bluuebunny/crossref_metadata_2025 huggingface dataset:
Microstructure and Transport Analyses in Polymer Electrolyte Membrane Fuel Cells: Comparing Modeling Approaches
Authors: Randall Corey R. , DeCaluwe Steven C.
Published: February 2020

Despite the recent entrance of proton exchange membrane fuel cells (PEMFC) into the automotive industry, performance under low platinum loading is still hampered by prohibitive and poorly understood transport losses inside the heterogeneous catalyst layer (CL). Predictive models do not yet sufficiently capture the transport of oxygen, water, and protons in the CL ionomer phase, due to the complexity of the CL microstructure. These transport rates are highly dependent on the substrate, film thickness, and relative humidity. Confinement effects limit water uptake and transport rates below roughly 100 nm thickness, and substrate effects can induce ionomer structures (i.e. lamellae) that further impact transport rates. Implementing these complexities into computational models allows for the microstructural and transport effects on PEMFC performance to be studied and better understood, especially in devices with low platinum loading.

Research presented here examines two pseudo-2d, Newman-type model approaches for examining microstructure and transport in PEMFC functional layers: particle-shell and flooded-agglomerate. Figures 1 and 2 show the differences in model domains for these two approaches, respectively. The particle-shell approach approximates a physically realistic structure by simulating a carbon particle at the center of a thin shell of Nafion. This thin shell is discretized to resolve the complex transport that takes place within it. At each vertical discretization, a single Nafion-wrapped carbon particle is taken to be representative of others at that same functional layer depth. The flooded-agglomerate model also simulates a representative spherical domain for each vertical discretization; however, the domain is made up of a cluster of Nafion-wrapped carbon particles enclosed in an additional layer of electrolyte.

The models predict cell polarization to examine the effect of CL microstructure as a function of RH- and thickness-dependent transport properties. Figure 3 shows an example overpotential curve from the flooded-agglomerate model in which interesting behavior can be seen with respect to the Nafion thickness. It shows that the CL overpotentials decrease with decreasing ionomer thickness down to 7 nm. Below 7 nm thickness, decreased proton conductivity limits transport, leading to increasing overpotentials at higher currents. The trends indicate that the balance between proton and oxygen transport rates in the CL Nafion can lead to possible trade-offs in optimizing CL design. These and other results will be presented and discussed, to demonstrate the coupled impacts of Nafion thickness and transport on PEMFC performance, and the impact of modeling approach on CL microstructure design.

Keywords
– Nafion, Transport, PEM, Fuel Cell, Modeling, Electrochemistry, Flooded Agglomerate

Figure 1
Influence of Ink Composition and Operation Parameters on the Performance of Fe-N-C
Authors: Gallenkamp Charlotte , Kübler Markus , Kramm Ulrike Ingrid
Published: February 2020

The application of proton exchange fuel cells (PEFCs) in the automotive sector is rising to be an alternative to petroleum fuel based transportation. Nevertheless, the obstacle of cost reduction of the PEFC remains, which is due to highly expensive Pt catalysts on the cathode side for oxygen reduction reaction (ORR).[1] A possible way to substitute Pt for ORR is the use of Fe-N-C-catalysts which have been shown to be a promising option.[2]

For Fe-N-C-catalysts the required catalyst loading needs to be significantly higher than for Pt-based catalysts in order to achieve sufficient current densities. This leads to a change in catalyst layer thickness of roughly one order of magnitude where transport phenomena of gases and liquids become more important.[3] Based on this, the gap between Pt/C and Fe-N-C at high current densities is significantly higher compared to the kinetic controlled region. Therefore, further optimization is needed in order to enhance activity also under high current flow. In addition to this, it need to be understood to what extent problems in the transport properties affect the durability behavior of Fe-N-C catalysts in fuel cells.

The ionomer distribution and loading of the catalyst layer has found to be crucial for proton transport towards the active sites, but also influences the hydrophilicity of the catalysts pores which enhances gas transport resistance. [1] In addition, it has been shown that the preparation of the membrane electrode assembly (MEA) for the fuel cell plays a key role. [3] The widely used hot-pressing technique might influence the catalyst layer pore size which is also an important parameter for species transport.

In this work, different catalyst to ionomer ratios are evaluated in fuel cell tests for Fe-N-C catalysts. Furthermore, the preparation by hot-pressing is investigated in respect to the application of different compression pressures. The results are brought in relation to structural investigations of the MEAs and serve for the validation of a theoretical model.

[1] S. Komini Babu, et al. ACS Appl. Mater. Infertaces 2016, 8, 32764-32777 (2016)

[2] U.I. Kramm, et al. J. Am. Chem. Soc., 138 (2), 635–640 (2016)

[3] X. Yin, et al. ECS Transactions, 77 (11) 1273-1281 (2017)

[4] S. Komini Babu, et al. Journal of The Electrochemical Society, 164 (9), F1037-F1049 (2017)
Fabrication of Nanofibrous La1-XSrxCoO3/GDC Composite Cathode Using a Combination of Chemically Assisted Electrodeposition and Infiltration Techniques for Solid Oxide Fuel Cells
Authors: Lee Seung-Bok , Rehman Saeed ur , Song Rak-Hyun , Lim Tak-Hyoung , Hong Jong-Eun
Published: February 2020

