bluuebunny/crossref_metadata_2025 huggingface dataset:
Preparation of Composites of Nano-Silicon and Spherical Natural Graphite for Li-Ion Batteries By a Drop-in Technology
Authors: Toupin Mathieu , Gauthier Véronique , Perrin-Sarazin Florence , Zhao Xiuyun , Naboka Olga , Yim Chae-Ho , Huot Jean-Yves , Abu-Lebdeh Yaser
Published: February 2020

We will describe a methodology to prepare nano-Si / natural graphite composite using an established transformation manufacturing process without significant changes to the initial process flow, thus minimizing the cost of implementation. First, a baseline was established by investigating half-cells made with anode using a mixture of coated spherical natural graphite, nano-Si and LiPAA binder. Then, a composite of graphite / nano-Si was prepared by carbonizing a dry mixture of spherical graphite, nano-Si and petroleum pitch. The silicon content was below 20 wt.% toward graphite and the pitch-to-nano-Si was optimized. Following these guidelines, a series of Si/graphite composites were prepared by first performing a spheronization process to a dry mixture of natural graphite flakes, nano-Si and carbon precursors to disperse the silicon in the core and on the surface of the graphite matrix. Followed by a carbonization step to form the amorphous carbon coating simultaneously on the graphite and nano-Si surface. The morphology and chemical composition of the composites' surface was investigated using XPS, SEM and HRTEM and the possible formation of silicon oxides or carbides was evaluated by XRD. Tap density, surface area and PSD were performed to assess if the prepared powders reached the battery grade specifications. The composites show very high reversible capacity when evaluated in coin-type, Li-ion half cells.
Fundamental Chemistry Behind Rechargeable Li-Based Batteries and Beyond: Theoretical and Computational Chemistry Approach
Authors: Dubey Satya Prakash , Widanage Widanalage Dhammika , McGordon Andrew , Marco James
Published: February 2020

Abstract: Motivated by energy security and environmental concerns, policymakers around the world are directing attention to electrified vehicles as a partial solution to reducing fossil fuel consumption and carbon emissions. In recent years, rechargeable Li-ion batteries emerge as an important power source, and their performance highlights the adoption into the automobile electrical vehicles (EV) sector as viable alternatives to combustion engines. The success of market penetration of these environmental-friendly vehicles strongly depends on the industrialization of new energy-storage technologies that must meet at the same time, performances, security, durability and cost requirements. However, the performance of today's battery chemistries relative to the battery weight is a limiting factor – there is a gap to close between today's technology and the requirements of future battery vehicles. The next-generation energy storage systems may be based on novel chemistries, such as all-solid-state, Li-ion, Li-S, and metal-oxygen, to achieve significantly higher energy density. Materials and their interfaces in these batteries are often the key limiting factors and origins of failures. For example, the degradation at the electrolyte-electrode interfaces causes poor cyclability, low capacitance, and premature failure in these new battery systems. It is crucial to focus on research which aligned towards, robust reaction kinetics modelling and its possible validation through experiments and discovering future advanced (Li, Si, Na-ion) batteries based on material chemistry and electrolyte design. To reveal such details, a fuller understanding of how the materials composition interact at the molecular level, which is not investigated in great detail so far is highly recommended by considering cost-effective computational chemistry tools (DFT, MD). Interaction of decomposed electrolyte/salt components with Li-ion is the key source of formation of SEI layer at the anode surfac such as LiF, Li2CO3, LiO, etc. To understand the stability and chemistry of SEI layer which is in general very complex, atomic level molecular chemistry simulation were performed. The perfect SEI would be a fast forming, flexible, stable and insoluble species with minimum electronic and maximum ionic conductivity. We use computational techniques to understand the limiting factors- such as reaction kinetics and chemistry involved for solid electrolyte interphase (SEI) growth and failure mechanisms at the interfaces, for the improvement of capacity and power fade to the new energy-storage technologies Fig. 1 [1].

[1] M. Datt Bhatt and C. O’Dwyer, “Recent progress in theoretical and computational investigations of Li-ion battery materials and electrolytes,” Phys. Chem. Chem. Phys., vol. 17, no. 7, pp. 4799–4844, 2015.

Figure 1
UV Photopolymerization of Vinyl Ether Based Polymer Electrolytes for Solid-State Lithium Batteries
Authors: Becker Melissa , Tenhaeff Wyatt
Published: February 2020

The utilization of solid lithium metal in lithium ion batteries increases performance and capacities but introduces safety issues when combined with liquid electrolytes. This prevents its use in practical energy dense electrochemical cells, like those required for electric vehicles or consumer electronics. Safety can be increased by using polymer or gel electrolytes which are less flammable and provide a more formidable barrier to dendrite formation. However, the production of polymer electrolytes can often be complicated and involve several stages, making the processing time-consuming and expensive to apply on the industrial scale.

