bluuebunny/crossref_metadata_2025 huggingface dataset:
Highly Efficient Electrogenerated Chemiluminescence of Au22SG18 Nanocluster in Aqueous Solution
Authors: Kim Jaeyoon , Pyo Kyunglim , Lee Dongil , Lee Won-Yong
Published: February 2020

Quantum sized metal nanoparticles have attracted wide attention in recent years because of their large potential of application. Among various metal nanoparticles, Au22SG18 nanocluster has unique optical and electrochemical properties. The Au22SG18nanocluster consist of 22 gold atoms and 18 thiolate ligands. In this study, the Au22SG18 nanocluster is synthesized and its electrogenerated chemiluminescence (ECL) properties have been characterized for the detection of amine compounds such as tripropylamine (TPA) and 2-(dibutylamino) ethanol (DBAE). Especially, ECL of Au22SG18 nanocluster can be generated in aqueous phase. Highly efficient ECL is achieved by using potential pulse method, which increases the ECL intensity. Experimental pulse condition has been optimized. The experimental result demonstrates that the ECL of Au22SG18 nanocluster holds great promise of ECL application in analytical sciences.
Specific Surface Nitride Groups on Glassy Carbon Model Surfaces to Catalyze the Vanadium Redox Reactions
Authors: Greese Tobias , Friedrich Franziska
Published: February 2020

Vanadium redox flow batteries currently have come closer to their suitability in the industrial as well as the private sector. However, they still suffer from high capital costs, mainly ruled by the conversion unit consisting of an assembly of sandwiched components, such as semipermeable membranes and carbon electrodes (MEA). The respective system power output scales with and determines the necessary geometric area of the MEA. By increasing the area specific power output of a MEA capital costs may be reduced. As electrodes commonly porous graphite felt (GF) electrodes are used which are made of a woven of carbon fibers. When pumping the (sulfuric acid) electrolyte through these graphite felts, the Vanadium (V) ions dissolved in the electrolyte can pass the carbon surface of the fibers where the anodic V2+/3+ and the cathodic V4+/5+ redox reactions take place, respectively. A big portion of the power losses result from the kinetic overpotentials that need to be applied on the porous carbon electrodes in order to drive the Vanadium reactions.(1)

In recent years various modification methods of the carbon electrodes have been proposed.(2,3) Besides surface oxide groups there were a few attempts that involved nitrogen atoms which were supposed to offer a catalytic activity for the Vanadium reactions. This work aims to resolve the variable catalytic activity coming from distinctive nitride surface groups.(4,5)

For this purpose, on glassy carbon there were synthesized artificial aromates containing a nitro group, which covalently bind to the carbon surface and provide an anchor site for the Vanadium redox reaction. The synthesis method is resulting in a narrow distribution of architecture of different surface nitrides. This allows for an exclusive examination of the catalysis of distinctive, specific nitrogen involving surface groups for the Vanadium reactions and shows pathways for advanced modification methods.

Experimental results will comprise rotating disk electrode (RDE) measurements in an electrochemical half-cell. Moreover, x-ray photoemission spectroscopy results depict the surface coverage of the newly created adsorbants. In addition, the performance and changed efficiency of a single cell is presented, which is equipped with GF electrodes comprising the surface nitrides evaluated before.

The project is financially supported by the Bavarian Ministry of Economics.

(1) Parasuraman et al. Electrochimica Acta (2013) 101 27–40.

(2) J.-Z. Chen et al. Journal of Power Sources (2015) 274 894–898.

(3) K.J.Kim et al. Mat. Chem. And Phys. (2011) 131 547-553.

(4) S. Wang et al. J. Phys. Chem. Lett. (2012) 3 2164−2167.

(5) Y. Shao et al. Journal of Power Sources (2010) 195 4375–4379.
Electrochemistry of Superatomic M@Au24(SR)18 (M=Pd, Pt) Clusters and Their Application in Electrocatalysis
Authors: Kwak Kyuju , Choi Woojun , Kim Minseok , Tang Qing , Jiang De-en , Lee Dongil
Published: February 2020

Atomically precise gold clusters containing from a few to a few hundreds of atoms have been the focus of recent investigations because of their unique electronic structures with high chemical and thermodynamic stability. In particular, the extraordinary stability of these superatom-like gold clusters, for example [Au25(SR)18]- where SR is organothiolate, arises from the closure of superatomic electron shells, leading to a noble-gas-like 8-electron configuration (1S21P6). In this presentation, we report that replacing the core Au atom with Pd or Pt results in stable bimetallic clusters, [MAu24(SR)18]0 (M = Pd, Pt), having a superatomic 6-electron configuration (1S21P4). These clusters exhibit dramatically different optical and electrochemical properties from those of the 8-electron [Au25(SR)18]-. The highest occupied molecular orbital−lowest unoccupied molecular orbital gaps of [PdAu24(SR)18]0 and [PtAu24(SR)18]0 determined by voltammetry were drastically decreased to 0.32 and 0.29 eV from that of [Au25(SR)18]- (1.32 eV), respectively, indicating their electronic structures were significantly altered upon doping of the foreign metal. The unique electrochemical properties observed from the stable bimetallic clusters suggest that doping of a cluster is a powerful means to fine-tune the redox properties of the cluster, offering special advantages in the development of new functional electrocatalysis. Voltammetric investigation shows that the PtAu24(SR)18 cluster exhibits exceptionally high catalytic activity for hydrogen evolution reaction (HER). The origin of the extraordinary catalytic activity of this cluster is discussed along with reaction mechanisms.
Elucidating the Synergetic Mechanism of Ni-Mo Electrocatalysts for the Hydrogen Evolution Reaction
Authors: Schwalbe Jay , McKay Ian Salmon , Cargnello Matteo
Published: February 2020

