bluuebunny/crossref_metadata_2025 huggingface dataset:
Exploring Catalytic Traits of so4
2--Functionalized Iron Oxides Exploited to Decompose Aqueous Recalcitrant Pollutants
Authors: Kim Jongsik , Choe Yun Jeong , Kim Sang Hoon
Published: February 2020

Iron oxides are considered as ubiquitous yet valuable carriers of surface Fe2+ activators to excite H2O2, which results in the production of •OH used to decompose refractory contaminants present in H2O. To exploit catalytic nature provided by surface Fe2+ species, Fe2+ species can experience their modification by S to form S-doped iron oxide, Fe3S4, and Fe7S8, etc.1,2 For instance, we have synthesized Fe2O3 and have functionalized its surface using S species.2 The resulting S-doped Fe2O3 has manifested itself as an intriguing catalytic solid for H2O2 activation. This was because of its several benefits including 1) the incorporation of large amount of surface Fe2+ species used to cleave H2O2 via heterogeneous catalysis, 2) meso-porosity allowing for improved accessibility of H2O2 into surface Fe2+ species, and 3) chemical rigidity leading to minimized loss of Fe2+ species during H2O2 scission reactions.2 Nonetheless, surface of S-doped Fe2O3 isn't disclosed in two particular aspects of 1) H2O2 scission mechanism on S-modified Fe2+ species and 2) their catalytic functions. To answer these questions, we strategized the functionalization of Fe2O3 (pristine) surface with SO4
2- species at 300-600 °C to generate S300-S600 and investigated their surface properties using chemi-sorption/spectroscopy techniques. We then performed reaction runs under regulated environments, while using phenol as a model compound of recalcitrant compounds. Apparently, phenol degradation was directed by the characters of SO4
2- functionalities dispersed on Fe2O3 surface, whose features were markedly varied upon the change in the temperatures utilized to modify Fe2O3 surface with SO4
2- functionalities. 500 °C was required to degrade phenol in the most efficient manner among all SO4
2- functionalization temperatures studied, as showcased below. (XPHENOL and kAPP
denote conversion of phenol and reaction rate constant, respectively.) In this presentation, we will address the answers to pivotal questions detailed above. In addition, we will also highlight our efforts for clarifying catalytic roles of surface SO4
2- functionalities via a series of kinetic assessment.

References

[1] J. Kim and co-workers, Appl. Catal. B 233 (2018) 272.

[2] S. H. Kim and co-workers, Appl. Catal. B 184 (2016) 132.

Figure 1
Thin Hematite Film Based Flavin Microsensor
Authors: Tibbits Gretchen , Wall Nathalie A , Beyenal Haluk
Published: February 2020

We developed a new microelectrode with a tip made of a hematite film for the detection of flavin using pulse voltammetry. Hematite has been used as a reducing agent for many metals and an electrochemical sensor for Riboflavin, hydroquinone, and dopamine because of its excellent adsorption capacity. Potentially, a thin hematite film can be used for microelectrodes for sensor development. We prepared hematite films on a microelectrode with a carbon fiber tip. Colloidal hematite was synthesized from iron nitrate and characterized using FTIR and EDX. In addition to microelectrode work, a hematite film was deposited on to a glassy carbon electrochemical quartz crystal microbalance (eQCM) to characterize the mechanism of deposition and physical sorption in a pH range of 5-8. Lastly, electrochemical impedance spectroscopy (EIS) was used to characterize the electrochemical processes. We found that the hematite film exhibited capacitive and resistive characteristics. We also found that the hematite film microelectrode detection limit improved compared to bare carbon fiber.
Nanoarray Device for Detection of Gas Phase I2
Authors: Klavetter Kyle Christopher , Coleman Jonathan Joseph , Perez Carlos R. , Siegal Michael P.
Published: February 2020

We report on a nanoelectrode array sensor for the detection of I2 (iodine gas) at levels as low as near 0,02 ppm within tens of seconds of exposure. The sensor is constructed on a free-standing anodic aluminum oxide wafer with nanopores of 120 nm diameter and 50 um length. On each wafer surface, continuous metal films of tens of nm thickness are deposited: on one surface, a gold film is deposited such that it covers the nanopores, and, on the opposite surface, a platinum film is deposited such that the nanopores remain open and their volumes in contact with the environment. The gold film serves as the working electrode and the platinum film serves as the auxiliary and pseudo-reference electrode. The nanopores are filled with a pH 9 buffer aqueous solution to create an array of electrochemical cells in parallel, and ionic conductivity is maintained for environments with relative humidity levels greater than about 30%. The detection mechanism is the electrochemical oxidation of anionic species of I2 that form from the dissolution and subsequent hydrolysis of gas phase I2 in the pH 9 buffer electrolyte: the gas phase I2 dissolves in the buffer in proportion to Henry's Law constant and then the dissolved I2 is hydrolyzed to several species, including the anionic species iodide and tri-iodide. The detection of I2 is achieved by measuring oxidizing current during the cyclic voltammetry technique bounded between -0,2 and 0,5 V vs the Pt pseudoreference electrode. The hydrolysis mechanism of I2 in the pH 9 buffer enables the buffer to function as a concentrator for the anionic species of I2. When the sensor is exposed to a gas stream containing I2, practically continuous accumulation of the electrochemically detectable anionic species of I2 is possible, with a saturation point where the pH 9 buffer contains > 100 ppm iodide anion. For context, the sensor can detect iodide anions in pH 9 buffer at levels as low as 0,01 ppm.