We developed a new method for the fabrication of La1-xSrxCoO3-GDC composite cathodes in a nanofibrous morphology combining chemically assisted electrodeposition and infiltration techniques for solid oxide fuel cells. Fabrication method of nanofibrous La1-xSrxCoO3-GDC composite cathode for solid oxide fuel cells consists of chemically assisted electrodeposition of La0.6CoO3 into a porous GDC scaffold followed by an infiltration of Sr to produce a La1-xSrxCoO3 phase after a heat treatment at 900 °C. The fabrication method for La1-xSrxCoO3-GDC composite cathode involves following steps: fabrication of a highly porous GDC scaffold on a dense ScCeSZ electrolyte of an anode supported button cell by screen printing a GDC ink containing 30 wt % PMMA pore former and then sintering at 1300 °C; infiltration of 0.5 M cobalt nitrate solution into porous GDC scaffold to act as seed for CNT growth by catalytic chemical vapor deposition of carbon 750 °C using ethylene as carbon source; deposition of La0.6CoO3 by chemically assisted electrodeposition of La and Co from an aqueous electrolyte containing La(NO3)3-6H2O and Co(NO3)2-6H2O; heat treatment of the electrodeposited GDC scaffold is in air at 750 °C for 5 h to remove the CNT; infiltration of strontium and heat treatment at 900 °C to form the La1-xSrxCoO3 phase. A detailed schematic of the fabrication of nanofibrous La1-xSrxCoO3-GDC composite cathode is shown in figure 1. The new fabrication method for nanofibrous La1-xSrxCoO3-GDC composite cathode uses a low fabrication temperature (900 °C) as compared to the conventional sintering which may avoids the formation of secondary phases with ScCeSZ electrolyte. The new fabrication method for nanofibrous La1-xSrxCoO3-GDC composite cathode also provides excellent control over La1-xSrxCoO3 loading and a desired loading can be achieved in a single electrodeposition step. Nanofibrous morphology of new cathode can provide large surface area and can also assist in transport of oxidant through nanoporous structure. The complete anode supported button cells produced by the new fabrication technique have shown a high electrochemical performance (613 mW cm-2 at 750 °C) while using humidified hydrogen as fuel
Modulating Proton and Electron Transfer Dynamics in Molecular Electrocatalysis Using Membrane-Covered Self-Assembled Monolayers
Authors: Mennel Jason , Gautam Rajendra , Supakul Skye , Barile Christopher J.
Published: February 2020

Many reactions central to the development of renewable energy devices such as the O2 reduction reaction, the O2 evolution reaction, and the CO2 reduction reaction require the transfer of multiple electrons and protons. These reactions proceed by a variety of mechanisms depending upon the relative rates of these transfer events. We are developing electrode frameworks that enable control over proton and electron transfer kinetics to molecular catalysts such that the selectivity of catalysts can be improved. These electrodes contain a transition metal catalyst such as a Cu-triazole or an Fe-porphyrin attached via a self-assembled monolayer (SAM), which is then covered by a proton-permeable membrane. Initial studies have utilized a lipid monolayer modified with aliphatic proton carriers as the proton-permeable membrane. The kinetics of proton transfer to the catalyst are controlled by changing the quantity and identity of proton carriers in the membrane. By altering the identity of the SAM, which can be facilely done using a modular azide-alkyne click chemistry approach, the kinetics of electron transfer to the catalyst can also be controlled.

One grand challenge in designing catalysts for both the O2 and CO2 reduction reactions is selectivity. We show that the selectivity of a Cu-based O2 reduction catalyst can be improved by controlling proton transfer rates such that the catalyst produces solely water. In contrast, the same Cu catalyst produces ~10% H2O2 side product when proton transfer is not regulated. We also discuss how modulating proton and electron transfer kinetics affects the selectivity of molecular CO2 reduction catalysts and the performance of Ni-based O2 evolution catalysts.
(Invited) The Legacy of Shimshon Gottesfeld: Early Work on Conducting Polymers at Los Alamos
Authors: Redondo Tony
Published: February 2020

Although Shimshon Gottesfeld was primarily hired at Los Alamos to conduct research and development in electrochemical fuel cells he had the vision to start an experimental project on electrochemically grown conducting polymers. This was a successful research program that produced new ideas in a field that was later on recognized with the 2000 Nobel Prize in Chemistry to Alan Heeger, Alan MacDiarmid and Hideki Shirakawa. I will describe some of the work that was done under Shimshon’s direction in the development of these interesting materials.
(Invited) Hydrogen and Fuel Cells Enabled through the U.S. Department of Energy
Authors: Satyapal Sunita
Published: February 2020

Today the technology around generating efficient and sustainable energy is rapidly evolving and hydrogen and fuel cells are emerging, versatile examples within a portfolio of options. Through the dedication and contributions of numerous researchers funded by the U.S. Department of Energy’s (DOE) in collaboration with the private sector, hydrogen and fuel cell technologies are now a commercial reality. This presentation will cover the history of DOE’s efforts along with examples of breakthroughs by leading contributors in electrochemistry. This is an exciting time in the fuel cell industry with over ten thousand commercial fuel cell vehicles sold or leased, hundreds of fueling stations worldwide, and more than a quarter of a million stationary fuel cells providing clean, reliable power. DOE’s Fuel Cell Technologies Office (FCTO) within the Office of Energy Efficiency and Renewable Energy (EERE) addresses key technical barriers faced by hydrogen and fuel cells through a comprehensive portfolio of early-stage research and development (R&D) with the potential to meet technical and cost targets that enable competitiveness with incumbent technologies in the market, aligned with national priorities.

