bluuebunny/crossref_metadata_2025 huggingface dataset:
(Invited) The Role of Electronic Bulk and Surface Structures for Efficient Photo-Electro-Synthesis
Authors: Jaegermann Wolfram
Published: February 2020

For an effective conversion of solar energy to a chemical fuel a lot of different materials as well as device structures have been suggested but only very few provide technological competitive conversion efficiencies. Limitations and loss processes can be deduced from a detailed consideration of the involved photovoltaic and electrochemical elementary steps. Optimized performance can only be reached when the photovoltaic and electrolytic boundary conditions of integrated systems are comparable to those of separated devices with no extra loss due to the coupling process.

Feasible solutions seem to be possible for water splitting and H2-generation, as we will show with a number of investigations performed recently combining electrochemical investigations with surface science studies. Especially photoemission results on the demands on the bulk and surface electronic structure provide clear boundary conditions on the material’s and surface properties: i) the semiconductors must provide a wide splitting of quasi Fermi levels which will be provided by multli-junctions but hardly can be expected for low band gap oxides based on localized d electron states as e. g. hematite due to polaron formation. ii) the interaction of H2O and their intermediates directly onto the light energy converting junction must be avoided because of possibly formed surface states. As a consequence a buried junction is needed. iii) Photocatalytic converters must be prepared which uses different junction properties in opposing directions (Janus type surfaces) as proven for facet engineering or hetero structure formation.

In summary, we do believe that effective photoelectrochemical devices need the input of different disciplines and expertise ranging from solid state physics, surface science to electrochemistry. Based on an improved understanding of the correlation of material’s properties with the involved elementary steps promising advanced technological solutions seem possible.
(Invited) Role of Surface States in Photocatalytic Oxygen Evolution with CuWO4 Particles
Authors: Osterloh Frank E. , Wu Zongkai , Zhao Zeqiong , Cheung Ghunbong , Doughty Rachel M , Ballestas-Barrientos Alfonso R , Hirmez Benel , Han Ruirui , Maschmeyer Thomas
Published: February 2020

CuWO4 is a medium bandgap (2.3 eV) n-type semiconductor capable of photoelectrochemical water oxidation under applied electrical bias. Here, we show for the first time that suspended microcrystals CuWO4 evolve oxygen photocatalytically under visible illumination from solutions of 0.05 M AgNO3(10.8 μmol/hour; AQE of 0.561% at 400 nm) and 0.0002 M FeCl3(1.5 μmol/hour). No oxygen is detected with 0.002 M [Fe(CN)6]3-as sacrificial agent. The activity dependence on the redox potential of the acceptors is due to the presence of Cu2+based electron trap states in CuWO4. According to surface photovoltage spectroscopy and electrochemistry, these states are located on the particle surface, 1.8 eV above the valence band edge of the material. Controlling the chemistry of these states will be key to uses of CuWO4particles in tandem catalysts for overall water splitting.

Figure 1
(Invited) Electrochemistry for Sustainable Solar Photovoltaics
Authors: Tao Meng
Published: February 2020

Commercial solar photovoltaic technologies such as Si and CdTe are traditionally considered to be in a separate domain from electrochemistry. Their device operation is governed by semiconductor physics and their production involves non-electrochemical processes such as diffusion, screen printing, fractional distillation, etc. However, electrochemistry will likely play an indispensable role in sustaining the commercial solar technologies. This talk will discuss three roadblocks to sustainable solar photovoltaics and how electrochemistry can remove these roadblocks: 1) storage of intermittent solar electricity, 2) scarce Ag used in today’s Si solar cells, and 3) high energy input in producing solar Si wafers. An off-grid route is proposed for solar electricity storage based on a closed loop of Zn↔ZnO [1], in which Zn rods are produced in a solar electrolyzer from ZnO. The Zn rods are shipped to homes, offices, factories, and electric vehicles to be inserted into mechanically-recharged Zn/air batteries, for electricity on demand. The spent Zn anodes are collected for regeneration of Zn in the solar electrolyzer. This Zn↔ZnO loop is advantageous over the H2↔H2O loop in terms of theoretical performance and technical readiness. Electroplated Al on Si is proposed to replace the screen-printed Ag electrode in Si solar cells [2]. 18% efficiency has been demonstrated in a Si solar cell with an electroplated Al front electrode and a screen-printed Al back electrode, i.e., an Ag-free all-Al Si solar cell. To overcome the high resistivity of the solar Si wafer, direct Al plating on Si without any seed layer is developed through light-induced Al plating. Direct Al plating on Si drastically simplifies the metallization process for Al, resulting in a significantly-lower cost than competing technologies. Finally, electrochemical refining of metallurgical-grade Si for solar-grade Si has been unsuccessful. While metals up to 99.99% purity are readily produced by electrolysis, solar-grade Si requires a purity of at least 99.99999%. This is coupled with non-electrochemical difficulties in Si purification such as oxidation of the Si anode and crystallinity of the Si cathode. An analysis will be presented on ultrapure materials by electrolysis [3]. The reason for unsuccessful Si electrochemical refining will be discussed through an analogy between electrochemical refining and fractional distillation. A revised method for electrochemical refining of Si is proposed.