Hydrogen is a potential future energy vector and a current industrial feedstock. Currently, most hydrogen is produced through the fossil fuel dependent steam reforming reaction. Water electrolysis is a promising alternative, but is currently limited by the availability of non noble metal catalysts that are stable in acid and by the lack of highly active non-noble metal catalysts in base. Nickel based electrcatalysts are a promising option for active catalysts in base. While it is well known that molybdenum enhances the activity of nickel catalysts, the heterogeneous nature of electrode surfaces complicates efforts to gain a fundamental understanding of this enhancement. In our work, we create a series of electrodes by depositing three different sizes of nickel nanoparticles onto molybdenum substrates. This allows us to investigate the effect that distinct domains of molybdenum, rather than an alloy or co-deposited material, has on nickel. We find that the activity is highest for the largest particles, a result that suggests that the enhancement is not occurring solely at the interface. As it is been demonstrated that the coexistence of multiple nickel oxidation states in pure nickel systems increases activity, we posit that the molybdenum acts to maintain the requisite plurality of oxidations states on the nickel nanoparticles.
Electrochemical Reduction of 2,2-Dichlorovinyl Dimethyl Phosphate (Dichlorvos) at Carbon and Silver Cathodes
Authors: Mali Sonali , Peters Dennis G
Published: February 2020

Despite their negative ecological effects, halogenated organophosphates have been used as pesticides.  For example, 2,2-dichlorovinyl dimethyl phosphate (or dichlorvos), found in many household and commercial insecticides, can lead to contamination of runoff and rinse water that is toxic to birds, bees, aquatic organisms, and mammals. Remediation of dichlorvos has focused either on electrochemical oxidation1 or on reductive cleavage of its carbon–chlorine bonds at mercury.2
 In this study, we have examined the direct reduction of dichlorvos in dimethylformamide and acetonitrile at both carbon and silver cathodes.

Shown in Figure 1 are cyclic voltammograms for reduction of dichlorvos at both carbon and silver electrodes. Whereas reduction of dichlorvos at carbon shows a single irreversible cathodic peak, reduction at a silver electrode results in two overlapping cathodic peaks. Controlled-potential (bulk) electrolyses at potentials corresponding to those of the voltammetric peaks indicate that dichlorvos undergoes carbon–chlorine bond cleavage. Catholytes have been analyzed by means of gas chromatography–mass spectrometry (GC–MS) to separate, identify, and quantitate the electrolysis products.

 

References

1. Lu, M.-C.; Chen, J.-N.; Chang, C.-P. Chemosphere, 1997, 35, 2285–2293.

2. Subbalakshmamma, M.; Reddy, S. J. Electroanalysis
1994, 6, 521–526.

 

Figure 1
Mechanism of CO2 Capture in 1-Alkyl-3-Methylimidazolium Acetate: Is N-Heterocyclic Carbene Involved?
Authors: Kim Hyung J , Yan Fangyong , Dhumal Nilesh R
Published: February 2020

Ionic liquids (ILs) offer a promising alternative absorbent for CO2 capture because of their unique properties, such as negligible vapor pressures, high thermal stabilities, excellent CO2 solubilities and tunability. More importantly, ILs consisting of 1-alkyl-3-alkyl’-imidazolium cations paired with acetate anions can react with CO2 and form carboxylate compounds. N-heterocyclic carbene that can be formed via proton transfer from an imidazolium cation to an acetate anion is often invoked in the mechanistic explanation of these CO2–IL reactions. However, the detection of the carbene species has been elusive experimentally. In this talk, we present our results for classical and ab initio molecular dynamics simulations as well as for density functional theory calculations to gain molecular insight into CO2 capture by 1-ethyl-3-methylimidazolium acetate. Our analysis indicates that N-heterocyclic carbene is not formed and thus not involved in CO2 capture at room temperature. Based on our computational results, a novel concerted mechanism is proposed.
Preparation of Functionalized Yarns Via Ionic Liquid Based Natural Fiber Welding
Authors: Ryall Katherine E. , Fahey Patrick J , Durkin David P. , Fox Eric T , Haverhals Luke M. , De Long Hugh C. , Trulove Paul C
Published: February 2020

Natural fiber welding (NFW) is a process that uses controlled amounts of ionic liquid and molecular co-solvent(s) to swell and mobilize portions of a natural polymer substrate. By carefully selecting factors controlling NFW such as time, temperature and solvent system composition, partial dissolution occurs, mobilizing and redistributing only a small portion of the natural polymer and leaving much of the underlying substrate intact. The NFW process results in fibers with a shell of dissolved/mobilized polymer, permanently adhered to both the outer diameter of the fiber and (depending on the extent of welding) to the surface of adjacent fibers. When polymeric and/or particulate materials are added during the NFW process, these substances can be integrated into the natural polymer matrix and modify its properties to include novel functionalities. In the present work we have applied the NFW process to the modification of natural polymer yarns. We have studied the processing conditions that impact the NFW of natural polymer yarns and the accompanied incorporation of functional materials (e.g., magnetic, conductive, and capacitive). We will discuss the preparation these functionalized yarns, and we will show data for their analysis using tensile testing, infrared spectroscopy, and scanning electron and con-focal fluorescence microscopies.
Protective Ceramic Coatings on the Base of the Refractory Metals Carbides
Authors: Stulov Yuriy V. , Dolmatov Vladimir S. , Kuznetsov Sergey A.
Published: February 2020

The aim of this work was obtaining of the protective coatings of the refractory metal carbides such as NbC, TaC, Cr7C3 on carbon steels and carbon fibers with further study their properties.

