bluuebunny/crossref_metadata_2025 huggingface dataset:
Robust Diamond Electrodes for Electrochemical Applications
Authors: Ensch Mary , Rusinek Cory Allen , Becker Michael , Rechenberg Robert , Hardy Aaron , Wehring Bettina , Schuelke Thomas
Published: February 2020

With one of the widest potential windows of any solid electrode material, boron doped diamond (BDD) has proven excellence as an electrochemical tool. From water treatment and chemical synthesis to electrochemical analysis and sensing, BDD has applications in a variety of sample media. This combined with its’ stability, low background current, and low double layer capacitance make BDD specifically useful in trace detection, such as the determination of toxic heavy metals and polycyclic aromatic hydrocarbons (PAHs) in water. We have developed several BDD electrode technologies, each tailored to a specific electroanalytical application. With a Nafion coated BDD optically transparent electrode (OTE) we engineered a fluorescence based spectroelectrochemical sensor for a common PAH, 1-hydroxypyrene, achieving a detection limit of 80 nM (17 ppb). With this, we fabricated BDD microelectrode arrays (MEAs) for the detection of toxic heavy metal ions where we obtained parts-per-trillion (ppt) detection limits for lead (Pb) using measurements taking no longer than 2 minutes. We also designed and produced BDD rod electrodes for general electroanalytical applications. These BDD rod electrodes exhibit superb electrochemical redox processes where we observed peak separations of 65 mV or less in cyclic voltammetry (CV) of potassium ferricyanide, K3Fe(CN)6. Lastly, we developed BDD electrode stacks for electrochemical oxidation processes including, general TOC/COD reduction, perfluoroalkyl substance (PFAS) degradation, and ammonia (NH3) removal. Near complete removal of PFAS and NH3 from wastewater samples­ was observed. This work further exemplifies BDD as an excellent electrode material while broadening its’ sensing applications and electrochemical capability.

Figure 1
Reduction in Diameters of Copper Nanowires Due to Low Energy Hydrogen Ions Beam Irradiation-Induced Sputtering Phenomenon
Authors: Honey Shehla , Morgan Madhuku , Ahmad Ishaq , Maaza Malik , Naseem Shahzad
Published: February 2020

Copper nanowires (Cu-NWs) are leading contenders to replace indium tin oxides (ITOs) based traditional transparent conducting electrodes from the market due to their high mechanical flexibility and low-cost. In this work, Kilo-electron-volt (KeV) hydrogen (H+) ions beam irradiation-induced reduction in diameters of Cu-NWs is examined through transmission electron microscope (TEM) and scanning electron microscope (SEM). The reduction in diameters of Cu-NWs is found to occur via H+ ions beam irradiation-induced collision cascade of atomic displacements mechanism lead to continual reorganizing Cu atoms in individual Cu-NWs lattices. Formation of defect clusters or loss of crystal structure is not found in x-ray diffraction (XRD) patterns due to H+ ions beam irradiation. These experimental findings may potentially be applied to enhance spaces between NWs in complex Cu-NWs meshes for application as transparent conducting electrodes. Moreover, this study has also significance in exploring the possibility for application of Cu-NWs meshes based optoelectronic devices in harsh environment containing plenty of H+ ions such as for use in spacecrafts for upper space missions.
Effects of Oxide Composition of Amorphous RuO2-Ta2O5 Catalyst on Electrochemical Sensing to Hydrogen Carbonate Ion
Authors: Iketani Chinami , Honda Ai , Morimitsu Masatsugu
Published: February 2020

Hydrogen phosphate (HPO4
2-) and hydrogen carbonate (HCO3
-) ions are major in environmental water and blood, and the quantification is normally carried out by molybdenum blue method for HPO4
2- and by titration method or the gas analysis of blood for HCO3
-, while no quantitative method by electrochemical sensing has been developed. We have recently reported that these ions can be detected and quantified by electrochemical oxidation with the novel catalyst, amorphous RuO2-Ta2O5 mixed oxide, prepared by thermal decomposition [1,2]. For practical uses of the amorphous oxide catalyst for the detecting electrode, it is important to know the effects of the oxide composition of the catalyst to the sensitivity and selectivity to HCO3
- and HPO4
2-. In this paper, we studied the sensing properties to these ions with RuO2-Ta2O5 catalysts prepared at different compositions.

RuO2-Ta2O5 catalysts were prepared by thermal decomposition of a precursor solution containing Ru (III) and Ta (V) painted on a titanium disk. The Ru:Ta mole ratio was 20:80, 30:70, 50:50, or 80:20, and thermal decomposition was carried out at 260 oC. The characterization of the oxide coating was done with XRD, SEM, and EDX. Electrochemical measurements were performed with a conventional three-electrode cell with KCl-saturated Ag/AgCl reference electrode and 50 mmol/L KCl solutions with or without various concentrations of KHCO3 or Na2HPO4. Cyclic voltammetry was carried out to analyze the oxidation reactions of these ions, and chronoamperometry was also used to measure the oxidation current at various concentrations of HCO3
- or HPO4
2-. All measurements were done at 30 oC.