[1] M. Tao, A Zn↔ZnO loop for terawatt-scale storage of solar electricity, 43rd IEEE Photovoltaic Specialist Conference (Portland, OR, 2016), p. 2011

[2] 1. L. Wang, W.-H. Huang, W. J. Shin, M. Tao, B. Deng, and D. Wang, Light-induced plating of aluminum on silicon in a Lewis acidic chronoaluminate ionic liquid, Journal of the Electrochemical Society, 165, D381 (2018)

[3] M. Tao, Impurity segregation in electrochemical processes and its application to electrorefining of ultrapure silicon, Electrochimica Acta, 89, 688 (2013)
(Invited) Materials By Design Principles in Artificial Photosynthesis: Discovery and Synergistic Integration of Light Absorbers, Electrocatalysts and Membranes for Complete, Stable, Efficient, and Safe Solar Fuels Generator
Authors: Lewis Nathan S
Published: February 2020

We are developing an artificial photosynthetic system that will utilize sunlight and water as the inputs and produce hydrogen and oxygen as the outputs. We are taking a modular, parallel development approach in which three distinct primary components-the photoanode, the photocathode, and the product-separating but ion-conducting membrane-are fabricated and optimized separately before assembly into a complete water-splitting system. The design principles incorporate two separate, photosensitive semiconductor/liquid junctions that will collectively generate the 1.7-1.9 V at open circuit necessary to support both the oxidation of H2O (or OH-) and the reduction of H+ (or H2O). The photoanode and photocathode will consist of rod-like semiconductor components, with attached heterogeneous multi-electron transfer catalysts, which are needed to drive the oxidation or reduction reactions at low overpotentials. The high aspect-ratio semiconductor rod electrode architecture allows for the use of low cost, earth abundant materials without sacrificing energy conversion efficiency due to the orthogonalization of light absorption and charge-carrier collection. Additionally, the high surface-area design of the rod-based semiconductor array electrode inherently lowers the flux of charge carriers over the rod array surface relative to the projected geometric surface of the photoelectrode, thus lowering the photocurrent density at the solid/liquid junction and thereby relaxing the demands on the activity (and cost) of any electrocatalysts. A flexible composite polymer film will allow for electron and ion conduction between the photoanode and photocathode while simultaneously preventing mixing of the gaseous products. Separate polymeric materials will be used to make electrical contact between the anode and cathode, and also to provide structural support. Interspersed patches of an ion conducting polymer will maintain charge balance between the two half-cells.
(Invited) Nanozyme Integrated Microfluidic Devices for Smart Health Monitoring
Authors: Li Chen Zhong , Zhang Chengxiao , Lin Tong
Published: February 2020

In recent years, much effort has been devoted toward developing point-of-care (POC) devices. Among them, smart phone enabled paper-based POC devices are a special category due to the advantages of being simple, rapid, on-site, and cost-effective; they have been widely used in home health care and medical testing, even environmental monitoring. The blood glucose meter is one of the most successfully commercialized diagnostic devices on the market because of its low cost, compact size, simple operation, and reliable quantitative results. However, the glucose meters are generally used for only glucose testings. Recently, many groups have reported methods establishing a direct relationship between the concentrations of the targets in the samples and the glucose detected by a glucometer, enabling a number of non-glucose biomarkers to be detected quantitatively.

In this talk, we describe a novel design that combines the traditional lateral flow strip with a commercialized smartphone-enabled glucometer for portable and quantitative detection of a non-glucose target. The concept is demonstrated by using an oxidative DNA damage biomarker, 8-hydroxy-2′-deoxyguanosine (8-OHdG). The basic design of the device a colorimetric visual detection platform based on the integration of nanozyme and immunoassay. The visual detection can provide only qualitative and semiquantitative results. Thus, to enable quantitative analysis, we establish a novel method that transforms the detection of the target to the detection of an nanozyme based converting enzymatic reaction. Considering the inherent advantages of the personal glucose meter, the demonstration of this device, therefore, should provide new opportunities for the monitoring of a wide range of biomarkers and various target analytes in connection with different molecular recognition events.

Acknowledgement : This work was supported by NSFC NSFC 21729501 project and.

the Engineering Research Centers Program of the National Science Foundation under NSF Cooperative Agreement No. EEC-1648451.
Advancing Electrochemical Microsensor Technologies Using Carbon Nanomaterials for Chronic Dopamine Detection
Authors: Chang An-Yi , Dutta Gaurab , Siddiqui Shabnam , Arumugam Prabhu U
Published: February 2020