Sandia National Laboratories is a multimission laboratory managed and operated by National Technology & Engineering Solutions of Sandia, LLC, a wholly owned subsidiary of Honeywell International Inc., for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-NA0003525.
Carbon Dioxide Sensing Characteristics of LaFe0.8Co0.2O3 – ZnO Thin Films: The Role of Homo and Heterojunctions
Authors: Bhowmick Tynee , Nag Sudip , Majumder Subhasish Basu
Published: February 2020

Carbon dioxide is a colourless and odourless gas and detection of carbon dioxide is critical to maintaining the quality of breathable air in the atmosphere. The current concentration of carbon dioxide in the atmosphere is 400 ppm and this concentration has increased manifold in the past 50 years or so leading to global warming and other climate phenomena.

Exposure to 2000 – 5000 ppm of carbon dioxide causes poor concentration, increased heart rate and nausea and when the concentration is > 5000 ppm, oxygen deficiency may occur. This creates an urgent need to develop sensors suitable to carbon dioxide detection. Semiconducting metal oxides such as SnO2 (n-type), CuO (p-type), ZnO (n-type) WO3 (n-type) etc. have long been considered for detecting reducing gases such as carbon monoxide, hydrogen and methane. However, such metal oxides perform poorly when it comes to carbon dioxide detection. Thus, we have proposed the formation of p-n junctions with n-type metal oxide (ZnO) and p-type perovskite (LaFe0.8Co0.2O3) that has been shown previously to aid carbon dioxide sensing. LaFe0.8Co0.2O3 (LFCO) – ZnO composite thin films have been synthesized using wet chemical synthesis in which the mol % of LFCO has been varied. The role of both homo and heterojunctions in carbon dioxide sensing can be elucidated from this configuration. This configuration is cross-sensitive to carbon monoxide and mathematical analyses has been performed to differentiate it from carbon dioxide. LFCO – ZnO thin films with a single p-n junction has also been synthesized and it has been found that this configuration is much more selective to carbon dioxide than the previous one. In addition to this, the role of LFCO – ZnO multi-layered thin films has also been explored with respect to carbon dioxide sensing.
Sandwiched Platinum Thin Film TCD for 3-Omega Technique for Detection of Ammonia Gas
Authors: Lotfi Ardalan , Navaei Milad , Hesketh Peter J
Published: February 2020

Over the past few decades, sensor technology has been revolutionized by exploring the disciplines of nanotechnology and nanofabrication process. As a result, environmental sensors including gas sensors have been miniaturized and become more advanced in the terms of sensitivity and accuracy. Todays, gas sensors can cover a broader range of volatile compounds with a limit of detection (LOD) as low as single ppm. Despite these advances, ammonia sensing is still challenging because of its corrosive nature. The chemical-based gas sensors for ammonia are not reliable due to several factors such as slow recovery time, sensor base-line drifting, vulnerability to degradation and false alarm [1]. On the other hand, physical-based ammonia sensing approaches have the advantage of fast response time and long-term durability [2].

The Thermal Conductivity Detector (TCD) limit of detection has been improved to 30 ppm by making use of the 3-omega measurement technique, however the sensor requires a robust geometrical design, and careful material selection to withstand the higher temperature during operation [3,4]. To enhance LOD further, a new design including design elements which eliminates the shortcomings in the current cantilever design. The temperature difference in the deposition process for Al203 and platinum layer causes the sensor to bend away from the silicon wafer surface, and be vulnerable to fluid velocity. Hence a supporting platinum layer has been added underneath of Al2O3 layer so that thermal stresses introduced during fabrication, and generated in operation are compensated. The new design of micro wire TCD also includes optimized shape to bear the high thermal stresses caused by continuous current needed for the 3-omega measurement technique, and a higher stability of the temperature coefficient of resistance with platinum film to improve reproducibility of response.

[1] Azad, A. M., Akbar, S. A., Mhaisalkar, S. G., Birkefeld, L. D., & Goto, K. S. (1992). Solid‐state gas sensors: A review. Journal of the Electrochemical Society, 139(12), 3690-3704.

[2] Mahdavifar, A., Navaei, M., Hesketh, P. J., Dimandja, J. D., Stetter, J. R., & McMurray, G. (2015). Implementation of a polysilicon micro electro-thermal detector in gas chromatography system with applications in portable environmental monitoring. ECS Journal of Solid State Science and Technology, 4(10), S3062-S3066.

[3]Lotfi, Ardalan, Milad Navaei, and Peter J. Hesketh. "A Platinum Cantilever-Based TCD for 3-Omega Sensing of Gas Mixtures." ECS Transactions 86.16 (2018): 79-86.

