bluuebunny/crossref_metadata_2025 huggingface dataset:
2D Layered Dichalcogenides As Active Cathode Materials for Magnesium-Ion Batteries
Authors: Filsinger Kai Alexander , Arnold Craig B.
Published: February 2020

Rechargeable battery chemistries that can circumvent some of the issues associated with modern lithium-ion technologies are in great demand for specialized application, where safety is more important than raw power density. Magnesium has been the focus of many alternative approaches, due to its high volumetric density, high abundance and its homogeneous electrochemical plating characteristics. In the past, a lack of suitable electrolytes with high oxidative stability and good conductivity as well as a paucity of viable cathode materials limited research to only a few standard materials, such as the Chevrel-phase Mo6S8. While providing a good benchmark system for comparison of different battery chemistries, such materials will not lead to a commercial success of the magnesium-ion technology. On the basis of our recently developed halide free electrolytes, we are able to investigate a wide range of new cathode materials for high voltage Magnesium-ion batteries. In this presentation we are focusing on 2D-layered metal-dichalcogenides and their capability to reversibly store magnesium. We investigate their electrochemical performance using a coin-cell platform. Ex-situ XRD, SEM and XPS experiments are performed to monitor changes in crystal structure or surface morphology and identify side reactions as well as the mechanism of magnesium storage.
Artificial Solid-Electrolyte Interphase Layer for Improved Electrochemical Window of Magnesium Ion Batteries
Authors: Nishitani Yu , Tsujita Takuji
Published: February 2020

As a type of next-generation secondary batteries, the magnesium ion battery achieves high energy capacity by using metal magnesium anodes. However, stable battery operation has only been confirmed when using a metal sulfide cathode [1], whose energy capacity and operating potential are lower than those of the latest lithium ion batteries.

One way to increase the output voltage is establishing a cathode / electrolyte interface that is compatible with the cathode redox reaction at a higher potential, where the liquid electrolyte is subjected to oxidization. To accomplish this, a solid-state electrolyte on the thin film cathode could be used to suppress the oxidative decomposition of liquid electrolyte in the magnesium battery. Since the electronically insulating solid state electrolyte inhibits the unwanted electron transfer between the cathode and the electrolyte solution, the electrochemical potential window of the liquid electrolyte could be widened. This solid-state electrolyte coating may be regarded as an artificial solid-electrolyte interphase (ASEI) [2]. We prepared a cell with V2O5 thin film cathode coated by a MgZrSiO amorphous solid-state electrolyte using RF sputtering technique. As a result, the cell had higher oxidative stability (decomposition at 4.5 V vs Mg2+/Mg) than the cell with the uncoated cathode (3.3 V vs Mg2+/Mg) (Figure 1).

Reference

[1] D. Aurbach, Nature, 407, 724 (2000).

[2] N. J. Dudney, J. Power Sources, 89, 176 (2000).

Figure 1 The cyclic voltammogram of the MgZrSiO-coated and bare V2O5 thin film cathodes in 0.5M Mg(TFSA)2/triglyme at 55℃. The scanning rate was 0.1 mV/s.

Figure 1
Molecular-Scale Insights of Aluminum-Ion Intercalation into Chevrel Phase Mo6S8
Authors: Jadhav Ankur , Messinger Robert J.
Published: February 2020

Rechargeable aluminum batteries are a promising alternative to lithium-ion batteries due to the high volumetric energy density (8040 mAh/cm3), high abundance in the earth’s crust, and low cost of aluminum metal. However, aluminum ion intercalation into crystalline electrode materials is challenging, as the high coulombic charge of trivalent aluminum ions significantly increases the activation energy of diffusion compared to monovalent ions. Chevrel phase Mo6S8 is one of the most well-studied and successful cathode materials for magnesium-ion batteries, partly due to the facile transport of divalent magnesium ions within its crystal structure. Reversible intercalation of aluminum ions within chevrel phase has been reported, though the intercalation mechanism is not well understood at a molecular level.

Here, we report enhanced understanding of aluminum-ion intercalation in chevrel using a combination of spectroscopic, diffraction, and imaging techniques.
Ex situ solid-state 27Al MAS NMR measurements were performed as a function of state-of-charge to observe changes in the environments and populations of aluminum ions within the host crystal structure, revealing both intercalated ions and additional aluminum species associated with surface layers and/or decomposition products. In situ diffraction methods were performed to observe changes in the crystal structure during the cycling process, while transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS) were conducted to characterize surface structures and compositions. Variable-temperature electrochemical measurements including cyclic voltammetry (CV), galvanostatic cycling, and electrochemical impedance spectroscopy (EIS) were performed to study the effects of temperature on the diffusion of Al3+ ions, electrochemical performance, and capacity retention. In combination, the results yield molecular-level insights into the aluminum-ion intercalation mechanism in the chevrel phase as well as changes of surface compositions and structures upon cycling in the ionic liquid electrolyte.

Figure 1
(Invited) Microscopic Study of Dopant Distribution in Phosphors: Impact on Thermal Quenching and Phosphor Performance
Authors: Martin Lisa I D J , Poelman Dirk , Smet Philippe F , Joos Jonas J
Published: February 2020

Inorganic luminescent materials or phosphors are currently applied on a large scale in white light-emitting diodes (LEDs) for lighting and display applications. These technologies rely on high-performance phosphors and require subtle fine-tuning of the material composition and the device manufacturing to achieve white LED devices with the desired characteristics1.

Synthesis conditions strongly affect phosphor properties, often in an unpredictable and hard-to-control way. This can be attributed to an incomplete understanding of the effects of local variations in composition, morphology and emission properties on the overall performance of the phosphor.

Since luminescent characterization methods are generally performed on a macroscopic scale, local variations are averaged out, and the detailed information on the interplay between structure and luminescence is lost.