Analytical microsensors that can reliably detect (bio)molecules in real-time long-term represent one of the greatest challenges for health and environmental monitoring. Developing such microsensors with high sensitivity and selectivity in minimally prepared complex samples is especially difficult. In recent years, the application of nanomaterials and advanced fabrication methods to microsensing has demonstrated major enhancements in key microsensor performance metrics and their ease of integration into miniaturized microelectrode microarray sensor platforms. In this work, we report the electrochemical response of a boron-doped ultrananocrystalline diamond (BDUNCD) microelectrode during long-term dopamine (DA) detection. Specifically, changes to its electrochemical activity and electroactive area due to DA-by products and surface oxidation are studied via scanning electron microscopy, energy dispersive spectroscopy, electrochemical impedance spectroscopy and silver deposition imaging (SDI). The fouling studies with amperometry (AM) and fast scan cyclic voltammetry (FSCV) methods suggest that the microelectrodes are heavily fouled due to poor DA-dopamine-o-quinone cyclization rates followed by a combination of polymer formation and major changes in their surface chemistry. SDI data confirms the presence of the insulating polymer with sparsely-distributed tiny electroactive regions. This resulted in severely distorted DA signals and a 90% loss in signal starting as early as 3 hrs for AM and a 56% loss at 6.5 hrs for FSCV. This underscores the need for cleaning of the fouled microelectrodes if they have to be used long-term. Out of the three in vivo suitable electrochemical cycling cleaning waveforms investigated, the standard waveform (-0.4 V to +1.0 V) provides the best cleaned surface with a fully retained voltammogram shape, no hysteresis, no DA signal loss (a 90±0.72 nA increase) and the smallest charge transfer resistance value of 0.4±0.02 MW even after 6.5 hrs of monitoring. Most importantly, this is the same waveform that is widely used for in vivo detection with carbon fiber microelectrodes. Future work to test these microelectrodes for more than 24 hrs of DA detection is anticipated.
(Invited) Electrochemically Tunable Sensors for Passive Sweat Analytics and Its Applications for Wearable Technologies
Authors: Prasad Shalini , Muthukumar Sriram , Kinnamon David , Munje Rujuta D. , Upasham Sayali , Lin Kai chun
Published: February 2020

Wearable electronic monitors hold great promise in helping people to reach their health goals. These increasingly sophisticated devices help the wearers improve their wellness by constantly monitoring their activities and bodily responses. While consumer wearables could be more useful for patients with conditions like diabetes or cardiac problems, current solutions are still in the early stages of development. Wearable devices hold the potential to transform some industries most importantly the health care industry. This talk will focus on designing the sensor building block towards achieving passive eccrine diagnostics. In this talk I will present a device for monitoring cortisol levels in a non-invasive manner from passively expressed human sweat. Noninvasive biosensing is achieved through the modulation of the sweat/electrode interface through a combination of inorganic and organic surface engineering towards achieving electrochemical double layer modulated sensors.

There is currently a small selection of portable or point-of-care diagnostic tools for detection of cortisol. Electroanalytical techniques are desired over other transduction methods due to increased accuracy and sensitivity with minimal instrumentation that utilize low power sources. The resulting electrochemical signal can be easily and reliably analyzed lending itself to a wearable form factor that is relevant for the presented applications. The use of portable electroanalytical techniques in sweat-based wearables ranging from amperometry, cyclic voltammetry, chronoamperometry, and electrochemical impedance spectroscopy (EIS) has been investigated with increased interest in recent years. Outside of our group, most efforts have been to monitor the general physiology of the user through measuring analytes such as sodium, zinc, ammonium, lactate, glucose, ethanol, or pH. For this work, non-faradaic EIS was targeted for its ability as a label-free method for rapid and highly specific affinity-based detection of target molecules. This can be accomplished by measuring effective changes in the resistive and capacitive behaviors of the sensor due to specific binding events of the specific biomarker, in this case; cortisol onto a transduction element to quantify cortisol levels present in low volumes of human sweat.

Figure 1
The Development of Redox-Active Helical Polypeptides for Battery Application
Authors: Nguyen Tan , Easley Alexandra Danielle , Yu Cheng-Han , Fan Jingwei , Letteri Rachel , He Xun , Su Lu , Lutkenhaus Jodie L. , Wooley Karen
Published: February 2020

This work seeks to develop polypeptide nanocomposites containing redox-active moieties as cathode and anode components to circumvent the drawbacks of conventional lithium ion batteries, e.g., use of scarce resources, high carbon emissions, and high-cost recycling. Polymer frameworks carrying 2,2,6,6-tetramethylpiperidine 1-oxyl (TEMPO) and viologen moieties are recognized as viable materials for next-generation battery cathodes and anodes, respectively, due to their stabilities and redox processes. Anticipating that the secondary structures adopted by polypeptides will provide opportunities to control the placement of radicals in three-dimensional space by tuning the distribution of radicals along polymer backbones, polypeptides containing TEMPO and viologen were designed for utilization in electrodes. This presentation will highlight the synthetic processes, followed by investigation of the physical and electrochemical properties of the materials, and their secondary structures, by utilizing a variety of thermal, spectroscopic, and imaging techniques. It is anticipated that the synthetic development of radical polypeptide nanocomposites will address needs in the advancement of high-performance and sustainable alternative energy sources (e.g., supercapacitors, and biosensors) towards a greener and more sustainable world, which is facing a never-ending demand for energy technologies.

