bluuebunny/crossref_metadata_2025 huggingface dataset:
Electron Transfer Reactions at Liquid-Liquid Interfaces
Authors: Girault Hubert H , Gschwend Gregoire , Peljo Pekka , Olaya Astrid
Published: February 2020

Liquid-liquid interfaces can be polarised to carry out charge transfer reactions, in particular electron transfer (ET) reactions between a hydrophilic and a lipophilic redox molecule. These reactions can be studied by classical electrochemical methods such as cyclic voltammetry.

By combining spectroscopic time resolved techniques such Surface Second Harmonic Generation with electrochemical methods, we have studied photo-initiated electron transfer reactions between adsorbed porphyrins and redox quenchers located in one of the adjacent phases. By this approach, we can measure the ET kinetics of adsorbed species located mainly at the interface. We have shown that these interfacial ET reactions involving surface species are not sensitive to the interfacial polarisation. More generally, ET reactions at polarised liquid-liquid interfaces will be discussed to place the present results in perspective.

In the second part of the talk, the concept of photo-ionic cells will be presented. Here, the photo-products of a photo-ET reactions occurring in the interfacial region are separated between the two adjacent immiscible phases, thereby resulting in energy storage. This electrochemical energy can then be recovered in a classical parallel plate flow cell. We shall discuss the pros and cons of this method of production of solar fuels.
Water Structure and Dynamics at Hematite Electrodes
Authors: McBriarty Martin Edwin , Stubbs Joanne E. , von Rudorff Guido Falk , Blumberger Jochen , Bylaska Eric J. , Eng Peter J. , Rosso Kevin M.
Published: February 2020

Electrocatalysis at a transition metal oxide (TMO) electrode in aqueous electrolyte is controlled in part by the behavior of interfacial water. Atomically precise measurements of TMO-electrolyte interfaces under electrocatalytic working conditions are therefore prerequisite for developing accurate models of interfacial reactions. We present the most detailed measurements to date of electrolyte ordering at the reactive hematite (α-Fe2O3) (1-102) (r-cut) surface at open circuit conditions and under applied cathodic bias in 5 mM Na2SO­4 solution. Interface structures are measured in situ by synchrotron X-ray crystal truncation rod (CTR) scattering using a novel electrochemical mini-cell. CTR results are interpreted in light of first-principles molecular dynamics simulations. We find that the equilibrium structure of the r-cut hematite-electrolyte interface is defined by frequent exchange of water molecules between terminal aquo ligands and solution, resulting in a steady-state partial coverage of undercoordinated surface iron sites. Under cathodic bias, the surface is excessively protonated, strengthening the near-surface hydrogen-bonding network. The steady-state coverage of terminal aquo ligands subsequently increases, armoring the hematite electrode against reductive dissolution. The ordering and separation of water layers depend on the cathodic bias magnitude. Taken together, these results reveal the fine details of the interface structure which underlie the electrical double layer models used to describe macroscopic electrochemical measurements. The methods developed through this work open a new frontier for the in situ characterization of TMO-electrolyte interfaces during electrocatalytic reactions.
FTIR Spectroelectrochemistry: Optimization of Experimental Setup
Authors: Shilov Sergey , Kessler Mathias
Published: February 2020

The combination of FT-IR spectroscopy with electrochemistry offers insight in the molecular change during electrochemical reactions in an addition to the electrochemical response of the studied media. This method can be applied for investigations of electrolytes or reactions at electrode surfaces. New accessories for the spectroelectrochemical studies will be presented. Accessories can be configured for the reflection-absorption or for the attenuated total reflectance (ATR) measurements. IR reflection-absorbance spectroscopy (IRRAS) set-up is used for the studies of the electrolyte and the electrode surface while ATR configuration is used to analyze the electrode surface without strong influence of the electrolyte. Optimization of spectroelectrochemical setup and details of communication between the potentiostat and the FTIR spectrometer will be discussed. Example of applications will include electro oxidation of metal-organic complexes, alcohols, and glycerol.
Benchtop, High-Resolution XAFS and Xes Spectrometers As Tools for Electrochemical Research
Authors: Jahrman Evan , Holden William , Seidler Gerald T. , Fister Timothy T
Published: February 2020

Advanced x-ray spectroscopies allow the direct and element-specific interrogation of local electronic structure, yet their scientific impact is necessarily constrained by access limitations. This is particularly evident for x-ray absorption fine structure (XAFS) and x-ray emission spectroscopy (XES) techniques. Here, the technical capability afforded by a synchrotron x-ray facility allows researchers to answer basic or applied research questions and push the forefront of science. These national-lab scale sources often provide the only means to perform these techniques, consequently slowing progress on critical projects, and also largely excluding routine analytical characterization.

Over the last four years, our group at the University of Washington has been developing several new families of lab-based instruments to expand the accessibility of advanced x-ray spectroscopies. [1-5] It is now possible to identify the electroactive element in a material and assess its oxidation state, spin state, and coordination chemistry – all with benchtop XAFS and XES. The feasibility of these studies is established by comparing performance of our benchtop instruments with various synchrotrons in the context of several electrochemical systems.

From the standpoint of materials inquiry, we will present a variety of measurements of lithium ion batteries, valence-to-core XES results from a series of oxides, and preliminary efforts toward solution-phase measurements will be presented. The latter will be done with an eye toward future electrolyte analyses.

