food safety and quality assessment, and neurotransmitter analysis over conventional analytical techniques. The development of a wide array of nanomaterials has paved the way for their applicability in the design of electrochemically-based sensing devices for medical diagnostics therapeutics, and imaging, energy, the environment, and food safety. The development of nanomaterials-based electrochemical sensors has garnered enormous attention due to their capacity for analytical quantification, high sensitivity and selectivity, real-time monitoring, and ease of use.

The issue of foodborne related illnesses due to additives and contaminants poses a significant challenge to food processing industries. The robust, efficient, economical, and rapid analysis of food additives and contaminants is therefore necessary in order to minimize the risk of public health issues. In this presentation, the synthesis and applications of different nanomaterials for the electrochemical determination of some common additives and contaminants such as hydrazine, caffeic acid, sulfite, and nitrite will be highlighted. In addition, neurotransmitters are molecules that transfer chemical signals between neurons to convey messages for any action conducted by the nervous system. Neurotransmitters are medically important; the detection and analysis of these molecules play vital roles in the diagnosis and treatment of diseases. The recent development and advance on the electrochemical sensing of neurotransmitters such as nitric oxide will be presented. Moreover, mercury has been recognized as a global pollutant because of its widespread presence, and bioaccumulative and toxic nature. The fabrication of the nanoporous gold microelectrode and its application for the sensitive detection of Hg(II) will be briefly discussed.
Low-Cost Colorimetric Textile Gas Sensor for Detection of Hydrogen Sulfide
Authors: Lee Junyeop , Kim Jae Keon , Jung Daewoong
Published: February 2020

Hydrogen sulfide(H2S) is a highly toxic, corrosive, flammable gas. It is produced from the microbial breakdown of organic matter in the absence of oxygen. H2S also occurs naturally in volcanic gases, hot springs, and industrially in waste water treatment, gas drilling, tanneries, etc. H2S is colorless, and it reacts with metal ions to form metal sulfides, which are insoluble. For example, lead(II) acetate, soluble white crystalline, is converted lead(II) sulfide(PbS) which is black colored insoluble solid when it exposed to H2S. Recently, there has been development in field of semiconducting metal-oxide sensors [1], optical sensors [2], electrochemical sensors [3] to real time, portable detection of H2S. This study aims to use of a cost-effective, easy to fabricate chemical textile sensor for the detection of H2S. Lead(II) acetate was chosen because of its white color crystalline and solubility. It is easy to recognize changes in color after exposure to harmful gas, H2S. Lead(II) acetate printed textile gas sensor demonstrated dark brown color upon exposure to the H2S under 1 ppm whereas no response was observed to other gas and ambient conditions. And the textile gas sensor was placed between a LED and photodiode to readout the electrical signal. Resistance of photodiode was increased with color change (H2S exposure). It can be noted that extremely small concentrations of H2S even under 1 ppm can be recognized and measured by naked eye and photodiode. This textile-based sensor is disposable, cost effective, easy to fabricate, and simple approach to detect H2S.

[1] G. F. Fine et al., “Metal Oxide Semi-Conductor Gas Sensors in Environmental Monitoring,” Sensors, vol. 10, no. 6, pp. 5469–5502, Jun. 2010.

[2] K. Hayashi, “Optical Chemical Sensor,” IEEJ Trans. Sensors Micromachines, vol. 135, no. 8, pp. 299–304, 2015.

[3] K. E. Kramer, S. L. Rose-Pehrsson, M. H. Hammond, D. Tillett, and H. H. Streckert, “Detection and classification of gaseous sulfur compounds by solid electrolyte cyclic voltammetry of cermet sensor array,” Anal. Chim. Acta, vol. 584, no. 1, pp. 78–88, 2007.

Figure 1
(Invited) Copper(I) Oxide Semiconductor Based Systems for Photoelectrochemical Reduction of Carbon Dioxide
Authors: Kulesza Pawel J.
Published: February 2020

There has been growing interest in the photoelectrochemical conversion of carbon dioxide (a potent greenhouse gas and a contributor to global climate change) to useful carbon-based fuels or chemicals. The reaction products are of potential importance to energy technology, food research, medical applications and fabrication of plastic materials. Given the fact that the CO2 molecule is very stable, its electroreduction processes are characterized by large over-potentials. It is often postulated that, during electroreduction, the rate limiting step is the protonation of the adsorbed CO product to form the CHO adsorbate. In this respect, the proton availability and its mobility at the photo(electro)chemical interface has to be addressed. On the other hand, competition between such parallel processes as hydrogen evolution and carbon dioxide reduction has also to be considered. By proper combination of certain metal (Au, Ag, Cu) nanoparticles with nonstoichiometric mixed-metal (WO3+ZrO2) selective reduction of CO2 to alcohols is in acid media feasible.