[4] Lotfi, A., Mahdavifar, A., Struk, D., Stetter, J. R., Navaei, M., & Hesketh, P. (2017). Ultimate Sensitivity of Physical Sensor for Ammonia Gas Detection Exploiting Full Differential 3-Omega Technique. ECS Transactions, 80(10), 1571-1578

Figure 1
Ion-Selective Electrode Based on Thiosemicarbazide Schiff Base As Ionophore for Pb (II) Ion Sensor
Authors: Mohan Chandra , Sharma Kusum , Kumari Sarla
Published: February 2020

Schiff bases ligands of thiosemicarbazide have received attention because of their biological and electrochemical activity as ionophore. For the present work, Schiff base was synthesised with thiosemicarbazide and thiophene-2 aldehyde in ethanol solvent. Pb (II) ion-selective electrode has been developed by using synthesized Schiff base ligand as ionophore in PVC matrix. This ISE was tested with various parameters such as slope of potential curve, linear response, effect of pH, selectivity and respose time etc. The prposed sensor can be used over a wide concentration range (1.0 ×10–7 to 1.0 ×10–2 M) for lead(II) with a slope of 29.4 ± 0.1 mV decade–1. It has releatively fast reasponse time (<10 s) with high selectivity in presence of various foreign ions. This ISE showed best performance with a membrane composition of PVC: DOP: Ionophore: NaTPB as 33: 59: 3.4: 4.6 (w/w %). The detection limit of the electrode was approximately 4.0 × 10–8 M and the electrode works well in the pH range of 2.4–8.0. The proposed electrode has found application as an indicator electrode for potentiometric titration of Pb(II) with EDTA. It can also be employed for the determination of Pb(II) ions in various wastewater samples.

Figure 1
(Invited) Interfacial Charge-Transfer Excitation at an Anatase-Rutile Junction: A Hypothesis
Authors: Ohtani Bunsho , Shen Yang , Nitta Akio , Takashima Mai
Published: February 2020

Titania, the most widely used metal oxide for photocatalytic applications, is categorized into semiconductor based on its electronic energy structure, and therefore its band structure, which must impact on the physicochemical properties of titania, is very important. We have developed a novel method for identification and characterization of metal-oxide powders with energy-resolved distribution of electron traps (ERDT) measured by reversed double-beam photoacoustic spectroscopy (RDB-PAS) [1,2]. In this study, ERDT patterns of anatase and rutile titania powders as well as their mixtures were measured and analyzed to elucidate the actual position of valence-band of two kinds of crystallites.

Figure 1 shows ERDT patterns of ST-21 (anatase), ST-G1 (rutile) and their thoroughly brayed 50/50 mixture as well as simulated patterns by summing up to ST-21 and ST-G1 patterns with and without lower-side energy shift (ΔE = 0.19 eV) of the former. The degree of coincidence in the ERDT-pattern shape of observed and simulated mixtures, ζ, was calculated by changing ΔE to obtain the maximum ζ, 0.70, at ΔE =0.19 eV. If valence-band (VB) electrons are excited to ETs during RDB-PAS process independently in two titania samples, the mixture may give an ERDT pattern as simple summation. The results suggest that interfacial electron excitation from VB of ST-G1, which is slightly higher than that of ST-21, to ETs in ST-21. As has been already claimed that energy of ETs measured as energy from VBT in the ERDT patterns might be overestimated and electrons in a high-DOS part of VB (h-DOS(VB)), not VBT of the least DOS, are excited to ETs [1,2]. The above mentioned consideration may suggest that h-DOS(VB) of rutile is ca. 0.19 eV higher than that of anatase.

Thus, RDB-PAS analysis of ERDT patterns of mixtures of different titania samples is a novel method to clarify the relative band position of semiconducting metal oxides such as titania.

[1] A. Nitta, M. Takase, M. Takashima, N. Murakami, B. Ohtani, Chem. Commun., 52, 12096–12099 (2016).

[2] A. Nitta, M. Takashima, N. Murakami, M. Takase, B. Ohtani, Electrochim. Acta, 264, 83–90 (2018).

Figure 1
(Invited) Multifunctional Nanoplatforms for Biomedical Applications
Authors: Ma Dongling
Published: February 2020

Near-infrared (NIR) absorbing and emitting nanomaterials attract significant attention in bioimaging, which shows great potential for disease detection due to its high sensitivity at the subcellular level and low cost of related imaging facilities. However, currently available optical probes are mainly based on visible-emitting materials. The tissue-induced optical extinction and autofluorescence in the visible range result in limited penetration depth and ambiguous photoluminescence signal, which restricts their in vivo use. To address this issue, photoluminescent probes, with both absorption and emission wavelengths operating in the biological windows in the NIR range, in which tissues are optically transparent, are highly desired. Their integration with superparamagnetic nanomaterials to make a multifunctional platform further opens a wide range of promising applications, including bimodal imaging (photoluminescence and magnetic resonance imaging), synergistic hyperthermia (magnetothermal and photothermal), magnetic confinement of trace amounts of biospecies for ultra high-sensitivity biodetection, etc. In this talk, I will present our most recent work on the synthesis of NIR-emitting water soluble, stable core/shell/shell quantum dots (QDs) and multifunctional (NIR photoluminescent and superparamagnetic) nanoparticles and their use in biomedicine. For instance, in one case, multifunctional particles contain single superparamagnetic nanoparticles as cores and NIR-luminescent nanomaterials as shells. In another case, the multifunctional nanoplatform is compose of multiple superparamagnetic nanoparticles and NIR quantum dots in single particles. These different types of multifunctional particles are designed for different biomedical applications.