The refractory metal carbides NbC, TaC, Cr7C3 were deposited on carbon steel and fibers by currentless transfer in molten salts at temperatures 1073-1123 K. The microhardness of refractory metal carbides on carbon steels at the cross section had the values 21 GPa, 29 GPa, 31 GPa for Cr7C3, NbC and TaC, respectively. The corrosion resistance of these carbides was studied in concentrated HCl, H2SO4 and H3PO4 acids at a room temperature during 48 hours. The corrosion tests were shown following rows of the chemical stability carbide coatings in HCl: Cr7C3>NbC>TaC; in H2SO4: TaC>Cr7C3>NbC; in H3PO4: Cr7C3>TaC>NbC. The wear resistance was evaluated by the mass loss of samples. The mass loss of a sample from a hardened St.3 was 35.2 mg cm-2 and that of a coated with a chromium carbide – 4.7 mg cm-2, niobium carbide – 2.9 mg cm-2 and tantalum carbide – 2.2 mg cm-2. Deposition of NbC coatings on parts of oil pumps increased their lifetime in several times. Coatings of Cr7C3 or TaC on the knifes for cutting rubber, made of St. 3, improve their wear resistance and increase a tool life in 2.0 – 2.5 times, respectively. Coatings of NbC or TaC on carbon fibers improve the mechanical resistance and they are compatible with fibers up to 1473 K in an aggressive atmosphere.
Effect of Electrolyte Composition on the Current Efficiency for Aluminium Deposition from Molten Fluoride Electrolytes with Dissolved Alumina
Authors: Morishige Taiki , Haarberg Geir Martin , Gudbrandsen Henrik , Skybakmoen Egil , Solheim Asbjørn
Published: February 2020

Aluminium is produced by electrolysis in molten cryolite alumina electrolytes according to the Hall-Heroult process. The current efficiency for aluminium in modern cells can be as high as 96 %. The main reason for loss in current efficency is the socalled back reaction between dissolved aluminium and the anode product CO2.

A laboratory cell to determine the current efficiency was recently modified to obtain more reliable results. Electrolysis was performed at constant current density, and the amount of deposited aluminium was determined. Effects of electrolyte composition and temperature were studied. The loss in current efficiency is strongly linked to the solubility of dissolved aluminium. Realistic values for the current efficiency were obtained. Further experiments to study effects of additions of impurities are under way.
"Solvate" Ionic Liquids, "Solvent-in-salt" Ionic Liquids, and "Deep Eutectic" Ionic Liquids. What are the Relationships - and the Ionicities?
Authors: Angell C Austen , Hasani Mohammad
Published: February 2020

Recently, in the search for alkali metal-containing electrolytes with higher conductivities than available in common ionic liquid systems, some interesting

systems have shown up. The most interesting ones are those that also have wide electrochemical windows and high alkali metal transport numbers, and when non-flammability is also included, the interest has indeed run high1
,
2. The aqueous systems ("water-in-salt" electrolytes) are the most recent on the scene, and are of special importance for obvious reasons, but they are closely related in principle to other also successful systems developed independently in different labs and so given different designations. All are characterized by being extremely concentrated in ions but modulated in properties by the presence of one or other type of molecular constituent in molar proportions up to 50% and in some cases greater. Some other examples, are the "solvate ionic liquids" of the Watanabe3 and Henderson4 laboratories in which Li+ ions exist 1:1 with polyglyme molecules, and the "deep eutectic" liquids used by Abbott and coworkers5 for the electrodeposition of higher valent metals, where again the autoionization of the multivalent ions is induced by equimolar proportions of a favorable (often oxygenic) ligand. Both are special cases of the more general "solvent-in-salt" class of electrolyte from the Chen-Armand collaboration6. In this talk we will review the relationship between these different types of ionic systems and examine their relative ionicities, ionic mobilities, and other key characteristic properties.

 

1 Suo, L. et al. “Water-in-salt” electrolyte enables high-voltage aqueous lithium-ion chemistries. Science
350, 938-943 (2015).

2 Suo, L. et al. Advanced High Voltage Aqueous Li-ion Battery Enabled by “Water-in-Bisalt” Electrolyte. Angewandte Chemie Int. Ed. (printed online) DOI (2016).

3 Ueno, K. et al. Glyme−Lithium Salt Equimolar Molten Mixtures: Concentrated Solutions or Solvate Ionic Liquids? J. Phys. Chem. B
 116, 11323-11331 dx.doi.org/11310.11021/jp307378j (2012).

