bluuebunny/crossref_metadata_2025 huggingface dataset:
Electrochemical Reduction of Primary Alkyl Halides with the Aid of a Structurally Modified Nickel Salen Catalyst
Authors: Goodson Austin , McGuire Caitlyn M. , Mubarak Mohammad S. , Peters Dennis G
Published: February 2020

Electrochemical reduction of primary alkyl halides has been extensively investigated through the use of [[2,2′-[1,2-ethanediylbis(nitrilomethylidyne)]bis[phenolato]]-(N,N′,O,O′)]nickel(II) (nickel salen) as a procatalyst. In these studies, there was a proclivity for the grafting of alkyl chains onto the imino (C=N) bonds of the nickel species, which lowers the yields of the desired reduction products significantly.1,2 In the present study, we have used a structurally modified nickel(II) salen-like species possessing methyl protecting groups to improve the performance of the catalyst.3 The efficacy of this modified nickel species as a procatalyst for electrochemical reductions of 1-bromo- and 1-iododecane has been studied with the aid of cyclic voltammetry and controlled-potential (bulk) electrolysis in N,N-dimethylformamide (DMF) containing tetra-n-butylammonium tetrafluoroborate (TBABF4) as a supporting electrolyte. Results indicate that a majority of the reduced substrate appears as a dimeric species (n-eicosane); in addition, smaller amounts of n-decane and 1-decene are found. A mechanism is proposed for the process that involves radical intermediates. Several products corresponding to the incorporation of DMF fragments into the reduced substrate were detected. Use of this procatalyst has also been investigated to overcome solvent incorporation under similar conditions in an acetonitrile medium.

References

Goken, D.M.; Ischay, M. A.; Peters, D. G.; Tomaszewski, J. W.; Karty, J. A.; Reilly, J. P.; Mubarak, M. S. J. Electrochem. Soc.
2006, 153, E71–E77.

Raess, P. W.; Mubarak, M. S.; Ischay, M. A.; Foley, M. P.; Jennermann, T. B.; Raghavachari, K.; Peters, D. G. J. Electroanal. Chem. 2007, 603, 124–134.

Ourari, A.; Ouennoughi, A.; Aggoun, D.; Mubarak, M. S.; Pasciak, E. M.; Peters, D. G. Polyhedron
2014, 67, 59–64.

Figure 1
(Invited) Electron-Transfer Approaches to Metal-Free Ring-Opening Metathesis Polymerization
Authors: Boydston Andrew J , Goetz Adam E , Pascual Laura M M , Ashikari Yosuke , Ogawa Kelli A
Published: February 2020

We have recently discovered a method of performing ring-opening metathesis polymerization (ROMP) via an electrochemically-mediated process involving electron rich olefin initiators and norbornene-based monomers. The method expands upon the powerful, metal-mediated approaches toward ROMP that have been successful for the production of polymers with precise structure and function. A key distinction is our ability to integrate organocatalysis and electro-organic synthesis to circumvent the need for metal-based initiators. In this way, electromediated ROMP has opened the doorway to metal-free protocols that have the potential to provide materials with unique optical, electronic, and materials properties.

Inspired by the pioneering work of Chiba and coworkers, we explored the hypothesis that anodic oxidation of vinyl ethers could be used to initiate and mediate polymerization of strained cycloalkenes via a ROMP mechanism. Toward this end, we evaluated vinyl ethers in combination with norbornene as a common ROMP monomer to determine the viability of electromediated ROMP. Although initial conversions of norbornene to polynorbornene were low, we were able to confirm initiation by the vinyl ether and successful polymer formation. Consideration of the key limiting factors in our initial electromediated ROMP conditions, which appeared to be poor solubility of norbornene and polynorbornene, led us to consider photoredox and indirect electrolysis approach. We will discuss recent successes with organic photo-oxidants capable of facilitating metal-free ROMP in high conversions with excellent temporal control. In addition, we will present our latest results on the use of organic mediators to facilitate metal-free ROMP via indirect electrolysis.
Highly Soluble Quinones As Active Materials for Nonaqueous Redox Flow Batteries
Authors: Takenaka Keisuke , Shimizu Akihiro , Yoshida Jun-ichi
Published: February 2020

The redox flow battery has received significant research interest as a large scale energy storage system for renewable-energy sources. Although the all-vanadium aqueous redox flow battery has been most developed, its energy density is not sufficient mainly because of narrow electrochemical stability window of water. Therefore, recent efforts have shifted to developing nonaqueous redox flow batteries because they can achieve higher voltage due to wider electrochemical stability window of nonaqueous electrolytes. However, nonaqueous redox flow batteries generally suffer from insufficient energy densities because of low solubility of organic active materials in nonaqueous electrolytes.

In this study, we designed and synthesized two highly soluble organic active materials, benzoquinone 1 and naphthoquinone 2 having diethylene glycol mono methyl ether groups. Both 1 and 2 were highly soluble in propylene carbonate (PC). Charge-discharge properties of the batteries using 1 and 2 as organic active materials were measured in LiBF4/PC using a cell equipped with a carbon fiber anode, a lithium-metal anode, and a glass filter separator. The charge-discharge measurements showed that 1 and 2 exhibited high voltages of ca. 3 V and good charge-discharge properties. Notably, 2 showed a higher energy density than conventional all-vanadium aqueous redox flow batteries.
(Invited) One-Step Aerobic Oxygenation of Hydrocarbons By Electron Transfer
Authors: Ohkubo Kei
Published: February 2020

Photoinduced oxygenation of neat cyclohexane in the presence of O2 occurred under visible light irradiation of 2,3-dichloro-5,6-dicyano-p-benzoquinone (DDQ) which acts as a super photooxidant [1-3]. The products detected by GC and NMR analyses were cyclohexanol, cyclohexanone and cyclohexane hydroperoxide with 70, 40, 210% yields, respectively. When cyclohexane was replaced by n-butane, n-pentane and 3-methylpentane, the oxygenation reactions also took place to form the corresponding oxygenated products under the otherwise same photochemical reaction conditions.