References: [1] ACS Nano 2018, accepted; [2] Adv. Funct. Mater. 2018, 1706235 (Inside Back Cover).
(Invited) Self-Powered Sensors Employing Biofuel Cells: Wearable and Ingestible Bioelectronics
Authors: Jeerapan Itthipon , Wang Joseph
Published: February 2020

Biofuel cells (BFCs), as energy harvesters, can be used as self-powered biosensors, simplifying sensing systems by minimizing power-consuming units. Such a unique feature allows two‐electrode BFC-based electrochemical biosensors to operate without externally applied voltage, which enables the miniaturization and convenient configuration of biosensors that traditional biosensors cannot offer. We have pioneered textile-based BFCs as highly stretchable self-powered sensors for wearable systems; these can autonomously extract the electrical power from perspiration to probe the sensing of metabolites, including glucose and lactate. Such BFCs with judicious serpentine designs are fabricated using screen-printing of nanomaterial-based engineered stress-enduring inks. Successful applicability to sock-based self-powered lactate biosensors with real-time wireless communication was also demonstrated on the human subject. These biodevices will contribute to the development of skin-worn energy harvesting systems, non-invasive sensors, and smart textiles. Furthermore, in order to expand a new spectrum of self-powered biosensors, we have demonstrated the first example of an edible ethanol BFC, based solely on highly biocompatible mushroom/plant extracts and food-based materials without any additional external mediators. The BFC anode and cathode materials consist of biocatalyst-rich mushroom and plant tissues, along with dietary charcoal and vegetable oils. These edible energy-harvesting BFCs hold great promise for revolutionizing ingestible bioelectronics and smart self-powered sensors for monitoring health and the digestive system.
(Invited) Using Fast Scan Cyclic Voltammetry to elucidate the mechanism of action of Deep Brain Stimulation
Authors: Lee Kendall H
Published: February 2020

Deep Brain Stimulation (DBS) is now an established neurosurgical therapy for variety of neurologic and psychiatric disorders. Investigations into the mechanism of action of DBS, using electrochemical recording techniques such as Fast Scan Cyclic Voltammetry (FSCV), has now demonstrated that DBS evokes release of neurotransmitter, including dopamine and adenosine depending on sites of stimulation. FSCV has been an established method for investigating neurochemical changes in animal models and is emerging as a potential method for monitoring neurotransmitter systems in humans undergoing DBS. At the Mayo Clinic, we have developed the WINCS (Wireless Instantaneous Neurotransmitter Concentration Sensing) system and its successor WINCS-Harmoni, a next generation device capable of combining brain stimulation with real-time neurochemical recording in vivo. Recently, we have also developed a novel technique termed multiple cyclic square wave voltammetry (M-CSWV) for quantifying tonic DA concentrations in vivo, which uses cyclic square wave voltammetric waveforms in conjunction with a delayed holding potential period to control adsorption. Here, a review of the technology development of WINCS and the use FSCV for elucidating the mechanism of action of DBS will be presented.
(Invited) Understanding Downstream Risk from Lithium-Ion Battery Thermal Runaway & Designing for Safety
Authors: Spray Ryan , Barry Michael , Vickery James
Published: February 2020

As battery technologies continue to advance, batteries are being placed in an increasing number of consumer products and being used for energy storage applications from microelectronics to the grid scale. Because of the high energy density in a battery, the sudden, unintended release of stored energy can have significant negative consequences. Consumer products are often in close proximity—and are even sometimes attached—to people, and large energy storage systems may be supporting critical infrastructure. Manufacturing variation (both within one supplier’s processes and between different suppliers producing “identical” batteries / cells) can lead to variations in the conditions under which the onset of thermal runaway occurs as well as the differences in the resultant evolved gases.

In this study, we subject lithium-ion cells produced by different commercial manufacturers to the same abuse conditions via external heating in both adiabatic (accelerating rate calorimetry or ARC) and non-adiabatic conditions. We examine the behavior of the cells during these abuse conditions, and analyze the volume and composition of the gases evolved due to thermal runaway in order to investigate potential differences in severity and/or mitigation strategies. Additionally, the potential effects of inert atmosphere on the failure severity will be evaluated. The general implications of this work as it relates to assessing hazards and designing for safety will be discussed.
Safety Assessment of Solid State Batteries
Authors: Masias Alvaro , Tawfik Samar , Sakamoto Jeff
Published: February 2020

The ubiquitous growth of personal electronics and increasing introduction of electrified vehicles have been enabled by continuous improvements in batteries. The state of the art technology, lithium ion, has evolved steadily since its introduction in 1991 with specific energy rising from 100 to 250+ Wh/Kg while costs have declined. However it is likely that more dramatic advancements in energy and cost (while maintaining high levels of safety) are necessary to enable the widespread adoption of electrified vehicles.

One of the leading candidates for next generation battery technology is the solid state (SS) battery in which the liquid electrolyte and thin film separator are replaced by an ionically conducting solid. By replacing the flammable electrolyte with a non-flammable ceramic, glass or polymer, it is generally assumed that safety may be enhanced. However, the addition of highly reactive lithium metal and potentially brittle separator materials can introduce new safety hazards. In this context a broad safety assessment of lithium metal solid state batteries is performed against existing international battery safety test standards and regulations.
Varying Thermal Runaway Mechanism Caused By Fast Charging for High Energy Pouch Batteries
Authors: Li Yalun , Feng Xuning , Ren Dongsheng , Ouyang Minggao , Lu Languang
Published: February 2020

Increasing charging rate is usually considered as safety issue inducements for lithium-ion batteries, especially for high energy batteries with thick electrodes. However, the interaction mechanism between charging rate and safety behavior still needs to be further explored.