4 Henderson, W. A. Glyme-lithium salt phase behavior. . J. Phys. Chem.
110, 13177-13183 (2006).

5 Abbott, A. P., Barron, J. C., Rydere, K. S. & Wilson, D. Chem.–Eur. J.
13, 6495. (2007).

6 Suo, L., Hu, Y.-S., Armand, M. & Chen, L. A new class of Solvent-in-Salt electrolyte for high-energy rechargeable metallic lithium batteries. . Nat. Commun.
4, 1481 (2013).
(Invited) Innovations in Ionic Liquids Electrodeposition of Metals
Authors: Reddy Ramana
Published: February 2020

A novel pathway for the high energy efficiency electrodeposition of metals from metal oxides and metal compounds by means of electrolysis in ionic liquids at low temperatures was investigated. Experimental results for electrochemical deposition of Zn from ZnO and Cu from Cu2O, Pb from PbO using Urea ((NH2)2CO) and Choline chloride (HOC2H4N(CH3)3
+Cl-) or (ChCl) are discussed. The results showed that pure metal was deposited on the cathode. Successful deposition of metal from metal oxide dissolved in Urea/ChCl (2:1) was accomplished with efficiency greater than 87%. Electrodeposition of aluminium and titanium using imidazolium chloride ionic liquids with the addition of AlCl3 and TlCl4 were carried out at low temperatures. The cathode deposits obtained were dendrite free pure aluminium (>99.9% pure) and Al-Ti (up to 37 wt %) alloy. Cathode current densities of up to 500 A/m2for electrowinning of aluminium were achieved.

The surface modification of electrodes not only improved the cathode current density but also eliminated the dendritic deposition of metals. Use of glassy surface finish, aluminum cathode and aluminum alloy anode improved the current density of the process. The critical cathode overpotential and limiting current density at which aluminum dendritic growth begins was determined as -0.53 V and 518 A/m2, respectively. Lower overpotentials (<0.42 V) prevent the dendrite formation in the aluminum deposits. It was concluded that the overpotential is the key in preventing dendrite formation.

A 3-D mathematical model (CFD) was developed for the batch reactor electrodeposition of metals process. The optimum conditions for electrodeposition of metals and alloys were determined. The model results are in good agreement with the experimental data for the Al electrowinning process.

The advantages of the electrodeposition of metals using ionic liquids compared to industrial aqueous metals processes are low temperature, low energy consumption, and low pollutant emissions.
(Invited) Towards Advanced Functional Natural Polymer Materials through Ionic Liquid Based Methods
Authors: Trulove Paul C , Durkin David P. , Fox Eric T , Haverhals Luke M. , Fahey Patrick J , Ryall Katherine E. , Head Audrey C. , Ye Tao , Shuai Danmeng , Fairbrother D. Howard , De Long Hugh C.
Published: February 2020

Throughout history humankind has exploited the remarkable properties of natural polymers such as silk and cellulose. In modern times, these natural materials still possess properties that rival the most advanced synthetic polymers. Recent work has shown ionic liquids (IL) to be effective solvents for the dissolution of a wide variety of natural polymers, and new materials can be created from these natural feedstocks by processes that involve their full dissolution and subsequent reconstitution. However, many reports show that the dissolution and reconstitution processes eliminate the native polymer structure, often with negative consequences to the physical properties of the resulting materials. Alternatively, if only the surface layers of these natural materials are mobilized through an ionic liquid facilitated process called Natural Fiber Welding (NFW), the underlying material retains its native character and mechanical properties while still allowing for significant material modification. Furthermore, the addition of functional materials (e.g. magnetic, conductive, antimicrobial) into the IL welding solution, allows for these substances to be entrained in and on the surface of the substrate imparting unique properties to the natural materials.

Our group has endeavored to utilize NFW to modify natural materials to introduce novel functionalities. This work has encompassed the incorporation of a wide variety of polymeric, organic and inorganic materials into natural fiber matrices. Through the introduction of the appropriate materials we have been able to impart capacitive, conductive, catalytic, magnetic, optical, antimicrobial, and/or fire retardant functionalites into natural polymeric materials. In this presentation we will show our most recent efforts utilizing NFW to prepare novel functional natural materials.
Towards Better Understanding of Molecular Solvent Behavior in Ionic Liquid-Biopolymer Mixtures
Authors: Fox Eric T , Fahey Patrick J , Gobet Mallory , Munoz Stephen , Head Audrey C. , Greenbaum Steven , De Long Hugh C , Trulove Paul C
Published: February 2020

Some ionic liquids (ILs) are notable for their ability to solubilize traditionally difficult to dissolve natural materials such as cellulose, silk, and wool keratin. NMR studies have shown that this ability is due predominantly to the interaction of chaotropic anions present in the IL, such as Cl- or acetate, with the hydroxyl groups present on polymeric materials. When molecular solvents are added to such mixtures, differing behaviors occur depending on the nature of the added solvent. Polar protic solvents generally serve as antisolvents, inducing the precipitation of dissolved materials. In contrast, polar aprotic solvents behave as cosolvents and are able to be added in significant fractions without causing the reconstitution of dissolved materials. It is generally understood that this differing behavior is the result of whether or not the molecular solvent preferentially interacts with the IL anion, thus preventing the anion from interacting with the polymer hydroxyl groups. However, little experimental work has been published to verify this hypothesis.

In this study, the physical and transport properties (density, viscosity, ionic conductivity, and ion diffusion coefficients) are reported for 1-ethyl-3-methylimidazolium acetate (EMIAc) containing dissolved cellulose. The properties of these EMIAc-cellulose solutions were studied with no added molecular solvent, with added acetonitrile, or with added water. The fraction of ions present in the IL that are “free” (the Ionicity values) were calculated for each solution. The addition of molecular solvents to an EMIAc-cellulose solution results in significant changes in the mobility of all species present, and offers a means to better understand the molecular interactions that govern biopolymer solvation in ILs.
SOFC Anode Process Characterization By Means of a Novel Spot-Sampling Set-up for in-Operando Gas Analysis
Authors: McPhail Stephen J. , Pumiglia Davide , Santoni Francesca , Conti Bruno , Boigues Muñoz Carlos , Bosio Barbara , Carlini Maurizio
Published: February 2020

The development and operation of an innovative experimental setup is presented for in-depth, in-operando characterization of anode processes of Solid Oxide Fuel Cells.