Figure 1
Exploring the Synergy between Nanoparticles and Passivation Film Chemistry Relevant to Cu Chemical Mechanical Planarization (CMP) Slurry Formulation
Authors: Graverson Carolyn F , Mikos Allie M , Salinas Maria G , Hill Madison , Mlynarski Amy , Keleher Jason J.
Published: February 2020

In order to extend Moore’s Law, chemical mechanical planarization (CMP) is used in the fabrication of semiconductors to achieve angstrom level uniformity. Utilizing abrasive silica (SiO2) nanoparticles, among other additives, Cu CMP slurries are formulated to enhance removal rate through both increased chemical and mechanical interactions. Understanding the dynamics of the interplay between nanoparticles and the passivation film chemistry is important to control material removal rate (MRR) and to improve defectivity in low friction, low downforce systems without etching. This work focuses on how the film formation mechanism and removal of two structurally different inhibition films are impacted by varying the SiO2 particle properties (i.e. size, charge, and functionalization). More specifically, glycine-based complexing chemistry coupled with either benzotriazole (BTA) or salicylic hydroxamic acid (SHA) was evaluated to determine the correlation between removal rate and the particle/chemistry combinations. To characterize the films formed under static and dynamic conditions, the coefficient of friction, open circuit potential (OCP), and contact angle were measured for each slurry formulation. Initial results indicate that abrasive properties affect film formation and subsequent performance during polishing, dependent on the inhibitor used. Therefore, the diameter of the SiO2 abrasive directly impacts the balance between mechanical force and chemical etching to achieve high MRR without inducing further defects.
Enhancing Post-Chemical Mechanical Planarization (CMP) Cleaning in the Presence of Polyelectrolyte-Based Chemistry Relevant to Shallow Trench Isolation
Authors: Mikos Allie M , Graverson Carolyn F , Zubi Tala B , Keleher Jason J.
Published: February 2020

Semiconductor manufacturing relies on the synergistic effects of both chemical and mechanical processes to produce ultra-flat, defect free semiconductor wafers for integrated circuits (IC). Chemical mechanical planarization (CMP) is used to selectively target and remove the excess tetraethyl orthosilicate (TEOS) overburden on silicon substrates with slurries that contain diverse (surface adsorbing, pH adjusting, and rheology modifying) chemistry and nanosized ceria (CeO2) abrasives. A fundamental challenge for CeO2 based slurries is the required presence of the Ce3+ state to enhance removal, which is likely to remain on the wafer surface and increases the potential to induce defectivity such as scratching and particle contamination. Current industrial standards utilize a chemical desorption method, standard clean-1 (SC-1), that is comprised of concentrated ammonium hydroxide and hydrogen peroxide to convert the adsorbed particle to the less reactive Ce4+ state. While effective at removing particle contaminants, literature has shown that not all abrasives and defects are mitigated in the presence of SC-1. The focus of this work is to provide an alternative to traditional cleaning methods that balances chemical surface modification and mechanical removal to limit defects and irregularities on the wafer substrate. The formulated cleaning chemistry was evaluated under small-scale brush cleaning and soft pad/low down force buff polishing to clean polished wafers, which were processed with fluorescence microscopy to determine particle removal efficiency. Furthermore, atomic force microscopy (AFM) and friction measurements were utilized to investigate surface topography as a function of cleaning solution. In comparison to SC-1, the proposed cleaning chemistry shows an increased performance by reducing particle contamination and limiting surface defectivity.
Eco-Friendly Electroreduction of Indium Tin Oxide Using SOM Anode in Molten Salts
Authors: Kwon Suk-Cheol , Lee Jong-Hyeon
Published: February 2020

Indium Tin Oxide(ITO) has been widely used at transparent electrode of Light Emitting Diode(LED) or the material of Liquid Crystal Display(LCD). However, waste ITO is generated after process and wet recycling technology has been used. In the case of wet recycling technology, a large amount of acid required and process time is so long. Then, if waste ITO could be recycled by dry process, electroreduction process, it is expected to solve the economic and environmental problems. However, when graphite is used as anode, it generates greenhouse gases such as CO or CO2 gas and causes formation of dirty C dusts. In this study, electroreduction of Indium Tin Oxide using Solid Oxide Membrane anode was investigated in a molten salt of CaF2-NaF-CaO at 1150 °C under the inert atmosphere to replacing previous anode materials. The SOM process is a direct electrolytic reduction process using a solid-oxide oxygen ion conducting membrane, namely, yttria-stabilized zirconia (YSZ), with high-temperature molten salts as a reaction medium. To verify the possibility of replacing, waste ITO was used because of the large use in industry. Electrochemical behavior was investigated by CV(Cyclic Voltammetry) in molten salts using waste ITO and inert working electrodes. As a result, InSn metal was reduced by SOM process. After electroreduction process, the optimum ITO particle size is considered to be the range of 600 μm to 1000 μm due to considering the maximum reduction efficiency dependent on the sedimentation rate, specific melt droplet growth, and reduced InSn film formation. The reduced InSn alloy was analyzed by XRD and EDS and they were confirmed as InSn alloy, which is almost the same as the initial ITO composition.
High-Temperature Stability of YSZ/Msz Membrane in Molten Salts
Authors: Ryu Hansik , Lee Jong-Hyeon
Published: February 2020