The reaction mechanism was clarified by femtosecond and nanosecond laser flash photolysis measurements. Femtosecond laser irradiation of DDQ in cyclohexane results in formation of the singlet excited state of DDQ (1DDQ*; * denotes the excited state) detected as a transient absorption band at 480 nm. The band of 1DDQ* decayed with increasing a new absorption band at 590 nm and 630 nm, which are assigned to 3DDQ* and DDQ semiquinone radical anion (DDQ•–), respectively. Thus, the photocatalytic reactions are initiated by electron-transfer oxidation of cyclohexane (CyH) with 1DDQ* to form the cyclohexane radical cation (CyH•+), which reacts with DDQ•– to produce the cyclohexyl radical (Cy•) and DDQ semiquinone radical (DDQH•). The triplet excited state (3DDQ*) generated by the intersystem crossing of 3DDQ* is also reacts with CyH to produce radical ion pair. Cy• reacts with O2to produce the final oxygenated products via radical chain process.

[1] Ohkubo, K.; Fujimoto, A.; Fukuzumi, S. J. Am. Chem. Soc.
2013, 135, 5368.

[2] Ohkubo, K.; Hirose, K.; Fukuzumi, S. Chem.–Eur. J.
2015, 21, 2855.

[3] Fukuzumi, S.; Ohkubo, K. Asian J. Org. Chem.
2015, 4, 836 (Focus Review).
Microelectrode Arrays and the Move Toward Practical Applications
Authors: Moeller Kevin D , Uppal Sakshi , Graaf Matthew , Yeh Nai-Hua , Li Weiqiang
Published: February 2020

Microelectrode arrays have great potential as a platform for monitoring the interactions between small molecules and biological receptors in “real-time”. For this reason, we have developed new polymer coatings for the arrays, new site-selective methods for building or placing molecules by electrodes in the arrays, new methods for characterizing molecules build on the arrays, and new approaches to detecting molecular interactions that occur on the array.1

      With these tools in place, attention is now being turned toward using the arrays to gather biological data on molecules of interest. That effort has at times been successful, and at times raised new challenges for controlling the surface of the arrays. The talk to be presented will focus on two such problems.

      One of the reasons the arrays were developed was so that we could examine “weaker” interactions without the washing steps required by many immunological studies. One such challenge involved the binding of the v107 peptide to its VEGF target (Scheme 2). In particular, we were interested in comparing the binding of peptide analogs to both the human and murine VEGF proteins. While homology studies suggested that the binding should be similar, we hoped to experimentally verify that suggestion and develop a cheap easy way to probe such interactions. V107 is known to bind the human VEGF with micromolar affinity (Scheme 2). The suitability of the arrays for this study will be highlighted with both receptors leading to very similar binding curves with the surface bound v107 peptide.

       While interactions with stronger affinity can be seen very well, there are challenges associated with the arrays amplifying the signals. For example, our interest in using the arrays to probe interactions between small molecules and their G-protein targets has been hampered by the signal being amplified to a point that cannot be observed on the arrays. In this talk, an approach to solving this problem will be presented.

 1. For an instructional review see: Graaf, M. D.; Moeller, K. D. Langmuir
2015, 31, 7697.

Figure 1
A New Family of Perovskite Catalysts for Oxygenevolution Reaction in Alkaline Media: BaNiO3 and BaNi0.83O
Authors: Han Byungchan , Hwang Jeemin
Published: February 2020

Establishment of sustainable energy society has been strong driving force to develop cost-effective and highly active catalysts for energy conversion and storage devices such as metal-air batteries and electrochemical water splitting systems. This is because the oxygen evolution reaction (OER), a vital reaction for the operation, is substantially sluggish even with precious metalsbased catalysts. Here, we show for the first time that a hexagonal perovskite BaNiO3 can be highly functional catalyst for OER in alkaline media. We identify that the BaNiO3 performs OER activity at least an order of magnitude higher than an IrO2 catalyst. Using integrated density functional theory calculations and experimental validations we unveil the underlying mechanism is originatedfrom structural transformation from BaNiO3 to BaNi0.83O2.5 (Ba6Ni5O15) over the OER cycling process.

Figure 1
Electrochemical Reduction of Hydrogen Carbonate Using Porous Diodes
Authors: Chipangura Yevedzo E , Chaparadza Allen
Published: February 2020

The electrochemical reduction of CO2 on metal electrodes is an intensively studied reaction. However, there has not been much attention for CO2reduction on photo based diodes. Aqueous hydrogen carbonate is carbon dioxide equivalent:

H2O +CO2 ↔ H2CO3 ↔ HCO3
- + H+ ↔ CO3
2-+ 2H+

Here we report the electrochemical reduction of aqueous of hydrogen carbonate to formate using porous diodes fabricated using platinum deposited Sb doped SnO2 (n-type) and Li doped CuO (p-type) nanowires. XRD, TEM and ATR-UV-Vis were employed to characterize the nanowires. Typical current-voltage curves of such devices resemble the behavior of a typical diode except for one key difference; the areas near the p-n interface and the p-and n-regions are accessible to analytes. Photo electrochemical reduction efficiency measurements were measured using cyclic voltammetry, as a function of UV light intensity and wavelength. GC, HPLC, NMR and IR were used to quantitatively and qualitatively analyze the reduction products. 13C enriched hydrogen carbonate NMR and infrared spectroscopy confirmed the reduction of hydrogen carbonate to formate. The reduction rate of hydrogen carbonate was 0.0015 mol min-1 cm-2at a bias voltage of 1.65 V. The rate of reduction decreased with increasing lithium doping up to 20% and increasing antimony up to 10% (moles in synthesis) with respect to copper and tin respectively.