In this work we developed a simple bulk polymerization method in the presence of lithium salt to produce quick-curing vinyl ether based polymer electrolytes in a one-step cationic UV photopolymerization. These electrolytes are composed of ethyl vinyl ether (EVE) monomer and poly(ethylene glycol) divinyl ether (DVEp) crosslinker with triarylsulfonium hexafluorophosphate salt photoinitiator and bis(trifluoromethane) sulfonimide (LiTFSI) lithium salt. Systems with varying crosslinker to monomer (DVEp:EVE) volume ratios and lithium salt concentration ratios were produced to see the effects of crosslinking density and [O]:[Li] ratio on electrolyte properties. Attenuated Total Reflectance Fourier-transform Infrared spectroscopy (ATR-FTIR) was used to quantify polymer composition and verify complete polymerization. Ionic conductivities were measured from 0 to 80 °C using electrochemical impedance spectroscopy. The highest ionic conductivities were seen in samples with the lowest crosslinker concentrations and the highest lithium salt concentrations. The most conductive sample produced had composition 10:1 [O]:[Li] and 15% crosslinker by volume and reached an ionic conductivity of 1.2x10-6 S/cm at 20°C. Glass transition temperatures (Tg) were measured with differential scanning calorimetry (DSC) for various salt-free DVEp:EVE ratios; Tg was determined to be -15°C for composition with 15% crosslinker in the absence of salt. Investigation of the effect of salt on Tg’s and the electrochemical stability of these compositions is currently underway and will be reported.
Effect of Formation Rates on Performance of Lithium Metal Batteries
Authors: Nagpure Shrikant C. , Wood Sean M. , Dufek Eric J. , Dickerson Charles C , Liaw Bor Yann , Hu Victor Waiman
Published: February 2020

Lithium metal rechargeable batteries (LRBs) have the potential to meet the 500 Wh·kg-1 energy density goal set by the US Department of Energy for high energy density batteries [1]. However, two issues need to be addressed in these batteries before their widespread commercialization: (1) safety concerns arising from dendritic growth and (2) limited cycle life due to low Coulombic efficiency and loss of active Li. Since organic solvents are thermodynamically unstable in the presence of highly-reducing Li, significant side reactions take place, the products of which form a solid electrolyte interphase (SEI) on the Li surface.

During the production process, Li-ion batteries undergo formation cycling to form a stable SEI and to evaluate the condition of the cell. However, the advantages of early cycle conditioning or formation are not well understood for LRBs, because new SEI forms on the Li surface during each cycle. The present study was undertaken to better understand how early cycling impacts interfacial processes in LRBs and ultimately how variation in the initial cycles impacts the life of the battery.

Cycling conditions, which include both charging (deposition) and discharging (stripping), affects the Li anode morphology [2, 3]. Build-up of a stable SEI layer and formation of a uniform Li surface during initial cycling of LRBs helps limit dendritic growth, and cell impedance in subsequent cycling. A stable initial SEI is also necessary to prevent corrosion of the Li metal electrode and to prolong the cycle and calendar life of the cells by limiting side reactions with the new Li surface. Using a high-Ni NMC cathode and a Li metal anode, an assortment of different cycling conditions which impact the dynamics of the Li-electrolyte interface were investigated. Performance was characterized with electrochemical diagnostic tools and surface morphology analysis. Both the deposition and stripping rate affected the impedance of the cell, surface kinetics, and interfacial mass transport, all of which impact the cycle life of LRBs.

References:

[1] Battery500 Consortium to Spark EV Innovations: Pacific Northwest National Laboratory-led, 5-year $50M effort seeks to almost triple energy stored in electric car batteries, in Office of Technology Transitions Energy.gov (2016).

[2] Hongfa Xiang, Pengcheng Shi, Priyanka Bhattacharya, Xilin Chen, Donghai Mei, Mark E. Bowden, Jianming Zheng, Ji-Guang Zhang, and Wu Xu, “Enhanced charging capability of lithium metal batteries based on Lithium bis(trifluoromethanesulfonyl)imide-lithium bis(oxalato) borate dual-salt electrolytes,” J Power Sources, 318, 170 (2016).

[3] Jiangfeng Qian, Wesley A. Henderson, Wu Xu, Priyanka Bhattacharya, Mark Engelhard, Oleg Borodin, and Ji-Guang Zhang, “High rate and stable cycling of lithium metal anode,” Nat Comm, 6, 6362 (2015).
Soldering a Gas Diffusion Layer Onto Stainless Steel Bipolar Plates Using Tin and Tin Alloys
Authors: McCay Katie , Kongstein Ole Edvard , Barnett Alejandro Oyarce , Seland Frode
Published: February 2020

Bipolar plates are a key component within a PEM fuel cell stack, with roles such as electron transfer, fuel and waste transport, and stack support. However, stainless steel as a bipolar plate material suffers from poor corrosion properties, with increasing interfacial ohmic resistances across the cell and stack due to the formation of non-conductive oxide layers reducing voltage efficiency over time. These increases in resistance can be mitigated by coating the steel with a conductive and corrosion resistant material.

In this work, we electrodeposited a thin layer of Sn onto a stainless steel bipolar plate (BPP) and joined (soldered) it with a gas diffusion layer (GDL) material through hot-pressing at a temperature just below the melting point of tin. This process solders the GDL to the BPP through the Sn, providing an uninhibited conduction pathway and a drastically reduced interfacial contact resistance. In addition, the Sn layer forms a passive oxide upon exposure to a PEM environment, preventing further corrosion whilst maintaining conductivity through GDL fibres that have infiltrated the Sn layer during hot-pressing (see figure 1). We have optimised the electrodeposition and hot-pressing procedure, with promising in-situ results even after 200 hours of operation in a working fuel cell. This confirms that the novel idea is successful in producing a coating with low contact resistance and promising longevity.

However, accelerated ex-situ testing in dilute sulfuric acid solution (pH 5.5) revealed instability of the SnO2 layer. We propose that introducing alloying elements, such as Bi and In, will increase the stability of the oxide formed and thus impede the degradation of the Sn coating. This work investigates that claim, by depositing Sn alloys containing up to 10 wt % Bi and In onto a stainless steel bipolar plate. Conventional electrochemical measurements such as chronoamperometry and cyclic voltammetry, as well as interfacial contact resistance were performed to investigate the performance of this system.