William M. Holden, et al. “A Compact Dispersive Refocusing Rowland Circle X-ray Emission Spectrometer for Laboratory, Synchrotron and XFEL Applications”, Rev. Sci. Instrum 88, 073904 (2017). [DOI: 10.1063/1.4994739]

T. Seidler, et al., “A Laboratory-based Hard X-ray Monochromator for High-Resolution X-ray Emission Spectroscopy and X-ray Absorption Near Edge Structure Measurements,” Review of Scientific Instruments 85, 113906 (2014). [DOI: 10.1063/1.4901599]

T. Seidler, et al., “A Modern Laboratory XAFS Cookbook,” Journal of Physics: Conference Series 712, 012015 (2016). [ http://iopscience.iop.org/article/10.1088/1742-6596/712/1/012015]

R. Mortensen, et al., “Benchtop Nonresonant X-ray Emission Spectroscopy: Coming Soon to Laboratories and Beamlines Near You,” Journal of Physics: Conference Series 712, 012036. (2016) [http://iopscience.iop.org/article/10.1088/1742-6596/712/1/012036]

G.T. Seidler, “The Case for Analytical XAFS”, https://www.linkedin.com/pulse/case-benchtop-analytical-xafs-gerald-seidler
Understanding the Electrochemical Behavior of Di-Sodium Carboxymethyl Trithiocarbonate (Orfom® D8) Depressant on Copper Metal and Chalcopyrite Surfaces
Authors: Timbillah Simon , Young Courtney , Das Avimanyu
Published: February 2020

This study shows the behavior of di-sodium carboxymethyl trithiocarbonate (Orfom® D8) depressant, an organic depressant used in the depression of copper in the differential separation of chalcopyrite-molybdenite during flotation to produce two saleable products. Fundamental electrochemical findings on possible adsorption modes by which the Orfom® D8 depressant adsorbs onto the target mineral surface are reported. Results show the use of Cyclic Voltammetry (CV), Electrochemical Impedance Spectroscopy (EIS) and Chronoamperometry as useful techniques in the evaluation of mechanistic interaction of Orfom® D8 depressant. The study compares how Orfom® D8 depressant adsorbs onto copper and chalcopyrite surfaces. The experimental responses were fitted to an equivalent circuit using data obtained from Nyquist and Bode plots to model the system. Information on the kinetic mechanisms (oxidation and reduction) were obtained by analyzing the capacitive responses on the phase spectra. The mechanism of adsorption of the Orfom® D8 on the substrate surfaces support a controlling mechanism via diffusion or charge transfer at either high or low potential. Results corroborate UV-Vis, Zeta-Potential, FT-IR and XPS measurements reported elsewhere.
Identification of Specific Eletrical Phenomena Driven By a Water Droplet Motion on Electrolyte-Insulator-Semiconductor Structure
Authors: Kim Youn Sang
Published: February 2020

Recently, various energy transducers driven by the relative motion of solids and liquids have been demonstrated. However, in relation to the energy transducer, a proper understanding of the dynamic behavior of ions remains unclear. Moreover, the energy density is low for practical usage mainly due to structural limitations, a lack of material development stemming from the currently poor understanding of the mechanisms, and the intermittently generated electricity given the characteristics of the water motion (pulsed signals). Here, we demonstrate a method by which to generate continuous electrical energy with the flow of a water droplet through an electrolyte-insulator-semiconductor (EIS) structure. The output power and energy conversion efficiency of the transducer are 0.373 uW/g and 29.8 %, respectively, where v is the speed of the water droplet. We propose and verify a hypothesis pertaining to the ion-dynamic operation mechanism of the transducer which holds that the electron flow is induced by the adsorption and desorption of ions. Further, we describe ion specificity and bio-functionality, an important characteristic of electrical signals generated by macroscopic droplet motion, in relation to the potential profile of electric double layer, which is determined by the characteristics of microscopic ion properties.
(Invite) Non-Noble Metal Cored Pt-Skin Catalyst and Its Highly Enhanced Stability in Oxygen Reduction Reaction By Controlling the Nitriding Level for the Core
Authors: Lee Eunjik , Kim Kyung-Hee , Yim Sung-Dae , Park Seok-Hee , Park Gu-Gon
Published: February 2020

Cost reduction is a key barrier for the commercialization of fuel cells, and the adaption of Core-shell type electrocatalysts is expected to play a major role. Core-shell electrocatalysts have shown remarkable results in terms of activity as well as durability. Electrocatalysts using Pd as a core material has been representative model. It is also announced that durability as well as activity is improved through the use of alloyed or doped Pd cores. In recent years, however, there is a request for a Pt-skin type electrocatalyst which does not use expensive Noble metals. Low-cost transition metals are considered candidates for core materials, but durability is still a challenging issue.