Figure 1
Metal Extraction Driven By Galvani Potential at the Interface Between Two Immiscible Electrolyte Solutions
Authors: Murtomäki Lasse , Nieminen Eemi
Published: February 2020

In an immiscible water-oil system, potential determining salts can be applied to establish Galvani potential across the interface (ITIES). These salts contain a common ion in the both phases and, therefore, via a Nernstian equation, determine the Galvani potential difference that can be used to boost electron or ion transfer reactions across the ITIES [1,2].

The contribution of potential difference and potential determining salts to solvent extraction of various metals (Co, Cu, Ni, In) was investigated with cyclic voltammetry (CV) in a four-electrode cell and with shake-flask experiments; the extraction ratios were analyzed either by atomic absorption spectroscopy (AAS) or by inductively coupled plasma atomic emission spectroscopy (ICP-AES). Di-2-(ethylhexyl)-phosphoric acid (D2EHPA) and diphenylthiocarbazone (Dithizone) were used as model ligands. While CV measurements showed ambiguous results - sometimes no ion transfer within the potential window was observed - shake-flask experiments showed clearly that the extraction ratio (co
/cw
) of some metals is enhanced in the presence of potential determining salts (Fig. 1).

Fig. 1. The contribution of the potential determining salt to the extraction ratio of Ni in pH 3 and 5.

[1] P. Peljo, L. Murtomäki, T. Kallio, H.-J. Xu, M. Meyer, C. P. Claude, J.-M. Barbe, H. H. Girault, K. Laasonen, K. Kontturi, Biomimetic Oxygen Reduction by Cofacial Porphyrins at a Liquid-Liquid Interface, J. Am. Chem. Soc., 134, 5972-5984, 2012.

[2] B. Su, R. Partovi-Nia, F. Li, M. Hojeij, M. Prudent, C. Corminboeuf, Z. Samec and H. H. Girault, H2O2 Generation by Decamethylferrocene at a Liquid|Liquid Interface, Angew. Chem., Int. Ed., 47, 2675-4678, 2008.

Figure 1
Electroswitchable Emission and Coloration Based on Single-Molecular Fluoran Derivatives
Authors: Nakamura Kazuki , Kanazawa Kenji , Kobayashi Norihisa
Published: February 2020

Multifunctional molecular switches exhibiting changes in both emission and coloration in response to various external triggers such as thermal, photo, and electric stimuli have attracted much attention for potential application as chemical sensors, biochemical labels, molecular logic gates, molecular memories, and display devices. In this study, we demonstrated reversible electrochemically induced high-contrast switching of the emission and coloration of fluoran molecules associated with changes in the intramolecular structure.

In order to investigate changes in the photophysical properties induced by electrical stimuli, we measured cyclic voltammogram, absorption spetra, emission spectra, and molecular orbital calculation. The mechanism for this electroswitching was attributed to the reversible electrochemically induced closing and opening of the lactone ring in the fluoran molecule. All neutral fluoran molecules were colorless and did not exhibit any fluorescence, while the oxidized (lactone ring-opened form) molecule was yellow and displayed a green fluorescence as a consequence of the extended, planar, conjugated system. Furthermore, this fluoran molecule achieved reversible electroswitchable emission and coloration with high on/off contrast[1].

In order to achieve a quick response time and high reversibility of the electroswitching optical device for modulating both emission and coloration, a 1,4-benzoquinone (BQ) molecule was introduced as a bifunctional material. The inclusion of a redox-active moiety on the auxiliary electrode maintained the charge balance and acted as an EC molecule (transparent/yellow in neutral/reduced state, respectively). BQ acted as a bifunctional molecule, leading to quick and stable switching of both emission and coloration[2].

Reference

[1] K. Kanazawa, K. Nakamura and N. Kobayashi, J. Phys. Chem. A, 118, 6026–6033 (2014).

[2] K. Kanazawa, K. Nakamura and N. Kobayashi, Sol. Ener. Mater. Solar Cell., 145, 42-53 (2016).

Figure 1
Electroactive, Multisensitive Nanocomposite. Electrocatalytic Activity and Attachement to Gold Electrode Surface
Authors: Mackiewicz Marcin , Karbarz Marcin , Romański Jan , Stojek Zbigniew Jan
Published: February 2020