Figure 1
Optimum Membrane for Formic Acid Electro Oxidation
Authors: Gonzalez Rodriguez Romeo , Perez-page Maria , Sellin Remy , Holmes Stuart
Published: February 2020

In recent years Direct Formic Acid Fuel Cells (DFAFCs) have attracted interest as alternative energy sources. Formic acid is abundant as it is a by-product of acetic acid and formamide industrial production or it can be obtained from the oxidation of biomass. In addition, due to the capacity to use high concentrations of fuel, DFAFCs are effective at room temperature. This is due to the low permeability of the fuel through the membrane when compared to other liquid fuel Polymer Electrolyte Membrane (PEM) fuel cell systems such as Direct Methanol Fuel Cells where fuel crossover is a problem. DFAFCs can generate power densities of ~85 mW/cm2 outperforming Direct Methanol Fuel Cells (DMFCs) with power densities of ~50 mW/cm2. However, no fundamental studies of the intrinsic conductivity and stability of the PEM have been carried out with formic acid. Understanding how the PEM behaves under such highly acidic conditions is vital for ensuring the long-term performance and durability of such fuel cells, should they be used on a wider scale. A comparative analysis of proton exchange membranes of the Nafion family was carried out and the intrinsic conductivity, dimensional stability as well as its operational temperature was observed for its use in formic acid fuel cells. From the results obtained a high performance was observed using a polytetrafluoroethylene reinforce membrane (Nafion XL). The membrane displayed a higher resistance to dimensional change when exposed to a wide range of formic acid concentrations, showing a maximum increase of 10% of its planar dimension while other membranes such as Nafion 117&115 had a significantly higher increase up to 45%. Results indicated that a reinforced membrane could be more suitable for DFAFCs, not only by possessing a higher dimensional stability but also due to it having a higher hydrophobicity due to the reinforcement and the lower content of sulfonic groups present in the copolymer. These changes would address the dehydration of the membrane, a factor substantially affecting the performance of the cell. This dehydration is known to be the result of an osmotic drag occurring from the anode to the cathode of the cell, added to the low content of water present in the reservoir result of the high concentration of the fuel feed. From the studies carried out, Nafion XL also presented a lower dehydration than the commonly used Nafion membranes allowing it to reach higher current densities and power densities. At the same time by comparing the individual Nyquist plots obtained by the electrical impedance spectroscopy for the different membranes, it was evident that the overall resistivity of the reinforced membrane was substantially lower and its proton conductivity higher making it a more adequate membrane for direct formic acid fuel cells.
Interfacial Characteristics of Graphene Containing Novel Microporous Layers for PEM FCs
Authors: Leeuwner Magrieta Jeanette , Wilkinson David P. , Gyenge Elod L.
Published: February 2020

The cathodic microporous layer (MPL) provides many beneficial properties for performance improvement of the H2 PEM FC, particularly with respect to water management and oxygen transport to the catalyst layer [1,2]. The MPL performance is highly dependent on its in-operando material properties such as morphology, porosity and electrical conductivity (in-plane and through-plane, respectively). Furthermore, the interfacial interconnectivity of the MPL material properties with the nano-scale features of the catalyst layer (CL) and the macro-scale characteristics of the gas diffusion layer (GDL) are essential, yet difficult to study, elements in the optimal operation of the fuel cell cathode. In this study diverse graphene based MPLs were investigated by comparison with conventional carbon black and graphite materials. The graphene MPLs were composed of: stand-alone graphene foam [3], electrochemically exfoliated graphene micro-flakes [4] and reduced graphene oxide [5]. The general performance trends revealed lower overpotentials for the graphene MPLs in the electrode kinetic and ohmic controlled regions. In the electrode kinetic region, the improvement was attributed to the unique stacked flake morphology of the graphene assuring excellent interfacial adhesion with the catalyst layer combined with graphene’s high electronic conductivity. The lower ohmic polarization resistance on the other hand, is due to the compact and tortuous morphology of graphene MPLs exhibiting a higher tendency for water retention and inducing, thereby, superior membrane humidification. The enhanced water retention of the graphene MPL, however, can cause catalyst layer flooding at current densities greater than 1000 mA cm-2. To overcome this limitation, composite MPLs containing graphene flakes and carbon black (e.g., Vulcan XC-72) in a 1:1 weight ratio were manufactured and investigated. The graphene – carbon black composite MPLs, demonstrated lower overpotentials throughout the entire polarization curve with maximum power densities 81% and 28% higher compared with the carbon black only MPL at 20% and 100% cathode relative humidity, respectively. In addition, the graphene composite MPLs showed vastly superior durability at 20% cathode humidity in 5 h galvanostatic polarization experiments at 1000 mA cm-2.

References:

M. Blanco, D.P. Wilkinson, Int. J. Hydrogen Energy, 39, 16390-16404 (2014).

T. Swamy, E.C. Kumbur, M.M. Mench, J. Electrochem. Soc., 157, B77-B85 (2010).

M.J. Leeuwner, D.P. Wilkinson, E. Gyenge, Fuel Cells, 6, 790-801 (2015).

A.T. Najafabadi, M.J. Leeuwner, D.P. Wilkinson, E. Gyenge, ChemSusChem, 9, 1689-1697 (2016).