XRD and SEM measurements revealed that the obtained RuO2-Ta2O5 catalysts were amorphous, irrespective of the oxide composition. The cyclic voltammograms presented an oxidation wave for each of HCO3
- and HPO4
2-, and the oxidation current density increased with increasing concentration of each ion, indicating that HCO3
- and HPO4
2- are oxidized on the catalyst prior to oxygen evolution. The onset potential and peak potential of the oxidation of HCO3
- or HPO4
2- shifted negatively with increasing Ru mole ratio of the catalyst, in which the onset potential of HCO3
- was 0.1 V nobler than that of HPO4
2-. The oxidation current at different ion concentrations measured by chronoamperometry revealed that the concentration of HCO3
- or HPO4
2- was linear to the oxidation current density for each ion at all oxide compositions from Ru = 20 mol% to 80 mol%. Among them, the sensitivity for HCO3
- or HPO4
2- was highest at Ru = 50 mol%. More detailed results will be shown in this paper.

This work was supported by “Kyoto Area Super Cluster Program” of Japan Science and Technology Agency (JST).

References

[1] T. Tsukuma and M. Morimitsu, The 66th Annual Meeting of International Society of Electrochemistry, Abs# s01-014, Taipei (2015).

[2] A. Honda and M. Morimitsu, PRiME2016, Abs# 3785, Hawaii (2016).
Hydrometallurgical Purification of Metallurgical Grade Silicon with Hydrogen Peroxide in Hydrofluoric Acid
Authors: Lai Huixian , Luo Xuetao
Published: February 2020

The effect of adding hydrogen peroxide (H2O2) as an oxidizing agent on purifying metallurgical grade silicon (MG-Si) by leaching with hydrofluoric acid (HF) was studied as a function of leaching temperature, particle size, leaching duration and concentration of leaching agents. It was found that the extraction capacity for metallic impurities could be significantly enhanced with introducing H2O2 into HF lixiviant showing litter dependence on HF concentration. By leaching with 1 mol· L-1 HF plus 2 mol· L-1 H2O2 for only 0.25 h at 55 ℃, the MG-Si purity could be upgraded from 99.74% to 99.96%, to 99.99% with further prolonging leaching duration. The sensitivity sequences of precipitates to each etchant were obtained through revealing the micro-structural evolution of MG-Si before and after etching. With the help of Raman spectrometry, it was reasonable that etching silicon starts with first oxidizing reaction by H2O2 and then dissolved by HF. Like Si-Si bonds, some Si-F and Si-O bonds could also be found on silicon surface after acid etching with HF plus H2O2 etchant. After acid leaching, the zigzag silicon surface had been detected by using transmission electron microscopy analysis and the formation mechanism was further discussed.

Figure 1
Effect of pH and Salinity on Polarization Behavior of Cathodically Protected HY80 Steel, Inconel 625 and Nickel-Aluminum Bronze in Mexican Gulf Seawater
Authors: Baturina Olga A , Strom Matthew James , Martin Farrel J
Published: February 2020

Metal structures submerged in seawater are subject to corrosion. Corrosion protection is usually implemented by applying negative potentials between -0.8 and -1.0 V vs Ag/AgCl reference electrode [1]. At these potentials, anodic metal dissolution is expected to be suppressed, and the typical dominant reactions that govern electron transfer on the protected surface in seawater are oxygen reduction reaction (ORR) and hydrogen evolution from water. The ORR in basic environments (pH~ 8.4) result in the generation of hydroxyl ions, eliciting an increase in the carbonate (CO3
2-) ions from the carbonate buffer system. When concentrations of CO3
2- and OH- near the electrode surface become sufficient to exceed solubility constants of CaCO3 and Mg(OH)2
compounds, they precipitate on the surface, decreasing the electroactive surface area, and making cathodic protection more efficient [2].

Formation of calcareous deposits on metal alloys is affected by applied potential, DO level, salinity, pH and temperature. Although the influence of DO, pH and temperature on the formation of calcareous deposits have been previously reported [3-5], the effect of salinity level has been overlooked. The effect of pH has been explored only minimally for a limited range of pH (usually ~ 7).

Here, we explore polarization behavior of three cathodically protected alloys (Inconel 625, HY 80 Steel, and C-632 Nickel-Aluminum Bronze used in marine environment as a function of seawater salinity and pH.

Electrochemical experiments were conducted in a three-electrode electrochemical cell (BioLogic, Inc). Freshly polished coupons of three different alloys served as working electrodes (WEs), while platinum mesh and Ag/AgCl in 3M NaCl (BioLogic, Inc) were used as a counter and reference electrodes, respectively. WEs held at -1.0 V were immersed into 0.5, 3.5 or 35 ppt seawater for 24 h, and polarization curves were recorded at 0.6 V/h prior and following the potential hold. Acetic acid, MES and MOPS organic buffers (Sigma Andrich) were used for maintaining pH levels of 5, 6, and 7, respectively. Seawater from Mexican Gulf was collected at Key West, FL.

The influence of salinity and pH on polarization behavior of HY 80 steel is shown in Figures 1 and 2, respectively. The presentation will discuss the reasoning behind the changes in HY 80 Steel, Inconel 625 and C-632 Nickel-Aluminum Bronze polarization behavior under different environmental conditions.