The presentation will cover technology status versus targets as well as an overview of the global landscape in hydrogen and fuel cells. International government collaborations through partnerships such as the International Partnership for Hydrogen and Fuel Cells in the Economy (IPHE) are contributing to progress and can enable large-scale deployment worldwide. The talk will cover the broad context of hydrogen within the energy system – the DOE’s H2@Scale initiative which will enable innovations to generate cost-competitive hydrogen as an energy carrier, coupling renewables, as well as baseload power generation, enhancing resiliency and avoiding curtailment. Hydrogen can be stored, distributed and used as a fuel or feedstock in transportation, stationary or back-up power and multiple industrial sectors, while creating an additional revenue stream for existing baseload and variable generation assets. The presentation will also provide an overview of national and regional efforts within the United States related to hydrogen and fuel cells and potential opportunities within the region.
(Invited) Materials and MEA Design Impact on the High-Current Density Performance of PEMFCs
Authors: Orfanidi Alin , Harzer Gregor S. , Madkikar Pankaj , Schulte Nicole , Rheinländer Philipp J. , El-Sayed Hany A , Gasteiger Hubert A.
Published: February 2020

In order to achieve platinum specific power densities of <0.1 gPt/kW, which are required for the large-scale implementation of fuel cell electric vehicles (FCEVs) powered by proton exchange membrane fuel cells (PEMFCs), both the mass activity of the catalyst for the oxygen reduction reaction (ORR) and the high-current density performance of PEMFCs must be improved [1]. The latter strongly depends on the membrane electrode assembly (MEA) materials and design, for example: i) on the morphology of the catalyst support [2]; ii) on the distribution of the Pt nanoparticles on/within the primary particles of the carbon support [3,4]; iii) on the surface functionalization of the carbon support [5]; and, iv) on the ionomer distribution in the electrode, which is affected by the solvents used for catalyst ink preparation [6].

In this contribution, we will examine the influence of Pt nanoparticle distribution, carbon support surface modification, and various catalyst ink solvents on the high-current density performance of MEAs under differential flow conditions. This will be accompanied by fuel cell diagnostics (oxygen and proton transport resistance measurements in the cathode electrode) and by ex-situ characterization methods.

References

[1] A. Kongkanand, M. F. Mathias; J. Phys. Chem. Lett. 7 (2016) 1127.

[2] V. Yarlagadda, M. K. Carpenter, T. E. Moylan, R. S. Kukreja, R. Koestner, W. Gu, L. Thompson, A. Kongkanand; ACS Energy Lett. 3 (2018) 618.

[3] Y.-C. Park, H. Tokiwa, K. Kakinuma, M. Watanabe, M. Uchida; J. Power Sources 315 (2016) 179.

[4] G. S. Harzer, A. Orfanidi, H. El-Sayed, P. Madkikar, H. A. Gasteiger; J. Electrochem. Soc. 165 (2018) F770.

[5] A. Orfanidi, P. Madkikar, H. A. El-Sayed, G. S. Harzer, T. Kratky, H. A. Gasteiger; J. Electrochem. Soc. 164 (2017) F418.

[6] A. Orfanidi, P. J. Rheinländer, N. Schulte, H. A. Gasteiger; J. Electrochem. Soc. 165 (2018) F1254.
(Invited) Polymer Hydrogel-Derived Carbon Supports for Highly Stable Pt/C Cathode Catalysts in PEM Fuel Cells
Authors: Qiao Zhi , Li Dongguo , Spendelow Jacob S , Wu Gang
Published: February 2020

Conventional carbon supports used in current Pt/C fuel cell catalysts are not electrochemically stable at high potentials (up to 1.5 V) with weak interaction with Pt nanoparticles, therefore leading to poor catalyst durability in proton exchange membrane fuel cells (PEMFCs). Increasing the degree of graphitization improves corrosion resistance seems an effective solution, but it often leads to low surface area and insufficient porosity, and poor Pt nanoparticle dispersion on the support. Here, we represent a new type of highly graphitized and porous carbon for Pt catalysts, showing significantly enhanced stability and high oxygen reduction reaction (ORR) performance in acidic media for PEMFCs. The approach uses an inexpensive polymer hydrogel precursor in combination with transition metals such as Fe, Co, Ni, Cu, or/and Mn, which followed by multiple annealing treatments. The 3D hydrogel provides high porosity at multiple scales while transition metals catalyzes the graphitization process. The resulting porous morphology helps to improve the dispersion and utilization of Pt nanoparticles. Among studied metals, Mn plays a critical role in improving the corrosion resistance by increasing the degree of graphitization. Compared to commercial Pt/C catalysts based on XC-72 carbon black support, the hydrogel based Pt/C catalyst exhibits remarkably enhanced stability and decreased carbon corrosion rates in accelerated stress tests (ASTs) in both aqueous electrolyte and membrane electrode assemblies (MEAs) via potential or voltage cycling from 1.0 to 1.5 V. The new Pt/C catalyst show excellent dispersion of Pt nanoparticles before and after durability testing, which may be attributed to strengthened interactions between carbon supports and Pt nanoparticles as well as the significantly mitigated corrosion rates of carbon. The highly stable new carbon supports provide a very promising solution to address the durability issue of PEMFCs partially caused by current cathode Pt/C catalysts.
(Invited) Polymer Electrolyte Fuel Cell Catalysis - Older Goodies and New Concepts
Authors: Schmidt Thomas J.
Published: February 2020

Polymer Electrolyte Fuel Cell (PEFC) Research has been performed over the more than 30 years now with the results that both stationary and automotive systems are commercially available. Two prominent examples are the Enefram stationary systems in Japan with more than 250 000 installed systems, and several commercial and pre-commercial fuel cell cars from e.g. Toyota, Hyundai and Honda.