M.J. Leeuwner, D.P. Wilkinson, E. Gyenge, manuscript in preparation (2017).
Proton-Conductive Block Copolyphenylchinoxalines Ionomers for Fuel Cells and Electrolysis
Authors: Janietz Silvia , Krüger Hartmut , Egorov-Brening Tatjana
Published: February 2020

The proton exchange membrane fuel cell (PEMFC) is considered to be the most promising power source for portable and automotive applications. Currently, perfluorinated polymers such as Nafion are the state of the art materials. However, high operation temperatures, cause weakening of their properties. In addition, their shortcomings such as high cost and high methanol permeation property, limit their application. To remedy these problems, aromatic hydrocarbon polymers have been extensively studied as alternative materials for proton exchange membranes (PEMs). Recently, introduction of block copolymer structures to PEMs has been considered as a strategy to overcome the weak points of a random copolymer system. Block copolymers composed of hydrophilic and hydrophobic segments are expected to form ion transport channels due to hydrophilic/hydrophobic phase separated structures and show improved proton conductivity. Poly(phenlyquinoxalines) are a family of aromatic condensation polymers known their outstanding thermal and chemical stability. Based on this polymer class new sulfonated block copolyphenylchinoxalines with hydrophilic and hydrophobic segments have been developed. The block copolymers were synthesized via polycondensation reactions between 3,3`-4,4`tetraaminodiphenylether and two different tetracetones (tetrafluorphenylbis-phenylethandion and phenylbisphenylethandion. High molecular Blockcopolyphenylchinoxalines with 20 000 in number average molecular weight were obtained. The sulfonation of these blockcopolymers was carried out in a mixture of concentrated sulfuric acid and oleum (4:1). In dependence of the reaction time blockcopolyphenyl-chinoxalines with ion exchange capacities of 0,6 - 2,35 mmol/g could be prepared. All sulfonated blockcopoly-phenylchinoxalines show good solubility in dimethylacetamide (DMAC). For the preparation of the membranes a phase inversion process via immersion precipitation was developed. The membranes achieved proton conductivities comparable to Nafion. Additionally the water uptake, oxidation and dimensional stability were investigated and presented.
Stable and Active Polymer Electrolyte Membrane Electrolyzers Utilizing Transition Metal Phosphide Hydrogen Evolution Catalysts
Authors: King Laurie Ann , Hubert McKenzie , Capuano Christopher B , Manco Judith , Danilovic Nemanja , Hellstern Thomas , Jaramillo Thomas F
Published: February 2020

Electrochemical water splitting utilizing renewable electricity is a promising technology for the production of clean and sustainable hydrogen. The most active electrocatalyst for the hydrogen evolution reaction (HER) is platinum. However, the high costs and scarcity associated with platinum motivate the search for alternative catalysts.1 Promising HER activities have been reported for many families of materials including transition metal chalcogenides, carbides and in particular, phosphides.2 Specifically, cobalt phosphide (CoP) is an interesting and active non-precious metal HER catalyst in acid media.3

In this work we synthesise active and stable CoP catalysts on carbon supports at the 1 – 5 g batch scale. The CoP catalysts are prepared by wetness impregnation Vulcan carbon followed by a red phosphorous based vapour phase phosphidation. The crystal structure and chemical composition of the CoP catalyst is verified by XPS and XRD. The morphology of the catalyst is shown to consist of <20 nm particles on the surface of Vulcan carbon support by SEM. The synthesised CoP catalysts are first screened by laboratory scale three-electrode electrochemistry and demonstrate good activity for HER requiring an overpotential of 154 mV to reach -10 mA.cm-2. Beyond three-electrode laboratory scale electrochemistry screening, the most active and durable HER catalysts were used to fabricate 25 cm2 single cell stack membrane electrode assemblies (MEA). The performance of the CoP MEAs was assessed by polarization curve as well as steady state measurements at various current densities and were found to be stable for >20 h of testing. This work highlights the remarkable stability and promise of transition metal phosphides in an MEA configuration.

References

(1) Ng, J. W. D.; Hellstern, T. R.; Kibsgaard, J.; Hinckley, A. C.; Benck, J. D.; Jaramillo, T. F. ChemSusChem
2015, 8 (20), 3512.

(2) Seh, Z. W.; Kibsgaard, J.; Dickens, C. F.; Chorkendorff, I.; Nørskov, J. K.; Jaramillo, T. F. Science
2017, 355 (6321), eaad4998.

(3) Hellstern, T. R.; Benck, J. D.; Kibsgaard, J.; Hahn, C.; Jaramillo, T. F. Adv. Energy Mater.
2016, 6 (4), 1501758.
Translational Electrochemistry
Authors: Baran Phil
Published: February 2020

Recent studies from our laboratory will be discussed regarding the use of synthetic organic electrochemistry to solve problems of interest to those making medicines and other useful materials.