The idea behind this project is to realize a setup enabling the measurement of temperature and gas compositions using eleven points of sampling distributed over the anode surface. Simultaneous temperature measurement and gas chromatography are employed to detect the variation of thermodynamic and chemical conditions across the anode surface in steady state and in real time. The particular location of each sampling point is chosen in such a way as to minimize interference in the flow pattern across the anode but maximizing the spatial information of the measurements taken. Thus, it is possible to investigate the evolution of chemical reactions occurring during the operation of the cell, identified with a spatial resolution covering the whole surface of the anode in order to distinguish edge effects from bulk processes. Sampling settings are tailored to analyse representative specimens of anode gas without altering local conditions. Moreover, the novel housing allows for full simultaneous (bulk) electrochemical characterization through polarization curves and electrochemical impedance spectroscopy (EIS), maximizing the data output from a given experiment without significantly affecting the cell response during the characterization.

This experimental setup is particularly important for the direct fuelling of SOFCs with natural gas, biogas or syngas, where the dynamic processes of internal reforming can create severe local gradients of temperature and gas compositions, inducing stresses and possible carbon deposition. Single cell tests have been carried out on intermediate-temperature, commercial SOFCs fed with simple hydrogen and selected syngas compositions to assess the thermochemical response of the SOFC at different current densities and create a detailed spatial mapping of critical hotspots correlated with operating conditions and inlet gas compositions. It is thus possible to identify areas within the operational space that are conducive to better uniformity of conditions, presumed to enhance SOFC durability, allowing to provide recommendations for fuel pre-conditioning processes as well as SOFC operation modes. Ultimately, it is envisaged to establish simplified but effective control algorithms based upon the correlation of the detailed, real-time spatial mapping with key parameters that are easily monitored in a real SOFC system.

Experimental data will be useful to investigate phenomena occurring on the cell plane also with the help of a model based on finite element method that can simulate locally the behavior of the cell in order to validate the experimental map of temperature and composition of gases on the cell.
Multilayer Active Nanostructures of Metal Oxide Semiconductors-Assisted Photooxidation of Wastewater for Voltammetric Determination of Heavy Metals
Authors: Miecznikowski Krzysztof , Biadun Ewa , Gajewska Sylwia , Krasnodebska-Ostrega Beata
Published: February 2020

The presence of organic matter (e.g. surfactants) is the most crucial problem in many analytical methods, such as inductively coupled plasma mass spectrometry (ICP MS), graphite furnace atomic absorption spectrometry (GF AAS) or electrochemical methods (stripping voltammetry). Voltammetry is a sensitive method of metal determination, only one an alternative to ICP MS. Only one limitation of the method is an influence of the organic matrix on the measurements. After the wet digestion with H2O2 accelerated with UV irradiation the evaporation of an excess of reagent is required. We present the application of “sunlight” assisted digestion in the presence of bare WO3 or multilayer metal oxide semiconductors (e.g. WO3 and Fe2O3) to the decomposition of dissolved organic matter, using the anionic surfactant sodium dodecyl sulfate (SDS) and the nonionic surfactant (1,1,3,3-tetramethylbutyl)phenyl-polyethylene glycol (Triton™X-114) in natural water samples, prior to the determination of traces residues of lead by stripping voltammetry methods. The results of the study showed firstly that the preparation of reproducible WO3 layers characterized by high mechanical and chemical resistance was possible, and secondly that it was also possible to obtain a high efficiency of decomposition, equal in efficiency to that of the reference method, which was the hydrogen peroxide oxidation assisted by UV, with evaporation nearly to dryness. The developed procedure is suggested to be a no-reagents method for the decomposition of added SDS, leading to 100 % recovery of added Pb (II). Physicochemical properties (structure, morphology and spectroscopic identity) of the resulting hybrid (composite) WO3 films were assessed using X-ray diffraction, scanning electron microscopy, as well as UV-Vis and Raman spectroscopies. The electrochemical method (anodic stripping voltammetric - ASV) will be applied in practical study of the determination of various trace metals in natural water samples. For comparison, GFAAS and ICP-MS measurements would be performed as reference methods confirming the correctness of electrochemical measurements due to their different tolerance to the presence of the organic matrix in the samples.
Photoelectrochemical Properties of Si-Doped InGaN Photoelectrode Grown By Plasma Assisted Molecular Beam Epitaxy
Authors: Shen Yu-Min , Chen Li-Chyong , Chen Kuei-Hsien
Published: February 2020

In this work, high quality epitaxial Si-doped InGaN films were grown on Si (111) substrate using plasma assisted molecular beam epitaxy (PAMBE) via controlling of Si flux. X-ray diffraction results showed controllable formation of c-axis Si:InGaN with different Si compositions, while XPS results indicate the Si was subsisted Ga site. Transmission electron microscope image showed the Si:InGaN films were grown epitaxially without phase separation with lattice mismatch between Si:InGaN and Si substrate of less than 1%. Photoelectrochemical (PEC) study was done under NaOH solution to achieve an optimum efficiency of 1.6% at 0V (vs. Ag/AgCl) with sample of Si flux at 6 x 10-9 torr. The series resistances of InGaN and Si:InGaN were reduced from 43.6Ω to 18.7Ω which was determined utilizing electrochemical impedance spectroscopy (EIS). The carrier concentration between Si:InGaN and InGaN were 9.4 x 1016 and 2.6 x 1018 cm-3, which was lead 2 times higher photocurrent density (0.8 and 1.6 mA/cm2, respectively) from Mott Schottky plot. Factors that might influence the PEC performance, such as the flat band position, crystallinity, and protons diffusion length will be addressed in this paper to obtain better insight into the issue of Si:InGaN for PEC.