Microgels are chemically cross-linked polymers with a network structure that are colloidal in size and swollen in a suitable solvent.1 Environmentally sensitive gels: “smart” nanogels sensitive to external stimuli such as temperature, pH, ionic strength, presence of specific ions, solvent composition and electromagnetic radiation can react quickly to environment changes.2 However, plain smart hydrogels are generally electrically nonconductive, while conductivity is required in such applications as supercapacitors, fuel cells and sensors.3 Our aim was to fabricate a new conductive multiple stimuli-responsive hybrid nanocomposite consisting of nanogel p(NIPA-BISS), AuNP’s and polyaniline (PANI). A combination of polymeric hydrogel and PANI-Au led to the materials that exhibited the properties characteristic for both components. We obtained thermally- and pH responsive, electroactive and conductive hybrid nanocomposites with good catalytic properties. We deposited them on the gold-electrode surface. The nanocomposite consisted of a nanogel containing disulfide groups in the crosslinkers to make possible its attachment to the gold-electrode surface and polyaniline nanofibers with embedded in them gold nanoparticles. The presence of polyaniline in the composite nanoparticles led to a substantial increase in conductivity and electroactivity of the nanogels and allowed elimination of aggregation of nanocomposites in acidic solutions at increased temperature. In the first step of synthesis, p(NIPS-BISS) nanogel, based on poly(N-isopropylacrylamide) cross-linked with N,N’-bisacryloylcystine, was prepared via surfactant-free emulsion polymerization (SFEP). Next, by soaking the nanogel with a solution of an oxidizing agent (chloroauric acid, HAuCl4) and placing the soaked gel in a solution of aniline in nitrobenzene, the conducting polymer and AuNPs were formed in p(NIPA-BISS) nanogel. The structure, morphology and swelling behavior of the nanogels were investigated using SEM, TEM and DLS. To evaluate the state of PANI oxidation the Raman spectroscopy was used. The electrocatalytic oxidation of ethanol at gold electrodes covered by the nanocomposites was examined using voltammetry.

This work was supported by a grant from the National Science Centre of Poland, Preludium 8, 2014/15/N/ST5/02937

1. B. R. Saunders, B. Vincent, Adv. Colloid Interface Sci., 1999, 80, 1.

2. Maćkiewicz, M.; Romański, J.; Karbarz, M. New Ampholytic Microgels Based On N-Isopropylacrylamide And Α-Amino Acid: Changes In Swelling Behavior As A Function Of Temperature, Ph And Divalent Cation Concentration. RSC Adv.
2014,4, 48905- 48911.

3. Zhai, D.; Liu, B.; Shi, Y.; Pan, L.; Wang, Y.; Li, W.; Zhang, R.; Yu, G. Highly Sensitive Glucose Sensor Based On Pt Nanoparticle/Polyaniline Hydrogel Heterostructures. ACS Nano
2013, 7, 3540-3546.

Figure 1
Selective Reversible Absorption of the Industrial Off-Gas Components CO2 and NOx by Ionic Liquids
Authors: Kaas-Larsen Peter Kjartan , Thomassen Peter , Schill Leonard , Mossin Susanne , Riisager Anders , Fehrmann Rasmus
Published: February 2020

Ionic liquids are promising new materials for climate and pollution control by selective absorption of CO2 and NOx in industrial off-gases. In addition pratical cleaning of industrial off gases seems to be attractive by use of ionic liquids distributed on the surface of porous, high surface area carriers in the form of so-called Supported Ionic Liquid Phase (SILP) materials. The potential of selected ionic liquids for absorption of CO2 and NOx will be demonstrated and the possible mechanism of absortion will be described on the molecular level. Our vision of application of these ionic liquids in the form of SILP filters to flue gas cleaning in power plants, waste incineration plants, cement and glass factories as well as unborad ships will be adressed.
Influence of Electrode Gas Flow Rate and Electrolyte Composition on Thermoelectric Power in Molten Carbonate Thermocell
Authors: Kandhasamy Sathiyaraj , Calandrino Luca , Burheim Odne Stokke , Solheim Asbjørn , Kjelstrup Signe , Haarberg Geir Martin
Published: February 2020

A thermo-electrochemical cell (thermocell) is an electrochemical system with two identical electrodes placed at different temperatures in an electrolyte solution. The ion migration between the electrodes due to the temperature gradient leads to thermoelectric conversion. Such systems represent a promising pathway to utilise dynamic heat as power source. A possible thermo-electrochemical cell with molten carbonate electrolyte and gas electrodes was recently reported [1,2]. The change in Seebeck coefficient (thermoelectric power) with electrode materials, electrode gas mixture, electrolyte composition and electrolyte support materials was studied [2]. Addition of support material (solid oxide) in the molten carbonate electrolyte, may reduce the thermal conductivity and maintain the temperature gradient between the electrodes. Thermal boundary layers may arise due to the electrode gas flow; slow flow rate seems to be preferred for obtaining a high value in thermoelectric power. In this study the system is further optimised with respect to the composition of electrolyte and supporting materials as well as electrode gas flow rate. The thermoelectric power is measured with various ratios of ((Li,Na)2CO3) molten carbonate to support (MgO) solid oxide in the electrolyte mixture and also with different gas flow rates at the electrode-electrolyte interface.

References

1. M.T. Borset, X. Kang, O.S. Burheim, G.M. Haarberg, Q. Xu, S. Kjelstrup, Electrochimica Acta 182 (2015) 699 - 706.

2. X. Kang, M.T. Børset, O.S. Burheim, G.M. Haarberg, Q. Xu, S. Kjelstrup, Electrochimica Acta 182 (2015) 342 - 350.
The Effect of Lengthening Cation Ether Tails on Ionic Liquid Properties
Authors: Lall-Ramnarine Sharon , Rodriguez Chanele , Fernandez Rahonel , Zmich Nicole , Fernandez Eddie , Dhiman Surajdevparkash , Wishart James F.
Published: February 2020