To gain more insight in how performance-determining mechanisms are influenced by synthesis conditions and sample composition, we combine cathodoluminescence (CL) spectroscopy in a scanning electron microscope (SEM) with an energy-dispersive X-ray (EDX) analysis. In SEM-CL-EDX, simultaneous identification of the morphology, the chemical composition and the spectral distribution of a phosphor with a spatial resolution down to 1 µm or less is achieved. For this work a heating stage was added to the setup, allowing to determine thermal quenching profiles on sub-micrometer sized areas.

Temperature-dependent SEM-CL-EDX mappings were performed on SrGa2S4:Eu2+, a material which is known as a saturated green phosphor, especially suitable for display applications2
. This case study revealed that samples with ill-distributed dopant ions show a broad range of local quenching temperatures, as can be seen in Fig. 1. For the associated activation energy an upper limit of 0.61 eV was identified, corresponding to the intrinsic thermal quenching of isolated europium ions. Furthermore, the results confirm a previously suggested thermal quenching model which involves the presence of both isolated and clustered dopant ions3.

References

Smet, P.F.; Parmentier, A.B.; Poelman, D. J. Electrochem.
Soc., 2011. 158(6): p. R37-R54.

Joos, J.J.; Meert, K.W.; Parmentier, A.B.; Poelman, D.; Smet, P.F. Opt.
Mater., 2012. 34(11): p. 1902-1907.

Martin, L.I.D.J.; Poelman, D.; Smet, P.F.; Joos, J.J. ECS J. Solid State Sci. Technol., 2018.
7
(1) p. R3052-R3056.

Figure 1: Distribution of local Eu concentration related to the distribution of local T
0.5 within a single phosphor grain for Sr1-x
Ga2S4:Eu
x
with x = 0.01, 0.03 and 0.07.

Figure 1
Change of the Reaction Pathway during the Phenols Anodic Cross-Coupling Oxidation Induced By Tertiary Amines. Anodic C-O Phenols Homo-Coupling a Direct Route to Diaryl Ethers
Authors: Frontana-Uribe Bernardo A. , Waldvogel Siegfried R.
Published: February 2020

C–C or C–O coupling reaction of two aryls is typically carried out using transition metal catalysts (Cu or Pd). For example, Ullmann aryl ether synthesis (Cu mediated) is one of the most reliable methods used for the preparation of this chemical motif.[1] Other routes require preparation of multi-step staring compounds to obtain halogenated or boron aryl derivatives to carry out the C-O coupling with phenols; here again palladium- and/or copper are present as catalyst.[2,3] Diarylethers are important scaffold in pharmaceuticals and natural products, therefore an alternative, direct, and more sustainable access to such structural features is highly desired. In the last years, Waldvogel research group has proven that the anodic C-C homo and cross coupling of phenols, using boron-doped diamond electrodes (BDDE) and hexafluoroisopropanol (HFIP), is a robust and reliable method that can be used in multi-gram scale and with a green chemistry vision.[4] In this contribution, is shown the dramatic effect of tertiary amines, which modify the reaction pathway and favor the C-O phenol homo coupling, instead of the classical C-C phenol homo coupling. With this small change in the electrochemical protocol of the anodic oxidation of phenols now it is possible to obtain diarylethers in good yields directly form the phenols.

References.

[1] Evano, G.; Blanchard, N.; Toumi, M. Chem. Rev.
2008, 108, 3054. [2] Fan, M.; Zhou, W.;Jiang, Y.; Ma, D. Angew. Chem., Int. Ed.
2016, 55, 6211. [3] Salvi, L.; Davis, N. R.; Ali, S. Z.; Buchwald, S. L. Org.Lett.
2012, 14, 170. [4] A. Wiebe, B. Riehl, S. Lips, R. Franke, S. R. Waldvogel, Sci. Adv.
2017, 3, eaao3920/1–7.

Acknowledgements.

S.R.W. thanks the DFG (Wa1276/14-1) for financial support and the research network ELYSION,. B. A. F.-U. thanks the Impulsfonds Pre-HIKE (JGU Mainz), PASPA-DGAPA UNAM, and CONACYT-Mexico for the support.

Figure 1
Electrochemical Synthesis of an Alcohol-Tolerant Platinum-Based Material for the Oxygen Reduction Reaction
Authors: Vargas-Ordaz Mariana , Velázquez-Hernández Isaac , Ledesma-García Janet , Álvarez-Contreras Lorena , Arjona Noé , Guerra-Balcázar Minerva
Published: February 2020

A prevalent problem in direct alcohol fuel cells (DAFCs) is the crossover of alcohol, which usually floods the cathode compartment and its effects reflect in the decrease of cell performance in terms of efficiency. This is due to the interference of alcohol molecules on the electrocatalyst surface during the oxygen reduction reaction (ORR), causing a competition between them. As this consequence is directly related to the low selectivity of catalyst, an alcohol-tolerant material is necessary; in order to inhibit its deactivation because of oxidized species on the electrode surface. Some approaches to avoid such decrease in activity consists in the incorporation of a secondary metal in the electrocatalyst with the aim of promoting selectivity. Furthermore, the implementation of bimetallic materials leads to the decrease in the Pt loading, as it represents a higher cost of the catalyst; in summary, the best option consists in preparing bimetallic mixtures. In the present work, Pt and Pt/Ag materials were synthesized by cyclic voltammetry (VC) and its behavior in basic medium was evaluated for the oxygen reduction reaction (ORR) in absence and in presence of 0.1 M of methanol, ethanol, ethylene glycol and glycerol. The results demonstrated that the use of PtAg as cathode electrode achieved higher selectivity and better performance compared with Pt catalyst in the presence of alcohol fuels. While Pt preferred to oxidize these fuels instead of taking the ORR, PtAg only carried out the ORR. The activity of PtAg catalyst towards oxygen reduction reaction resulted in an overpotential of 90 mV compared with pure Pt, after the electrochemical activation. Pt showed no tolerance to any tested alcohol-based fuels but, PtAg exhibited excellent tolerance to methanol, ethanol and ethylene glycol.
Structure Sensitivity of Electrochemical Reactions from First Principles: Applications to Nitrogen and Water Cycles
Authors: Chun Hee-Joon , Deshpande Siddharth , Apaja Vesa , Honkala Karoliina , Zeng Zhenhua , Greeley Jeffrey
Published: February 2020