In this work, thermal runaway process of commercial NMC532/graphite pouch cells are compared after undergoing increasing charging rates, and decreasing trends of self-heating temperature, onset temperature and maximum temperature are observed, which poses potential danger for battery applications after fast charging. Through the ARC test of corresponding card cells and DSC test of active materials, it was found that the full cell’s characteristic temperature of thermal runaway evolution and active energy of the self- heating process under high charging rate are similar to the reaction between anode and electrolyte, while those under low charging rate are similar to the reaction between cathode and anode. Moreover, the thermal runaway behavior at middle charging rate is influenced by both reactions simultaneously. Under condition where reaction between anode and electrolyte is the dominant factor of thermal runaway process, the lithium plating which discovered on the graphite surface, is found to trigger the strongly exothermic reaction around 110℃ and heat the cell to thermal runaway. It was concluded that the thermal runaway mechanism changes from cathode and anode reactions to anode and electrolyte reactions after batteries are fast charged.

This work will help researchers understand more about the principle of thermal runaway process under different charging rates, and develop more reasonable charging profiles for high energy batteries avoiding deteriorated battery’s safety performance.

Figure 1
Chemically-Engineered Host Materials Enabling Safe Sodium Metal Anodes
Authors: Wang Chuanlong , Wang Huan , Luo Jianmin , Li Weiyang
Published: February 2020

As an anode material, sodium (Na) metal is the most promising alternative for lithium for the next‐generation energy storage systems. Nevertheless, its practical implementation is impeded by the huge volume change and severe Na metal dendrite growth during electrochemical stripping/plating. Herein, the employment of chemically-engineered porous copper (Cu) and titanium carbide (Ti3C2) MXene as stable host for metallic Na anode is presented. By treating the commercial Cu foam through a facile and cost‐effective method, a composite matrix consists of cylindrical core–shell skeleton is achieved, facilitating uniform impregnation and confinement of Na within the matrix pores promoted by the chemical interaction between Na and the matrix. While by treating Ti3C2 via a facile cetyltrimethylammonium bromide prepillaring followed by subsequent Tin cation (Sn2+) pillaring, a Sn2+ pillared Ti3C2 MXene matrix is obtained, guiding the Na nucleation/growth within the matrix interlayer space and contributing to uniform Na deposition facilitated by the chemical interaction between Na and Sn-based nanocomplexes encapsulated within the MXene layers. The unique characteristic of the chemically-engineered host materials can well accommodate hostless Na+, suppressing the volume change and mossy/dendritic Na growth during cycling. A stable Na cycling behavior is demonstrated in carbonate electrolyte without any additives at a high capacity up to 3 mAh/cm2 with a current density up to 2 mA/cm2. While in ether electrolyte, a stable Na performance at a high capacity up to 5 mAh/cm2 along with a high current density up to 10 mA/cm2 is achieved. Furthermore, electrochemical measurements of a full cell made of the Na composite matrix anodes clearly reveal the superior performance over that using bare Na metal. We believe that our approach provides facile approaches to the fabrication of stable Na metal anodes for high‐energy Na‐based batteries, and could be a viable strategy for other metallic anode systems.[1,2]

Reference：

[1] C.Wang, H. Wang, E. Matios, X. Hu, W. Li, Adv. Funct. Mater, 2018, 28, 1802282.

[2] J. Luo, †
C. Wang, † H. Wang, X. Hu, E. Matios, X. Lu, W. Zhang, X. Tao, W. Li, Adv. Funct. Mater, 2018, 1805946.

Figure 1
(Invited) Large Low Temperature Thermoelectric Power Factor from Nanostructured Carbon-Based Nanocoatings
Authors: Grunlan Jaime
Published: February 2020

In an effort to create a paintable/printable thermoelectric materials, comprised exclusively of organic components, polyaniline (PANi), graphene, and double-walled carbon nanotubes (DWNT) were alternately deposited from aqueous solutions using the layer-by-layer assembly technique. Graphene and DWNT are stabilized with an intrinsically conductive polymer, poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS). A 1 µm thick film, composed of 80 PANi/graphene-PEDOT:PSS/PANi/DWNT-PEDOT:PSS quadlayers (QL) exhibits electrical conductivity (σ) of 1.88 X 105 S/m and a Seebeck coefficient (S) of 120 µV/K, producing a thermoelectric power factor (S
2∙σ) of 2710 µW/(m∙K2). This is the highest value ever reported for a completely organic material measured at room temperature. Furthermore, this performance matches or exceeds that of commercial bismuth telluride. Air-stable n-type organic thermoelectric nanocomposites were achieved by depositing layers of double-walled carbon nanotubes (DWNT), stabilized with polyethylenimine (PEI), and graphene oxide (GO) in a layer-by-layer fashion from aqueous solutions. A 30 bilayer film (~ 610 nm thick), comprised of this DWNT-PEI/GO sequence, exhibits electrical conductivity of 27.3 S/cm and Seebeck coefficient of -30 µV/K, producing a power factor of 2.5 µW/(m∙K2). Low temperature thermal reduction (150 °C for 30 min) of this composite thin film significantly improves its thermoelectric performance. An electrical conductivity of 460 S/cm and Seebeck coefficient of -93 µV/K are achieved. A 30 BL DWNT-PEI/reduced graphene oxide (rGO) film (~480 nm thick) exhibits a power factor as large as 400 µW/(m∙K2), which is one of the highest values reported for an organic n-type material. The combination of water-based processing, air stability and high power factor is a major step toward producing efficient thermoelectric devices on flexible substrates (e.g. textiles for clothing). For the first time, there is a real opportunity to harness waste heat from unconventional sources, such as body heat to power devices in an environmentally-benign way.