Ionic liquids (ILs) are attractive alternative solvents in a variety of applications such as in supercapacitors, batteries, solar energy conversion and for the storage and clean-up of nuclear waste. However, their high viscosities impede their adoption in many large scale processes. Ether side chains have been shown to lower the viscosity of ILs. In this work, we have synthesized a series of ten pyrrolidinium ionic liquids and ten imidazolium ionic liquids bearing ether and alkyl side chains of varying lengths (4 to 10 atoms in length). Their physical properties, such as viscosity, conductivity and thermal profile were measured and compared. Results reveal a dramatic decrease in viscosity with the substitution of alkoxy (ether) side chains for alkyl side chains on the pyrrolidinium cation. However, as the length of the ether chain increases there is negligible change in the viscosity (of about 50 cP). In contrast, a consistent increase in the viscosity was observed as the length of the alkyl side chain increases. Preliminary results of the imidazolium series show a similar trend. These results provide significant insight on the choice of starting materials for researchers designing ILs for specific applications. The work at BNL was supported by the BNL Office of Educational Programs and the U.S. Department of Energy, Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences and Biosciences under contract DE- SC0012704.
Electrochemical Synthesis of LaSi2 from a NaCl-Naf-LaF3-K2SiF6 Melt at 1023 K
Authors: Kochetova Svetlana , Savchuk Ruslan N , Pisanenko Alexandr Dmitrievich , Devyatkin Sergei Vladimirovich
Published: February 2020

Lanthanum silicides (La5Si4, La5Si3, La4Si, LaSi and LaSi2) are metal-like compounds with semiconductor properties. If this were true, it could become technologically important as an infrared detector material [1]. The possibility of electrochemical synthesis of lanthanum silicides from molten salts were investigated in this work. It can be concluded from thermodynamic calculation that silicon discharge from molten salts more positive than La (~ 0.8 V), in this case electrochemical synthesis possible only in two step, first deposited of Si, next step deposition of La onto Si with formation of lanthanum disilicide:

I. 2Si + La(III) +3 e = LaSi2 ΔE0
10233 K = ΔG0
1023 K/ (nF) ≈ 0.500 V,where ΔE0 – is potential (V), ΔG0
- is the Gibbs energy of the reaction I. (J), n – is the number of electrons involved in the reaction (in our case, n = 3), F – is Faraday constant.

The electrochemical behaviour of the molten salts system NaCl-NaF-LaF3-K2SiF6 was studied by cyclic voltammetry. A glassy carbon crucible served as a vessel for the melt and as an auxiliary electrode; a W wire was used as the working electrode; the measurements were made with respect to glassy carbon reference electrode 1023 K in argon atmosphere. Typical cyclic voltammogram for molten salts system NaCl-NaF-LaF3-K2SiF6 show two step process of electrochemical synthesis of LaSi2at 1023 K in Ar on W working electrode (Fig. 1 .).

On the base of thermodynamic calculation and voltammetric investigation, it has been show that lanthanum disilicide can by electrochemical synthesized from a NaCl-NaF- LaF3-K2SiF6
melt at 1023 K in two step. References

R.G. Long, M.C. Bost, J.E. Mahan., Appl. Phys. Lett. 5
3, 1272 (1988).

Fig. 1. Voltammogram of a NaCl-NaF-LaF3- K2SiF6 melts on a W working electrode, v= 0.1 V/s.

Figure 1
Porous Ionic Liquids: Challenges and Opportunities
Authors: Dai Sheng
Published: February 2020

Functional materials using or in the presence of ionic liquids represents a burgeoning direction in materials chemistry. Ionic liquids are a family of non-conventional molten salts that can act as both functional materials and solvents. They offer many advantages, such as negligible vapor pressures, wide liquidus ranges, good thermal stability, tunable solubility of both organic and inorganic molecules, and ion conductivity. The unique solvation environment of these ionic liquids provides new reaction and separation media for controlling many energy-related processes.  We have recently developed a class of ionic liquids with intrinsic porosities based on nanoscopic building blocks. Challenges and opportunities in synthesizing and using these porous ionic liquids in energy-related applications will be discussed.
Aqueous Solid-Liquid Interfaces at Atmoci Scale
Authors: Lopes Pietro Papa , Strmcnik Dusan , Markovic Nenad M , Stamenkovic Vojislav
Published: February 2020

Atomic scale insight at the aqueous electrified solid-liquid interfaces is considered critical in further advancement of materials that could be implemented in electrochemical systems such as electrolyzers, batteries and fuel cells. The research effort aimed to fundamental understanding of processes that are relevant for energy conversion, storage and biomedical applications will be presented.

It has been demonstrated that fine tuning of the material properties can lead towards unprecedented improvements in their functional properties [1]. This presentation will address unique research approach that is capable of revealing structure-function relationships in the design of nanomaterials for electrochemical systems. The following topics will be discussed: 1) well-defined materials obtained by varying their surface structure, composition profile and electronic properties [2]; 2) atomic/molecular insight into electrified solid-liquid interfaces; 3) identification of the active and the most vulnerable surface sites under reaction conditions; 4) insight into chemical nature between the surface atoms, reactants, and molecular species in the electrolyte; 5) engineering of advanced nanomaterials with desired size, shape and composition profile [3,4]; 6) ex-situ and in-situ characterization of tailored nanostructured electrochemical interfaces.

References:

[1] Stamenkovic et al. Science 315 (2007) 493.

[2] Stamenkovic et al. Nature Mat. 6 (2007) 241.

[3] van der Vliet et al. Nature Mat. 11 (2012) 1051.

[4] Chen et al. Science 343 (2014) 1339.
Potential-Dependent Structure of [BMIM][FSA]/Au Interface Studied By Surface Enhanced Infrared Absorption Spectroscopy
Authors: Motobayashi Kenta , Uchida Ken-ichi , Osawa Masatoshi
Published: February 2020

Room temperature ionic liquids (RTILs) are promising electrolyte materials for Li ion batteries and other electrochemical devices due to high ionic conductivity and wide electrochemical windows. It has been reported that the cathodic decomposition potential of the FSA-based RTIL is much lower than that of TFSA-based RTIL when Li salt is added, despite the similar chemical structures of FSA and TFSA anions. A mechanism for stabilization of the FSA-based RTIL on the electrode involving an interfacial structure of the RTIL has been proposed.1 The interfacial structure itself, however, has not been well elucidate yet. Surface-enhanced infrared absorption spectroscopy (SEIRAS) that can selectively probe solid/liquid interfaces is suited for direct observation of the structure of RTIL/metal electrode interface.2 In the present work, we investigated the potential-dependent structure of [BMIM][FSA] with and without Li ion on an Au electrode by using SEIRAS.