Figure 1
Chemical Imaging of Single-Particle Photoelectrocatalysis for Energy Conversion
Authors: Mao Xianwen , Hesari Mahdi , Zou Ningmu , Chen Peng
Published: February 2020

Photoelectrochemical energy conversion represents a promising energy technology that converts solar energy to useful chemical fuels and electricity. The key component in a photoelectrochemical cell is a semiconductor material that upon illumination generates charge carriers (electrons and holes). Evaluation of the photoelectrocatalytic properties of these semiconductor materials are usually performed at an ensemble level. Here we use a single-molecule fluorescence microscopy technique to interrogate the photoelectrocatalytic process, at the single-particle and sub-particle level, of a semiconductor material with facet-dependent electronic structure. Using redox-selective probe molecules coupled with electrochemical modulation, we visualize the spatial distributions of the activities of both electrons and holes under different electrical potentials, providing for the first time quantitative information on the facet and potential dependences of charge carrier activities. Furthermore, using focused-laser beam illumination at a sub-facet level combined with theoretical simulation of charge carrier behaviors, we demonstrate intra-facet variation of important physical properties (photocurrent, incident-photon-to-current efficiency, flat band potential, quasi Fermi level) that are considered crucial performance metrics for photoelectrochemical energy devices. Our findings reveal the importance of edges in three-dimensional semiconductor crystals with facet-dependent electronic structure, opening up new opportunities in the rational design of energy materials with complex morphological and electronic properties.
Size-Dependent Electrochemistry of Silicon and Gallium Phosphide Ultramicroelectrodes
Authors: Lancaster Mitchell , Acharya Saurabh , Maldonado Stephen
Published: February 2020

Semiconductor ultramicroelectrodes have emerged as new tools for investigating charge transfer kinetics at semiconductor/electrolyte interfaces relevant to photoelectrochemical energy conversion. This presentation will report recent results describing the size- and solvent-dependent voltammetry obtained at unilluminated microscopic and nanoscopic Group IV and III-V semiconductor/electrolyte contacts. Three topics will be discussed. First, the experimental design for charge transfer measurements with semiconductor nanoelectrodes will be presented. This will include highlighting strategies to reduce the large capacitive contribution to the observed current and utilization of a flow cell-type design for non-aqueous electrochemical measurements. In addition, the method to extract heterogeneous rate constants and diode-quality factors directly from the carrier concentration-dependent voltammetric response will be reviewed. Next, a description of the size-dependent surface quality of semiconductor electrodes will be presented. Specifically, an examination of the diode quality factors at n-Si UMEs ranging from 10 um to 100 nm radius will be described. This will include discussion of the possibility for creating nominally defect-free semiconductor/electrolyte interfaces. Finally, charge transfer measurements at microscopic n-GaP/fullerene contacts will be demonstrated. Rate constants and diode quality factors of each observed redox transition will be presented, including solvent dependence on the wave position and diode quality factor. The implications of these results to verification of fundamental charge transfer theories will be detailed.
(Invited) Observation of the Marcus Inverted Region of Electron Transfer from Asymmetric Chemical Doping of Pristine (n,m) Single-Walled Carbon Nanotubes
Authors: Kunai Yuichiro , Liu Albert Tianxiang , Cottrill Anton , Koman Volodymyr , Liu Pingwei , Kozawa Daichi , Gong Xun , Strano Michael S
Published: February 2020

The concept of electrical energy generation based on asymmetric chemical doping of single-walled carbon nanotube (SWNT) papers is presented. We explore 27 small, organic, electron-acceptor molecules that are shown to tune the output open-circuit voltage (VOC) across three types of pristine SWNT papers with varying (n,m) chirality distributions. A considerable enhancement in the observed VOC, from 80 to 440 mV, is observed for SWNT/molecule acceptor pairs that have molecular volume below 120 Å3 and lowest unoccupied molecular orbital (LUMO) energies centered around −0.8 eV. The electron transfer (ET) rate constants driving the VOC generation are shown to vary with the chirality-associated Marcus theory, suggesting that the energy gaps between SWNT and the LUMO of acceptor molecules dictate the ET process. When the ET rate constants and the maximum VOC are plotted versus the LUMO energy of the acceptor organic molecule, volcano-shaped dependencies, characteristic of the Marcus inverted region, are apparent for three distinct sources of SWNT papers with modes in diameter distributions of 0.95, 0.83, and 0.75 nm. This observation, where the ET driving force exceeds reorganization energies, allows for an estimation of the outer-sphere reorganization energies with values as low as 100 meV for the (8,7) SWNT, consistent with a proposed image-charge modified Born energy model. These results expand the fundamental understanding of ET transfer processes in SWNT and allow for an accurate calculation of energy generation through asymmetric doping for device applications.

Reference: J. Am. Chem. Soc., 2017, 139 (43), 15328–15336
Lithium-Ion Battery Recycling Process Comparison
Authors: Gaines Linda , Spangenberger Jeffrey , Dai Qiang
Published: February 2020

We will need recycling facilities to handle the avalanche of batteries reaching their end-of-life, estimated to be over 20,000 metric tons from electric vehicles alone in the U.S. by 2025. Even if the batteries do find a second use (which is in question), they will eventually be unsuitable for further use and require some sort of environmentally acceptable and economically viable end-of-life handling. Disposal is not a suitable option; the batteries will need to be recycled to deliver better environmental and economic benefits. This presentation will examine barriers to recycling, compare available processes, and suggest ways to optimize the battery life-cycle.
A Closed Loop Process for the End-of-Life Electric Vehicle Li-Ion Batteries
Authors: Wang Yan
Published: February 2020