Keywords: plasma assisted molecular beam epitaxy, Si:InGaN, water splitting, carrier concentration

Figure 1
Can Platinum Scale for PEC Hydrogen Evolution at the Terawatt Level?
Authors: Vesborg Peter C. K. , Bodin Anders , Pedersen Thomas , Sebok Bela , Mei Bastian Timo , Seger Brian , Hansen Ole , Chorkendorff Ib , Kemppainen Erno , Halme Janne , Lund Peter
Published: February 2020

Recent years has seen enormous and impressive progress in the search for non-precious hydrogen evolution reaction (HER) catalysts for both electrolysis and photoelectrochemical water splitting (PEC) with the molybdenum sulfide– and the cobalt phosphide families of HER catalysts showing great potential [1]. Despite the progress, no non-precious catalyst which matches platinum in HER performance has yet been found. To a large degree, the hunt for non-precious HER catalysts is motived by the notion that the physical scarcity and high price of platinum precludes it from usage on the terawatt scale. Using numerical modelling supported by benchmarking experiments on very well-defined platinum-based PEC electrodes we demonstrate that platinum in principle offers sufficiently fast kinetics to be useful on the terawatt level. As may be seen in the insert in figure 1 just 54 tons of platinum (which corresponds to ca. 30% of the global annual production [2]) would in principle be enough to support 1 TW of HER at a PEC current density of 10 mA/cm2 at a modest overpotential of 50 mV.[3] We discuss the platinum requirement under different assumptions and also the potential problems of using platinum in real-world PEC systems.

Refs

[1] P.C.K. Vesborg, et al., J. Phys. Chem. Lett., 6, (6) p. 951-957, (2015)

[2] P.C.K. Vesborg & T.F. Jaramillo, RSC Advances, 2, (21), p. 7933-7947, (2012)

[3] E. Kemppainen et al., Energy & Environmental Science, 8, p. 2991-2999 (2015)

Figure: Overpotential vs. of platinum loading for PEC-relevant current densities and (insert) total platinum requirement to implement 1 TW (average power, at a 15% capacity factor) of PEC hydrogen production.

Figure 1
Development of Efficient, Stable and Intrinsically Safe Photoelectrochemical Solar-Hydrogen Prototypes
Authors: Xiang Chengxiang("CX")
Published: February 2020

Artificial photosynthesis offers an attractive way to store solar energy in the form of fuels at the terawatt scale. An integrated solar-driven water-splitting cell has great promise in producing cost competitive, renewable hydrogen from the sun at large scale. The key performance requirements for such an integrated system include high conversion efficiency, long-term stability, earth-abundant materials and product separation for safety. While significant advances in photoelectrochemical water-splitting have been made in the materials discovery, component integrations, cell designs and full device demonstrations, proof-of-concept demonstrations in literature have failed to meet all four requirements simultaneously.

Recently, in Joint Center for Artificial Photosynthesis (JCAP) at Caltech, we have developed several high efficiency photoelectrochemical water-splitting prototypes based on InGaP/GaAs tandem photoabsorbers. The custom designed tandem stack produced optimal current voltage characteristic for direct solar-hydrogen generation. I will briefly talk about the development of both photocathode-based and photoanode-based prototypes that were designed and constructed for different electrolyte and operational conditions. I will focus on one specific prototype design that employed a bipolar membrane. The integrated photoelectrochemical cell showed spontaneous solar-driven water splitting at the 1 sun illumination and operated sustainably under a steady-state pH gradient. A record performance combination (>10% efficiency, >100 hours stability, full product gas separation and all earth-abundant electrocatalysts ) in a relatively large area (> 1 cm2) photoelectrochemical system has been achieved. The performance of prototypes under the realistic outdoor conditions will also be discussed.
The Effect of Anisotropic Physical Properties of Cu(InxGa1-x)(Se,S)2 (CIGS) Single Crystal Photocatalysts on Water Splitting
Authors: Frick Jessica Jane , Kushwaha Satya K , Krizan Jason W , Baruch Maor , Cava Robert J , Bocarsly Andrew B.
Published: February 2020

The photoelectrochemical splitting of water to produce H2 and O2 is an attractive process for the large-scale production of clean, recyclable H2. The field of solar water splitting has gradually divided into either using conventional materials as thin films with stabilization layers or developing new materials that are themselves stable in electrolyte solutions under illumination. Divergent from these paths, we are investigating semiconductors in their single crystal form in order to take advantage of the physical properties unique to crystalline materials that are likely to cause a significant impact on photoactivity. Due to crystalline anisotropy, the crystallographic orientation of the exposed electrode surface is anticipated to affect the overall efficiency of the photocatalytic water-splitting process and the photostability of the material.