For pure [BMIM][FSA], Potential-dependent SEIRA spectra indicated that at negative potentials, BMIM cations exist in the first ionic layer on the electrode and reorients depending on the potential, as previously reported for [BMIM][TFSA].2 For [BMIM][FSA] with 10 % Li salt, SEIRAS spectra suggested that BMIM cations moved further away from the electrode at negative potentials where Li UPD did not occur although electrode is negatively charged. FSA anions also did not approach to the surface. A possible interpretation of such behavior is that decomposition products of [BMIM][FSA] or Li+ ion on the electrode inhibit cations from approaching to the electrode at negative potentials, which can be the origin of the stabilization of FSA-base RTIL. Details will be shown in the presentation.

Reference: 
1M. Yamagata et al.,

Electrochim. Acta 110, 181 (2013).

2

K. Motobayashi et al.,

J. Phys. Chem. Lett. 4, 3110 (2013).
Nano-Particle Metals Modified Boron Doped Diamond Electrode for Determination of Heavy Metal Ions
Authors: Yoon Jang-Hee
Published: February 2020

Boron doped diamond (BDD) thin film can be developing applications in variety broad areas such as which includes the purification of wastewater and the disinfection of drinking water and electro-analysis and sensor technology. Especially, BDD electrode is applied to detected heavy metal ion in water. We are prepared that BDD electrodes of bare state synthesized with boron concentration of [B]/[C]=8000 ppm. The structural and electrical properties of BDD electrodes were characterized by X-ray diffraction (XRD), potentiostat measurement system. Suitability of BDD electrodes for electroanalytical applications is exemplified by sensing the heavy metal ions, such as Cu, Hg and Pb. In order to increasing of sensitivity, BDD electrodes surface was modified using various nano-particle metal materials by the Au, pt and Ti. Nano-particle modification on BDD electrodes are reduced potential windows. But it is stability and sensitivity are better than bare BDD electrode.

Figure 1
(Invited) Si Photoelectrodes with Patterned Catalysts for Efficient and Stable Photoelectrochemical Solar Chemical Production
Authors: Oh Jihun
Published: February 2020

Solar fuel production using sun, CO2, and water at a semiconductor/water interface attracts intense interest for converting solar energy into storable and distributable chemicals. While numerous semiconductors have been investigated, a tandem cell comprised of semiconductors with two different bandgaps is considered one of the most promising candidates for realization of for unassisted efficient and stable solar chemical production. Si has a bandgap of 1.12 eV and can be used as an ideal bottom cell in a tandem configuration.

Here, I’ll present our recent works on Si photoelectrodes with patterned co-catalysts for efficient and stable photoelectrochemical (PEC) solar chemical producing cells. In the first part of the presentation, I’ll talk about PEC properties of Si photoanode for oxygen evolution reaction with enhanced stability. Our Si photoanode is covered with chemically stable and electrically passivating SiO2 layer to prevent corrosion of Si in water. Since SiO2 is insulating, we locally pattern the oxide to expose Si surface and deposit Ni co-catalysts on the exposed Si. By controlling surface coverage of Ni co-catalysts, we achieve 27 mA/cm2 of oxygen evolving current density at 1.23 V (vs. RHE) for more than 24 hours. I'll present PEC device modeling of our Si photoelectrode structures. In the second part of talk, I’ll present Si photocathodes with nanoporous Au mesh for solar CO2 reduction reaction. Our Si photocathode with the nanoporous Au mesh shows CO2 reduction selectivity more than 90% at more positive potential than CO2/CO redox potential. In the presentation, PEC performance of our Si electrode will be presented in detail.
(Invited) Photocurrent Generation of PbS Nanopartciles with Narrower Bandgap Coupled with Localized Surface Plasmon Resonance
Authors: Murakoshi Kei , Li Xiaowei , Minamimoto Hiro
Published: February 2020

Confined photon field generated by localized surface plasmon resonance could provide the chance to excite electrons in materials via exotic routes. Coupling with tunable electronic structures leads to successful tuning for electrochemical potentials of excited electrons/holes. We know that PbS quantized dots (PbS QDs) sensitized photocurrent generation system has been proved to be one of the promising candidates for next photoenergy devices owing to valuable tuning of the band gap via quantization because of relatively large Bohr radius of 18 nm due to its metallic properties. By well coupling with Au NPs, PbS QDs are able to enhance the localized electric field generated by Au NPs and consequently uplift the photoelectric conversion across a wide visible light region. In this work, photocurrent of size-controlled PbS QDs with the sizes from 2.3 nm to 4.8 nm excited by localized surface plasmon resonance was observed to determine the effect of photoexcitation, especially at the energy two times higher that PbS QDs’ bandgap.
Active Sites of Plasmon-Induced Charge Separation
Authors: Nishi Hiroyasu , Saito Koichiro , Tatsuma Tetsu
Published: February 2020

Plasmon-induced charge separation (PICS) occurs at the interface between plasmonic nanoparticles (e.g. gold, silver, and copper nanoparticles) and a semiconductor such as titanium oxide or zinc oxide.1,2 Plasmon-induced charge separation involves carrier transfer from the plasmonic nanoparticle to the semiconductor. It can be applied to photovoltaics and photocatalysis under visible and near infrared light, localized plasmon sensors for chemical sensing and biosensing, photochromic materials, and photoactuators. We have studied the active sites of plasmon-induced charge separation taking advantage of electrochemical reactions caused by the charge separation. For instance, we monitored dissolution of metal nanoparticles3,4 or metal nanostructures5 and redeposition of small metal nanoparticles resulting from recombination of released metal ions and electrons injected into semiconductor. We found that the active sites are localized at around the sites where optical near field is localized. In addition, we prepared porous nanoparticles on the basis of the metal dissolution caused by plasmon-induced charge separation.