In this study, we introduced Co as a core material and tried to improve the durability through nitriding treatment. The durability of the electrocatalyst was clearly influenced by controlling the nitriding level of Co. CoN@Pt/C was prepared by sonochemical reaction followed by nitriding treatment. Nitriding levels were controlled through pressure control (1, 40, 80 bar) during the ammonia heat treatment process. We confirmed that the active metal has a particle size of (3 - 4) nm and a Pt-skin structure, and confirmed the improved ORR activity over commercial Pt/C catalysts. Most importantly, we have achieved excellent durability when the nitriding level of Co is controlled high. In the accelerated stress test (AST), the electrocatalyst nitrided at the elevated pressure showed little change in ECSA and ORR. It’s confirmed that through the control of the nitriding level for low-cost transition metals, a highly durable Core-shell electrocatalyst can be successfully fabricated.

Figure 1
(Invited) Instability of Pt-Based Catalysts for Fuel Cell Applications
Authors: Shao-Horn Yang
Published: February 2020

I am delighted to join this symposium and celebrate not only the scientific accomplishments of R. Adzic and but also his contributions to the mentoring of generations of scientists in the electrochemistry and electrocatalysis community. Without formal training in electrochemistry, learning and making high-quality electrochemical measurements is not straightforward. R. Adzic not only has trained a large number of students and postdocs but also has opened his laboratory to other research groups throughout his career, shaping and mentoring future generations of researchers. My own involvements in electrocatalysis in the past decade would not be possible without individuals like R. Adzic who is committed to mentoring and collaborating with researchers coming from other disciplines.

In this talk, I will discuss the mechanisms of Pt and Pt alloy catalyst instability and activity loss in fuel cells (1-2), limiting the lifetime of fuel cells, and how morphologies of Pt alloy particles can influence activity and stability (3-4).

Chen, S., H.A. Gasteiger, K. Hayakawa, T. Tada, and Y. Shao-Horn, Platinum-Alloy Cathode Catalyst Degradation in Proton Exchange Membrane Fuel Cells: Nanometer-Scale Compositional and Morphological Changes, Journal of the Electrochemical Society, 157, A82–97 January 2010.

Ferreira, P.J., G.J. la O’, Y. Shao-Horn, D. Morgan, R. Makharia, S. Kocha and H. Gasteiger, Instability of Pt/C Electrocatalysts in Proton Exchange Membrane Fuel Cells: A Mechanistic Investigation, Journal of the Electrochemical Society, 152, A2256–A2271 2005.

Chen, S., W.C. Sheng, N. Yabuuchi, P.J. Ferreira, L.F. Allard and Y. Shao-Horn, The Origin of Oxygen Reduction Activity of “Pt3Co” Nanoparticles: Atomically Resolved Chemical Compositions and Structures, Journal of Physical Chemistry C, 113, 1109–1125 2009.

Han, B., C.E. Carlton, A. Kongkanand, R.S. Kukreja, B.R.C. Theobald, L. Gan, R. O'Malley, P. Strasser, F.T. Wagner, and Y. Shao-Horn, Record Activity and Stability of Dealloyed Bimetallic Catalysts for Proton Exchange Membrane Fuel Cells, Energy & Environmental Science, 8, 258-266 2015.
(Invited) Surface Sites Probing and Electrocatalytic Property of Atomic Sub-Monolayer and Multilayer on Tetrahexahedral Nanocrystals
Authors: Tian Na , Lin Yan-Fen , Sun Shi-Gang
Published: February 2020

Tetrahexahedral nanocrystals (THH NCs) of fcc metals such as Pt, Pd, Rh possess a high catalytic activity due to their open surface structure and high surface energy.1 It has been determined that the THH Pt NCs are enclosed by {hk0} facets that can be decomposed with different subfacets. As an example, the most frequently prepared THH Pt NCs are bounded with {730} facets, which can be decomposed into (310) + 2(210) or 3(100)´(110) + 2(100)´(110) + 2(100)´(110). 1,2 It is obvious that the high catalytic activity of the THH Pt NCs originates from the high density of surface active sites.

In the current study through applying cyclic voltammetry (CV) and in situ FTIR spectroscopy, CO adsorption and oxidation were used as probe reactions to investigate the surface sites on THH Pt NCs, in order to understand their role in practical electrocatalysis. Furthermore, the electrocatalytic property towards small organic fuel molecule oxidation of sub-monolayer of adatoms as Bi, Ru and Au on THH Pt NCs, and multi Pt atomic layer on THH Pd NCs were studied to gain knowledge on surface structure effects of high-index faceted nanocrystals in electrocatalysis.

Acknowledgement: This work was supported by Natural Science Foundation of China (21573183, 21621091).

References:

Tian et al. Science, 2007, 316, 732-735.

Hermann, “Crystallography and Surface Structure, an introduction for surface scientists and nanoscientists”, Wiley-VCH, Berlin 2011, ISBN 978-3-527-41012-5.

S. Chen et al. J. Am. Chem. Soc. 2011, 133, 12930.

X. Liu et al. ACS Catalysis, 2012, 2, 708.

X. Liu et al. PCCP, 2012, 14, 16415.

X. Liu et al. Faraday Discuss. 2014, 176, 409.

F. Lin et al, Chem. Sci., 2017, submitted
Electrochemical CO2 Reduction on Oxide-Derived Cu Surface with Various Oxide Thicknesses
Authors: Liang Zhixiu , Fu Jie , Vukmirovic Miomir B , Adzic Radoslav R.
Published: February 2020

A steadily raising amount of carbon dioxide (CO2) released in atmosphere due to increased consumption of fossil-fuel causes harmful climate change. Additionally, limited reserves of fossil-fuel put a pressure on their future availability thus setting a stage for increased interest in utilizing renewable energy. Electrochemical reduction of CO2 (CO2RR) is a promising way to reduce amount of CO2 as well as generate ‘carbon neutral fuels’ [1]. Among the various CO2RR products, ethylene (C2H4) and ethanol (C2H5OH) are of higher energy density and commercially are more valuable than carbon monoxide (CO) and methane (CH4). Oxide-derived Cu surface is a good candidate for electrochemical CO2 reduction to C2H4 and C2H5OH due to its high activity as well as selectivity [2].