Catalysis in PEFC has been mainly dominated by research on the oxygen reduction reaction over the last 20 years; however specifically for the stationary system, anode catalysis using impure CO containing hydrogen streams from reforming reactions are still quite important but less prominent nowadays.

In this contribution, a subjective selection of important new PEFC catalysis concepts as well as still important elder goodies from the last 20 years will be given and an attempt is made to connect this summary to Shimshon Gottesfeld's work.
(Invited) Insights from the inside: Imaging Water in the Porous Structures of Fuel Cells
Authors: Büchi Felix N. , Eller Jens , Xu Hong , Boillat Pierre
Published: February 2020

Imaging is a powerful tool to understand and optimize the water management in acidic and alkaline fuel cells. A topic that has also been a subject of collaboration between the authors and Shimshon Gottesfeld.

Neutron radiography is a truly non-destructive method with the advantage of large fields of view, easy penetration of structural materials and negligible radiation damage. This allows for exposure over long periods of operation and therefore dedicated parameter studies. In alkaline fuel cells the water management is of high importance and a crucial point to optimize performance. Insight will be presented fon different scales, from the differential cell to the stack level using neutron radiography (Figure 1).

X-ray tomographic microscopy is a complementary imaging method when information on the pore scale in a small field of view and fast dynamics are required. Recent developments and insights from sub-second synchrotron based tomographic imaging on the dynamics of water in the gas diffusion layer will be discussed. Figure 2 shows a series of 0.1s tomographic scans after a current jump from OCV to 0.5 A/cm2, showing the dynamic development of liquid saturation in the GDL.

Figure 1
(Invited) Performance of Nanofiber Meas in a Hydrogen/Air Fuel Cell with Low Relative Humidity Feed Gases
Authors: Pintauro Peter N. , Waldrop Krysta , Slack John , Powers Devon , Wycisk Ryszard , Gumeci Cenk , Parrondo Javier , Dale Nilesh
Published: February 2020

Membrane-electrode-assemblies (MEAs) with particle/polymer nanofiber mat electrodes produce high power and exhibit excellent durability at low platinum loadings in a H2/air proton exchange membrane fuel cell [1-4]. The morphology of an electrospun mat electrode is well-suited for fuel cell applications due to: (1) a high interfacial electrode area, with both inter- and intra-fiber porosity which improves oxygen access to catalytic sites while providing pathways for proton transport, electron conduction, and the removal of product water and (2) a well-dispersed mixture of catalyst and binder along the fiber length and cross-section with a conformal coating of binder on catalyst particles (a consequence of shear mixing, rapid solvent evaporation, and fiber elongation during electrospinning). The focus of this talk is on the design and fabrication of nanofiber-based MEAs (anode, cathode, and membrane) that produce high power at both high and low relative humidity (RH) feed gas conditions. Procedures for electrospinning fiber mat electrodes with low EW PFSA binders will be described and the effect of electrode binder type on power output will be presented. As an example, one nanofiber-based MEA had a 20 μm thick composite membrane (725 EW PFSA with reinforcing PVDF fibers), a 725 EW PFSA binder for the anode and cathode, a Pt/C anode at 0.10 mg/cm2, and a PtCo/C cathode at 0.10 mg/cm2. The measured maximum power density for this MEA in a H2/air fuel cell at 200 kPa pressure, 80oC, and 125/500 sccm H2/air flow rates was 940 mW/cm2 at 100% RH, 924 mW/cm2 at 30% RH, and 804 mW/cm2 at 20% RH.

Acknowledgments

This work was funded by the Fuel Cell Consortium for Performance and Durability, DOE-EERE FC-PAD Project DE-EE0007653. The authors thank Mike Yandrasits at 3M Co. for providing the 725 EW PFSA ionomer used in the experiments.

References

Zhang and P. N. Pintauro, ChemSusChem, 4, 1753-1757 (2011).

Brodt, R. Wycisk, and P. N. Pintauro, J. Electrochem. Soc., 160, F744-F749 (2013).

Brodt, T. Han, N. Dale, E. Niangar, R. Wycisk, and P. Pintauro, J. Electrochem. Soc., 162, F84-F91 (2015).

Brodt, R. Wycisk, N. Dale, and P. Pintauro, J. Electrochem. Soc., 163, F401-F410 (2016).
(Invited) Switching from Low-Density to High-Density Polyethylene As a Base Material for Radiation-Grafted Anion-Exchange Membranes Leads to Much Higher Alkaline Membrane Fuel Cell Performances
Authors: Wang Lianqin , Varcoe John R.
Published: February 2020

This presentation will describe the development of a new type of radiation-grafted anion-exchange membrane (RG-AEM) made from high-density polyethylene (HDPE) base material, which contains benzyltrimethylammonium cationic head-group chemistry. This RG-AEM has an ion-exchange capacity (IEC) of 2.4 meq g-1, and is less than 30 μm in thickness (when fully hydrated) with an ultimate tensile strength of ca. 35 MPa (elongation to break of 280 %). It exhibits a hydroxide conductivity of 214 ± 2 mS cm-1 at 80 °C in a 100% relative humidity (RH) atmosphere, which decays to 195 mS cm-1 after 500 h exposure to these same ex situ conditions.