The Lithium ion (Li-ion) battery industry has been growing exponentially since its initial inception in the late twentieth century. As battery materials evolve, the applications for Li-ion batteries have become even more diverse. To date, the main source of Li-ion battery use varies from consumer portable electronics to electric/hybrid electric vehicles. In order for Li-ion batteries to be used in electric vehicles, recycling is one of the major issues. In this talk, I will discuss our efforts on lithium ion batteries in the past few years. In this project, a new technology has been developed which is capable of recovering LiNixMnyCozO2 cathode material from a hydrometallurgical process making the recycling system as a whole more economically viable. By implementing a flexible recycling system that is closed-loop, recycling of Li-ion batteries will become more prevalent saving millions of pounds of batteries from entering the waste stream each year.
Combined Experimental and Numerical Analysis of Surface-Modified Solid Oxide Fuel Cell Cathodes
Authors: Yang Tao , Lee Shiwoo , Lin Ye , Li Wenyuan , Liu Jian , Liu Xingbo , Abernathy Harry , Hackett Gregory A
Published: February 2020

In this study, the effects of surface modification on the performance of composite solid oxide fuel cell (SOFC) cathodes are investigated through a series of experiments and relevant multiphysics simulations. Experimentally, the LSM/YSZ composite cathodes of commercial fuel cells are surface-treated with various electrocatalysts, and datasets of both polarization curves and electrochemical impedance spectra are collected. The multiphysics simulations consider both charge conservation and species transportation, as well as a multi-step oxygen reduction reaction (ORR) mechanism with parallel pathways. The numerical simulations are developed and then calibrated against data from baseline cells. Based on changes in microstructural properties and rate constants, the performance of the modified fuel cells is then predicted using reaction mechanism parameters recalibrated from experimental data. Analysis is also performed to separate and quantify the effect on cell performance from the changes in microstructural properties and reaction mechanism parameters resulting from surface modification. This study provides insights into the tuning of electrochemical processes when modifying the surface of cathodes and guides further performance improvements.
Conversion Reaction Synthesis: A Versatile Route to Nanoporous Transition Metals
Authors: Coaty Christopher , Zhou Hongyao , Liu Haodong , Liu Ping
Published: February 2020

Nanoporous Metals (NPMs) are nanostructured pure metals with pores ranging from approximately 1-100 nm in diameter. They have been sought-after for their unique combinations of metallic characteristics and nanostructured size-effect properties, ranging from catalysis, plasmonics, battery electrodes to actuators. Many synthesis routes for nanoporous metals have been developed in the past 30 years, the oldest and most popular being the dealloying method. This method involves chemically or electrochemically removing the less-noble element from an alloy, leaving behind a nanoporous metal. Other techniques include combustion synthesis, block-copolymer templating, or directed assembly of metal nanoparticles.

Here, we demonstrate a scalable, room temperature synthesis method capable of producing a variety of nanoporous metal structures. Nanoporous Fe, Co, Au, Cu, Ag and Ni were formed by reacting metal-halide salts with organolithium reducing agents to form a metal/lithium salt nanocomposite. During this conversion reaction, the metal phase coalesces into an interconnected network of fine metal filaments surrounded by a lithium salt matrix. When the lithium salt is removed via dissolution in a polar organic solvent, the metal filament network remains and is an effective nanoporous pure metal (See Figure 1 for representative images). Nitrogen adsorption analysis and microscopy studies showed that these materials have high specific surface area (up to ~160 m2/g) with pore diameters ranging from 2 nm to 50 nm. This technique can also synthesize hybrid nanoporous structures of two or more metals by performing the conversion reaction on mixed precursors. Metals (e.g. Co and Cu) were found to stabilize each other when converted into a hybrid nanoporous structure, resulting in a mixed nanoporous metal with smaller pore sizes and higher surface areas than each respective element in its pure nanoporous metal form. This synthesis pathway greatly expands our access to new compositions and microstructures of nanoporous metals.

Figure 1
(Invited) Functional Metal-Organic Frameworks: From Design to Implementation
Authors: Farha Omar K.
Published: February 2020

Over the past two decades metal–organic frameworks (MOFs) have emerged as an intriguing class of solid-state materials. This has been fueled by the synthesis of thousands of discrete examples of these materials through the judicious choice of their components, inorganic nodes organic linkers. MOFs are held together by coordinate bonds which bestows MOFs with a highly attractive set of characteristics; including: (i) crystallinity, leading to precise structural determination; (ii) synthetic tunability—pore size, shape, and functionality; and (iii) porosity, MOFs possess some of the highest known surface areas and pore volumes reported to date, and can be ultramicroporous, microporous, and/or mesoporous. These characteristics give rise to new and unique physical and chemical properties that are driving researchers to investigate the suitability of MOFs in a handful of practical applications. Examples include gas storage, chemical separations, catalysis, sensing, conductivity, solar fuels conversion, light harvesting and energy conversion, and magnetic materials amongst others.
(Invited) Engineering the Bio-Interface at the Nanoscale for Diagnostics and Therapeutics Applications
Authors: Fatanat Didar Tohid
Published: February 2020

Miniaturized platforms such as micro/nano patterned interfaces and microfluidic devices provide powerful tools to study biological phenomena at micro and nano scale and to develop novel technologies for a variety of biomedical applications such as point of care diagnostics, cell sorting and dug discovery. The biological/non-biological interface system is an important cornerstone for the fabrication of biomedical devices. Platforms as diverse as lab-on-chip and point-of-care diagnostics, 3D tissue culture scaffolds, organs-on-chips and implants all rely on the effective interaction of cells and/or bio-recognition elements (proteins/peptides, enzymes, antibodies, etc.) with non-biological surfaces. An overview of our research on micro/nano-scale design of novel biomedical coatings and their integration into medical devices such as biosensors, catheters, vascular grafts as well as flexible sensing interfaces will be presented. More specifically, I will discuss our recently developed technologies for the design and development of devices with omniphobic lubricant-infused coatings that provide simultaneous repellency and targeted binding of desired biological species where bio-fouling and coagulation is minimized.
Electrochemical Assessment of Nitric Oxide Spatial Distribution at Single Organ Level in Live Zebrafish Embryos
Authors: Dumitrescu Eduard , Wallace Kenneth , Andreescu Silvana
Published: February 2020