Moderate band gap ternary chalcopyrites are a promising class of semiconductors for photoelectrochemical water splitting. Specifically, copper-indium-gallium dichalcogenides (diselenide or disulfide) [Cu(InxGa1-x)(Se,S)2]—abbreviated as CIGS—appear interesting due to their ideal, tunable light-absorption properties and band edge positions. To date, CIGS research has focused solely on thin film of nanoparticle materials. Electrodes based on these materials have demonstrated activity as photocathodes in photoelectrochemical cells (PEC) for water splitting.

The role of crystallographic quality of CIGS in single crystal form has yet to be examined in PEC water splitting studies. The tetragonal crystal lattice structure of CIGS (Figure 1) gives a degree of asymmetry to the crystals, generating anisotropic properties in different lattice planes. Anisotropic variability has been shown to affect the optical, magnetic, and thermal expansion properties of CIGS. These differences in physical properties are expected to generate a crystal face dependence on the photoelectrochemical response of CIGS. In this presentation, we will report on the solid-state synthesis of oriented CIGS single crystal electrodes, along with the effects of crystallographic orientation on the efficiency of water-splitting.

Figure 1: Tetragonal crystal structure of CIGS chalcopyrite semiconductors. View along the c-axis (left); view along the a-axis (right). Cu atoms are copper, In/Ga atoms are teal, and Se/S atoms are yellow.

Figure 1
Interfacial Charge Dynamics of in2S3-Decorated TiO2 Nanowires
Authors: Hsieh Ping-Yen , Hsu Yung Jung
Published: February 2020

Ultrafast laser spectroscopy such as time-resolved photoluminescence is a powerful tool to retrieve dynamical information on the early steps of charge carrier transfer. In the past few years, considerable efforts have been devoted to studying interfacial charge dynamics of semiconductor heterostructures and realizing their implications in the photocatalytic processes. On the other hand, electrochemical impedance spectroscopy has demonstrated practical capability of revealing the reaction kinetics at the electrode/electrolyte interface, which is important for estimating the electrode efficiency for electrochemical reactions. Here we present the interfacial charge dynamics for In2S3-decorated TiO2 nanowires, which represent a typical TiO2-based type-II heterostructure system that has been widely used for photoelectrochemical water splitting. Because of the band alignment, the photoexcited electrons would preferentially transfer from In2S3 to TiO2, while the photogenerated holes were transported in an opposite direction from TiO2 to In2S3. Time-resolved up-conversion photoluminescence and electrochemical impedance spectroscopy were utilized to monitor the generation of charge carriers, the subsequent relaxation and recombination processes as well as their further involvement in the water splitting reaction. A temporal scheme which depicts the carrier lifetime at each of the above deactivation pathways was established to fully understand the fate of charge carriers within the In2S3-decorated TiO2 samples. The in-depth understanding of charge carrier dynamics can boost insights into the factors dictating the overall carrier utilization efficiency, which is imperative to the intelligent design of optimalsemiconductor nanostructures for photoelectrochemicalapplications.
Highly Stable Catholyte Based on Vanadyl Acetylacetonate for Non-Aqueous Redox Flow Batteries
Authors: Tung Siu on , Thompson Levi T , Kucharyson Jonathan F.
Published: February 2020

The electrochemical oxidation of vanadium acetylacetonate produces vanadyl acetylacetonate limiting its use in non-aqueous redox flow batteries. The vanadyl has also drawn little interest as a catholyte active species despite its favorable voltage potential (0.7V vs. Ag/Ag+). This is mainly due to its low solubility (0.05M) in acetonitrile. Our recent bulk electrolysis studies, however, indicate that the reduction of vanadyl is highly reversible. For example, there was no capacity fade for >100 cycles at 70% state of charge. In this paper, we investigate the charge storage capabilities and stability of vanadyl acetylacetonate. Long term (10+ days) charge/discharge experiments are performed with vanadium acetyacetonate as the anolyte at various C-rates. While the relationship of increasing coulombic efficiency with increasing C-rates seems obvious at first, further analysis by normalizing the coulombic inefficiency with cycle time shows that the parasitic reaction rate of these experiments are identical. This suggests that the degradation in each experiment is independent of cycle number, but simply dependent on time. We attributed these parasitic reactions to either active species crossover or material degradation. Permeability experiments and shelf life studies are then performed to quantify the individual contributions of crossover and material degradation to the observed parasitic reactions. The results suggest that crossover accounts for more than 95% of the inefficiency during charge/discharge, while degradation of the catholyte and anolyte have minimal contribution. This work emphasizes the growing need for better membranes and separators for non-aqueous redox flow batteries. Work is also ongoing to further improve the stability and solubility of vanadyl acetylacetonate using design strategies previously reported for vanadium acetylacetonate.
Room Temperature, Hybrid Na-Based Flow Batteries with Organic Catholytes and Multi-Electron Transfer Redox Reactions
Authors: Shamie Jack , Liu Caihong , Shaw Leon , Sprenkle Vincent
Published: February 2020