Here we report a systematic study of CO2RR on oxide-derived Cu surface with various oxide thicknesses. The oxide-derived Cu surfaces were prepared via thermal annealing at different temperatures and electrochemical Cu2O plating on Cu foil. The distribution of the CO2RR products, such as CO, CH4, C2H4 and C2H5OH, as well as the rate of hydrogen evolution reaction are highly dependent on the morphology and thickness of the oxide layer. Thus, we can fine tune the performance of the catalyst via deliberate engineering of the oxide-derived Cu surface, Fig. 1. More detailed discussion on the CO2RR performance of these catalysts will be presented at the meeting.

Acknowledgements

This manuscript has been authored by employees of Brookhaven Science Associates, LLC under Contract No. DE-SC0012704 with the U.S. Department of Energy. The publisher by accepting the manuscript for publication acknowledges that the United States Government retains a non-exclusive, paid-up, irrevocable, world-wide license to publish or reproduce the published form of this manuscript, or allow others to do so, for United States Government purposes.

References

Sheng, S. Kattel, S. Yao, B. Yan, Z. Liang, C. J. Hawxhurst, Q. Wu, J.G. Chen, Energy Environ. Sci., 10, 1180 (2017).

W. Li, M.W. Kanan, J. Am. Chem. Soc., 17, 134 (2012).

Figure 1
Precipitated and Chemically-Crosslinked Enzymes over Polyaniline Nanofibers for High Performance Biosensors & Biofuel Cells
Authors: Garcia-Perez Tsai , Kim Jae Hyun , Kim Ryang Eun , Wee Youngho , Kim Jungbae , Ha Su
Published: February 2020

The enzyme catalysts can be successfully used for bioelectrocatalytic applications such as biosensors, biofuel cells, and even CO2 conversion. However, the short lifetime of enzymes and the slow electron transfer are two critical problems against the practical applications of enzymes in bioelectrocatalysis. Nanobiocatalysis, using conductive nanomaterials for enzyme immobilization, has gathered growing attention due to its recent successes in stabilizing the enzyme activity and expediting the electron transfer. In this study, we employed three different approaches to stabilize glucose oxidase (GOx) and laccase (LAC), which are widely used enzymes for enzymatic biosensors and biofuel cells, on polyaniline nanofibers (PANFs): enzyme adsorption (EA), enzyme adsorption and crosslinking (EAC) and enzyme adsorption, precipitation and crosslinking (EAPC) approaches. Several successful examples of nanobiocatalysis in improving both lifetime and performance of bioelectrocatalytic systems will be introduced in details. Especially, the use of conductive nanomaterials could improve the rate of electron transfer from the enzyme active site to the main electrode.
Enhancing the Redox Conductance of Biofilms in Microbial Fuel Cells
Authors: Li Cheng , Liu Hong
Published: February 2020

Mixed species biofilms have been able to generate current densities of over 20 A/m2 in microbial fuel cells (MFCs), while also offering advantages in stability, substrate flexibility, and culture maintenance costs. To further increase the current density, a possible approach is to enhance the conductivity of biofilms and thereby the direct extracellular electron transfer within the biofilms and to the anode. While examination of conductivity in microbial samples is still in its relative infancy and conceptual models in terms of conductive mechanisms are still being developed and debated, our study has demonstrated that current-producing mixed species biofilms can exhibit high conductivity across non-conductive gaps. Differential responses observed over varying potentials also suggest that a redox driven conductivity mechanism is dominant in the tested mixed-species biofilms. Considering that some redox conductive organic polymer films possess negative magnetoresistance property (resistivity of a conductive material decreases as the magnetic field strength increases) and magnetic field may stimulate enzyme activity in certain anaerobic wastewater treatment systems, our mixed species biofilms were exposed to low intensity magnetic field to investigate the conductivity change and performance enhancement. Exposure of the biofilms to magnetic field has led to an over 100% increase in biofilm conductance and over 300% increase in current density. Application of the low intensity magnetic field also encouraged the enrichment of Geobacter spp. in biofilms. Short term application of magnetic field also increased the conductivity of anodic biofilms, resembling the negative magnetoresistivity that has not been observed in conductive biofilms before. These results not only enhance our understanding of the electrical conductivity in microbial aggregates, but also inform rational design and operation of microbial-based fuel cells.
Electron Transfer Rates of Anodic Biofilms at Different Sizes
Authors: Tutar Secil , Mohamed Abdelrhman , Ha Phuc Thi , Beyenal Haluk
Published: February 2020