Nitrogen cycle electrochemistry is an emerging area of interest in the electrocatalysis community, with applications ranging from removal of nitrates from wastewater streams to the development of fundamental understanding of NO electrochemistry. In spite of a significant amount of fundamental research for this chemistry on single crystal surfaces, however, the mechanistic details of the reactions are not fully known, and even such basic information as the nature of the rate-limiting step is not understood.

In this work, we apply some of the innovations in theoretical electrochemistry that have emerged over the past 5-10 years to the study of NO and nitrate reduction on transition metal surfaces. We begin with a simple Density Functional Theory analysis of direct NO reduction in acid on Pt(111), Pt(100), and Pt(211) surfaces, and we identify potential- and rate-determining steps on each surface, using extensive ab-initio molecular dynamics simulations to estimate the impact of the aqueous environment on surface thermodynamics and kinetics (Ang. Chem. Int. Ed. 2015). We next introduce a novel approach that couples DFT calculations with rigorous kinetic Monte Carlo (kMC) simulations to understand, in unprecedented detail, the effect of higher adsorbed NO coverages on these chemistries, and we demonstrate that these coverage-dependent effects are essential for describing experimentally measured polarization curves (ACS Catalysis 2017).

We subsequently generalize our analysis by developing universal Brønsted-Evans-Polanyi relationships that rigorously relate barriers for proton-coupled electron transfer to surface species to the corresponding thermodynamics across a large space of different transition metals and potentials. These relationships, combined with the potential- and coverage-dependent energetics determined on platinum, provide a basis to extrapolate our mechanistic analyses to other transition metals, including PtSn and related alloys. We employ these techniques to propose design strategies to tune selectivity of NO electroreduction to desired products, including N2 and hydroxylamine, on these different transition metals and alloys.

If time permits, we will briefly describe some additional work on the development of structural and catalytic reactivity models at the interface between thin hydroxyoxide films and precious metal platinum substrates. We will examine the kinetics of the hydrogen evolution reaction as a function of the structure and oxidation state of these interfaces and will demonstrate that the bifunctional nature of the interfaces plays a key role in their electrocatalytic properties.
PGM-Free and Iron-Free Catalysts for Oxygen Reduction in Acids
Authors: Wu Gang
Published: February 2020

Due to the Fenton reaction, the presence of Fe and peroxide in electrodes generates free radicals causing serious degradation of the organic ionomer and the membrane. Pt‐free and Fe‐free cathode catalysts therefore are urgently needed for durable and inexpensive proton exchange membrane fuel cells (PEMFCs). Herein, a high‐performance nitrogen‐coordinated single Co atom catalyst is derived from Co‐doped metal‐organic frameworks (MOFs) through a one‐step thermal activation. Aberration‐corrected electron microscopy combined with X‐ray absorption spectroscopy virtually verifies the CoN4 coordination at an atomic level in the catalysts. Through investigating effects of Co doping contents and thermal activation temperature, an atomically Co site dispersed catalyst with optimal chemical and structural properties has achieved respectable activity and stability for the oxygen reduction reaction (ORR) in challenging acidic media (e.g., half‐wave potential of 0.80 V vs reversible hydrogen electrode (RHE). The performance is comparable to Fe‐based catalysts and 60 mV lower than Pt/C ‐60 μg Pt cm−2). Fuel cell tests confirm that catalyst activity and stability can translate to high‐performance cathodes in PEMFCs. The remarkably enhanced ORR performance is attributed to the presence of well‐dispersed CoN4 active sites embedded in 3D porous MOF‐derived carbon particles, omitting any inactive Co aggregates.
Electron Transfer Reactions in Three-Nuclear Ti Complexes with π-Acceptor Ligands
Authors: Markovic Aleksandra , Sander Pia , Dosche Carsten , Beckhaus Rüdiger , Wittstock Gunther
Published: February 2020

Multinuclear transition metal complexes bridged by ligands with extended π-electronic systems such as hexaphenyl-5,6,11,12,17,18-hexaaza-tribiscyclopentadienyl titaniumnaphtylene [(Cp2Ti)3HATN(Ph)6] show a variety of complicated electronic transitions and electron transfer reactions [1]. Therefore, they are intensively investigated as artificial analogues to a number of natural systems capable of converting light into chemical energy by translocating charges over large distances or to generate light efficiently [1]. While a systematic understanding of the photochemistry and electrochemistry has been atained for binuclear complexes [1], much less is known about trinuclear and multinuclear complexes [2].

Trinuclear titanocene(II) complexes include formally three titanocene(II) fragments with two d-electrons, i.e. they contain six potential d-electrons. In this study the complex has been characterised by electrochemical measurements and absorption spectroscopy. The voltammogramm of [(Cp2Ti)3HATN(Ph)6] shows three reduction waves and six oxidation waves.