References

[1] V. Ashworth, C.J.L. Booker. Cathodic Protection, Theory and Practice; Ellis Horwood: Chichester, UK, 1986

[2] S.L. Wolfson, W.H. Hartt. Corrosion, 37 (1981) 70

[3] J.S. Luo, R.U Lee, T.Y. Chen, W.H. Hartt, S.W. Smith. Corrosion, 47(1991)189

[4] C. Barchiche; C. Deslouis; O. Gol; P. Refait; B. Tribolett. Electrochim. Acta, 49(2004)2833

[5] P. Refait; M. Jeannin; R. Sabot; H. Antony; S. Pineau, Corros. Sci 90(2015)375

Figure 1
Quantitative Examination of Porous Rust on Steel
Authors: Curry Nicholas , Wills Trevor , Gibbon Simon R , Lyon Stuart B
Published: February 2020

Despite innumerable years of research, very little is known about the physical structure of rusts on steel, which are presumed to possess a complex structure of pores of various shapes and sizes. There have been few detailed investigations into rust pore structure and no studies that focus specifically on understanding the role that rust porosity plays on the adhesion and performance of protective organic coatings. It is commonly believed that paints that are formulated for “compromised” (i.e. rusty and salty) steel penetrate surface and through thickness pores in order to stabilise and bind the rust together. However, no convincing experimental evidence exists for such a mechanism.

Here we develop a detailed, quantitative, understanding of the porous structure of rust and attempt to directly measure its evolution over time. Characterization of porosity in rust layers is non-trivial, as pore sizes span many orders of magnitude and there is no single technique that can measure across the size range. Thus, a range of complementary techniques have been utilised to measure pore sizes: gas (BET) sorption, mercury porosimetry and helium pycnometry, each of which measures different porosity characteristics across different length scales from the “microporous” (i.e. < 2 nm) through the “mesoporous (2 – 50 nm) to “macropores” of size > 50 nm. We find that for rusts developed using cyclic corrosion testing up to 50% of the porous volume exists in the mesoporous and microporous size ranges with surface areas between 20 and 40 m2 g-1 and that there is significant stratification of porosity between "inner" and "outer" rust layers

X-ray computerised tomography (XRCT) has been subsequently used to directly image pores at a voxel size of around 1 micron in order to follow the evolution of the pore structure with time as a function of environmental exposure. The figure shows the experimental protocol whereby projection images of a corroded wire sample are obtained using x-ray absorption contrast and later combined to generate the 3D volume reconstruction.

Figure 1
Corrosion Behavior of Non-Vascular, Double-Layer, Surgical Esophageal Nitinol Stent in Phosphate Buffered Saline Solution
Authors: Kim Yong-Sang , Kim Jung-Gu
Published: February 2020

In the present work, the corrosion behavior of a double-layer stent, which is the combination of an uncoated outer stent and silicon-coated body stent, was assessed by the use of electrochemical methods in phosphate buffered saline solution at 37 °C. Although each stent comprising the double-layer stent showed favorable corrosion properties, the double-layer stent showed a significant diminishment of these corrosion properties. Also, the corrosion was focused on the uncoated outer stent on the double-layer stent and the instability surface condition was observed in the double-layer stent. The cathodic reaction was activated on the outer stent of the double-layer stent by the galvanic effect, and the hydrogen thus generated was detrimental to the surface film. In addition, hydrogen had a synergic effect with chloride and accelerated the corrosion reaction on the outer stent.
Fabrication of Metal-Supported Solid Oxide Fuel Cells by Sinter-Joining Method with Silver Bonding Layer
Authors: Lee Sanghun , Jang Young-hoon , Shin Hoyong , Bae Joongmyeon
Published: February 2020

Solid oxide fuel cell (SOFC) is an energy conversion device which generates electricity from hydrogen. SOFC is attracting attentions because of its high energy conversion efficiency and low material cost. For these reasons, SOFC are widely studied to be applied to various power generation systems such as stationary power plant, residential power system, auxiliary power unit (APU), etc. For APU applications, high mechanical strength is required to endure mechanical vibration and external shock during the driving of vehicles, which makes ceramic-based SOFC unsuitable. To overcome this limitation, metal-supported SOFC has been proposed. Metal-supported SOFCs are composed of metal substrate which supports ceramic layers of anode, electrolyte, and cathode. For more than past ten years, various types of metal-supported SOFC have been developed in many organizations. However, conventional metal-supported SOFCs had limitations of high cost thin film coating process such as sputtering, plasma spray, etc, sintering at reducing atmosphere, and unsintered cathode. In our research group, metal-supported SOFCs fabricated by sinter-joining method were developed. To fabricate metal-supported SOFCs by sinter-joining method, metal substrates were bonded to conventional ceramic cells by bonding paste composed of mixture of stainless steel, nickel oxide, yittria-stabilized zirconia (YSZ). Recently, silver has been proposed as bonding materials. By using silver as bonding materials, bonding of ceramic cell can be performed at temperature lower than 950 °C at air atmosphere, which enables full sintering of cathode. This has been rarely reported because conventional metal-supported SOFCs were fabricated by sintering at reducing atmosphere to prevent oxidation of metal substrate during the sintering. Furthermore, it is believed that electrical conductivity, thermal conductivity are improved, leading to lower ohmic resistance and better temperature distribution of metal-supported cells.