The SOM process is a direct electrolytic process using an ion conductive solid oxide membrane. It is a next-generation innovative metal direct electroreduction process technology that can reduce the production cost of rare metal smelting and recycling by reducing greenhouse gas emissions and manufacturing high purity metals. The SOM process is that operates in a high temperature molten salt bath, and therefore it is required to evaluate the integrity of the structural materials of the unit process equipment applied to the anode. In this study, high-temperature stability tests were carried out on high-temperature CaF2-MgF2-MgO system for evaluating the integrity of structural materials, yttria stabilized zirconia (YSZ) and magnesia stabilized zirconia (MSZ) for 24, 72, 120, 168 hours and MgO concentration for 1, 2.5, 5, 10 wt.% in the CaF2-MgF2 system for 168 hours. As the results; YSZ case: at the beginning of the reaction (24 hours), the surface of the specimen showed an m-ZrO2 peak containing some YF3 peak. The volume fraction of m-ZrO2 was 72% (72 hours), and the volume fraction of m-ZrO2 was 60% at MgO concentration of 2.5 wt.% and that was 49% at which of 10wt.% at 168 hours. MSZ showed better stability at higher temperature than YSZ, and showed better stability than other concentrations when MgO concentration was 10 wt.%.
Efficient and Inexpensive All-Iron Alkaline Water Electrolyzer
Authors: Mitra Debanjan , Zayat Billal , Narayanan S. R.
Published: February 2020

Electrolysis of water is an attractive technique for the production of clean hydrogen. We have focused on alkaline water electrolysis as it is potentially a lower cost system and avoids the need for precious metals and perfluorinated membranes. At the oxygen electrode, transition metal oxides with a nickel substrate are commonly used 1,2while transition metals such as molybdenum and nickel on a nickel substrate are used at the hydrogen electrode. However, the overpotentials for the oxygen evolution reaction and the hydrogen evolution reaction are about 300 mV and 180 mV respectively, at 10 mA/cm2.3,4Therefore, there is a need to improve the catalyst performance and also reduce the cost of nickel-based substrates.

We report here on the performance characteristics of an “all-iron” electrolyzer cell that uses Ni-treated steel mesh as the OER catalyst5,6and nickel-molybdenum co-sputtered on steel mesh as the HER catalyst, as shown in Figure 1. A commercially available Zirfon (Agfa) was used as the separator and 30% potassium hydroxide as the electrolyte. A cell voltage of 2.05 V and 1.79 V was obtained at room temperature and 80oC, respectively, at 100 mA/cm2. The cell could be operated at 80oC and at current densities up to 1 A/cm2. Furthermore, the cell was operated continuously for 100 hours at 1 A/cm2and showed no measurable loss in performance. Thus, a device that is based on the significantly less expensive iron as the substrate was demonstrated to be a promising approach to reducing the cost of alkaline water electrolysis systems.

M. Gong et al., J. Am. Chem. Soc.,
135, 8452-8455 (2013).

L. Trotochaud et al.,J. Am. Chem. Soc., 136: 6744-6753 (2014).

L. Zhang et al., J. Power Sources, 297, 413–418 (2015).

C. Tang et al., Angew. Chem. Int. Ed.,
54, 9351-9355 (2015).

D. Mitra and S. R. Narayanan, Top. Catal., 61, 591–600 (2018).

D. Mitra et al., J. Electrochem. Soc., 165, F392–F400 (2018).

Figure 1
The Role of H-Bonding in Proton-Coupled Electron Transfer: The Reduction of N-Methyl-4,4’-Bipyridine Radical in Acetonitrile in the Presence of Acidic Alcohols
Authors: Pavlova Ksenia , Smith Diane K
Published: February 2020

Proton-coupled electron transfer reactions (PCET) play a significant role in many chemical and biological mechanisms. However, although these reactions have been known and studied for over a century, it is only within the last few decades that the importance of H-bonding intermediates in these reactions has come to be appreciated. In previous studies, we examined how explicit consideration of electron transfer and proton transfer within a H-bond intermediate (the “wedge” scheme) could explain the voltammetry of oxidation reactions involving phenylenediamines and bases in acetonitrile. The focus of this new study is to see if the wedge scheme can also explain the chemically reversible PCET reaction due to addition of acidic alcohols to the N-methyl-4,4’-bipyridinium redox couple (commonly called “monoquat” or MQ) in acetonitrile. MQ, which starts out as a +1 cation, undergoes two reversible reductions in acetonitrile, first to an uncharged radical and then to a quinoidal anion. For this study, different types of acidic alcohols, such as trifluoromethanol, methanol, and dichloroethanol, were added at different concentrations. The cyclic voltammetry shows a positive shift in the E1/2 of the second reduction after adding the acidic alcohol as a guest. This is likely due to protonation of the monoquat anion by the alcohol. The overall reaction was expected to be MQ + ROH + e- = MQH + RO-, which would show a 60 mV per log[ROH] change in E1/2. However, analysis of the collected data contradicts this hypothesis by giving a 180 mV per log[ROH] E1/2 shift, indicating that three alcohols are involved in the overall reaction. Since it is highly unlikely that the MQ anion would be triply protonated, our current hypothesis is that the product conjugate base of the alcohol forms a strongly H-bonded complex with two other alcohols, making the overall reaction, MQ + 3ROH + e- = MQH + (RO-)(ROH)2. Results of on-going research to either disprove or provide further support for this hypothesis will be reported.
Uio-Type Metal-Organic Framework Thin Film with Redox-Active Linkers: Development and Charge Transport Behavior
Authors: Johnson Ben A , Bhunia Asamanjoy , Fei Honghan , Cohen Seth M , Ott Sascha
Published: February 2020

Designing redox-active metal-organic frameworks (MOFs) that can be synthesized as thin films is a key challenge towards their application in electrocatalysis.1 In addition, highly stable MOFs are often electronically insulating in nature, resulting in poor charge transport to redox-catalysts within the MOFs. To overcome these obstacles, we have developed a novel MOF-based thin film platform, which provides electron transport pathways for molecular electrocatalysis.2 The material was rationally designed utilizing the robust Zr-based UiO/PIZOF topology3 and redox-active naphthalene diimide-based linkers (dcphOH-NDI). In addition, hydroxyl groups were included on the dcphOH-NDI linker to facilitate proton transport through the material.