Solution spectra of [(Cp2Ti)3HATN(Ph)6] and of the electrochemically formed oxidation products show electronic transition in the UV, visible and the NIR ranges. The existence of a single occupied molecular orbital (SOMO) populated by an electron transferred from one of the Ti(II) centers to the HATN(Ph)6 ligand gives rise to several characteristic electronic transitions from which the most prominent is the intervalence charge transfer (IVCT) transition between the Ti(III) center and the remaining Ti(II) centers. Another transition related to the SOMO is the ligand-centered transition from the SOMO to the lowest unoccupied molecular orbital (LUMO). When oxidized to [(Cp2Ti)3HATN(Ph)6]+, the SOMO orbital becomes the LUMO’. If the complex is oxidized to [(Cp2Ti)3HATN(Ph)6]2+, one electron is extracted from the Ti(II). For the reduced form [(Cp2Ti)3HATN(Ph)6]-, the Ti(III) accepted an electron an no IVCT can be observed. In further reduction the “SOMO” is fully occupied and becomes the new HOMO'. In the last reduction an electron is accepted to the one orbital of the Ti(II) and attaining a mixed valence states again.

Finally, the orbital diagram in the accurate energy scale was constructed from the assignment of the transitions, the spectra and the formal potentials obtained from the voltammetric data. From this diagram it becomes evident that removal of an electron from the orbitals of the ligand does not change the energetic position of the Ti orbitals, whereas removal of an electron from one of the Ti centers affects the energy of all orbitals in the complex.

Figure 1: Structure of [(Cp2Ti)3HATN(Ph)6].

References:

[1] S. Kitagawa, S. Masaoka, Coord. Chem. Rev., 246 (2003) 73-88.

[2] I. M. Piglosiewicz, R. Beckhaus, W. Saak and D. Haase, J. Am.
Chem. Soc., 127 (2005) 14190-14191

Figure 1
Application of Electrochemical Impedance Spectroscopy for Evaluating Nanoparticle Agglomeration
Authors: Peters Dennis G , Pence Michael Andrew , Hosseini Seyyedamirhossein
Published: February 2020

Metallic nanoparticles form dendrite assemblies when they are used as modifying agent in electrochemical reactions.1 These dendrites and the process of their formation can be visualized by application of imaging techniques such as scanning electron microscopy (SEM) and atomic force microscopy (AFM). Although these approaches provide local information about specific imaging points, electrochemical techniques offer a powerful means to probe the entire electrode surface. For instance, particle coagulation and dendrite formation drastically influence double-layer capacitance and charge-transfer resistance of modified electrodes. Consequently, variation of these parameters during electrochemical reactions can be probed by application of electrochemical impedance spectroscopy (EIS).2

In this work, a modified electrode was fabricated through electrophoretic deposition of copper sulfide nanoplates onto a detachable glassy carbon surface. Then a potential of –1.5 V vs. SCE was applied to a modified electrode for 2 h. Finally, the morphological evolution of the electrode was investigated by application of EIS and SEM methods. Moreover, a random-walk simulation was used to model the agglomeration process. The simulation results were compared to the morphology and EIS spectra of the modified electrode to correlate the simulation with physical information.

References

Manthiram, K.; Surendranath, Y.; Alivisatos, A. P., Dendritic Assembly of Gold Nanoparticles during Fuel-Forming Electrocatalysis. J. Am. Chem. Soc.
2014,
136, 7237–7240.

Gao, S.; Sun, Z.; Liu, W.; Jiao, X.; Zu, X.; Hu, Q.; Sun, Y.; Yao, T.; Zhang, W.; Wei, S., Atomic layer confined vacancies for atomic-level insights into carbon dioxide electroreduction. Nat. Commun.
2017,
8, 14503–14509.
Enhancing the Activity and Stability of Manganese Oxide-Based Catalysts for the Electrochemical Oxygen Evolution Reaction
Authors: Morales Dulce M. , Masa Justus , Antoni Hendrik , Muhler Martin , Schuhmann Wolfgang
Published: February 2020

Finding efficient non-expensive materials for the electrocatalytic oxygen evolution reaction in alkaline media is one of the major challenges in the development of green energy conversion technologies. Transition metal oxides represent an attractive alternative to the state of the art noble metal-based catalysts due to their high abundance, low cost, and wide versatility regarding structure, composition, oxidation state, morphology and surface area. However, a major drawback of most transition metal oxides is their poor electric conductivity, which hinders their electrocatalytic properties.

In this context, we present manganese oxide-based materials as alternative oxygen evolution electrocatalysts and we discuss different synthesis routes which aim, firstly, to overcome their conductivity limitations, and, secondly, to improve their overall performances regarding activity and stability, by embedding metal oxide particles in a conductive carbon matrix, such as few-layer graphene[1] or carbon nanotubes[2], followed by a thermal treatment step[3]. Since it has been reported that the presence of metal impurities in the carbon supports can substantially promote the electrocatalytic activity of carbon containing catalysts[4,5], we include as a design strategy the incorporation of small amounts of metal particles, such as iron, cobalt and nickel, into the manganese oxide-based composites, and we further discuss their impact on the overall electrocatalytic performance. Finally, we demonstrate the importance of coupling electrochemical methods with spectroscopic techniques for an in-depth characterization of the electrocatalytic materials under reaction conditions.

References:

[1] D.M. Morales, J. Masa, C. Andronescu, Y.U. Kayran, Z. Sun, W. Schuhmann, Electrochim. Acta
222 (2016) 1191–1199.

[2] K. Elumeeva, M. Kazakova, D.M. Morales, D. Medina, A. Selyutin, G. Golubtsov, Y. Ivanov, V. Kuznetzov, A. Chuvilin, H. Antoni, M. Muhler, W. Schuhmann J. Masa, ChemSusChem (2018) DOI: 10.1002/cssc.201702381.

[3] J. Masa, W. Xia, I. Sinev, A. Zhao, Z. Sun, S. Grützke, P. Weide, M. Muhler, W. Schuhmann, Angew.
Chem. Int.
Ed.
53 (2014) 8508–8512.