Figure 1
(Invited) Tailoring Mesoporous Carbons and Related Materials for Energy-Storage and Energy-Conversion Applications
Authors: Dai Sheng
Published: February 2020

Carbon materials are ubiquitous in catalysis, separation, and energy storage/conversion. The creation of well-defined carbon architectures is essential for a number of the aforementioned applications. Recently, we have developed several methods for the synthesis of carbon materials with controlled mesostructures and compositions. The mesostructures of these carbon materials are highly stable and can be further tailored via graphitization and surface functionalization for energy-storage and energy-conversion applications. This presentation will be focused on our recent development in (a) self-assembly approaches to the preparation of carbon composite materials for controlling mesostructures and morphologies and (b) surface modification techniques to control the interfacial chemistry of carbon materials for energy-storage and energy-conversion applications.
(Invited) Correlations in Photon Emission from Neutral and Charged Exciton States in Functionalized Carbon Nanotubes
Authors: Högele Alexander
Published: February 2020

Covalently functionalized carbon nanotubes support localized excitons with a discrete photoluminescence spectrum and single photon emission statistics [1,2]. The spectrum of hexyl-modified nanotubes features two distinct photoluminescence bands attributed to neutral and charged configurations of exciton-localizing sp3-defects [3]. Here we report correlations in photon emission events by the respective states of neutral and charged defect-trapped excitons, and explain the observations in the framework of different exciton manifolds that compete for the photogenerated population.

[1] X. Ma, N. F. Hartmann, J. K. S. Baldwin, S. K. Doorn, and H. Htoon, Nat. Nanotechnol.10, 671 (2015).

[2] X. He, N. F. Hartmann, X. Ma, Y. Kim, R. Ihly, J. L. Blackburn, W. Gao, J. Kono, Y. Yomogida, A. Hirano, T. Tanaka, H. Kataura, H. Htoon, and S. K. Doorn, Nat. Photon. 11, 577 (2017).

[3] H. Kwon, M. Kim, M. Nutz, N. F. Hartmann, V. Perrin, B. Meany, M. S. Hofmann, C. W. Clark, S. K. Doorn, A. Högele, and Y. Wang, submitted.
The Ability of PVD Chromium (III) Oxide Films to Inhibit the Corrosion-Driven Cathodic Delamination of Organic Coatings from the Surface of Mild Steel
Authors: McMurray Hamilton Neil , Wint Natalie , de Vooys Arnoud C.A. , Warren David
Published: February 2020

This paper describes a systematic study into the role of metallic chromium and chromium (III) oxide films of varying thickness in slowing or preventing the corrosion-driven cathodic disbondment of an organic overcoat applied to chromium/oxide coated steel. A graded wedge of chromium metal or chromium (III) oxide is applied to a steel substrate using physical vapour deposition (PVD) in conjunction with a stepping motor driven sliding shutter arrangement. An overcoat of electrically insulating polyvinyl butyral (PVB) lacquer is then applied and this acts as model organic coating. Corrosion is initiated from an artificially created coating defect, penetrating to the steel substrate, though the introduction of an aqueous sodium chloride electrolyte. Scanning Kelvin probe (SKP) potentiometry is then used to follow the resulting kinetics of PVB coating delamination in air at high relative humidity. The variation in layer thickness across the PVD wedge allows for a high-throughput investigation of the effect of the layer thickness for both metallic chromium and chromium (III) oxide on the rate of corrosion driven cathodic coating delamination, as shown schematically in the figure below. Varying chromium metal layer thickness between 100 nm and 1000 nm produced very little change in the rate of PVB film delamination and the delamination kinetics remained parabolic throughout. Parabollic kinetics are consistent with rate limitation by the mass transport of (sodium) cations through electrolyte layer forming beneath the delaminated coating. Conversely, increasing the thickness of chromium (III) oxide from 10nm to 200 nm (applied over a 500 nm metallic chromium layer), resulted in a significant decrease in rates of PVB delamination. At chromium oxide layer thicknesses ≥ 120 nm delamination kinetics became linear (zero order with respect to time). Linear kinetics are consistent with rate limitation by cathodic electron transfer to oxygen across the chromium (III) oxide layer. For chromium (III) oxide thicknesses of 200 nm PVB delamination was prevented over the entire 48 hour experimental time period. This level of inhibition is comparable to the protection provided by electroplated hexavalent chromium/ hydrated chromium oxide (ECCS) material used in packaging steel products. These finding indicate the ability of PVD to produce corrosion resistant coatings of controlled thickness and composition and provides relevant information regarding the likely relative importance of metallic metal and chromium (III) oxide in potential alternatives to coatings produced using hexavalent chromium.

Figure I. Schematic representation of: a) the process by which a wedge of chromium metal or chromium (III) oxide is formed using a sliding shutter mechanism and b) how the PVB overcoated wedge sample is oriented with respect to the cathodic delamination cell.