When grown on conducting substrates (fluorine-doped tin oxide, FTO), this material forms thin films (Zr(dcphOH-NDI)@FTO) that display reversible electrochromic behavior. Importantly, nearly all (97%) of the NDI sites are electrochemically active at applied potential. The method of charge propagation through the film was found to proceed via an electron hopping mechanism that is accompanied by counter ion transport. Finally, the MOF thin films were found to function efficiently in aqueous solutions, adding to their potential usefulness in electrocatalytic applications.

The fabrication of a UiO/PIZOF-type MOF thin film with linkers having a well-defined electrochemical response, confers unprecedented versatility to utilize postsynthetic methods to introduce catalytic units into a robust and widely studied framework that is now redox-active. In the future, this will allow for the roles of charge propagation and catalysis to be carried out by separate linkers within the MOF film, enabling the individual optimization of each process.

Downes, C. A.; Marinescu, S. C. ChemSusChem, 10, 4374−4392 (2017).

Johnson, B. A.; Bhunia, A.; Fei, H.; Cohen, S. M.; Ott, S. J. Am. Chem. Soc., 140, 2985−2994 (2018).

Cavka, J. H.; Jakobsen, S.; Olsbye, U.; Guillou, N.; Lamberti, C.; Bordiga, S.; Lillerud, K. P. J. Am. Chem. Soc., 130, 13850−13851 (2008); Schaate, A.; Roy, P.; Preuße, T.; Lohmeier, S. J.; Godt, A.; Behrens, P. Chem. - Eur. J., 17, 9320−9325 (2011).
Study of Electrochemical Behavior of Gases in Ionic Liquids
Authors: Zhang Yuteng , Xue Juanqin
Published: February 2020

The electrochemical behavior of different gases performs divergently in different ionic liquids. The hydrogen and oxygen were selected as the target study gases in this article, the cyclic voltammetry and the chronoamperometry were applied to study and analyze the electrochemical behavior including response time and sensitivity of these gases in ionic liquids [Bmpy][NTf2] and [Bmim][NTf2] based electrochemical sensor, respectively. The results showed that: the sensitivity of H2 detection in [Bmpy][NTf2] and [Bmim][NTf2] are 4.93µA/% and 0.03 µA/%, respectively. Furthermore, the relationship between the current signal and concentration of H2 is linear; the sensitivity of O2 detection in [Bmpy][NTf2] and [Bmim][NTf2] are -0.055mA/% and -0.002mA/%, respectively. Furthermore, the relationship between the current signal and concentration of O2 is linear The research showed that gases tend to have better sensitivity and response ability in [Bmpy][NTf2] compared with [Bmim][NTf2]. This work optimized the better ionic liquid electrolyte and could provide both of the theoretical and mechanical support for further study on electrochemical gas sensors.
Bismuth Conversion Electrodes in Water De-Ionization: Potentials, Limitations and the Case of Nitrate Removal
Authors: Shanbhag Sneha , Whitacre Jay , Mauter Meagan
Published: February 2020

Electrochemical methods such as capacitive deionization and electrosorption have gained significant interest as energy-efficient approaches to traditional pressure-based or thermal approaches in desalinating low salinity waters.1 While, capacitive and pseudocapacitive electrodes are the most commonly used anode materials in these processes, they offer low capacities and suffer from capacity loss due to oxidation. Certain conversion electrode materials also demonstrate anion removal functionality,2, 3 and are expected to offer higher gravimetric and volumetric ion removal capacities over capacitive and pseudocapacitive electrodes.

In this work, we demonstrate the functionality of Bi/C composite electrodes as anion-extracting conversion electrodes with notable electrochemical activity in solutions containing monovalent anions Cl- ions and, for the first time, NO3
- ions. Ion removal capacities of 0.5 – 1.2 mmol/g are obtained in dilute solutions which translate to nearly 0.75 - 1.8 mmol/cm3 and are an order of magnitude higher than capacitive carbon materials. The ion removal capacity of the Bi electrode is dependent on the ionic strength and composition of the solution. In waters containing both NO3
- and Cl-, a mixture of oxynitrate and oxychloride phases are formed. The simultaneous presence of NO3
- and Cl- in solution reduces their individual ion removal capacity while improving the net ion removal capacity of the material. We also find that the presence of multivalent ions such as SO4
-2 only slightly reduces the ion removal capacity in presence of Cl- and significantly diminishes the ion removal capacity in presence of NO3
-.

The Bi electrode undergoes significant morphological changes during the electrochemical conversion reaction which in turn results in significant capacity loss at the electrode level. We also evaluate electrode design and operational strategies to limit the capacity loss and increase the cycle life of these conversion electrodes in practical electrochemical desalination processes.