Despite exhibiting similar ex situ characteristics to a low-density polyethylene (LDPE) analogue RG-AEM (of similar hydrated thickness and IEC), the HDPE-RG-AEM yields significantly higher beginning-of-life H2/O2-benchmark alkaline membrane fuel cell power densities (see Figure): 2.55 W cm-2 peak power density was achieved at 80 °C with 92% RH H2/O2 gas supplies (no back pressure applied). Internal area specific resistances of < 30 mΩ cm2 were recorded.

Figure 1
Scale up of Biofilm Electrodes
Authors: Mohamed Abdelrhman , Tutar Secil , Ha Phuc Thi , Beyenal Haluk
Published: February 2020

Bioelectrochemical systems (BESs) utilize the ability of microbes to exchange electrons with solid inert electrodes to convert chemical energy to electrical energy, and have potential applications in wastewater treatment, chemical synthesis, and resource recovery. Optimization of large scale systems is required in order to implement BESs at industrial scale. Several reports documented the loss of current density in large scale biofilm electrodes. We hypothesize that the loss of current density is attributed to substrate transport limitations. The heterogeneity of local conditions on biofilm electrodes at low substrate environments are expected to decrease the current density of large electrodes. In this work, we tested the effect of substrate concentration on current density of anodes and cathodes. Anodic and cathodic biofilms are enriched on electrodes of different electrode sizes (15-460 cm2). Following enrichment, the anodes are tested in synthetic wastewater medium with varying electron donor concentrations, while the cathodes are tested in synthetic wastewater with varying oxygen partial pressures. Our results demonstrate the relationship between substrate concentration and the scaleup of anodic and cathodic biofilms.
Immunosensor for Early Diabetes Markers
Authors: Krishnan Sadagopan , Premaratne Gayan , Niroula Jinesh
Published: February 2020

To increase detection sensitivity, sensor surface modifications with various nanomaterials or selective isolation of analytes from complex clinical sample matrices by nanomaterials for amplified detection have been developed. As a novel class of two-dimensional nanocarbon material, graphene has recently attracted researchers in biomedical sciences for the development of electrochemical and optical devices. The high surface area to volume ratio, electrical conductivity, and aqueous dispersibility suitable for screen-printed electrode surfaces, thin structure and apparent biocompatibility of carboxylated graphene makes it a unique carbon nanomaterial for biosensing applications. Although, glucose and insulin biosensors are useful for diabetes management, non-glucose biomarkers are critical for potentially enabling early diabetes detection in children and adults. We present herein a quantitative comparison between carboxylated graphene and mercapto-monolayer surface for measuring serum glutamic acid decarboxylase-65 autoantibody, a biomarker of type 1 diabetes, by an electrochemical immunoassay design combined with surface plasmon binding kinetics. Knowledge gained from the combined sensing and binding assessment is useful for reliable large-scale production of clinical immunosensors for biomarker based diagnostic assays.
Charge Fluence As a Predictor for the Atmospheric Plasma Inactivation of E. coli Cultures
Authors: Otten Alex , Jaroszeski Mark , Gilbert Richard , Vangapattu Ravi , Hoff Andrew
Published: February 2020

Bacterial resistance to chemical agents has caused increased interest in more direct forms of bacterial treatment and control. A charged charge-based approach to predict bacterial activation in-vitro using atmospheric helium plasma on Escherichia Coli (E. Coli) as a model is presented. The electric charge dependence and the impact of polarity for this protocol was established. The results indicate a 30% increased log reduction in positive versus negative plasma, as well as a relationship between treatment time at given charge fluence rates and the diameter of the targeted treatment area.
Electrochemical Reduction of Chlorpyrifos at Silver Cathodes in Dimethylformamide
Authors: McKenzie Eric C.R. , Peters Dennis G
Published: February 2020

Once a widely popular insecticide, Chlorpyrifos (O,O-diethyl-O-3,5,6-trichloropyridin-2-yl phosphorothioate) has been the center of controversy in recent years. Rauh and co-workers found the compound to be neurotoxic; severe developmental defects were found in children up to three years of age.1 Regardless of these findings, a political divide over continued use of the compound has led to inaction over its regulation. In 2015, the EPA responded to a petition filed in 2007 by proposing a complete ban on the compound for use on food crops. However, the EPA reversed course in 2017, denying the proposed ban and deciding to study further the pesticide’s possible toxicity until 2022.2 Given our laboratory’s long-standing history of environmental remediation, we decided to be proactive and to investigate the electrochemistry of Chlorpyrifos, with the hope of degrading the compound into some compound less harmful to the environment. Cyclic voltammetry at silver cathodes in dimethylformamide containing 0.10 M tetramethylammonium tetrafluoroborate shows four reduction events at –1.05 V, –1.25 V, –1.43 V, and –1.75 V, all versus a cadmium-mercury amalgam (Cd/Hg) reference electrode. As a means of comparison, cyclic voltammetric behavior of TCPy (3,5,6-trichloro-2-pyridinol), a metabolite of Chlorpyrifos, was also investigated. A single cathodic peak was observed at –1.77 V vs. Cd/Hg. Surprisingly, controlled-potential (bulk) electrolyses conducted at silver cathodes showed unreduced Chlorpyrifos as the major product with less than one electron transferred per molecule of substrate (n < 1), regardless of the potential applied. However, bulk electrolyses performed in the presence of a suitable proton donor result in a substantial increase in the n value as well as a wide range of products including, but not limited to, dechlorinated, monochlorinated, and unreduced Chlorpyrifos.