[4] M. Pumera, H. Iwai, J. Phys. Chem. C
113 (2009) 4401–4405.

[5] C.H.A. Wong, Z. Sofer, M. Kubesova, J. Kucera, S. Matejkova, M. Pumera, Proc. Natl. Acad. Sci. U.S.A.
111 (2014) 13774–13779.

Acknowledgment: The authors are grateful to the BMBF in the framework of the project “Mangan” (FKZ 03EK3548). D. M. Morales acknowledges the financial support from Deutscher Akademischer Austauschdienst (DAAD) and from Consejo Nacional de Ciencia y Tecnología (CONACyT).
Effect of Chloride Ions on Electrochemical Behaviors of Magnesium Anode in Ionic Liquids Based on TFSA-
Authors: Matsumoto Hajime , Kubota Keigo
Published: February 2020

Imide anions such as bis(trifluorosulfonyl)amide (TFSA-) have been widely investigated as the most typical perfluoroanion, which forms ionic liquids (ILs) with various onium cations like dialkylimidazolium and the good electrochemical and thermal stability have been attracted attention as a unique liquid electrolyte for secondary batteries especially lithium batteries. [1] Recently, research and developments of post-lithium ion battery, so called next-generation batteries, have been intensively investigated. Especially, the use of multivalent metal as an anode like magnesium, zinc and aluminum have been attracted attention due to their high volumetric energy density. However, in many case, slow diffusion of multivalent cation in a layered oxide cathode might be one of the severe problems. The use of thermally stable and less volatile ionic liquids might be one of the promising choice to enhance the diffusion in a cathode material at enough higher temperature. However, no good magnesium redox have been observed in a conventional and typical ionic liquids containing the TFSA- .[2] In this study, we investigated the electrochemical responses of a magnesium metal and also much cheeper alloy (AZ31B) in a various molten salt such as a conventional TFSA ionic liquids, onium chloride and alkali metal intermediate temperature molten TFSA salt to discuss the reason for the poor redox in a conventional ionic liquids and the effect of the addition of halogenide like chloride.

References

[1] H. Matsumoto, Recent Advances in Ionic Liquids for Lithium Secondary Batteries, R.T.Jow, K. Xu, O. Borodin, M. Ue, (Eds.), Electrolytes for Lithium and Lithium-Ion Batteries, Chapter 4, pp.209-225, Springer, 2014, and references therein.

[2] G. Vardar, A. E. S. Sleightholme, J. Naruse, H. Hiramatsu, D. J. Shiegel and C. W. Monroe, ACS Appl. Mater. Interfaces, 6 (2014) 18033.

Acknowledgment

This study was financially supported by ALCA-SPRING, JST, MEXT, Japan.
Corrosion Resistance of Hastelloy G-35 Nickel-Based Superalloy in Various Aggressive Media
Authors: Abramov Aleksandr V. , Dedov Kirill V. , Gibadullina Alfiya F. , Zhilyakov Arkadiy Yu. , Karpov Vyacheslav V. , Volkovich Vladimir A. , Polovov Ilya B.
Published: February 2020

Nickel-based superalloys are widely used in various fields of engineering and technology in contact with aggressive liquid media. High-temperature molten salts are one of the types of such corrosive liquids. Molten electrolytes are widely used in technologies for the electrowinning and refining non-ferrous and rare metals, in nuclear industry and solar storage systems.

In the present study the corrosion resistance of Hastelloy G-35 Аlloy (UNS N06035) nickel-based alloy was investigated. Corrosion properties of the material were examined in NaCl–KCl melt at 750 °C under inert (Ar) and oxidizing (air) atmosphere, and in acidic KCl–AlCl3 melts under an inert atmosphere (Ar). KCl–AlCl3 melts were chosen in addition to NaCl–KCl as having higher oxidation ability. Samples were kept in contact with the melts for 30 h. Additional corrosion tests were performed in a boiling sulfuric acid solution in the presence of iron (III) sulfate (according to the ASTM G28-02A procedure) and these lasted for 120 h.

The corrosion rates of the alloy samples in various molten media were calculated and are given in Table 1. The slowest corrosion was observed in NaCl–KCl melt under an inert atmosphere. The corrosion rate in NaCl–KCl melt increased noticeably in the presence of oxygen in the atmosphere, and the corrosion resistance of the alloy under these conditions was low. The rate of the alloy corrosion in KCl–AlCl3 melt at 750 °C was extremely high, and this alloy cannot, therefore, be recommended for application as a construction material in this melt under the conditions studied.

The data obtained were compared with results of corrosion tests performed according to the ASTM G-28-02A standard. Samples of Hastelloy G-35 alloy were examined in the initial state and after preliminary aging in KCl–AlCl3 at 650 °C for 200 hours (Table 2). The corrosion rate of the alloy in boiling sulfuric acid solution in the presence of iron (III) sulfate was comparable to that in the NaCl–KCl melt under an inert atmosphere. Preliminary aging in the KCl–AlCl3 melt led to intensification of the corrosion processes in aqueous solutions.