In this work, 5 x 5 cm2 metal-supported SOFCs with silver bonding layer was successfully fabricated. The microstructure of bonding layer was investigated, which showed good adhesion of silver bonding layer. Electrochemical performance and impedance spectra were studied. Power density of 433 mW/cm2, ohmic resistance of 0.52 Ω cm2, polarization resistance of 0.16 Ω cm2 at 800 °C were obtained, and it is believed that high power density was attributed to low polarization resistance by full sintering of cathode. Metal-supported SOFCs fabricated by sinter-joining method showed 10 times higher mechanical strength than conventional ceramic cells.
Suppression of Chromium Poisoning in SOFC Cathode Using Chromium Trapping Materials
Authors: Lee Jong-Ho , Kim Hyojin , Yoon Kyung Joong , Park Mansoo , Kim Hyoungchul , Son Ji-Won , Kim Byung-Kook , Lee Hae-Weon
Published: February 2020

Solid oxide fuel cells (SOFCs) represent one of the most environmentally friendly and versatile technologies for generation of electrical power and heat from a variety of fuels through electrochemical reactions. Currently, one of the major challenges for commercialization of SOFC technology is the lack of long-term reliability at high temperatures. Especially the high-temperature degradation of SOFC materials with respect to contaminants, structural degradation and material decomposition is known to be the main cause of poor reliability of SOFCs which makes significantly mitigating a broad implementation of SOFCs. Thus, a fundamental understanding of the degradation mechanisms of SOFC materials is needed to find the best degradation mitigation strategies and apply them in order to advance the commercialization of SOFCs.

Among many sources of degradation of solid oxide fuel cells (SOFCs), chromium poisoning of cathode has been one of the major concerns for commercial development and deployment. Chromium evaporates from the metallic components of the stack and system in oxidizing atmosphere, and deposits on the active sites of the cathode, leading to degradation of electrode performance. One of the most general approaches to suppress chromium poisoning is to cover the metallic components with protective coating, and various coating materials and deposition techniques have been proposed. However, it is difficult to form sufficiently dense and stable coating on entire part of the potential chromium source of the system. Therefore, solely relying on protective coating for suppression of chromium poisoning is not considered to be reliable, and it is desirable to have additional means to further block chromium vapor from reaching cathode.

In this presentation, effect of chromium poisoning on cathode reaction was studied using impedance spectroscopy to illuminate the degradation process in SOFC cathode. From this investigation, especially focused on the air side of SOFCs which occupies the largest portion of SOFC deterioration, we want to identify the underlying degradation mechanisms and propose possible mitigation strategies based on our experimental results.
Methane Partial Oxidation-Assisted H2O/CO2 Co-Electrolysis for Syngas Production in Both Electrodes
Authors: Wang Yaqi , Han Minfang
Published: February 2020

In conventional solid oxide electrolysis mode, most of the electric power is consumed to overcome the high chemical potential in forcing the oxygen to diffuse through the electrolyte. In this paper, a novel methane-assisted H2O/CO2 co-electrolyzer was designed by combining solid oxide electrolysis cell (SOEC) with partial oxidation of methane (POM) to generate syngas in both sides. In POM-SOEC mode, methane is fed to the oxygen electrode to react with the oxygen produced by the electrolysis process, thus to reduce the chemical potential. Experiment performed on the Ni-YSZ/YSZ/SFM-YSZ single cell showed a voltage reduction from 1.2 V to 0.2 V compared to the conventional electrolysis mode at the same current density. The constant current test indicated that no obvious degradation was detected in 50 h operation.
Development of Ceramic Materials and Application of Novel Physical Analysis Methods to Enhance Solid Oxide Fuel Cells and Solid Oxide Electrolysis Cells
Authors: Lust Enn , Lillmaa Kadi , Nurk Gunnar , Kanarbik Rait , Möller Priit , Kivi Indrek , Vestli Mihkel , Maide Martin , Korjus Ove , Salvan Laur Kristjan , Kukk Freddy
Published: February 2020

Various physical methods (SEM-EDX, TEM, EXAFS, FIB-TOF-SIMS, high temperature X-ray diffraction, gas adsorption, etc.) and electrochemical methods have been used complexly for detailed analysis of ceramic materials with the perovskite structure, considered as promising alternatives to Ni-based solid oxide fuel cell (SOFC) anodes as well as solid oxide electrolysis cell (SOEC) cathodes. Comparative analysis of the data obtained by novel in situ/in operando and electrochemical methods used for characterizing the electrode materials and processes gives deeper insight into the background of various processes taking place in the materials and enables to develop new materials for various purposes. Some examples including in operando high-temperature X-ray diffraction, in operando X-ray absorption and FIB-TOF-SIMS studies will be discussed. Unit cells relaxation and interdiffusion in solid oxide fuel cells and carbon dioxide and water co-electrolysis cells will be discussed. Influence of chemical composition and preparation methods of the materials for electrolytes, electrodes and chemical barrier layers on the SOFC and SOEC characteristics will be analyzed.
Quality Assurance of Solid Oxide Fuel Cell (SOFC) and Electrolyser (SOEC) Stacks
Authors: Lang Michael , Auer Corinna , Couturier Karine , Sun Xiufu , McPhail Stephen J. , Malkow Thomas , Fu Qingxi , Liu Qinglin
Published: February 2020

Many research facilities and industrial companies worldwide are engaged in the development and the improvement of solid oxide fuel cells/stacks (SOFC) and also of solid oxide electrolysis cells/stacks (SOEC). However, the different stacks cannot be easily compared due to non-standardized test programs. Therefore the EU-funded project “SOCTESQA” which started in May 2014 has the aim to develop uniform and industry wide test modules and programs for SOC cells/stacks. New application fields which are based on the operation of the SOC cell/stack assembly in the fuel cell (SOFC), in the electrolysis (SOEC) and in the combined SOFC/SOEC mode are addressed. This covers the wide range of power generation systems, e.g. stationary SOFC µ-CHP, mobile SOFC auxiliary power unit (APU) and SOFC/SOEC power-to-gas systems.