Figure 1
Stability of Fluorine Doped Tin Oxide (FTO) Coated Substrates Under Extreme Polarization Conditions
Authors: Korjenic Alen , Raja Krishnan S.
Published: February 2020

Fluorine doped tin oxide (FTO) is a transparent conducting oxide which is widely used in different applications ranging from sensors, digital displays, smart window coatings, catalysts supports, and electrode substrates for various electrochemical applications. The FTO coated glass slides were evaluated for their chemical stability in different pH solutions at room temperature by carrying out potentiodynamic polarization and cyclic voltammetry (CV). Accelerated stress tests were carried out in 0.1 M HCl and 0.1 M NaOH solutions by scanning the potential from -2 V to 2 VRHE at a scan rate of 1 V/s. Ex-situ vibrational spectroscopy and in-situ photo absorption spectroscopy were carried out to evaluate the material degradation when electrochemically polarized.

The FTO was more stable in 0.1 M HNO3 and 0.1 M NaCl solutions under both anodic and cathodic polarization conditions. Oxygen reduction reaction (ORR) and hydrogen evolution reaction (HER) were the cathodic reactions observed during cathodic polarization of the FTO. The activity of FTO for HER was higher in the acidic solutions than that in the neutral or alkaline solutions. Cathodic polarization in 0.1 M HCl solution resulted in a reduction of SnO2 to lower valent species. The semiconductivity of FTO, which was n-type at low anodic potentials, was p-type at high anodic potentials possibly due to the formation of a SnO-type surface layer by the removal of lattice oxygen during the oxygen evolution reaction. Cyclic stability of the FTO was evaluated by conducting CV between -2.0 and vbn 2.0 VAg/AgCl at 1 V/s. Intergranular corrosion was observed and the stability was completely lost after 215 cycles in the 0.1 M HCl solution, as seen in Fig. 1. The stability of FTO was better in the 0.1 M NaOH solution, wherein the electro-catalytic activity degraded after 500 cycles, the electrical connectivity was maintained even after 4500 cycles.

Figure 1
(Invited) Negative Capacitance III-V FinFETs for Ultra-Low-Power Applications
Authors: Chang Edward Yi , Luc Quang-Ho , Tran Nhan-Ai , Lin Yueh-Chin
Published: February 2020

Owing to its superior carrier transport, InxGa1-xAs materials are considered as the potential n-channels to replace Si for future CMOS technologies beyond the 7-nm technology node. Negative capacitance (NC) FETs with steep SS characteristics are extensively studied to lower the supply voltage (Vdd) for ultra-low-power applications. NC effects can be realized by using ferroelectric (FE) materials in the dielectric gate stack. Among the variety of FE materials, hafnium zirconium oxide (HfZrOx-HZO), which can be employed by atomic layer deposition (ALD) technique, is well-known as the most CMOS-compatible material. There have been various reports that show steep switching behaviors by applying HZO materials on both Si and Ge channels. Recently, NC InGaAs MOSFETs with FE HZO have been presented for steep subthreshold slope (SS) behaviors. However, NC effects have not been presented for nonplanar InGaAs FinFETs yet. In this work, we demonstrate NC In0.53Ga0.47As FinFETs with ferroelectric FE HZO as gate dielectric, exhibiting bi-directional sub-60 mV/dec (SS) at room temperature, for the first time. We show minimum SSrev of 23 and SSfor of 34 mV/dec on InGaAs NC FinFETs with 5 nm HZO thin film. III-V NC FinFETs with HZO FE materials can be very promising for extremely high performance and ultra-low-power CMOS applications.
Electro-Assisted Recycling of Lithium Ion Batteries
Authors: Diaz Luis A. , McNally Josh S. , Klaehn John R. , Gao Ningshengjie , Dufek Eric J. , Jones Michael , Adhikari Birendra , Lister Tedd E.
Published: February 2020

The fast growth of the electric vehicle (EV) market is generating increasing anxiety regarding the sources and availability of minerals required to meet with a growing demand for lithium ion batteries (LIBs). Critical elements (lithium, cobalt, and graphite) are crucial to sustain the manufacturing of a growing EV market as well as thriving wireless demand. However, the geographical concentration of mining and refining of cobalt and graphite constitute a supply chain risk for the global production of LIBs. This is driving technical development, which in turn, is leading to a dynamic change in battery chemistry. Lithium sources are more diverse in nature and geographical distribution, and current lithium reserves are enough to cover projected scenarios within the next twenty years. Nevertheless, the main question is whether the extraction technologies can keep up with the pace of market growth for EV.

Interest in LIBs recycling is surging as a path to a circular battery economy and supply chain stabilization for critical materials on LIBs. Industrial processes for the recycling of LIBs are already operating around the world. However, these processes are almost exclusively focused on the recovery of Co, Ni and Mn from battery cathodes as the most valuable metals in the LIBs. Hydrometallurgical processes have been proposed for a comprehensive recovery that includes lithium and graphite, but the high operating costs and intensive chemical consumption do not support a cost-effective recovery of Li at industrial level.