Figure 1
Electrochemical Obtaining and Studying Structural Characteristics of Nanopowders of Intermetallides of Golmium and Nickel
Authors: Ligidova Marina , Kushkhov Hasbi , Borukaeva Inna , Kardanova Ranetta
Published: February 2020

This research is devoted to an electrochemical way of synthesis holmium and nickel compounds nanopowders from chloride melts and also identification of samples by methods of the X-ray phase analysis and the scanning electronic microscopy. The conducted researches have shown a possibility of synthesis of intermetallic compounds of holmium and nickel by electrolysis from the halide melts; Results of the high-temperature electrochemical synthesis carried out in the galvanostatic mode at a temperature of 973K are presented. As a result of researches optimum conditions of holmium and nickel compounds synthesis i.e. optimum composition of an electrolysis bath KCl-NaCl-HoCl3-NiCl2, a cathodic current density, a duration of electrolysis and temperature of process are found. The received results on the X-ray phase analysis and the laser diffraction analysis of the size of particles of the synthesized powders show existence of various phases of alloy of holmium with nickel (HoNi, HoNi5, HoNi3) and confirm a possibility of synyhesis their nanodimensional powders (more than 51% of particles up to 100 nanometers).
Improving the Thermal Stability of Textile Fibers By Natural Fiber Welding
Authors: Durkin David P. , Tang Xiling , Frank Benjamin P. , De Long Hugh C. , Haverhals Luke M. , Trulove Paul C.
Published: February 2020

Natural Fiber Welding (NFW) is an Ionic Liquids (IL) based engineering process that can manipulate biopolymer matrices without destroying their underlying structure. It can be used to incorporate functional materials into the biopolymer matrix. In this study, we evaluate how NFW can be used to improve the thermal stability of natural textile fibers. First, a variety of synthesized and/or commercially available flame-retardant micro/nanomaterials are welded onto the surface of the fibers. Then, using thermogravimetric (TG) analysis, we demonstrate how each coating can enhance the thermal stability of the textile yarn. In some cases, thermal stability improves by as much as 25 °C, primarily through delays in the onset of thermal decomposition and increased char yield. Our data reveal strong potential for NFW to be used to deliver fiber-welded textile yarns with improved thermal stability.
Ionic Liquids As Electrolytes for Post Li-Ion Batteries
Authors: Iliev Boyan , Schubert Thomas J. S. , Cadu Svetlana
Published: February 2020

Ionic liquids (ILs), a class of compounds composed entirely of ions, are prominent candidates for battery electrolytes, as they allow for increased safety due to their negligible vapor pressure, non-flammability and high thermal and electrochemical stability. Another benefit of ILs is their tunable properties, including solvating power, polarity and surface tension. Those could be used to influence the SEI formation as well as modify the overpotential on the electrodes. This effect can be used in different metal-air batteries, where the use of IL-based electrolyte allows for high electrolyte stability combined with the use of a normal gas diffusion electrode. [1] Further advantages that ILs bring, especially in the context of lithium sulphur batteries are their ability to reduce the formation of soluble polysulfides and to reduce dendrite formation. [2] This feature can be also beneficial for other types of lithium metal batteries.

The major problem of using ILs as electrolytes - their high viscosity - can be overcome by using mixtures of selected ILs in specific ratios, thus reducing viscosity and increasing performance of the electrolyte. [3] In connection with that, our latest developments on use of ILs as electrolytes for different types of batteries will be presented. We will focus on physicochemical properties of selected ILs, their mixtures and possible additives, designed for specific batteries applications. The compatibility of the particular ILs with battery materials will be also discussed.

References:

[1] Liu, G. Pulletikurthi , A. Lahiri , T. Cui, F. Endres, Dalton Trans.,
2016, 45, 8089.

[2] W. Park, K.Ueno, N. Tachikawa, K. Dokko, M. Watanabe, J. Phys. Chem. C. 117 , 20531–20541.

[3] A. Taige, D. Hilbert, T. J. S. Schubert Z. Phys. Chem. 226, 129.

Figure 1
(Invited) Photocatalytic Conversion of Methane to Hydrogen
Authors: Hu Yun Hang
Published: February 2020

In the recent years, we made great efforts to develop: (1) efficient photocatalytic processes and photocatalysts for water splitting and methane conversion, (2) advanced materials for dye-sensitized solar cells and perovskite solar cells, and (3) efficient electrode materials with large accessible surface areas for supercapacitors. In this talk, I will discuss our recent success of efficient visible light photocatalytic conversion of methane to hydrogen, with emphasis on the design of processes and catalyst systems.
Development and Photoelectrochemical Performance of Copper Oxides Based Heterojunctions for Enhanced Production of Solar Fuels
Authors: Solarska Renata , Bienkowski Krzysztof , Arasimowicz Monika , Jelińska Aldona
Published: February 2020

The need for renewable and sustainable energy might be a concern for the society if we are not able to provide this energy with concomitant environmental protection and economic competitiveness. A technology which allows exploiting sunlight, water, and CO2 to produce solar fuels will certainly contribute to high rate of solar energy conversion and reduction of global warming. However, major considerations are paid to the construction of heterogenous junctions & surfaces allowing better charge transport kinetics and selective simulative proceeding of desired products in appropriates ratios. For that reason, design and construction of different types of joined semiconductors systems aiming enhancement of charge carrier excitation, separation and their transport dynamics followed by recognition of their intrinsic limitations and enhanced efficiency towards CO2 conversion, becomes a priority in terms of global advancement in the field.

Recent advances regarding construction of a such heterojunction, consist of coupling of high photocatalytic activity of Cu2O towards CO2 reduction with high stability and electric conductivity of substoichiometric titanium oxide. This approach allowed to convert the CO2 to methanol with high efficiency and at relatively positive potential of 0.1 V vs RHE. The stable and reproducible photocurrents reached more than 1.2 mA/cm2 and were attained at standard conditions. Then, the substoichiometric titanium oxide has been replaced by the WO3 containing more than bare, oxygen deficiencies. Further, change in its crystal lattice system allowed better stabilization of the overall working system and higher rate of solar energy conversion to CO2 reduction products. The mechanism which has been pointed as responsible for better charge separation in the junction relied onto indirect charge transfer between components and could be diversified by the content of carbon in the upper layer. Design, construction and performance of those systems will be an objective of this presentation.
High Performance Si-Based Photoanodes Using a Conformal Co-Based Catalysts By Electrodeposition
Authors: Lee Sol A , Jang Ho Won
Published: February 2020

Converting and storing solar energy has been regarded as a promising approach to address the current global reliance on fossil fuels. The generation of hydrogen from water using sunlight can form potentially the basis of a clean and renewable source of energy. Solar water splitting system requires stable light-absorbing electrodes for both the oxidative and reductive half-reactions. However, the kinetically slow oxygen evolution reaction (OER) is a bottle-neck process for producing sustainable solar-driven fuels using water.