In order to optimize the test programs, which consist of different test modules, several testing campaigns have been performed. The project partners apply the developed test procedures on identical SOC stacks. In this project 5-cell short-stacks with anode supported cells (ASC) were used, which were provided by an established stack supplier. Altogether 10 pre-normative test modules were developed: Start-up, current-voltage curve, electrochemical impedance spectroscopy, reactant utilization, reactant gas composition, temperature sensitivity, operation at constant current, operation at varying current, thermal cycling and shut-down.

The presentation compares the results of the test modules of the different project partners. Important aspects are the evaluation of the results in terms of repeatability of the different testing campaigns and the reproducibility of the results among the partners. Electrochemical properties, e.g. open circuit voltage (OCV), area specific resistance (ASR), power density, fuel utilization (FU) and impedance values of both stack and repeat units (RU) are presented. Moreover, the results are discussed in context to the test input parameters. Another important issue is the reproducibility of the different test methods, e.g. jV-characteristics and EIS-spectra. Finally, important aspects for the determination of reproducible degradation rates of SOC stacks will be presented and discussed.
In-Situ Formation of Nano-Structured Cathode on Metal Supported SOFC
Authors: Zhu Tenglong , Zhong Qin , Han Minfang
Published: February 2020

Metal supported solid oxide fuel cells (MS-SOFC) possess several advantages like good mechanical property, easy assembling, fast start-up and capability to maintain redox stable due to fuel leakage. However, it has been a critical challenge to deposit cathode on the metal supported cell in the oxidizing atmosphere, which is mainly limited by the low calcination temperature yielding vulnerable electrolyte-electrode interface. The cathodes prepared in the protecting atmosphere are also not satisfied, instead it will increase the complexity of the cell fabrication process.

Lower down the cathode deposition temperature using aqueous infiltration has become one of the optimized methods for MS-SOFC. Also, we have proposed an alternative way for the fabrication of metal supported single cell with robust cathode through whole cell reduction. Here, we present results of both above two approaches for the fabrication of nano-structured cathodes in MS-SOFC. The cells in this study are based on Fe-Ni (1:1 in mol ratio) support, Fe-Ni/YSZ anode and YSZ electrolyte prepared through tape-casting, thermal isostatic pressing and co-firing.

As illustrated in the following schematic configuration, La0.6Sr0.4Co0.2Fe0.8O3-δ (LSCF) cathodes were deposited in the porous YSZ layer of the pre-reduced Ni-Fe|Ni-Fe-YSZ||YSZ||P-YSZ substrate by infiltration and fired at the cell operation temperature around 700 oC. A-site deficiency of ~4-8% was introduced into LSCF cathode and was expected to enhance the sintering activity of LSCF nano particles at low calcination temperature and to enhance the cathode performance by the excess cobalt and iron oxide at LSCF surface. As in the second approach, Sr0.95Ti0.3Fe0.63Ni0.07O3-δ – Gd0.1Ce0.9O1.95 (STFNi-GDC) graded cathode will be screen printed on the NiO-Fe2O3|NiO-Fe2O3-YSZ||YSZ|GDC substrate and fired at high temperature in air as normal cathode preparation procedure. Then the whole cell will be reduced in H2-Ar to obtain Fe-Ni alloy support and reduced STFNi cathode with in-situ exsolved (Fe,Ni) alloy nano particles anchored in the oxide surface. During the cell test, the reduced STFNi-(Fe,Ni) will be re-oxidized in air, forming the surface decorated iron and cobalt oxide particles, which were presumably to be expected to increase the cathode performance through improvement of oxygen surface exchange coefficient.

Figure 1
All-Solid-State “Lithim-Free” Microbatteries Characterization By Electrochemical Impedance Spectroscopy Coupled Wih X-Ray Photoelectron Spectrometry
Authors: Ferreira Gomes Franck Ferreira , Franger Sylvain , Guy-Bouyssou Delphine
Published: February 2020

For several decades, the miniaturization of nomadic electric systems has made the world of energy storage evolve. Indeed, these devices are getting progressively smaller and smaller, and more powerful. This makes more difficult the integration of conventional batteries into these modern devices including; incompatibilities due to their sizing, life-time and limited cyclability, risks of inflammation, risk of liquid electrolyte leakage. In response to these difficulties, the "lithium-free" all-solid-state thin film microbatteries provide answers to the manufacturers. They can reach a potential of 0V [1], far below the capability of lithium and lithium-ion batteries. Furthermore, these micro batteries are thinner, more flexible, safer due to the absence of liquid electrolyte. These micro-devices can be integrated into diverse applications as connected watches, SmartCards, RFID Tags, or even be integrated into contact lenses to power the autofocus system.

Li-Free microbatteries are composed of a platinum current collector, LiCoO2 as positive electrode, LiPON glass as solid electrolyte and a current collector of copper. The lithium initially contained in the cathodic insertion material is electroplated on the copper current collector during the initial charge, to create a metallic lithium anode and make the battery operational. However, this technology, offering a lot of advantages, still remains not fully understood and consequently difficult to control.