Recently, we have concentrated on the development of hybrid materials by utilizing combination of metal oxide semiconductors thus capable of effective photoelectrochemical reduction of carbon dioxide. For example, the combination of conducting polymers, or titanium (IV) oxide, and copper (I) oxide has been considered before and after sunlight illumination. Application of the hybrid system composed of both above-mentioned oxides resulted in high current densities originating from photoelectrochemical reduction of carbon dioxide mostly to methanol (CH3OH) as demonstrated upon identification of final products. Among important issue is intentional stabilization, activation, and functionalization of the mixed-metal-oxide-based photoelectrochemcal interface toward better long-term performance and selectivity production of small organic molecules (C1-C4) and other chemicals. In this respect, ultra-thin films of conducting polymers (simple or polyoxometallate-derivatized) and supramolecular complexes (with nitrogen containing ligands and certain transition metal sites), sub-monolayers of metals (Cu, Au), networks of noble metal (Au, Ag) nanoparticles or layers of robust bacterial biofilms have been considered.

The photo-biocathode with Cu-containing enzyme has induced the reduction of not only oxygen but carbon dioxide as well, under illuminations with photon energies higher than silicon band gap.

In the presentation, special attention will be paid to mechanistic aspects of electroreduction of carbon dioxide, fabrication and characterization of highly selective and durable semiconductor photoelectrode materials and to importance of the reaction conditions.
(Invited) Mixed-Metal Oxides: Tuning Their Structures and Properties for Uses in the Capture and Conversion of Solar Energy
Authors: Maggard Paul A.
Published: February 2020

The conversion of solar energy to chemical fuels, e.g., in the renewable production of hydrogen, has attracted intense research interest as both a practical and environmentally responsible way to meet our growing energy needs. Semiconducting p-type and n-type films can facilitate solar-driven reduction and oxidation reactions of water to produce molecular hydrogen and oxygen, respectively. Our research efforts have focused on promising new mixed-metal oxide systems (i.e., M = Cu(I) or Sn(II) with M’ = Nb(V), Ta(V), or Ti(IV)) that exhibit bandgap sizes spanning a wide range of visible-light energies, e.g. for CuNbO3, Sn2TiO4, Cu5Ta11O30, as well as for related solid solutions. These mixed-metal oxides can be prepared as p-type or n-type polycrystalline films. Electrochemical impedance spectroscopy shows that their conduction-band energies are located at suitable energies for driving fuel-producing reduction reactions at their surfaces, while their bandgap sizes range from ~2.8 eV to ~1.5 eV as a function of chemical composition and structure. For example, the n-type Sn2TiO4 phase was synthesized using flux methods and found to have one of the smallest visible-light bandgap sizes known that also maintains suitable conduction and valence band energies for driving photocatalytic water-splitting reactions. Further, as a suspended powder it is active for both oxygen and hydrogen production in aqueous solutions. Electronic structure calculations have also been used to probe the nature and type of the bandgap transitions. For the Cu(I)-niobates and Cu(I)-tantalates, the relationship of their reactivity to surface nanostructuring of the polycrystalline films has been determined and found to be responsible for the significant enhancements of their cathodic photocurrents under irradiation. Photocatalytic activities for hydrogen and oxygen production have been investigated in the form of suspended powders in solution, as well as in the form of p-type and n-type photoelectrode films. These results reveal new routes to tuning the band energies and bandgap sizes of mixed-metal oxides for the efficient use of sunlight for fuel producing redox reactions.
(Invited) Anodic TiO2 Nanotube Layers: Efficient Photocatalyst
Authors: Sopha Hanna , Krbal Milos , Ng Siowwoon , Motola Martin , Dvorak Filip , Zazpe Raul , Prikryl Jan , Macak Jan M.
Published: February 2020

The self-organized TiO2 nanotube layers have attracted considerable scientific and technological interest over the past 13 years motivated by their possible range of applications including photocatalysis, solar cells, hydrogen generation and biomedical uses [1,2]. The synthesis of these 1D TiO2 nanotube layers is carried out by a conventional electrochemical anodization of valve Ti metal sheet.