Silicon has a suitable band gap (1.12 eV) to absorb the wide range of the solar spectrum and has high carrier mobility. For this reason, silicon is an attractive candidate among the various materials such as transition metal oxides and semiconductors. Since the silicon photoanode is unstable at electrolyte and suffers from fast photocorrosion due to the position of thermodynamic redox potentials, the solar to hydrogen conversion efficiency of bare silicon photoanode is largely suppressed. To solve those problems of silicon, recent studies on silicon photoanode has focused on designing a surface passivation layer that protects against chemical and photo-induced corrosion without degrading the inherent photoactive ability of silicon and promotes the chemical adsorption of water molecules to lower the overpotential at the solid/liquid interface.

Herein, we report the synthesis and photoelectrochemical properties of multifunctional cobalt based catalysts on a n-type silicon photoanode by using facile electrodeposition. This method not only significantly reduces the synthesis time and costs, but also easily control reaction by changing applied voltage or current. The solution-processed n-Si photoanode showed large photovoltage and superior catalytic behavior. By using efficient oxygen evolution catalysts, onset potential shifted to cathodic direction, leading to highly efficient Si-based photoanodes.
Surface Plasmon Resonance of Au Thin Films Modified By Pt and Pd Monolayer Catalyst
Authors: Artur Camille , Shan Xiaonan , Brankovic Stanko
Published: February 2020

Surface plasmons (SP’s) or surface plasmon polaritons are longitudinal electromagnetic waves which propagate at the interface between a metal and a dielectric. They are localized in the interface and are sensitive to the optical properties of the materials comprising the interfacial region. As such, the SP present a unique probe to study the electrochemical interface and double layer [[1],[2]].Typical plasmonic metals/electrodes are Au and Ag thin films, which have been a subject of studies where the SPs have been used to probe the electrochemical processes such as adsorption and underpotential deposition [1,[3],[4]]. The most recent developments indicate that the SPs can be used to enhance certain electro-catalytic and photocatalytic reactions [[5]].

In this report, we present the results investigating the catalyst monolayer modification effect on plasmon resonance of Au thin films. The experiments are conducted using an attenuated total reflection arrangement in which p-polarized light is incident through a prism onto a thin (-400 A) Au film deposited on the mica substrate. (Kretschmann configuration [[6]]). The angle of incidence on the base of the prism is greater than the critical angle for the prism: electrolyte interface and SPs are excited by the evanescent wave generated under these conditions of total internal reflection. The excitation is manifested by a decrease in the intensity of reflected light. The Pd monolayer on Au were electrodeposited using procedure reported by Kolbe et al [[7],[8]], while the Pt submonolayer/monolayers were deposited on Au using Surface Limited Redox Replacement (SLRR) of Pb UPD monolayer [[9]]. The plasmon resonance frequency of Au(hkl), PdML/Au(hkl) and PtML/Au(hkl) and PtSML/Au(hkl) were investigated as a function of the applied potential in the range between -0.24 V to 0.4 V vs. SCE. The comparative analysis, between Au and catalyst monolayer modified Au(hkl) samples indicate that SP resonant frequency change is induced by both; surface charge and adsorption of H on the catalyst monolayer surface in the UPD region. The latter effect is quantified using subtractive analysis between the Au and catalyst modified Au surface and solutions with different pH. In conclusion, we present a simple model describing the catalyst monolayer effect on plasmon resonance of Au films.

[1] J.G. Gordon II and S. Ernst, Surface Science, 101 (1980) 499

[2] R. Kotz et al, Surface Science, 69 (1977) 359

[3] D.M. Kolb, D. Leutloff and M. Prasnyski, Surface Science, 47 (1975) 622

[4] A. Bewick, and B. Thomas, J. Electroanalytical Chem., 65 (1975) 911

[5] S. Linic, U. Aslam, C. Boerigter and M. Morabito, Nature Materials, 14, (2015) 567.

[6] E. Kretschmann and H. Raether, Z. Natutforsch. 23a (1968) 2135.

[7] L.A. Kibler, M. Kleinert, R. Randler, D.M. Kolb, Surface Science, 443 (1999) 19.

[8] J. Tang, M. Petri, L.A. Kibler, D.M. Kolb, Electrochimica Acta, 51, (2005) 125

[9] K. Sasaki et al, Electrochim. Acta, 55, (2010) 2645.
Electrochemical Fabrication of Cu2o-Nanowires-Based Photo-Cathodes for Enhanced Solar Water Splitting
Authors: Hamdani Iqra Reyaz , Bhaskarwar Ashok N.
Published: February 2020