1. Y. Tian and T. Tatsuma, J. Am. Chem. Soc., 127, 7632 (2005).

2. T. Tatsuma, Bull. Chem. Soc. Jpn., 86, 1 (2013).

3. E. Kazuma, N. Sakai, and T. Tatsuma, Chem. Commun., 47, 5777 (2011).

4. I. Tanabe and T. Tatsuma, Nano Lett., 12, 5418 (2012).

5. L. Wu, H. Nishi, and T. Tatsuma, APL Mater., 3, 104406 (2015).
Modification of the Electronic Structure and Surface State of LaFeO3 for Improved Visible Light Photoelectrochemical Water Oxidation
Authors: Peng Qi , Wen Yanwei , Shan Bin , Chen Rong
Published: February 2020

Photocatalytic hydrogen generation by solar energy is a promising approach to clean energy resource and has attracted great attention over the past decades. [1] Perovskites ABO3 structures provide the basic stable framework to both crystal and electronic structures modification, which have found extensive applications in photocatalysis, solar cells and photoelectrochemical (PEC) water splitting. [2] LaFeO3 has a suitable band gap of 2.07eV [3, 4] and exhibits excellent visible light photocatalytic performance. However, the poor charge transport and slow reaction kinetics at the surface [3, 4] are the main factors limiting its further improvement on photocatalytic application.

To overcome these obstacles, transition metals (Mn, Co, Cu) are introduced into LaFeO3 and the photocurrent of 10% Cu doped sample is improved by three times than that of LaFeO3. The reduced charge transport resistance owing to the Fe3+ discharge is identified to benefit the PEC performance improvement after TM doping. On the other hand, the surface state of LaFeO3 is modified by electrodepositing of amorphous cobalt-phosphate (Co-Pi). It shows that the presence of Co-Pi down-shifts the onset potential by ~ 560 mV for anodic photocurrent and the improvement can be attributed to the enhanced water oxidation due to the CoII/CoIII-OH discharge on Co-Pi decorated layers. The transition anodic photocurrent is improved by about six times after Co-Pi coating under visible light at 0.50 V vs. Ag/AgCl and the electrochemical impedance spectroscopy certifies the enhanced charge transfer, which contributes to the meliorative anodic photocurrent. The incident photon-to-current conversion efficiencies of LaFeO3 can be promoted from 1.37% to 2.14% at 400 nm after Co-Pi coating. Our results demonstrate that modification of the electronic structure (TM doping) and surface state (Co-Pi coating) are the promising way to promote the photoconversion efficiency of LaFeO3-based PEC cells under visible light.

References:

X. Lu, S. Xie, H. Yang, Y. Tong, H. Ji, Chem. Soc. Rev., 43, 7581 (2014).

Z. G. Yi and J. Ye, Appl. Phys. Lett., 91, 254108 (2007).

K. M. Parida, K. H. Reddy, S. Martha, D. P. Das and N. Biswal, Int. J. Hydrogen Energy, 35, 12161 (2010).

Q. Peng, B. Shan, Y. Wen and R. Chen, Int. J. Hydrogen Energy, 40, 15423 (2015).
Synthesis of Gallium Nitride Photocatalysts By Reaction of Solution Synthesized Gallium Oxide and Solid Nitrogen Sources
Authors: Sugiura Takashi , Sano Tatsuya , Manseki Kazuhiro
Published: February 2020

Solar energy-driven water splitting is receiving considerable interest in hydrogen production as a renewable energy source. Various semiconductor materials for the photodecomposition of water have been investigated for solar energy conversion such as TiO2, TaON and BiVO4. GaN, GaN : ZnO and GaN : InN solid solution are also considered as the photoelectrochemically active material for solar energy-driven water splitting. And its band gap can be controlled by the composition of these solid solutions. We have reported a new technique to synthesize low cost GaN powder under moderate condition, Li3N or LiNH2 were used as a high reactive solid nitrogen source to improve the reaction rate and lowering the reaction temperature. A high yield and high purity GaN with wurtzite structure was synthesized [1, 2]. In this report we studied the method to synthesize GaN powders by the reaction of solution synthesized Ga2O3 powder with solid nitrogen sources. In previous reports commercially available Ga2O3 powder was used. When commercial Ga2O3 powder was used, by the inhomogeneous size, the reaction occurred partially and the yields became small. So the gallium oxide powder with homogeneous size was synthesized by the use of solution process. The photoelectrochemical properties of particulate electrode with synthesized GaN powder were also investigated.

The GaCl3 was dissolved in 2-buthyl alcohol under stirring. Then the purified water was added gradually to the Ga containing solution to get the white precipitate. XRD analysis demonstrate that the synthesized powder is Ga2O3. The crucible with starting materials, Ga2O3 and Li3N were put into a sealed stainless steel reaction vessel and it was set vertically in an electric furnace. Then it was heated at 550 – 700°C, 2 hours in N2 atmosphere. After the reaction, the products were washed by alcoholic HCl solution and distilled water.

Crystalline wurtzite GaN powder with several hundred nanometer size was successfully synthesized. The reaction yield for the GaN synthesis with solution processed Ga2O3 is higher than that with commercial Ga2O3 powder. Anodic photocurrent was clearly observed for the paste electrodes with GaN and this observation indicates that the GaN synthesized in this study shows n-type semiconductivity.