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Electrochemical Investigation of Halogenated Hydroxybenzonitriles at Silver Cathodes in Dimethylformamide
Authors: Nugen Tyler J , McKenzie Eric C.R. , Peters Dennis G
Published: February 2020

Chloroxynil (3,5-dichloro-4-hydroxybenzonitrile), Bromoxynil (3,5-dibromo-4-hydroxybenzonitrile), and Ioxynil (3,5-diiodo-4-hydroxybenzonitrile) belong to a group of halogenated phenols commonly used as herbicides to control broad-leaved weeds. Functioning as disruptors of oxidative phosphorylation, these compounds have grown in popularity in recent years as alternatives to atrazine, particularly bromoxynil (1800–2200 tons applied per year).1,2 In the environment, all three herbicides can undergo hydrolysis as well as enzymatic degradation to the corresponding benzamide (3,5-dihalo-4-hydroxybenzamide) and subsequently to the benzoic acid (3,5-dihalo-4-hydroxybenzoic acid), both of which have the possibility of persisting in soil.3,4 As a result, an efficient means of degrading the parent compounds is necessary. Sokolova and co-workers5 have investigated the electrochemical reduction of these hydroxybenzonitriles; however, their studies employed mercury working electrodes, which are known to be extremely toxic and hazardous.

Silver has long been praised as an advantageous cathode for remediation of environmental pollutants due to its affinity for halides.6 In the present study, we propose to use silver cathodes to investigate the electrochemical behavior of chloroxynil, bromoxynil, and ioxynil in dimethylformamide (DMF). Cyclic voltammograms for each compound in DMF containing 0.05 M tetramethylammonium tetrafluoroborate (TMABF4) show widely different behavior between the three herbicides: chloroxynil exhibits one cathodic peak (–0.74 V), whereas bromoxynil displays four cathodic peaks (–0.40 V, –0.65 V, –1.23 V, and –1.51 V) as does ioxynil (–0.20 V, –0.30 V, –0.58 V, and –1.66 V). All potentials are versus a cadmium-mercury amalgam reference electrode. Bulk electrolyses performed with 0.05 M TMABF4–DMF result in a wide product distribution in addition to different n values for each substrate.

Holtze, M.; Sorensen, S. R.; Sorensen, J.; Aamand, J. Environ. Pollut.
2008,
154, 155–168.

Lovecka, P.; Thimova, M.; Grznarova, P.; Lipov, J.; Knejzlik, Z.; Stiborova, H.; Nindhia, T. G. T.; Demnerova, K.; Ruml, T. BioMed Res. Int.
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2007,
63, 141–149.

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2016,
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Electrochemical Behaviors of Some Metallic Materials during Biofilm Formations in LB Liquid Culture with Escherichia coli
Authors: Kanematsu Hideyuki , Tazaki Akito , Itoh Reo , Yamada Hirohisa , Barry Dana M. , Hirai Nobumitsu , Ogawa Akiko , Kogo Takeshi , Kuroda Daisuke , Tsunashima Katsuhiko , Katakura Katsumi
Published: February 2020

Biofilms formed on materials by bacterial activities affect many industrial problems as well as those in daily lives. Therefore, it is very important to monitor biofilm formation/growth processes properly. Biofilms are generally composed of water (more than 80%), exopolymeric substances and bacteria themselves. They exist on material surfaces inhomogeneously. From the electrochemical viewpoint, the interfacial structure would be equivalent to that of metallic electrode/organic solution, when the substrate materials would be metallic ones. In recent years, we have realized that the redox reaction in biofilms would play an important role for many matters relating to biofilms and the effects on industrial/medical/daily problems. And the electrochemical approach to the inside of biofilm and its analysis by micro electrodes have been carried out. However, the analysis from the metallic sides have not been investigated so much. In this study, we focused on the side of metallic electrodes and carried out the electrochemical investigation for some metallic materials, when biofilms by Escherichia coli formed and grew in liquid LB culture. And we analyzed the results and discussed about the application possibility to the evaluation of biofilms and materials deterioration.
Mechanistic Insight into Photoelectrochemical Conversion of Alkyl Monohalides to Aldehydes
Authors: Lee Ryan , Hosseini Seyyedamirhossein , Peters Dennis G
Published: February 2020

Aldehydes are important starting materials for a variety of chemical processes such as the synthesis of food preservatives. For example, certain aldehydes may be used for improving sensory quality and shelf-life of milk.1 Synthesis of aldehydes from alkyl monohalides involves a multi-stage reaction which various reagents are needed for each step of the conversion.2 Previous works from our laboratory showed that simultaneous introduction of UV radiation and oxygen during electrolysis of an alkyl monohalide with electrogenerated nickel(I) salen affords the corresponding aldehyde or ketone with relatively high yield (Figure 1). 3,4

The purpose of the present work is to elucidate the mechanism for the above-mentioned conversion. For this purpose, a solution of 1-bromooctane (5 mM) and nickel(II) salen (5 mM) was electrolyzed at –1.0 V in DMF–water containing TMABF4 (0.10 M). At the end of the electrolysis, modified nickel(II) salen was separated from the electrolysis mixture with application of normal phase flash chromatography. Modified nickel(II) salen was dissolved in DMF–water containing TMABF4 (0.10 M) and exposed to UV radiation (440 nm); the product of the photoreaction was identified as octanal. In respect, we believe the reaction passes through a series of the intermediates are proposed in Figure 2. This reaction features a single-step and efficient method for transforming alkyl monohalides into the desired aldehydes.