Solar-power driven photoelectrochemical (PEC) water splitting using semiconductor photoelectrodes is one of the most promising approaches for energy conversion, in terms of production of renewable hydrogen with a minimum carbon footprint. There are, however, enormous challenges to be overcome to obtain sufficient solar water-splitting efficiency, such as over-potential losses due to fast recombination rates of charge carriers, electrode photo-degradation, limited light-harvesting capacities, to name a few. In this work, we report an extensive study on Cu2O based photocathode for hydrogen evolution reaction (HER) in terms of enhancing its solar-to-hydrogen (STH) conversion efficiency, while using low-cost fabrication methods. We have addressed the inefficiency of Cu2O which mainly arises due to incompatible light absorption and charge carrier diffusion lengths, by fabricating highly reproducible Cu2O-nanowire arrays on Cu substrate. The reported optimal thickness of Cu2O for efficient absorption of sunlight is around 2-4 µm, while the minority charge carrier diffusion length is limited to 200-250 nm only. The nanostructured Cu2O, especially in the form of nanowire arrays, improves its performance through morphology control, by improving the light-harvesting capacity along the full length of wire and providing a shorter diffusion path length corresponding to the radial distance in the wire, towards the electrolyte. We prepared the photocathode by anodizing Cu foil to Cu(OH)2 nanowires at 10 mA/cm2, followed by oxidation to Cu2O nanowires in an inert atmosphere. Experimental measurements showed that the process was highly reproducible and resulted in an increased current density from 0.5 mA/cm2 for planar Cu2O to 82.3 mA/cm2 for Cu2O nanowires, both at 1 V cathodic bias. The photocurrent density was enhanced from 0.15 mA/cm2 for planar Cu2O to 5.54 mA/cm2 for the nanowire morphology, while using visible light source in all cases. All the photoelectrodes were reproducible in the regime of 4 µm thicknesses of Cu2O nanowires, oxidized over Cu-foil substrates. The STH efficiency calculated for all the fabricated photoelectrodes was as high as 3.54±0.21%, in comparison to 0.24% for the planar Cu2O photoelectrodes.

Keywords: Cu2O, nanowires, photocathode, solar water splitting, photoelectrochemistry, STH efficiency, PEC.
(Invited) The Mechanisms of Hot-Electron Generation in Plasmonic and Hybrid Nanomaterials: Comparing Different Material Systems and Geometries
Authors: Govorov Alexander , Besteiro Lucas V. , Kong Xiang-Tian
Published: February 2020

Generation of energetic (hot) electrons is an intrinsic property of any plasmonic nanostructure under illumination. Simultaneously, a striking advantage of metal nanocrystals over semiconductors lies in their very large absorption cross sections. Therefore, metal nanostructures with strong and tailored plasmonic resonances are very attractive for photocatalytic applications in which excited electrons play an important role. However, the central questions in the problem of plasmonic hot electrons are the number of optically excited energetic electrons in a nanocrystal and how to extract such electrons. Here we develop a theory describing the generation rates and the energy distributions of hot electrons in nanocrystals with various geometries [1-4]. In particular, we show that nanostructures with strong and extended plasmonic hot spots generate unusually large numbers of energetic electrons, which can be observed using the ultra-fast transient spectroscopy [2,4,5] as well as photochemistry. Hot-electron generation together with non-radiative plasmonic transfer [6] represent efficient methods to transfer and localize optical and photo-chemical energies.

A.O. Govorov, H. Zhang, V. Demir, and Y. K. Gun’ko, Nano Today, 9, 85 (2014).

H. Harutyunyan, A. B. F. Martinson, D. Rosenmann, L.K. Khorashad, L.V.Besteiro, A.O.Govorov, and G.P. Wiederrecht, Nature Nanotechnology 10, 770–774 (2015).

L.V. Besteiro, X.-T. Kong, Z. Wang, G. V. Hartland, A.O. Govorov, ACS Photonics, DOI: 10.1021/acsphotonics.7b00751 (2017).

M.E. Sykes, J. W. Stewart, G. M. Akselrod, X.-T. Kong, Z. Wang, D. J. Gosztola, A.B.F. Martinson, D. Rosenmann, M. H. Mikkelsen, A. O. Govorov, G. P. Wiederrecht, Nature Communications, 8, 986 (2017).

G.V. Hartland, L. Besteiro, P. Johns, A. O. Govorov, What’s so Hot about Electrons in Metal Nanoparticles? (perspective paper), ACS Energy Letters, 2, 1641–1653 (2017).

E.-M. Roller, L.V. Besteiro, C. Pupp, L. Khosravi Khorashad, A. O. Govorov, T.Liedl, Nature Physics, 13, 761-765 (2017).
The Fundamental Cytotoxicity of Redox Polymer Based Enzymatic Biofuel Cell
Authors: Jeon Won-Yong , Choi Young-Bong , Kim Hae-Won , Kim Hyug-Han
Published: February 2020

The biologist has been using electrical stimulation via DC, AC, or Hz for cell culture system. However, those electrical stimuli are having inconvenience to use the machine. The enzymatic biofuel cell is one of the alternatives for electrical stimulation in the cell study. This study highlighted that the redox polymer based enzymatic biofuel cell, having suitable concentrations, which provides the biocompatibility and convenient to use for cell culturing. Also, this work suggests what concentration of redox polymer and enzyme should be used to the cellular level. Our enzymatic biofuel cell, including two kinds of traditional osmium redox polymer mediators (PAA-PVI[Os(dmo-bpy)2Cl] as an anode and PAA-PVI[Os(dCl-bpy)2Cl] as a cathode), two kinds of enzymes (glucose oxidase (GOx) as an anode and bilirubin oxidase (BOD) as a cathode), and poly(ethylene glycol) diglycidyl ether (PEGDGE) as a cross-linker, were prepared onto 2D screen printed carbon electrode (SPCE). The electrical characterization of the anode and cathode electrodes were examined by cyclic voltammetry (CV) and amperommetry (I-t curve). All electrodes were used after sterilization and we checked the cell viability using CCK-8 and Live&Dead staining. Also, the continuous electrical current under similar condition to the cell culturing were measured by i-t curve. Our enzymatic biofuel cell can be easily immersed into the cell culture media, and it showed good biocompatibility. In this work, we exhibited main consideration when enzymatic biofuel cell applied to the cellular level. The enzymatic biofuel cell will be applied to the in vitro and in vivo system as an electrical stimulating source in the near future.