Bioelectrochemical systems (BESs) have emerged as a promising technology with applications in wastewater treatment, energy recovery, and chemical synthesis. However, several challenges, including the optimization of electrode materials and geometries, microbial community enrichment, reactor design and scale up, have delayed the transition of these technologies out of the laboratory to larger industrial process. The goal of the present work is to study the effect of electrode size of anodic biofilms and substrate concentrations. The anodic biofilms were enriched on electrodes under two conditions: 1) in raw domestic wastewater and 2) in domestic wastewater supplemented with 20 mM acetate. After enrichment, the media were replaced with various COD values to test the effect of COD loading on current density at pseudo-steady-state conditions. We demonstrated how current densities of various electrode sizes depend on the bulk COD concentration after enrichment of anodic biofilms.
Mapping Charge Carrier Dynamics of Photoactive Material Surfaces in Space and Time
Authors: Mohammed Omar
Published: February 2020

Understanding light-triggered charge carrier dynamics on photovoltaic-material surfaces and at interfaces has been a key element and one of the major challenges for the development of real-world energy devices. For this reason, studying charge carrier dynamics at photoactive material surfaces and interfaces have been among the most active areas of research in the last decade [1-4]. However, the ability to access carrier dynamics selectively on material surfaces with high spatial and temporal control in a photo-induced reaction is a particularly challenging task that can only be achieved by applying four-dimensional (4D) ultrafast electron microscopy (4D UEM) along with time-resolved laser spectroscopy. For this purpose, we established and developed the second generation 4D S-UEM and demonstrate the ability to take time-resolved secondary electrons images (snapshots) of material surfaces with 650 fs and ~ 4 nm temporal and spatial resolutions, respectively. In this method, the surface of the photoactive materials is excited by a clocking optical pulse and the photo-induced changes will be imaged using a pulsed primary electron beam as a probe pulse, generating secondary electrons, which are emitted from the top surface of the material in a manner that is extremely sensitive to the localization of the electron and hole on the surface and at the donor-acceptor interfaces. This method provides direct and controllable ultrafast dynamical information in many photoactive materials commonly used in solar cells and photo-catalysis. For instance, we have clearly demonstrated in space and time how the surface morphology, surface passivation, thickness of the absorber layer, grains, surface defects and nanostructured features can significantly impact the overall dynamical processes on the surface of absorber layers including nanomaterials and single crystals [5-8]. Finally, charge carrier dynamics in semiconductor quantum dots and perovskite single crystal using femtosecond laser spectroscopy will be also presented and discussed.

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M. Bakr, O. F. Mohammed.,
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Adiabatic and Nonadiabatic Charge Transport in Li-S Batteries
Authors: Park Haesun , Kumar Nitin , Melander Marko , Vegge Tejs , Garcia Lastra Juan Maria , Siegel Donald J
Published: February 2020

The insulating nature of the redox end members in Li-S batteries, a-S and Li2S, has the potential to limit the capacity and efficiency of this emerging energy storage system. Nevertheless, the mechanisms responsible for ionic and electronic transport in these materials remain a matter of debate. The present study clarifies these mechanisms – in both the adiabatic and nonadiabatic charge transfer regimes – by employing a combination of hybrid-functional-based and constrained density functional theory calculations. Charge transfer in Li2S is predicted to be adiabatic, and thus is well described by conventional DFT methodologies. In sulfur, however, transitions between S8 rings are nonadiabatic. In this case, conventional DFT overestimates charge transfer rates by up to 2 orders of magnitude. Delocalized holes, and to a lesser extent, localized electron polarons, are predicted to be the most mobile electronic charge carriers in a-S; in Li2S hole polarons dominate. Although all carriers exhibit extremely low equilibrium concentrations, and thus yield negligible contributions to the conductivity, their mobilities are sufficient to enable the sulfur loading targets necessary for high energy densities. Our results highlight the value of methods capable of capturing nonadiabadicty, such as constrained DFT. These techniques are especially important for molecular crystals such as a-S, where longer-range charge transfer events are expected. Combining the present computational results with prior experimental studies, we conclude that low equilibrium carrier concentrations are responsible for sluggish charge transport in a-S and Li2S. Thus, a potential strategy for improving the performance of Li-S batteries is to increase the concentrations of holes in these redox end members.
A Tale of Two Fridges: Temperature Implications on Long Term Fading, Material Degradation, and Performance Recovery in Lithium-Ion Batteries
Authors: Bommier Clement , Kim Andrew , Steingart Daniel A
Published: February 2020

A high capacity retention, along with a long battery life, are two aspects paramount towards the economic viability of large-scale Lithium-Ion battery (LIB) applications. As such, it is important to understand the mechanisms underlying capacity decay, as to mitigate them, if not outright reverse them. To that end, there have been many studies addressing this issue. However, most of these studies have relied on varying only a limited amount of parameters, thus limiting the scope, and depth of their conclusions: if two variables have a covariant relationship, yet the experiment only accounts for one, the presence of that relationship will be obscured.

Herein, the current research explores the long-term fading in lithium-batteries, and how it is affected by a host of different factors, ranging from cycling temperature, and current rate, to initial formation, and restive period at the top of charge. These studies go on to reveal that there exists a very strong relationship between current rate, and temperature, as it pertains to fading, with higher temperatures showing surprisingly high capacity retention over the long term (Figure 1). Furthermore, we are further able to demonstrate that under certain conditions, capacity losses are recoverably, which thus alludes to the possibility of being able to prolong, if not recycle, LIBs currently in use.