References

Kelly, P. Woonton, B. W. Smithers, G. W. Woodhead. Woodhead Publishing Ltd. 2009. 170.

Hendrickson, J. B., Sternbach, D. D. J. Org. Chem. 1975, 40, 3450.

Vanalabhpatana, P.; Peters, D. G. Tetrahedron Lett.
2003, 44, 3245.

Vanalabhpatana, P.; Peters, D. G. J. Electroanal. Chem.
2006, 593, 34.

Figure 1
Construction of Dawson-Type Molybdovanadophosphoric Acid-Based Electrochemical Sensor and Its Application in Sensing Folic Acid
Authors: Xu Hengbin , Zhang Milin
Published: February 2020

In current work, vanidium-substituted polyoxometalate clusters H8P2Mo16V2O62 and carbon nanotubes (CNTs)@Au NPs were incorporated into a multilayer composite film via combining layer-by-layer self-assembly. The result showed that the incorporation of the three kinds of active components would improve the electrocatalytic activity to the oxidation of FA and electron transfer rate greatly. In 0.2 M phosphate buffer solution (pH = 7.35), the composite film (PEI/P2Mo16V2/PEI/CNTs@Au)2 had a linear range of FA from 4.99 × 10-7 M to 1.29 × 10-5 M and 1.29 × 10-5 M to 1.21 × 10-3 M, and a limit of detection to be 3.96 × 10-8 M (S/N = 3). In addition, the composite film has an excellent anti-interference property to potential co-exist interfering species like inorganic ions and biomolecules (including NaCl, K2CO3, NH4Cl, NaNO2, Na2SO4, fructose, L-glutamate and glucose). The developed sensor has a good working and long-term stability as well. Besides, the sensor was applied in detecting FA in vitamin b tablet, the recoveries were all in the allowable error range. (This paper is funded by the International Exchange Program of Harbin Engineering University for Innovation-oriented Talents Cultivation.)

Figure 1
Inkjet Printing on PET Substrate: Printing Properties Investigation and Performance Analysis
Authors: Riheen Manjurul Ahsan , Saha Tonmoy Kumar , Sekhar Praveen K.
Published: February 2020

The research aims to propose guidelines for inkjet printing of highly conductive and mechanically stable printed patterns on the Polyethylene terephthalate (PET) substrate. The key printing parameters: drop spacing, the number of layers, sintering temperatures as a function of time were determined through experimental analysis. The test specimens were printed utilizing silver nanoparticle ink and Dimatix 2831 inkjet printer. The printed samples were characterized using conductivity, surface roughness, bending, and adhesion measurements. The Analysis of Variance (ANOVA) analysis showed the number of layers and sintering temperatures were significant factors (p < 0.05) to ensure the desired pattern conductivity. The proposed optimum printing parameters for this substrate are 20 µm drop spacing, three layers of printing, and 120˚C sintering temperature for 30 minutes. The measured optimum resistivity was found 5.25 µΩ-cm. The repetitive bending and adhesion test using varied cylindrical patterns and ASTM tape test yielded excellent mechanical stability under harsh condition. Based on these attractive features, this research can provide useful information to the wearable and reconfigurable electronic industries to produce Internet of Things (IoT) products on PET substrates.
Suppression Effects of Oxygen Deficient on Ultrathin Indium Oxide Electrochemical Transistors-Based Biosensors
Authors: Park Joon Hui , Choi Yun Young , Rim You Seung
Published: February 2020

Recently, the necessity of real-time and non-invasive detection-based biosensors has been increasing by using electrical device platforms. Metal oxide semiconductors-based electrochemical transistors (MOECTs) have many advantages, such as easy processing, good chemical resistance, high sensitivity, and universal surface complexation for biomolecule detection for continuous healthcare monitoring. A specific pH in each organ is required to maintain health and the health problems or diseases can be predicted by pH changes. Thus, high sensitivity of biosensors is essential to apply real-time sensor platforms. Here, we proposed solution-processed ultrathin indium oxide-based ECTs, which had an ultrathin metal oxide semiconductor of ~4 nm thick. This platform shows a high sensitivity for the pH variations but intrinsic surface defects (i.e., oxygen deficient) influences the sensitivity. In order to reduce these effect, we studied the surface defect passivation effect of Ga doped In2O3 (GIO)-based ECTs by using solution process. The change of sensitivity and reliability of GIO-based ECTs were confirmed clearly at the range of 2-12 pH for the different gallium contents (5-40%). As an increase of gallium contents, the oxygen deficient of GIO films was gradually reduced and the sensitivity of the device was improved. However, excessive Ga added In2O3-based ECTs showed poor sensitivity for the pH variations. As a result, we found that optimal gallium doping concentration is an important factor to construct high sensitivity and reliability of MOECTs under diverse physiological environment.
Electrochemsense: Electrochemical Real-Time Pesticide Sensing System
Authors: Dhamu Vikram Narayanan , Sankhala Devang , Jagannath Badrinath , Prasad Shalini
Published: February 2020