I. Cohen, E. Avraham, A. Soffer and D. Aurbach, ECS Transactions, 45, 43 (2013).

M. Pasta, C. D. Wessells, Y. Cui and F. La Mantia, Nano Letters, 12, 839 (2012).

D.-H. Nam and K.-S. Choi, Journal of the American Chemical Society, 139, 11055 (2017).
Research on Potentiostatic Accelerated Test Method for Fuel Cell Metal Bipolar Plate
Authors: Zhang Ruofan , Yang Daijun , Zhu Hui , Zhang Cunman
Published: February 2020

The development of high corrosion resistance and low contact resistance fuel cell metal bipolar plates is the focus of current research in the field of fuel cells. In order to test the performance of metal bipolar plates more accurately and rapidly, it is necessary to further study and discuss its effective test methods. Based on the electrochemical corrosion mechanism and the high potential state existing in the fuel cell, this paper studied the state of the metal bipolar plate under different corrosion stages by changing the electrochemical test parameters. The combination of high potential and an accelerated solution has a significant acceleration effect. By increasing the test potential, metal corrosion can be accelerated, and the surface morphology, corrosion products, corrosion rate and contact resistance of the sample under different corrosion stages can be observed or analyzed in a short time. As shown in the experiment, the method of " potentiostatic i-t curve versus time integral" proposed in this paper can more accurately quantitatively analyze the long-term corrosion resistance of samples under different working conditions.

In addition, according to the test results of this paper, if the fuel cell is in a long-term high interface potential situation such as fuel starvation, the fuel cell metal bipolar plate, and its coating will be seriously damaged, the contact resistance will increase significantly, and the surface morphology will be seriously damaged.

Figure 1
Electrodeposition of Silicon with a Liquid Gallium Cathode in Molten Salts
Authors: Haarberg Geir Martin , Kato Tomonori , Norikawa Yutaro , Nohira Toshiyuki
Published: February 2020

Further development of solar power depends largely on the availability of inexpensive solar grade silicon. Electrodeposition is a candidate method to produce high purity silicon at a reasonable cost.

We have previously studied electrodeposition of silicon from molten calcium chloride based electrolytes and molten fluoride electrolytes. Recent experiments were carried out by using a liquid gallium cathode. The approach is based on studies by Stephen Maldonado and coworkers [1] of electrodeposition of silicon by using a liquid gallium cathode in an organic based electrolyte. Silicon has a low tendency to alloy with gallium.

Electrochemical studies and electrolysis to deposit silicon from molten eutectic KCl – KF with 2 mol% K2SiF6 were carried out at 650 oC. Silver wire and glassy carbon rod were used as working electrodes, while glassy carbon rod or silver wire were counter electrodes. A silicon flag reference electrode was used. Liquid gallium in a small alumina tube with tungsten lead was the cathode during electrolysis while glassy carbon or silicon was the anode.

Silicon deposition is diffusion controlled on silver cathode, while silicon deposition is charge transfer controlled on liquid gallium cathode.

Silicon was found to deposit using a liquid gallium cathode, both during galvanostatic and potentiostatic electrolysis. The current efficiency was found to be quite high, and consistently above 80 %. Some silicon particles were found on top of gallium after cooling down. A much larger amount of gallium was used in recent experiments. This helped to form silicon particles inside the liquid gallium cathode.

Silicon was recovered after experiments by physical separation from liquid gallium followed by dissolution of gallium in concentrated HNO3. High purity silicon was obtained. Gallium can form alloys with many impurity elements which may cause a refining effect of silicon.

The use of a liquid gallium cathode is promising for the prospect of developing a new process for producing high purity silicon by electrolysis in molten salts.

References

1. L. Ma, S. Lee, J. DeMuth, and S. Maldonado, Direct electrochemical deposition of crystalline silicon nanowires at T ≥ 60 o C, RSC Adv., 6, 78818 (2016).
(Invited) Gaining Insight into Decomposition Reactions within Energy Storage Systems: Use of Operando Isothermal Microcalorimetry
Authors: Takeuchi Esther S , Marschilok Amy C. , Takeuchi Kenneth J
Published: February 2020

Conversion-type materials for next generation lithium ion systems are of particular interest due to the opportunity for high delivered capacity. However, implementation of conversion materials has been hindered by the phase transformations and large volume changes occurring during cycling. An associated factor is that liquid electrolytes are often not thermodynamically stable at the potentials of the active electrodes while the battery is functioning. This results in the decomposition of electrolyte leading to organic and inorganic interphases formed at the electrode surface. The influence of the interphases can be particularly profound for conversion materials where phase change takes place during (de)lithiation. Notably, the interfaces are critical factors in determining the transport of electrons and ions, the resultant polarization, and associated heat generation.