Lastly, this work also explores one of the big divides that still exists within the battery community: the testing of long-term cycling in Li-metal half cells, as opposed to full cells. Our experimental results show that the nature of fading mechanisms in full-cells versus half-cells are not analogous to one another. Certain mechanisms that dominate in one medium, have a greatly diminished presence in the other. As such, this work concludes by stressing the question: what is the proper way, if any, to look at long term fading mechanism in LIBs?

Figure 1
Recycling Lithium Batteries Using Membrane Technologies
Authors: Lien Larry
Published: February 2020

MDS has developed a process using a series of proprietary acid stable membranes and process equipment to recover all the components from used or damaged lithium ion batteries. The process consists of discharging, disassembly of parts for both flat and cylindrical battery types, digestion of the batteries in a mild acid solution, then recovery of copper and aluminum strips, cobalt, lithium and the graphite. The membrane steps are UF-NF and RO—each step purifies as permeate or concentrates valuable metals and graphite. In addition, the process recovers all the water and acid used for the digestion of disassembled batteries. Because of the complete recycling of acid and water coupled with the recovery of all the components of the batteries including plastics, the process is sustainable, environment friendly and zero liquid discharge.

Figure 1
The Use of Temperature-Programmed Desorption to Explain the Electrochemical Behaviour of PGM-Free PEFC Cathode Catalysts
Authors: Boldrin Paul , Malko Daniel , Brandon Nigel P. , Kucernak Anthony R. J.
Published: February 2020

Oxygen reduction catalysts in PEFCs have traditionally contained relatively high amounts of platinum or other platinum group metals. There has been a drive towards reducing the loading, but a promising alternative has been discovered in the form of iron and nitrogen-doped carbon. However, their activity is still not acceptable, and their improvement is hampered by the lack of knowledge about the chemical structure of the materials and in particular the active site(s). There is still disagreement over whether the active site is organic or metallic, or even both.

Temperature-programmed techniques such as temperature-programmed desorption (TPD) and temperature-programmed reaction spectroscopy (TPRS) are powerful techniques used in conventional catalysis for probing active sites. Molecules which interact with the active sites are adsorbed on the catalyst, then the system is heated and the desorption of the initial molecule or products can be measured by mass spectrometry. These techniques allow quantification of number of active sites, heats of desorption and reaction, assessment of reaction mechanisms and studies of poisoning behaviour.

This study reports extensive TPD and TPRS work done on an iron and nitrogen doped carbon-based oxygen reduction catalyst. Interactions between various molecules and the active site(s) on the catalyst have been studied and quantified. Correlations between TPRS and TPD studies and electrochemical studies have been made from fresh, aged and poisoned materials, and these have been compared to studies on similar materials containing either no iron, or no iron and nitrogen. In addition, ex situ measurements including EXAFS and Mössbauer on the same materials will be reported on. Together these experiments are used to draw conclusions about the nature of the active site(s) in these materials.

Figure 1
A Comparative Study of Ligand Modification to Pt Surface for Enhanced ORR Catalyst Activity and Durability
Authors: Kobayashi Masaya , Huang Kan , Jones Michael , Nagai Tomoyuki , Jia Hongfei
Published: February 2020

Last decade witnessed significant advances of polymer electrolyte membrane fuel cell (PEMFC) R&D and the exciting transition of such development into the commercialization of fuel cell vehicles. While the low temperature PEMFC represents the state-of-art technology for transportation applications, substantial challenges remain in finding better catalysts for oxygen reduction reaction (ORR), which accounts for the biggest loss of energy efficiency and the highest cost of material components of FC stacks. ORR involves multiple steps of proton coupled electron transfer processes and a “scaling” issue makes it difficult to optimize every elemental reaction step simultaneously. [1] In addition to the improvement of catalyst itself, engineering catalyst electrolyte interface properties may offer a separate venue to tackling the problem. One recent effort involves the modification of Pt catalyst surface with organic ligands and has demonstrated some successes in enhancing catalyst activity. The effect was mostly attributed to either the change of surface electronic structure of the catalyst or the protection of Pt active sites from poisoning by strong anion adsorption. [2-4] However, the impact of ligand modification on catalyst durability and the stability of the ligand itself on the catalyst surface have not been thoroughly investigated. In this study, we systematically examined a series of organic ligands with different structures and anchoring groups. Coupling material characterization with electrochemical analyses allowed us to assess both the catalyst durability and the ligand stability. Such a comparative study is expected to lead the development of design principles to further improve this technology towards MEA and FC stack applications.