Contamination of food and water samples in the United States has been a drastic problem to address and one of the reasons for that is the high overhead costs and logistics associated with its screening in produce samples, with another being the inability to report data in real-time-accurately. Based on reports back in 2007, Glyphosate was the most widely used pesticide in the US agricultural sector. More recently, the use of Glyphosate-based herbicides (GBH) has been reported to have increased more than 100-fold with the emergence of glyphosate resistant weeds. While there is high interest and a requirement to detect this compound, due to it being possibly carcinogenic to humans and causing chromosomal damage to cells, the challenge however lies in designing a low volume sensor that can screen for glyphosate directly from produce run-off and report it as useful concentration information. To highlight one such major challenge, the resolution of a portable sensing system is weaker compared to laboratory instruments, making it difficult to build a system that characterize electrical signals in the range as a low as Nano-amperes (nA) into corresponding contaminant concentration. In this study we work on a portable bio-sensing device that can identify and report trace levels of pesticide through an optimized label-free assay protocol developed in our laboratory. We have built a sensing system that utilizes chronoamperometry to characterize concentration of chemical as a measure of current. To further explain this, when the produce run-off is added to the sensing surface specifically functionalized with antibodies to detect the presence of pesticide- the binding between the target and analyte causes the flow of electric charges between the electrodes to get modulated, and this charge modulation is quantified by studying the current characteristics obtained by chronoamp method. Using this system makes it possible to detect concentrations as low as 0.001ppb (1pg/mL), with this being the sensor’s limit of detection (LOD), and the device then reports contaminant concentration of glyphosate determining the metrics for low or high threshold based on maximum residue limit (MRL)/residue tolerance values for each produce or food item, hence making it possible to screen for pesticide contamination in real-time and a portable setting without further need for laboratory and instrument assistance for both the consumers and industry personnel to keep a check on food quality.

Figure 1
Disposable and Inexpensive Electrochemical Biosensor to Detect Ciprofloxacin
Authors: Trevino Nicholas Paul , Ganta Deepak , Montes William , Guzman Carlos
Published: February 2020

Ciprofloxacin hydrochloride, USP, a fluoroquinolone, is the monohydrochloride monohydrate salt of 1-cyclopropyl-6-fluoro-1, 4-dihydro-4-oxo-7-(1-piperazinyl)-3-quinolinecarboxylic acid. Ciprofloxacin (Cipro) is an antibacterial medicine used to treat infected open wounds, by targeting bacteria infiltrating and rendering useless to multiplying using attacking its genetic makeup directly. In 2010, over 20 million prescriptions were written, making it the 35th-most commonly prescribed generic drug and the 5th-most commonly prescribed antibacterial in the U.S. There is also a huge demand for the inexpensive and compact sensor to detect the presence of ciprofloxacin in water. Its wide use motivated us to develop an electrochemical sensor to detect the presence of the ciprofloxacin in aqueous solutions.

Inexpensive and disposable screen-printed electrode was used as our electrochemical sensor. We tested different aqueous solutions with varying concentrations of Cipro, and measure the sensitivity. The sensors have three electrodes, with the working and counter electrode being composed of graphite, and the reference electrode composed of Ag/AgCl and sodium hydroxide (NaOH) is the supporting electrolyte. During the preparation of the Ciprofloxacin, NaOH is added in order to neutralize, which also acts as a supporting electrolyte. Finally, Cipro is then added to 2mL of DI water and disturbed until a solution is formed. The prepared solution is varied for the desired concentration is then drop-coated onto the sensing part in the electrochemical sensor, making sure the entirety of the sensing section is covered. The sensor is then connected to the potentiostat, and the test is performed. The redox reaction was measured using a potentiostat (Biologic). With these different concentrations, testing was conducted through the use of cyclic voltammetry (CV) and chronoamperometry (CA). From the CV curves, we were able to determine the relationship between the concentrations(nM) and the current. Our data shows that the current has a steady decrease as the concentrations increase. The slope provided from this relationship is used to provide the sensitivity of the testing method produced. The sensitivity was measured to be found to be .0029nM over a linear range of (0.1nM - 2nM).
Ultrasonic Spray Pyrolysis Deposition of NiO Thin Film for Efficient Perovskite Solar Cell
Authors: HU Chen , Yang Shihe
Published: February 2020

NiOx is one of the most promising choices for hole transporting layer in p-i-n structure perovskite solar cells for its negligible hysteresis, impressive stability and hole extraction efficiency. However, traditional sol-gel process leaves resulted NiO thin film with pin-holes and flawed contacts between NiO layer and FTO electrode below. Herein, ultrasonic spray pyrolysis technique is introduced for the preparation of continuous, pin-hole free NiOx film for the application in perovskite solar cells. The concurrently sprayed and pyrolyzed NiO film exhibits supreme contact bridging FTO substrate and light-harvesting perovskite layer. As a result, solar cells based on ultrasonic-sprayed NiO thin film demonstrates enhanced power conversion efficiency 27% higher than sol-gel prepared scenario. Electrical and morphological studies are carried out and it is found that improved conductivity, reduced pin-holes and improved perovskite growth are three main reasons reducing unfavored charge transfer processes in the operation of solar cell.