The presence of reactive oxygen/nitrogen species (ROS/RNS) has been linked with both beneficial and harmful effects in living organisms. In order to study the role of ROS/RNS in health and disease states, there is a need to develop methods to quantify reactive species at the production site in live biological models. However, the detection of oxidative/nitrosative stress markers is a great challenge due to their low concentration, high reactivity, and short life-time. Zebrafish (Danio rerio) embryos are a powerful biological model for disease modeling and developmental studies. In this presentation we describe the development and use of electrochemical microelectrodes that allow for in vivo detection of ROS/RNS at single organ level in embryonic zebrafish, with a specific example for detection of nitric oxide (NO) as a representative nitrosative stress marker. Customized carbon fiber microelectrodes were used to assess the spatial distribution of NO along the intestine of zebrafish embryos. The electrochemical measurements were cross-validated by the use of fluorescence imaging and NO-specific pharmacological manipulations. These studies contribute to a better understanding of the role of ROS/RNS in a model of inflammatory intestinal disease.
An Advanced Magnetoelastic (ME) Sensing of Salmonella By the Improvement of Pathogen Recovery Rate Using Tween20 Modified Swabs
Authors: Liu Yuzhe , Du Songtao , Horikawa Shin , Chen I-Hsuan , Xi Jianguo , Lu Xu , Huang Tung-Shi , Chin Bryan A.
Published: February 2020

Swabbing, as an inexpensive, easy-to-use, and widely accepted sampling method, has been used to help magnetoelastic (ME) biosensing system for the surface pathogen quick detection. This paper introduced a modification method using a surfactant, Tween20, to help to improve the recovery rate of different swabs. In our previous research, swabbing substituted the direct ME sensor detection on the sample surfaces, which improved the detection area of one sensor from 0.2X1 mm2 into 30X30 mm2. This amendment altered the former surface spot measurement into a large area measurement. To improve the accuracy of this swabbing technique to a better level, a higher recovery rate is needed. Tween20, a stable and relatively non-toxic surfactant, was employed to modify the fibers of swabs so that after the pathogens are picked up, they would be easier to be released into DI water and detected by ME sensors. In this research, traditional swabs, such as cotton-tipped, rayon-tipped, and novel flocked swabs are used for comparison.
Impact of Praseodymium Content on the Structural and Sensing Characteristics of Sol-Gel Synthesized PrTixOy Sensing Films
Authors: Wang Chih-Wei , Chan Chi-Lin , Pan Tung Ming
Published: February 2020

In this paper, we developed a low-cost, simple and rapid fabrication for PrTixOy electrolyte-insulator-semiconductor (EIS) sensors by sol-gel spin-coating technique. The influence of praseodymium content on the structural properties and sensing characteristics of PrTixOy sensing membranes was explored. We used X-ray diffraction, atomic force microscopy, and X-ray photoelectron spectroscopy to examine the structural, morphological and chemical features of these films as functions of the growth conditions (Pr concentrations ranging from 0.1 to 0.3 M), respectively.The observed structural properties were then correlated with their sensing performances. The PrTixOy EIS device treated at a Pr concentration of 0.2 M with showed the best sensing characteristics, including pH sensitivity, hysteresis and drift. We attribute this behaviour to the optimal praseodymium content in the PrTixOy film forming a well-crystallized Pr2TiO5 structure and a smoother surface.
Structural and Electrical Characteristics of Oxygen Annealed ALD-ZrO2/Sion Gate Stack for Advanced CMOS Devices
Authors: Gupta Richa , Vaid Rakesh
Published: February 2020

Keeping in view the potential demands of 22 nm (and beyond) technology nodes for high-k dielectric materials, the device reliability was taken into consideration by selecting appropriate atomic scale deposition techniques and device characterization methods. This paper presents the fabrication of n-Si/ALD-ZrO2 gate stack with an ultra-thin silicon oxynitride (SiON) as an interfacial layer (IL). The problem of the gate leakage current has been resolved by post deposition annealing (PDA) of ZrO2 film ~ 11.63 nm in oxygen ambient on the silicon substrate followed by the pre-growth of SiON IL ~ 6.92 nm. The structural, morphological and film thickness studies have been performed by the characterization techniques such as XRD, AFM and FESEM respectively. Electrical characterizations such as capacitance-voltage (C-V) and current density-voltage (J-V) reveal the improved results for O2 annealed ZrO2 sample relative to the as-deposited ZrO2 sample in terms of suppressed gate leakage current (~ 2.8 × 10-8 A/cm2), increased dielectric constant (~ 33) and reduced effective oxide thickness (EOT~ 1.37 nm). Furthermore, in this paper, we will present comparative studies on types of gate stacks viz. HfO2/SiO2
, HfO2/SiON, Ar-annealed ZrO2/SiON, N2 annealed ZrO2/SiON and O2 annealed ZrO2/SiON and their comparative analysis indicates better results for O2 annealed ZrO2/SiON in terms of reduced EOT, reduced leakage current and increased dielectric constant.