Redox flow batteries (RFBs) have attracted significant interest lately for use in grid-scale electrochemical energy storage. One of the most studied RFB systems is the all vanadium RFB. Due to a phenomena known as crossover, RFBs suffer from rapid capacity decay in which the catholyte and anolyte become mixed during cycles. In addition, the energy density of RFBs is low. To increase the cell voltage and thus energy density, organic electrolytes can be used to replace aqueous electrolytes. However, to date the organic electrolyte based RFBs have not offered higher energy densities due to the low solubility of ions in electrolytes. Recently, we have introduced a new concept of hybrid Na-based flow batteries (HNFBs) with a molten Na alloy anode in conjunction with a flowing catholyte separated by a solid Na-ion exchange membrane. This new type of room temperature flow batteries address low energy density and crossover issues simultaneously. In this study we have investigated the redox reaction mechanism of an organic catholyte made of vanadium acetylacetonate, V(acac)3, in acetonitrile solvent. We demonstrate that with the newly invented HNFB the V(acac)3 catholyte can provide multi-electron transfer redox reactions per vanadium ion to enhance the energy density of the HNFB while possessing tolerance to the impurity water in the system. In conventional RFBs the impurity water reacts with oxidized V(acac)3 to become vanadyl acetylacentonate, VO(acac)2, leading to gradual degradation of the cell. This study, for the first time, shows that the reaction between the impurity water and oxidized V(acac)3 can be utilized as an energy storage mechanism enabled by HNFBs to enhance the energy density of the cell.
Synthesis and Electrochemical Performance of CuxSy Miro-Sphere As an Anode Material for Sodium Ion Battery
Authors: Shin Donghyeok , Park Hyunjung , Song Taeseup , Kim Youngsik , Paik Ungyu
Published: February 2020

Sodium ion batteries (SIBs) have risen as an alternative to lithium ion batteries due to abundant on the earth’s crust and low cost. Many cathode and anode materials for SIBs have been explored, however, many challenging issues are still remained for commercially use. Copper sulfides (CuxSy) were proven to be potential anode materials for lithium-ion battery due to their high specific capacity and excellent rate capability. Here, we report the synthesis of CuxSy micro-sphere and their electrochemical performance as a new anode material for SIB was investigated. CuxSy micro-sphere have been synthesized by a solvothermal method and heat treatment with an average diameter of these particles are about ~5μm. CuxSy mirco-sphere electrode shows a high reversible discharge capacity of ~350 mAh/g at 0.1C, stable cycle performance and capacity retention of ~ 300 mAh/g even at 2C.

Figure 1
Prussian Blue Analogue Materials for Sodium-Ion Batteries
Authors: Lee Hyun-Wook , Cui Yi
Published: February 2020

Battery-based electrochemical storage is particularly attractive because of its high energy efficiency and ease of deployment, and lithium-ion batteries (LIBs) are one of the most well developed of these options. Sodium-ion batteries (SIBs), which replace lithium with abundant and inexpensive sodium, have received a great deal of attention recently. Similarities in manufacturing techniques between SIBs and LIBs may significantly accelerate their technological advance. Nevertheless, several scientific challenges still need to be resolved before the performance of SIBs becomes competitive with that of LIBs. In particular, the higher negative redox potential of Na compared to that of Li results in lower cell voltages and consequently lower energy densities. Moreover, the larger size of Na+ relative to Li+ causes slower solid-state diffusion in the active materials and leads to lower energy efficiencies when the batteries are rapidly charged or discharged. High capacity electrode materials with fast solid-state kinetics are therefore required in order to compensate for these intrinsic limitations.

In this presentation, I will introduce low-vacancy, sodium manganese hexacyanomanganate (MnHCMn) as a viable cathode material for SIBs. The as-synthesized MnHCMn shows a monoclinic crystal structure composed of nonlinear Mn–N≡C–Mn bonds and containing eight large interstitial sites occupied by Na+ ions. Our experiments demonstrate a high specific capacity of 210 mAh g-1 and excellent capacity retention at high rates in a propylene carbonate electrolyte. We discovered a novel mechanism wherein small lattice distortions allow for the unprecedented storage of 50% more sodium cations than in the undistorted case. These results represent a step forward in the development of sodium-ion batteries.
In Searching for Electrolyte Compatible with NaMnO2 Cathode Material in Sodium Ion Battery
Authors: Ma Tianyuan , Xu Gui-Liang , Li Yan , Song Boao , Zeng Xiaoqiao , Sun Chengjun , Ren Yang , Heald Steve M. , Jorne Jacob , Shahbazian-Yassar Reza , Amine Khalil , Chen Zonghai
Published: February 2020

In the past few years, concerns over lithium reservoir depletion have driven researchers to go beyond lithium ion battery[1]. Sodium ion battery (SIB) has been considered as a promising candidate as sodium is highly abundant and widely distributed around the world.

One of the challenges in state of the arts sodium ion battery is searching for cathode materials that can provide electrochemical performance comparable to lithium ion battery and electrolytes compatible with the related cathode materials. Among the reported cathode materials for SIB, O3 or O'3 type layered transition metal oxides are of great interest due to their high specific capacities[2]. In order to get a better understanding on these transition metal oxides, it is important to decouple the mixing transition metals and carry out a thorough investigation on the end member of the series. One of the end members, NaMnO2, has been reported with high specific capacity but shown low coulombic efficiency[3], which may be associated with electrolytes decomposition. Therefore, it is critical to search for a suitable electrolyte as well as additives.

The influence of FEC (Fluoroethylene Carbonate) additive and some commonly used electrolytes in sodium ion battery were examined in NaMnO2/Na coin cells. For the cell using 1M NaClO4/PC as electrolyte, coulombic efficiency is relatively low at first but increases to 94% within ten cycles. While the coulombic efficiency of NaPF6/EC+DMC stays as low as 80% till 40 cycles. Apparently, the coulombic efficiency can be improved by adding FEC as additive in both electrolytes. The study regarding function mechanism for the FEC additive will be comprehensively understood by in-situ high energy X-ray diffraction and high precision electrochemical test, which could serves a good guide for the exploration of suitable electrolytes for high performance cathode materials of SIB.

Figure 1