GaN : InN solid solution was also successfully synthesized by the reaction with GaCl3, InCl3 and LiNH2. Photo-electrochemical properties of its paste electrode was also studied.

References

T. Zhang, A. Mabuchi, T. Sugiura, H. Minoura, Trans. Mater. Res. Soc. Jpn., 33(4), 1277-1280 (2008).

T. Zhang, A. Kouyama, M. Miura and T. Sugiura, Trans. Mater. Res. Soc. Jpn., 36(3), 513-516 (2011).
Tuning V Redox Couple By Metal-Ion Substitution in Na3V2(PO4)3 Cathode Material for High Energy Density Na-Ion Batteries
Authors: Sohn DongRak , Lim Sung-Jin , Nam Do-Hwan , Hong Kyung-Sik , Kim Tae-Hee , Kwon HyukSang
Published: February 2020

Recently, the demand for renewable energy has raised with the increase of environmental issues and exhaustion of crude oil. To acquire efficient utilization of the renewable energy, large-scale energy storage systems (ESSs) are necessary that balance the discrepancy between production of and the time required to consume renewable energy. Li-ion batteries have been considered as candidates for large-scale ESSs because they provide high energy density and a long cycle life. However, due to the lack of Li reserves in the Earth and the corresponding growing cost problems, Na-ion batteries have been received great attention as alternative candidates for Li-ion batteries. The Na-ion batteries can replace the Li-ion batteries in the aspects of abundant Na resources, low cost, and easily accessible reserves. Furthermore, the similarity of the electrochemical reaction mechanisms of Na-ion batteries to that of Li-ion batteries has accelerated the development of the Na-ion batteries; thus, various research studies have been conducted to find proper electrode materials for Na-ion batteries.

Among various cathode materials of sodium-ion batteries for large-scale applications, NASICON-Na3V2(PO4)3 is an attractive candidate for the cathode material of Na-ion batteries due to its thermal and structural stabilities. Also, Na3V2(PO4)3 shows 117.6 mAh·g-1 theoretical capacity at 3.4 V vs. Na/Na+ using the V3+/4+ redox couple. However, the operating voltage of Na3V2(PO4)3 should be improved to replace the conventional Li-ion battery cathode materials. If V4+/5+ redox reaction, which utilizes higher operating voltage, can be employed in this material, higher operating voltage could be achieved. Herein, we suggest a simple method to enhance the operating voltage of Na3V2(PO4)3.

In this work, non-transition metal ions are substituted for V-ions in Na3V2(PO4)3 to utilize V4+/5+ redox reaction. During the (de)intercalation of Na-ions, the oxidation state of the non-transition metal ions is not changed. Hence, some V3+ ions in Na3V2(PO4)3 should be oxidized until V5+ instead of non-transition metal ions while two Na-ions are extracted. Therefore, some part of capacity reacts at 3.4 V using V3+/4+ redox couple and the other part reacts at voltage higher than 3.4 V using V4+/5+ redox couple. Through the tuning of V redox couple, not only the enhancement of energy density of the cathode material but the cost reduction of expensive V source also is possible. The figure shows the initial charge profiles of Na3V2(PO4)3/C and metal-ion substituted Na3V1.5M0.5(PO4)3/C. In case of Na3V1.5M0.5(PO4)3/C, a high voltage V4+/5+ redox reation was clearly observed as the cell was charged above 3.5 V vs. Na/Na+. In the presentation, the detailed structural analyses and electrochemical performance of the materials will be shown.

Figure 1
A New Concept of Flexible Electrodes for Lithium/Sulfur Batteries
Authors: Park Jin-Woo , Choi Sun-Hwa , Kim Hui-Hun , Kim Ki-Won , Ahn Jou-Hyeon , Cho Gyu-bong , Ahn Hyo-Jun
Published: February 2020

According to the progress of electronics industry, electronic devices have been diversified to various forms such as roll-up displays, smart cards, and wearable devices. Flexible electronic devices are demanding has various properties such as lightweight, ultrathin, and flexibility. Therefore, batteries as their power sources are required to have same properties. In addition, high energy density and operational safety are needed. Until now commercial lithium-ion batteries (LIBs) are the only viable candidates for flexible devices.

Recently, the flexible lithium/sulfur (Li/S) battery has been proposed with a high theoretical energy density of 2600 Wh kg-1. As most active materials considered in these studies are rigid and brittle, flexible cathodes were achieved by the physical combination of rigid active materials with flexible current collectors such as carbon-based materials or polymers. This integrated design has two inevitable disadvantages; (1) during deformation the active material can detach from the current collector; (2) the capacity per electrode is reduced by the presence of electrochemically inactive materials such as current collector, binder and conducting agents. Therefore, there is a strong need for a new approach to the flexible cathode which consists of only active material without a separate current collector.

Sulfurized polyacrylonitrile (SPAN) composite could be a good candidate due to its good electric conductivity, high sulfur utilization, and stable cycle life. In addition, it can be fabricated as either particle or nanofiber. However, the SPAN electrodes reported so far were prepared by mixing SPAN, conductive agent, and binder which were pasted on metallic current collector.

In carbon nanotube paper and graphene paper, it is well-known that the strain during deformation decreases with the diameter of the fiber. Therefore, in this work, the SPAN nanofiber web cathode which does not include conductive agent, binder, as well as current collector was fabricated from PAN nanofiber web and sulfur by heat treatment process. Also, pre-lithiated carbon felt was used as anode in order to make all flexible full cell and investigated its electrochemical properties.