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Proton Reduction Catalysis at a Modified Gallium Phosphide Photocathode Surface
Authors: MacInnes Molly , Acharya Saurabh , Lehnert Nicolai , Maldonado Stephen
Published: February 2020

Gallium phosphide (GaP) is a semiconductor with conduction and valence bands that straddle the potential of the proton reduction half-reaction and a bandgap of 2.26 eV, allowing for absorption of a significant portion of the solar spectrum and generation of a large photovoltage. These properties give GaP great potential as a photocathode material for the solar-driven water splitting reaction. However, a hurdle that needs to be overcome for the implementation of this material in photoelectrochemical cells is the large overpotential for the proton reduction half-reaction. This study investigates the pairing of cobalt bis(dichlorobenzenedithiolate) ((TBA)[Co(Cl2bdt)2]) – a molecular HER catalyst – with GaP photocathodes. (TBA)[Co(Cl2bdt)2] demonstrates good catalytic activity for proton reduction in acidic media and has previously been shown to strongly physisorb to graphitic surfaces through π-interactions. Herein is presented investigations into the physisorption of (TBA)[Co(Cl2bdt)2] to single crystal GaP wafers through a transparent, conductive graphitic thin film. Reduced graphene oxide (RGO) thin films are prepared on GaP through a novel method that is exceedingly gentle towards the underlying semiconducting material. Because of their graphitic character, these RGO films can participate in the π-interactions necessary for catalyst adsorption. X-ray photoelectron spectroscopy and electrochemistry are used to detect the presence of the catalyst on the RGO films. Photoelectrochemical experiments have been performed investigating the effects of an RGO thin film on homogeneous light-driven electrocatalysis at GaP photocathodes. Further experiments will delve into heterogeneous catalysis in which the catalyst is physisorbed to the GaP/RGO photocathode. Additionally, finite-element models of catalyzed photoelectrochemical reactions at a GaP-electrolyte interface will be discussed.
Catalytic Nanoparticles Prepared By Atomic Layer Deposition
Authors: Wang Xiaofeng , Liang Xinhua
Published: February 2020

Heterogeneous catalysts normally consist of small metal particles dispersed on a high surface area porous support. Traditional methods, such as wet-chemical processing, can produce metal particle catalysts as small as several nanometers, but these methods cannot precisely control the size of the catalytic nanoparticles and disperse them homogeneously within the porous substrates. In addition, heterogeneous catalysts cannot selectively convert specific molecules in the reactant mixture to catalyze only desired reactions. Novel approaches are required to synthesize stable metal nanoparticles catalysts with tightly controlled sizes to further advance the knowledge of their unique size-dependent catalytic behavior. Recently, atomic layer deposition (ALD) has been used to prepare highly active, highly dispersed metal nanoparticles. In this presentation, we will introduce some examples of nanostructured catalysts prepared by ALD, such as Pt nanoparticles, Ni nanoparticles, Pt-Co bimetallic nanoparticles, and CeO2 doped TiO2 nanoparticles.
Maskless Photoelectrochemical Fabrication of Anisotropic Three-Dimensional Nanostructured Semiconductors
Authors: Hamann Kathryn R , Carim Azhar I , Thompson Jonathan R , Batara Nicolas A. , Atwater Harry A , Lewis Nathan S
Published: February 2020

Binary and ternary IV-VI and II-VI semiconductor materials were photoelectrochemically deposited from aqueous precursors, yielding highly periodic nanostructured films over macroscopic square centimeter areas despite the absence of any templating agents or lithographic steps. Electro-/chemical modification was performed following deposition to tune the elemental stoichiometry of the deposits without a concomitant loss in structure fidelity nor crystallinity. The morphology of these features was controlled by the optical inputs to the deposition: extremely anisotropic lamellar-type features formed spontaneously under the presence of linearly polarized light and the periodicity of the features scaled with illumination wavelength. The deposition process was simulated using a two-step iterative model which included a finite-difference time domain method to model light absorption and a Monte Carlo method to model mass addition; these simulations matched the experimentally observed morphologies. This approach offers a method by which highly nanostructured materials that are of interest for photon-harvesting applications can be deposited in a manner that allows for self-optimization in order to maximize light absorption. This work demonstrates that photoelectrochemical deposition can be utilized to provide rapid, template-free fabrication of 3D semiconductor nanopatterns over macroscale areas for a variety of material systems. Extension of this technique to group IV materials is underway.
A Single Energy Conversion and Storage Device of Cobalt Oxide Nanosheets and N-Doped Reduced Graphene Oxide Aerogel
Authors: Sawangphruk Montree
Published: February 2020

A single hybrid energy conversion and storage (HECS) cell of asymmetric Cobalt oxide (Co3O4)//N-doped reduced graphene oxide aerogel (N-rGOAE) in 6 M KOH is proposed in this work. The Co3O4 serves as a photo-positive electrode material having an energy bang gap of 2.45 eV which can absorb all visible light region. Whilst, the N-rGOAE as a negative electrode material can balance all the charges and excited electrons from the Co3O4 positive electrode due to its interconnected three-dimensional structure with nitrogen doping. Under red LED light source (627 nm = 1.98 eV), the current densities and specific capacitances of the as-fabricated asymmetric Co3O4//N-rGOAE HECS cell are 1.4-fold higher than that under dark condition due to the photovoltaic effect. In addition, the charge storage mechanism and photo-charging behaviour of the Co3O4 electrode were also investigated by in situ electrochemical X-ray absorption spectroscopy and I-V characterization, respectively.