References

(1) M. T. M. Koper, et al., J. of Electroanal. Chem., 2011, 660, 254-260

(2) Y. H. Chung, et al., J. Phys. Chem., Lett. 2013, 4, 1304-1309

(3) Z. Y. Zhou, et al., J. Phys. Chem., C, 2012, 116, 10592-10598

(4) D. Strmcnik, et al., Nature Chem., 2010, 2, 771
Development and Evaluation of in-Situ Instrumentation for Li-Ion Cells
Authors: Fleming Joe , Amietszajew Tazdin , McTurk Euan , Greenwood David , Bhagat Rohit
Published: February 2020

This work demonstrates the development and evaluation of sensing technology for monitoring the distributed in-situ in-operando temperature of lithium-ion cells. The influence of the sensing element on the electrochemical system was evaluated using EIS, CT scanning and cell cycling characterisation and was proven to be negligible. Furthermore, the thermal sensors were proven to be resistant to the strain imposed during the cell instrumentation procedure and the harsh chemical environment inside the Li-ion cells. The sensing methodologies and modification techniques developed in this work can be applied to large scale battery modules and pack systems and integrated within the cell manufacturing process. This work identified a clear and significant difference between the cell’s can and core temperatures, as well as axial temperature gradient. The findings of this study are of significance to the performance and safety limits of energy storage systems. This research indicates the clear need for reliable sensing systems that enable accurate in-situ in-operando monitoring of lithium-ion energy storage systems.
(Keynote) Recent Progress in Nanomaterials and Smart-Phone Based Biosensors for Biomedical, Environmental, and Food Safety Applications
Authors: Du Dan , Lin Yuehe
Published: February 2020

In this talk, I will briefly discuss our recent progress in synthesis of functional materials based on protein cages, graphene, and nanoflowers for biosensing and bioimaging. I will discuss the development of various biosensors based on DNA assays and immunoassays for point-of care diagnostics and for cancer biomarker detection [1-3]. Nanomaterials loaded with optical or electroactive signal molecules were used for signal amplification tags for enhanced sensitivity for detection of disease biomarkers, environmental pollutants, and food pathogens. I will also discuss the recent work in 3D printing and smart-phone based biosensors for food safety applications [4-5].

References:

1. W. Wen, D. Du, Y. Lin. Recent Advance in Electrochemical Immunosensor. Analytical Chemistry 2017, 89, 138-156.

2. C. Zhu, G. Yang, H. Li, D. Du, Y. Lin. Electrochemical Sensors and Biosensors Based on Nanomaterials and Nanostructures. Analytical Chemistry 2015, 87, 230-249.

3. R. Ye, C. Zhu, Y. Song, Q. Lu, X. Ge, X. Yang, M. Zhu, D. Du, H. Li, Y. Lin, Bioinspired Synthesis of All‐in‐One Organic–Inorganic Hybrid Nanoflowers Combined with a Handheld pH Meter for On‐Site Detection of Food Pathogen. Small 2016, 12, 3094-3100.

4. Y. Wang, M. Zeinhom, M. Yang, R. Sun, S. Wang, J. Smith, C. Timchalk, L. Li, Y. Lin, D. Du, A 3D-Printed, Portable, Optical-Sensing Platform for Smartphones Capable of Detecting the Herbicide 2, 4-Dichlorophenoxyacetic Acid. Analytical Chemistry 2017, 89, 9339-9346.

5. N. Cheng, Y. Song, M. Zeinhom, Y. Chang, L. Sheng, H. Li, D. Du, L. Li, M. Zhu, Y. Luo, W. Xu, Y. Lin, Nanozyme mediated dual-immunoassay integrated with smartphone for use in simultaneous detection of pathogens. ACS Applied Materials & Interfaces 2017, DOI: 10.1021/acsami.7b12734
Synthesis and Characterization of Carbon Quantum Dots for Use in FRET Sensors
Authors: Linhart Abigail N. , Keleher Jason J.
Published: February 2020

Semiconductor quantum dots (CdSe and PbS) have commonly been used in solid state lighting and biomedical applications, however, these particles exhibit high toxicity and low biocompatibility. As an alternative, carbon quantum dots (C-dots) have recently gained much attention due to their increased biocompatibility and low toxicity while maintaining fluorescence and high photostability. The focus of this research is to optimize the synthesis of C-dots for use in fluorescence resonance energy transfer (FRET) sensors, such as ion sensors, biosensors, and pH sensors. This work has studied the kinetics of the acid catalyzed hydrolysis of biomimetic precursors, more specifically sugars, through fluorescence and absorbance measurements to explore the impact on the optical properties of the resultant C-dots. In addition, based on the mechanism of the particle nucleation, the synthesized C-dots can be easily modified for specific applications through interactions with the functional groups (alcohols and carbonyls) present on the surface. Future work will incorporate the optimized C-dots into polymeric media for use as a solid state FRET sensor.
Simulation of Correlated Motion of Li+ Vacancies in Lithium-Oxyhalide Anti-Perovskites
Authors: Mehmedović Zerina , Wei Vanessa Yi Zhen , Adelstein Nicole
Published: February 2020

Introduction

This research addresses the long-standing dilemma in solid-state batteries, the low ionic conductivity across solid-solid interfaces and through the solid electrolyte. Understanding the mechanism behind lithium ion diffusion in solid electrolytes can provide significant insights in developing new battery materials. This study focuses on tuning the conductivity of lithium-oxyhalide anti-perovskites by optimizing the Cl to Br ratio, increasing Li vacancies, and engineering the crystallinity. To explain the variations in conductivity, we simulated Li3OCl and Li3OCl1-xBrx with varying vacancy concentrations, including both Li and Cl vacancies. The hypothesis that correlated motion affects conductivity is quantified with a novel analysis.