The thin-film design makes individual characterization difficult after cycling. Analysis of the surface with X-ray Photoelectron Spectrometry (XPS) and Auger Electron Spectroscopy (AES) enable determining the chemical composition of the Li-Free microbatteries after cycling. The use of Electrochemical Impedance Spectroscopy (EIS), can also provide information about the operating behaviour and ageing of these technologies and finally help in better manufacturing. This study is focused on the non-destructive characterization of lithium-free microbatteries by means of the Electrochemical Impedance Spectroscopy coupled with X-ray Photoelectron Spectrometry and Auger Electron Spectroscopy, and shows necessary mechanisms during the first charges and discharges of the battery for ulterior good performances upon cycling. With this adapted protocol [2], the battery can now exhibit a lifetime and cyclability similar to conventional lithium metallic and lithium-ion microbatteries.

References :

[1] Neudecker and al., J. Electrochem. Soc., 147 (2) 517-523 (2000)

[2] Larfaillou and Guy-Bouyssou. U.S. Patent 2015325878 (2015)
Increasing the Capacity of Nano-Structured LiMn2O4 Pseudocapacitors by Selective Crystallization of Dissolution Resistant Surface Facets
Authors: Yan Yan , Lesel Benjamin , Szeto Nathaniel , Chen Jiaming , Robbennolt Shauna , Tolbert Sarah H
Published: February 2020

Pseudocapacitive materials are important for high power energy storage devices that can help meet the increasing need for mobile power. While good progress has been made in pseudocapacitive anode materials, less work has been done on fast charging cathodes. We have previously reported on nanoporous LiMn2O4 as an exciting pseudocapacitive cathode, however, the capacity is compromised in nanosized LiMn2O4 due to surface manganese dissolution. Here, we designed LiMn2O4 with different nanostructures: round-LMO (R-LMO) and needle-like LMO (N-LMO) using two different precursors: acetate and nitrate salts, respectively. We examined the effect of this nanoscale structure on electrochemical performance and found that N-LMO displayed higher capacity than R-LMO, despite similar kinetics. Unlike the R-LMO which showed no preferred surface faceting, N-LMO was found to be dominated by (111) surface facets, which have been shown to be more resistant to surface manganese dissolution. XPS studies on the Li counter electrodes corroborated this idea, showing less manganese dissolution and replating on the counter electrode in the case of N-LMO. Together, this study provides insights into how surface structure affects the electrochemical properties of nanostructured LiMn2O4 and presents a facile, low cost synthetic methodology for the production of a high performance pseudocapacitive cathode material.
Assembling 2D Mxene into 3D Ordered Structures for High Power Li-Ion Capacitors
Authors: Orangi Jafar , Beidaghi Majid
Published: February 2020

MXenes are a family of two-dimensional (2D) materials with interesting electrical and electrochemical properties and their high potential as electrode materials for Li-ion capacitors has been recently demonstrated. However, the conventional methods for electrode assembly and device fabrication are limiting factors in exploiting the full potential of these electrode materials. The research on the development of electrochemical energy storage devices in the past few years has led to the realization that improved performance can be achieved by assembling the electrode materials into three-dimensional (3D) architectures instead of the conventional 2D “laminate” architecture. In this talk, we present a simple, efficient, and scalable method to assemble 2D Ti3C2 into ordered 3D and porous aerogel structures with high specific capacitances and rate capabilities. MXenes aerogels are fabricated by directional freeze casting and show large specific surface areas. The porous structure of MXene aerogels is dependent on the processing conditions and affect their mechanical and electrochemical properties. MXene aerogels show significantly high specific capacities (1200 mAh/g at 0.05 A/g), excellent rate capability (200 mAh/g at 10 A/g) and outstanding cycling performance for reversible lithium-ion energy storage. We believe that the fabricated 3D MXene structures are promising for a broad range of applications.
Thick Binder-Free Electrodes for Li-Ion Battery Fabricated Using Templating Approach and Spark Plasma Sintering Reveals High Areal Capacity
Authors: Elango Rakesh , Demortiere Arnaud , De Andrade Vincent , Morcrette Mathieu , Seznec Vincent
Published: February 2020

The templating approach is a powerful method for preparing porous electrodes with interconnected well-controlled pore sizes and morphologies. The optimization of the pore architecture design facilitates electrolyte penetration and provides a rapid diffusion path for lithium ion, which becomes even more crucial for thick porous electrodes. In the present work, we used NaCl micro-size particles as templating agent for the fabrication of 1 mm-thick porous LiFePO4 (LFP) and Li4Ti5O12 (LTO) composite electrodes using Spark Plasma Sintering (SPS) technique. These sintered binder-free electrodes are self-supported and present a large porosity (40%) with relatively uniform pores. The electrochemical performances of half and full batteries reveals a remarkable specific areal capacity (20 mAh/cm2), which is four times higher than those of 100 µm thick electrodes present in conventional tape-casted Li-ion batteries

(5 mAh/cm2). 3D morphological study of both electrode types was carried out using µCT full field TXM technique to obtain tortuosity values and pore size distributions leading to a strong correlation with their electrochemical properties. These results also demonstrate that the coupling between salt templating method and SPS technique turn out to be a promising way to reach the ultimate goal in the fabrication of thick electrodes with high energy density.
Quantification of Ion and Solvent Content within Charged Micropores of Bimodal Carbide-Derived Carbons Using Small Angle Neutron Scattering
Authors: Sacci Robert L , Van Aken Katherine L , Thompson Matthew W , Rother Gernot
Published: February 2020