Among other TiO2 nanomaterials, these nanotube layers stand out due to their directionality, tunability of dimensions, ability to absorb significant amount of incident light and the possibility to utilize nanotube interiors and exteriors for decoration-coating of secondary materials.

One of the most significant applications of TiO2 nanomaterials is photocatalysis, which is very effective to decompose various pollutants (e.g. dyes) and kill bacteria [3,4].

The presentation will focus on the utilization of the nanotube layer for photocatalytic removal of various species in the liquid phase [5, 6] as well as gas phase [7]. We will also show that various secondary materials have a positive influence on photo-electrochemical properties of nanotube layers [8, 9]. Experimental details and some recent photocatalytic results will be presented and discussed.

References:

[1] J. M. Macak et al., Curr.
Opin. Solid State Mater.
Sci.,
2007, 1-2, 3.

[2] K. Lee et al., Chem. Rev., 2014, 114, 9385.

[3] K. Rajeshwar et al., J. Photochem. Photobiol. C: Photochem. Rev.
2008, 9, 171.

[4] Ch. Wei et al., Environ.Sci. Technol.
1994, 28, 934.

[5] J.M. Macak et al., Small, 2007, 3, 300.

[6] H. Sopha et al., Appl. Mater. Today,
2017, 9, 104.

[7] H. Sopha et al., Electrochem. Commun.,
2018, 97, 91.

[8] S. Ng et al., Adv. Mater. Interfaces
2017, 1701146.

[9] F. Dvorak et al., Appl. Mater. Today,
2019, 14, 1.
(Invited) Garment Integrated Sensors Created Using Reactive Vapor Deposition
Authors: Andrew Trisha L.
Published: February 2020

Wearable sensors are uniquely suited for personalized health monitoring and activity tracking. In particular, fiber- and fabric-based sensors that can be seamlessly integrated into everyday clothing have the power to create smart garments that can monitor health statistics and alert a wearer to impending medical problems or chemical/biological threats. However, natural fibers and fabrics--which would be the preferred platform for such garment-integrated sensors--are demanding substrates, and printing electronic materials and electrochemically-active sensors onto natural fibers and fabrics is nontrivial. Solution-processed active materials either soak into natural fibers or nonhomogeneously wet their surfaces, thus creating buried/inaccessible active sites or broken conduction pathways, respectively, that prevent isolation of functioning sensors. Further, the rough and disordered structures of fibers and fabrics also attenuate the baseline bulk conductivities of any electronic material, creating troublesome series resistances that are otherwise absent in conventional, glass- or plastic-backed devices.

Our lab uses reactive vapor coating to form conjugated polymer films directly on the surface of any premade garment, prewoven fabric or fiber/yarn, without the need for specialized processing conditions, surface pretreatments, detergents or fixing agents. This feature allows for electronic coatings to be applied at the end of existing, high-throughput textile and garment manufacturing routines, irrespective of dye content or surface finish of the final textile. Further, reactive vapor coating produces conductive materials without any insulating moieties and yields uniform and conformal films on fiber/fabric surfaces that are notably wash- and wear-stable and withstand mechanically-demanding textile manufacturing routines. These unique features mean that rugged and practical textile electronic devices can be created using sewing, weaving or knitting procedures without compromising or otherwise affecting the surface electronic coating.

In this talk, we will highlight selected electronic garments and garment-integrated sensors created by melding reactive vapor deposition with traditional textile manipulation processes, including: (1) smart joint braces for movement/activity sensing; (2) fabric electrodes for bioimpedance spectroscopy; (3) fiber-based radiation monitors; and (4) garment-integrated chemiresistive sensors for detecting selected biomarkers in sweat.
(Invited) Stochastic Sensors As Screening Tools for Fast and Early Detection of Illnesses
Authors: Stefan-van Staden Raluca-Ioana
Published: February 2020

Fast and early detection of illnesses such cancer, hepatitis and diabetes is extremely important for the life of the patient. Unfortunately, at the moment the standard methods cannot detect very small amounts of the biomarkers needed for early detection of such illnesses.

We proposed a screening method based on stochastic sensors able to perform both qualitative and quantitative determination of panels of biomarkers used in early detection of illnesses such as cancer, diabetes, and hepatitis.

Results obtained for the screening of whole blood, saliva, and urine samples from confirmed will be shown.