Methods

First principles Density Functional Theory – Molecular Dynamics was performed on 4x4x4 supercells using VASP. The size of the supercell (320 atoms) allows for a higher percentage Br substituted doping, comprising of 22% and 30% Br:Cl. The simulations each ran for at least 20 ps. The supercells had at least one and up to four Li+ and Cl- vacancies, as the conduction mechanism is vacancy mediated. Analysis was performed to determine how polarization of anions affects Li+ ion diffusion. Maximally Localized Wannier Functions (MLWF) are used to quantify the covalent character of the Li-anion bonds, in particular their dynamic behavior. As is standard, the diffusion coefficient for each compound was determined using the mean squared displacement.

Results

We identified how the number of Cl and Br bonds and changes in covalency during Li+ jumping affects the diffusion pathway. The bonding characters that were determined from the MLWF analysis show that the bromine has more covalent bonds with Li+ than the chlorine. We quantified how the concentration of Li+ vacancies and fluctuations in polarization of anions affects the diffusion mechanism. The polarizability of the anions was calculated using MLWF and showed that the Li+ diffusion affects the polarization of the second nearest neighboring anion by increasing its polarization. We found that correlated motion between Li+ vacancies increased diffusion; the more vacancies, the more pronounced the effect of correlation on diffusion.

References

Adelstein, N. and Wood, B. Li+ conductivity in a superionic electrolyte driven by dynamically frustrated bond disorder. Journal of Materials Chemistry (2016).

Zhang, Y., Zhao, Y., & Chen, C. (2013). Ab initio study of the stabilities of and mechanism of superionic transport in lithium-rich anti-perovskite. Rev. B Physical Review B,
87(13).
Evaluation of Barrier Properties of Organic Coatings By Electrochemical Permeation and Electrochemical Methods
Authors: Nardeli Jéssica Verger , Fugivara Cecilio Sadao , Benedetti Assis Vicente
Published: February 2020

This study aims at investigating the transport through free-films of organic coatings derived from vegetable oils (crambe oil and castor oil) plus pre-polymer based on hexamethylene diisocyanate and castor oil, which were used in our previous studies to protect aluminum alloy (AA1200) against corrosion in NaCl solution [1]. The free-films were characterized by Raman, NMR, FTIR and AFM (roughness and texture), and the permeability to KCl in aqueous solutions was investigated by electrochemical impedance spectroscopy (EIS) and open circuit potential (E
OCP) measurements as function of time. Different coating formulations were tested to demonstrate the influence of their structure and chemical composition on electrolyte permeability. The good corrosion resistance of these coatings encouraged us to investigate the KCl permeability to assist in understanding the mechanism of corrosion protection of the aluminum alloy surface. The measurements were done by using a setup similar to that employed by Armstrong et al. [2] in 0.1 mol L-1 KCl aqueous solution, at 25 oC and atmospheric pressure. Raman, NMR, and FTIR spectra, and AFM images were taken before and after four months of immersion in the electrolyte and no significant differences between spectra or images were found. These results allowed concluding that no compositional and / or chemical structural and topological changes have occurred in the free-films. EIS and E
OCP measurements were conducted with the free-film of organic coatings immersed in 0.1 mol L-1 KCl aqueous solutions for four months at 25 oC and atmospheric pressure. The modulus of impedance remained between 1.2 to 1.7 GΩ cm2 suggesting that the coating is not degraded by the solution and K+ and Cl- ions permeability is practically insignificant.

References

[1] J.V. Nardeli, D.V. Snihirova, C.S. Fugivara, M.F. Montemor, E.R.P. Pinto, Y. Messaddecq, A.V. Benedetti, Localised corrosion assessement of crambe-oil-based polyurethane coatings applied on the ASTM 1200 aluminum alloy, Corros. Sci. 111 (2016) 422-435.

Acknowledgments

Process FAPESP: 2015/10554-9.
Understanding Amyloid-Beta Plaque Formation By Monitoring the Redox Activity of Copper at the Active Site
Authors: Qadir Saniya , Tabaka Amber Lynn , Kissel Daniel S. , Keleher Jason J. , Havens Mallory A.
Published: February 2020

Alzheimer’s patients are found to have high concentrations of Amyloid-Beta peptide (Aβ-42), an overexpressed 42 amino acid sequence, along with a high concentration of copper ions in the brain. The Aβ-42 peptide results from the cleavage of a precursor protein (APP) and aggregates to form beta sheets during post-translational modification due to oxidative stress. Free metal ions, particularly Cu2+, initiate this oxidative stress by binding to the 14th Histidine residue in the primary structure of Aβ-42 and undergoing a single electron-transfer reduction to Cu+. This redox activity ultimately generates reactive oxygen species (ROS) through Fenton Decomposition to produce hydroxyl radicals within the brain. ROS initiate the progressive transitive states of Aβ-42 from fibril to oligomer to finally aggregate plaque formation, which causes cellular degeneration. The work presented here specifically focuses on the copper redox activity in the biological pathway leading to Alzheimer’s disease. The redox activity of copper at the active site is monitored and correlated to the degree of Aβ-42 fibrillization and aggregation, which is examined using Atomic Force Microscopy (AFM). Evaluating the copper-mediated toxicity will allow for a better understanding of the electrochemical process that initiates ROS and ultimately leads to Aβ-42 plaque formation.