To target this issue, an electro-assisted reduction technology, based on the use of electrons as green reagent, has been proposed for the extraction and recovery of critical materials from LIBs. Through this process, high extraction efficiencies (>98%) can be achieved at solid to liquid ratios up to 120 g/L and in a peroxide free environment. The process is suitable to different battery chemistries and allows for the recovery of graphite as bi-product. A description of the process, as well as a flowsheet, that describes a comprehensive recovery for different value streams will be discussed.
Percolation Behavior in Catalytic Porous Material
Authors: Alofari Karrar Takleef , Medici Ezequiel , Tajiri Kazuya , Allen Jeffrey S
Published: February 2020

Proper water management in Polymer Exchange Membrane (PEM) fuel cell is important to achieve high performance. Understanding the percolation of the produced water at the cathode catalyst layer (CL), is critical for any robust water management technique. The CL consists of a complex structure to allow reactants to pass through and reach the reaction catalyst site. The complex structure is made by a support structure (mostly carbon) that allows the transport of electrons, an ionomer that conducts protons, and voids that have the double role of oxygen breathing and exit paths for the generated water. In this work, a pseudo-Hele–Shaw experimental setup is used to investigate immiscible fluid displacement inside the CL under controlled conditions. Since water can be retained by ionomer, making it swell and caused a shift in the pore size distribution, fluor-inert is used as a working fluid. The evolution of percolation pressure and the projected area of the injected fluid are recorded simultaneously. Preliminary results show a high consistency in the measured data at high flow rate percolation. However, at low flow rate there is some variation in the data due to relative humidity effect. The experimental data is considered as an input to the (Ce-t^*) scale. This scaling has been previously developed (Medici & Allen, 2011) to study two phase flow in thin porous layers. The dimensionless energy scale (Ce) based on the ratio between the injected and dissipated energies. The other dimensionless time scale (t^*) is arises from the important of the time of percolation, where in capillary regime is in order of hours while in stable displacement is in order of minutes, so it characterizes the relative effects of viscous and capillary effect. This scaling collapses transient pressure and saturation to a linear, non-dimensional and unique correlation for each material.
Tailored Catalyst Layer and Micro-Porous Layer Porosity and the Effect on the Performance and Water Content in PEMFC
Authors: Mohseninia Arezou , Kartouzian Dena , Wilhelm Florian , Markötter Henning , Scholta Joachim , Manke Ingo
Published: February 2020

In this study, the effect of the catalyst layer (CL) and the cathode microporous layer (MPL-C) porosity on the performance and water content of the polymer electrolyte membrane (PEMFC) is investigated. Monodispersed polystyrene (PS) particles are used as pore formers to fabricate CL and MPL with different degrees of porosities. Specially developed miniature Single single cells for neutron imaging experiments with an active area of 8 cm² are implemented with the in-house made catalyst coated membranes and cathode MPLs. The cathode MPLs were coated on a 29 BA substrate, and commercial 29 BC SGL were used on the anode side as the gas diffusion layers (GDLs). Neutron tomography is used to investigate the water content and distribution inside the operating fuel cells. The quantitative analysis of the water thickness under the channels of the cells at RH=120% and I=1 A.cm-2 is shown in figure 1.a.

It is observed that the water content has decreased for cell 3 ( CL: 10 wt.% PS, MPL: 10 Vol.% PS) compared to cell 2 ( CL: 5wt.% PS, MPL:10 Vol.% PS) and cell 1 (Reference CL and MPL (without PS)). Polarisation curves for these three cells are provided in Figure 1.b. At current densities higher than I=1 A.cm-2 performance has increased for cell 2 and 3 where the components had higher porosity degree compared to the cell 1 which has a reference CL and reference cathode MPL. The results show that addition of macropores could facilitate the transport of gases and the removal of water at the mass transport regions. This method is currently under investigation by the authors. Further results will be provided in the presentation.

Figure 1
Carbon Effect on the Synthesis and MEA Performances of L10 CoPt Intermetallic Catalysts
Authors: Wang Chenyu , Li Dongguo , Kim Yu Seung , Spendelow Jacob S
Published: February 2020

Incorporation of base metals to carbon supported Pt catalysts is known to enhance oxygen reduction reaction (ORR) activity. Therefore, Pt-base metals random alloys, such as Pt-Co, are often applied as cathode catalysts in proton exchange membrane fuel cells (PEMFCs). However, poor stability of Co under oxidative and acidic conditions makes the enhancement limited during long-term fuel cell testing. Recently, we have developed a robust method to prepare L10 ordered CoPt catalysts that exhibit superior fuel cell performances compared with the random alloy counterpart. In this systematic study, we observed that carbon supports impose strong effects not only on the growth of CoPt L10 intermetallic nanoparticles but also on the fuel cell performances.

Solid carbons, including Vulcan other highly graphitized carbons, have moderate surface areas and relatively higher degree of graphitization. CoPt L10 intermetallic particles prepared such type of carbons usually have a large size distribution. But their fuel cell performances are still desirable, showing high current densities at low voltages and less carbon corrosion. Moreover, we found that surface functionalization can improve the size distribution and dispersion of nanoparticles, thus improving the fuel cell performances. In parallel, porous carbons of high surface areas were also applied as the supports for depositing CoPt L10 intermetallic nanoparticles. Different from the particles on surface of solid carbons, a large number of nanoparticles are located in the micropores of porous carbons. These nanoparticles can maintain their small particle size and a narrow size distribution after heat treatment. CoPt L10 intermetallic nanoparticles on porous supports exhibit excellent performances at high voltage end in fuel cell testing.