Given that the kinetics of ion insertion into and adsorption within micropores are two foundational phenomena in charging and discharging of electrochemical double layer capacitors, methods must be developed to characterize ions within micropores of charged porous materials. Here we will discuss the use of electrochemical small angle neutron scattering (ecSANS) to characterize ion insertion into micropores carbide derived carbons from imidazolium based-salts in acetonitrile using the Extended-Q SANS instrument at the Spallation Neutron Source (SNS-ORNL). Effects of ion insertion into micropores were also followed as a function of alkyl chain length of the imidazolium cation, e.g. EMIM vs HMIM (ethyl vs hexyl).
Fabrication of Flexible Optoelectronic Devices Based on MoS2/Graphene Hybrid Patterns By a Soft Lithographic Patterning Method
Authors: An Ki-Seok , Kang Min-A , Song Wooseok , Myung Sung , Lee Sun Sook , Lim Jongsun , Lim Yi Rang
Published: February 2020

In this presentation, cross-stacking MoS2/graphene hybrid patterns for the application to advanced flexible opto-electronic devices have been performed by the soft-lithographic patterning method. Well-defined MoS2/graphene hybrid pattern was produced simply by a soft lithographic patterning technique without any defects. In-depth exploration for the optical properties of diverse cross-stacking photodetectors based on MoS2/graphene patterns was also implemented. Furthermore, cross-stacking MoS2/graphene based on the woven structure was transferred onto a flexible polyethylene terephthalate (PET) substrate for the analysis of mechanical properties of devices. Eventually, this method should pave the way for practical applications of transparent and flexible nano-electronic devices based on 2D materials.
Enhancing Light Emission Efficiency without Color Change in Post-Transition Metal Chalcogenides
Authors: Ataca Can , Grossman Jeffrey C , Tongay Sefaattin
Published: February 2020

Two-dimensional (2D) materials can take a large amount of mechanical deformation before reaching the fracture limit due to their high Young's modulus, and this in return, provides a way to tune the properties of 2D materials by strain engineering. Previous works have shown that the optical band gap of transition metal chalcogenides (TMDs) can be modulated by strain, resulting in a drift of the photoluminescence (PL) peak position and a decrease (or little change) in PL intensity. Here, we report a member of the post-transition metal chalcogenides (PTMCs), 2D-GaSe sheets, displaying vastly different phenomena under strain. Strained 2D-GaSe emits photons at almost the same wavelength as unstrained material but appears an order of magnitude brighter. In contrast to TMDs, optical spectroscopy measurements reveal that changes in the optical properties are mostly related to the colossal optical absorption anisotropy of GaSe, instead of commonly accepted strain-induced band renormalization. Results suggest that the light–matter interaction and the optical properties of 2D-GaSe can be controlled at will by manipulating the optical absorption.
(Invited) Exploring Exciton Physics in Liquid-Exfoliated 2D Materials
Authors: Rashvand Farnia , Synnatschke Kevin , Chernikov Alexey , Coleman Jonathan N , Backes Claudia
Published: February 2020

Transition metal dichalcogenides (TMDSs) are a diverse source of semiconducting 2D materials interesting for a number of application areas. Group VI-TMDs are direct bandgap semiconductors in the monolayer form making them attractive in optoelectronics due the possibility of efficient light emission. Their optical properties are dominated by tightly bound excitons with typical binding energies of 100s of meV – significantly larger than in bulk materials or traditional inorganic semiconductors. The physics of these excitons is of both fundamental interest and importance for exploiting these properties in applications and has been explored by linear and nonlinear optical techniques typically on micromechanically cleaved nanosheets.

In this talk I will review our progress on investigating the exciton physics of layered materials exfoliated in the liquid phase. Liquid phase exfoliation has become a popular technique to obtain nanosheets in the form of colloidally stable dispersions suitable for solution processing. It’s an extremely versatile technique that can be applied to a whole host of layered crystals. While dispersions of nanosheets are usually polydisperse containing broad distributions of lateral sizes and thicknesses, they can nonetheless be used to study fundamental physical properties once the distributions are quantified by statistical microscopy. The advantage of the technique is the broad applicability and characterisation of an ensemble eliminating potential variations across different nanosheets. In addition, environmental effects can be conveniently studied by exchanging the liquid environment.
Characterization of Carbon Materials and Electrolytes for Redox Flow Battery By Potential-Sweep Coulometry
Authors: Ohira Akihiro , Negishi Akira , Hozomi Eiji , Sato Yukari
Published: February 2020

Redox flow batteries (RFB) have been investigated actively now. New redox materials such as metal ions, non-metals, organic molecules are using for the RFB [1-3]. Non-metal RFB are strongly expected by the increasing in needs for the low-cost, safe, and trusted energy storage applications. Since Redox active materials and cell systems have made great progress in recent years, it has been required easy and versatile determination of characteristics of electrode and electrolyte for RFB.

Here we report evaluation of the performance of various types of carbon electrodes and redox behavior with vanadium electrolyte solution by potential-sweep coulometry method. This technique expanded the voltage-step coulometry method which we reported previously [4]. Other electrolytes such as organic redox solution and Ti-Mn were also evaluated by this method [2].

Figure 1 showed the model of the half-cell of the small-scale test cell for potential-sweep coulometry. Electrolyte solution was filled up in the test cell and then stopped, and the current and amount of electricity were measured during for the potential sweep to positive and negative potentials. Figure 2 showed current-potential responses of carbon felt electrode measured in vanadium solution (0.1 M VOSO4/ 3.5 M H2SO4) with different potential sweep rate (0.1, 0.2, and 0.5mV/s). In this case, electrochemical reaction of this carbon felt electrode showed good responses for both charging and discharging process. We also investigated other electrolytes and other carbon felt and paper electrodes.