The use of isothermal microcalorimetry (IMC) will be described as an operando tool to determine the heat evolved due to parasitic or decomposition reactions during lithiation. The total heat measured is assessed in light of the contributions from cell polarization, entropic contributions and the parasitic reactions. This study will describe the use of complementary ex-situ and operando characterization techniques to provide insight into decomposition reactions taking place within energy storage systems.
Design Considerations for Lithium-Ion Battery Safety Used in Unique/Military Platforms
Authors: Andrukaitis Ed
Published: February 2020

For current and future military and other unique applications, lithium-ion batteries (LIB) require several design considerations and improvements to meet safety requirements. An overview of the basic cell design for high power requirements and aspects of battery safety, such as, the nature of the combustion products are examined at Defence Research and Development Canada (DRDC) using a special facility for controlled burning of items and chemical analysis of the smoke and ash. Also, to pass requirements for a military environment, important extreme physical abuse tests, which are not part of the UN procedure are conducted to understand battery safety and failure modes. For example, nail penetration tests are relevant to EV market as well, where vehicle collisions can occur and a severe internal short-circuit may be induced. There are two versions of the nail penetration test that are typically conducted (slow and fast). The slow test uses an electric motor to push the nail into the battery and the fast test uses a nail gun. In both tests the nail is left imbedded in the cells, imposing a severe short-circuit and examples will be shown. Historically for some tests, pouch cell designs do not appear to be as safe as metal cylinder cells. This is in part because that cell design allows air to enter the cells more readily. However, it has been observed that the fire produced by a pouch cell is less intense than the flames emitted from cylindrical cells when they vent. Thus, cell/battery designs have a significant impact on a large format lithium-ion battery safety test performance. Impact tests are highly relevant to many lithium-ion battery applications, especially for future large format battery designs. The data shows that, although a battery may have passed a certain series of tests, it does not necessarily mean that it is safe to physical abuse when in the fully-charged state. It is important to understand what testing was carried out and the condition of the battery. For example, one severe test is bullet penetration, which can have a range of results depending on the cell materials and state of charge. An example of such a test at the cell level is shown in the figure below for the bullet penetration of a 4.5 Ah lithium cobalt oxide pouch cell and a 2.3 Ah lithium iron phosphate spirally wound cell. Both are fully charged lithium-ion cells that did not catch fire when penetrated, with only some frothing of the electrolyte seen in the spirally wound cell. However, when multiple cells are placed in a battery pack it will be discussed that in most circumstances they behave more hazardously. A brief history of design failures observed will also be presented.

Figure 1
(Invited) The Scalability of Accelerating Rate Calorimetry (ARC) with State of Charge and Capacity
Authors: Lamb Joshua , Torres-Castro Loraine , Karulkar Mohan , Stanley June
Published: February 2020

Sandia National Laboratories has used Accelerating Rate Calorimetry (ARC) as a means to evaluate and compare the total energies of thermal runaway. This has been an invaluable tool for evaluating the behavior of new chemistries as they become available in commercial and prototype cells. However, this testing has typically been performed in 18650 cells of ~1-1.5 AH and on cells at 100% state of charge. This has been invaluable for the evaluation and comparison of the thermal runaway of different lithium ion battery chemistries, however it leaves open questions as how changes to energy density, cell size and state of charge impact the results from calorimetry testing.

This work examines the results of accelerating rate calorimetry testing on different lithium ion cathode chemistries (LCO, NCA, NMC, LFP) different formats (18650, pouch, large format cylindrical) and states of charge to understand how ARC results are impacted by both energy density and total energy. Also studied are how thermal runaway is impacted by energy in general, looking at both the total energy release during thermal runaway as well as the peak heating rates observed. While the total energy release is expected to correlate with the stored energy of the cell, the peak heating rates will impact how cells might behave in a variety of conditions. This has implications for battery design, as data suggests that even cells at relatively low states of charge may be hazardous if sufficiently insulation allows self-heating to occur even at relatively low rates; figure 1 shows data collected on 14 AH pouch cells summarizing the observed runaway energies and peak heating rates. This shows a relatively linear response as the stored energy increases, however an exponential response is observed with respect to state of charge. While this affirms the conventional wisdom that low state of charge cells are unlikely to go into thermal runaway in most environments, we can still see significant stored energy even at relatively low states of charge. The right conditions may still make these cells hazardous, making it important to fully understand the thermal decomposition of cells under a wide variety of conditions.

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.

Figure 1 Comparison of total enthalpy observed during runaway of a 14 AH pouch cell to the peak heating rates at various states of charge.

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The Comparison of Thermal Stability and Safety between Fresh and Aging Large Capacity Lithium Ion Battery with Silicon Carbon Anode
Authors: Hsu Hungjen , Liu Xiang , Feng Xuning , Lu Languang , Ouyang Minggao
Published: February 2020

Due to the high energy density, lithium ion battery (LIB) plays an important role in electric vehicle (EV). However, the requirement to the energy density keeps increasing. More and more materials are selected to improve the energy density to provide more distance for EV. Silicon, as a famous anode material, provides much higher specific capacity (3579-4200 mAh/g) than graphite (372 mAh/g) does. This research focused on thermal stability and safety of a 30Ah battery with silicon carbon anode. Aging battery would also be compared with the fresh battery after several cycles to different state of health (SOH). The batteries would be analyzed by accelerating rate colorimeter (ARC) to determine the safety. The differential scanning colorimeter (DSC) evaluated the thermal stability of the batteries. The thermal stability of ARC is decided by T1, T2 and T3 which are the self-heating temperature, thermal runaway triggered temperature and the highest temperature, respectively. The scanning electron microscope (SEM) could observe the surface differences with different SOH and various silicon proportion. The research revealed an overall safety assessment of the lithium ion battery with different content of silicon anode under different SOH.

Keywords: Lithium ion battery, silicon carbon, thermal runaway, thermal stability

Figure 1