Figure 1
Linked Anolyte-Catholyte Materials for Redox Flow Battery Applications
Authors: Mann Shane C. , Dumitrascu Adina , Mortimer Nicholas J. , Scott Jessica D. , Henton Daniel R. , Guarr Thomas F.
Published: February 2020

The emphasis on bringing additional sources of renewable energy online serves to highlight the increasingly critical need for inexpensive and durable means of energy storage. Nonaqueous redox flow batteries (RFBs) may represent an attractive solution, but the cost and efficiency of currently available ion exchange membranes remains problematic. One promising approach to the elimination of membrane crossover issues involves the covalent attachment of an electron acceptor A to an electron donor D via a suitable linker (L) to form a bifunctional compound D-L-A. Such systems would have at least three accessible stable redox states: the “parent” D-L-A, an oxidized form D+-L-A (catholyte), and a reduced form D-L-A-
(anolyte). Since operation of the RFB would involve the production of D-L-A at both anode and cathode, crossover becomes essentially irrelevant.

A number of D-L-A compounds have been prepared using phenothiazine or carbazole donors and pyridinium acceptors (see examples I and II above); several of these exhibit chemically and electrochemically reversible oxidation and reduction, yielding RFB cell voltages over 2 V. Additionally, multiple examples of the related D-L-A-L-D compounds that incorporate acceptors based on various p-phenylene-bridged bis(4-pyridinium) derivatives have also been synthesized and characterized (example III). These latter materials are of particularly interest, displaying 2e- redox activity at nearly 2.4 V with excellent stability.

The electrochemical properties of several representative D-L-A and D-L-A-L-D systems will be described, and recent progress in the development of nonaqueous RFBs employing covalently linked anolyte-catholyte compounds as active materials will be presented.

Figure 1
Cycling Properties of Fe-Al Chloride Electrolytes for Non-Aqueous Potassium Redox Flow Batteries
Authors: Poletayev Andrey D , Baclig Antonio , McConohy Geoff , Chueh William C
Published: February 2020

Iron chlorides are potentially some of the most inexpensive energy-dense positive electrodes for non-aqueous redox flow batteries. So far, solutions of FeClx in ethylene glycol have achieved concentrations of over 4 mol/liter, but experience significant capacity fade upon cycling [1,2]. We study FeClx solutions in carbonate solvents as positive electrolytes in non-aqueous potassium-ion redox flow batteries [3]. While FeClx species alone do not yield reversible cycling, the addition of formally redox-inactive AlCl3 enables in model solutions Coulombic efficiencies over 99%, and capacity fade under 20% over 200 cycles. We further discuss the evolving speciation of Fe2+/3+ in solution from electron spin resonance and cycling data, the role of common-ion and supporting salts, and the mechanism by which Al species enhance the cycle life of FeClx positive electrode solutions.

A. Miller, J. S. Wainriht, R. F. Savinell, Journal of the Electrochemical Society, 164 (2017) A796–A803.

A. Miller, J. S. Wainright, R. F. Savinell, Journal of the Electrochemical Society, 163 (2016) A578–A579.

Xue, H. Gao, W. Zhou, S. Xin, K. Park, Y. Li, J. B. Goodenough, Advanced Materials, 28 (2016) 9608-9612.
High-Throughput Electrosynthesis with Flow-through Electrodes Made from Cu Nanowires
Authors: Wiley Benjamin J. , Kim Myung Jun , Yang Feichen
Published: February 2020

The high surface area per unit volume and large mass-transfer rates offered by three-dimensional porous electrodes have resulted in their use in a wide variety of electrochemical processes.1-4 Several types of porous electrodes are commercially available, including carbon paper, graphite felt, reticulated vitreous carbon (RVC), metal mesh, and metal foam. Metal foam offers relatively high conductivity (1.5x10-5 ohm m) but low specific surface area (<4x104 m-1),5 whereas carbon paper has one of the highest specific surface areas (up to 1.6x105 m-1) but lower conductivity (4.7x10-5 ohm m).6 An improved flow-through electrode would have the electrical conductivity of metals, a surface area greater than carbon paper, and a hydraulic permeability comparable to carbon paper.

This presentation will describe the characteristics of a Cu nanowire electrode that has 15 times more surface area (2.4x106 m­-1) and is 32 times more conductive (1.4x10-6 ohm m) than carbon paper. The improvement in surface area is due to the small diameter of the nanowires relative to carbon fibers. The higher conductivity is due to the intrinsically higher conductivity of Cu, and the fact that the metal nanowires can be sintered together. The porosity of the nanowire electrode is 0.94, but its hydraulic permeability was 89 times lower than carbon paper. For Cu ion reduction, the Cu nanowire electrode can achieve the same single-pass conversion as carbon paper at flow rates up to 1000 times greater under mass transport-limited conditions, and 10 times greater under kinetically limited conditions. We will also report results for the hydrogenation of furfural and for water oxidation. Future work will focus on improving the hydraulic permeability of flow-through electrodes while maintaining a >10x increase in surface area relative to carbon paper.

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Figure 1. Images for Cu nanowire-based electrode and carbon paper.

Figure 1