bluuebunny/crossref_metadata_2025 huggingface dataset:
(Invited) Surfactant-Exchange Equilibrium Constants for Each Semiconducting Single Wall Carbon Nanotube Type
Authors: Ziegler Kirk J
Published: February 2020

The high surface area of single-walled carbon nanotubes (SWCNTs) dictates that the interface with their surroundings is important in determining their properties or functionality. For example, the interface of SWCNTs with their surroundings is important to their application in polymer composites, devices, drug delivery, bioimaging and biosensing. Understanding and ultimately controlling these surface layers is important because of its influence on reactivity, adsorption of pollutants, and interaction with biological materials. For example, the surfactant orientation on the SWCNT surface plays an important role in their separation by nearly any method. Our group has focused on characterizing and controlling these SWCNT interfaces. Here we present the equilibrium constants associated with surfactant exchange on the surface of different (n,m) SWCNT types using optical spectroscopy. The exchange of surfactant is found to be reversible and occurs at specific co-surfactant mixtures for each (n,m) type. Comparing the equilibrium states with the desorption characteristics during chromatographic separation enables a better understanding of the surface state that leads to desorption from the hydrogel.
(Invited) Localized Covalent Defects on Carbon Nanotube Devices for Sensor Applications
Authors: Bouilly Delphine
Published: February 2020

Functionalization of carbon nanotube devices is essential to tailor their affinity with other molecules, which is especially critical for applications as sensors. Among functionalization approaches, covalent chemistry produces stable moieties on nanotubes sidewalls, but the chemistry is invasive and alters the electronic properties of the material. In this presentation, I will describe recent efforts to control covalent diazonium chemistry on carbon nanotubes and understand its impact on electrical conductance. In particular, I will contrast experiments between extended and localized defect coverage of adducts on the electrical response of devices, and present applications in single-molecule sensors.
Dielectrics & Electrostatics: Their Effect on Carbon Nanotube Network Field-Effect Transistors and Gas Sensors
Authors: Lapointe François , Malenfant Patrick R. L. , Lefebvre Jacques
Published: February 2020

Due to their high surface area, monoatomic wall thickness, electronic structure (band gap, van Hove singularities) and properties (high mobility, ambipolar transport), single-walled carbon nanotubes (SWNTs) stand as a promising active material for chemical sensors. In a sensor context, they however suffer from lack of selectivity. For the same reasons that they are highly sensitive to analytes, they will be affected by their environment: interference from ambient gases (i.e. O2 / H2O redox couple) are to be expected [1,2], and vicinal charges and dipoles [3,4] will change the local electrostatics felt by the SWNTs. The dielectric environment being an integral part of the field-effect transistor (FET) stack, we sought to understand its effect on the transfer characteristics of devices with a carbon nanotube network as the active channel component.

References

[1] Aguirre, C. M. et al. The Role of the Oxygen/Water Redox Couple in Suppressing Electron Conduction in Field-Effect Transistors. Adv. Mater.
21, 3087–3091 (2009).

[2] Lefebvre, J. et al. Hysteresis free carbon nanotube thin film transistors comprising hydrophobic dielectrics. Appl. Phys. Lett.
107, 243301 (2015).

[3] Kobayashi, S. et al. Control of carrier density by self-assembled monolayers in organic field-effect transistors. Nat. Mater.
3, 317–322 (2004).

[4] Lee, S.-H. et al. Effect of Polymer Gate Dielectrics on Charge Transport in Carbon Nanotube Network Transistors: Low-k Insulator for Favorable Active Interface. ACS Appl. Mater. Interfaces
8, 32421–32431 (2016).
(Invited) Design and Synthesis of Hybrid Nanomaterials for Electrochemical Energy Storage Applications
Authors: Song Min-Kyu
Published: February 2020

The aspiration to lessen the dependency on fossil fuels and the desire to secure a clean, sustainable energy system have become stronger, resulting in endeavors headed for developing next-generation batteries. Currently, Li-ion batteries are the most commercially successful and dominating battery system. It is well known, however, that the energy densities of current Li-ion batteries are unable to meet the ever-increasing demands of newly emerging technologies. Therefore, investigations of new materials/chemistries and novel architectures are required to go beyond incremental developments in the energy densities of existing batteries.

Silicon or Tin-based anodes and Chalcogen group-based (Sulfur and Oxygen) cathodes have gained much attention for next-generation batteries because they have the potential of providing much higher specific energy than those of current Li-ion batteries. However, there remain fundamental challenges for these systems to be considered as a practically viable option. In this presentation, a brief discussion of scientific challenges and some latest developments in hybrid nanostructured materials for advanced batteries will be provided. In particular, the direct utilization of CO2 in synthesis of Silicon or Tin-based composite materials will be discussed in the context of improving the energy/power density of current Li-ion batteries. Furthermore, if time allows, our group’s recent efforts based on metal-organic frameworks to extend cycle life of beyond Li-ion (Li/S and Li/O2) batteries will be introduced.
(Invited) Two-Dimensional Organic Network Structures for Energy Conversion and Storage
Authors: Mahmood Javeed , Baek Jong-Beom
Published: February 2020

Since the discovery of graphene in 2004,1 conjugated two-dimensional (2D) organic network structures have attracted immense interest due to their unusual electronic, optoelectronic, magnetic and electrocatalytic properties. In addition, their tunable structures and properties promise to offer more opportunities than graphene in various applications. However, even after years of intensive exploration of 2D materials in science and technology, facile and scalable methods capable of producing stable 2D network polymers with uniformly decorated heteroatoms with/without holes remain limited. To overcome these issues, new layered 2D organic network structures have been designed and synthesized. They have uniformly distributed heteroatoms,2 holes with heteroatoms3 and transition metal nanoparticles on the holes.4 The structures were confirmed by scanning tunneling microscopy (STM). Based on the stoichiometry of the basal plane, they were, respectively, designated C3N, C2N and M@C2N (M = Co, Ni, Pd, Pt, Ru). Their electronic and electrical properties were evaluated by electrooptical and electrochemical measurements along with density-functional theory (DFT) calculations. The results suggest that these newly-developed 2D network polymers offer greater opportunities, from wet-chemistry to device applications.

References:

[1] Konstantin Novoselov, et al. Electric field effect in atomically thin carbon film. Science 2004, 306: 666.

[2] Javeed Mahmood, et al. Two-dimensional polyaniline (C3N) from carbonized organic single crystals. Proceedings of National Academy of Sciences, USA 2016, 113: 7414.

[3] Javeed Mahmood, et al. Nitrogenated holey two-dimensional structure. Nature Communications 2015, 6: 6486.

[4] Javeed Mahmood, et al. An efficient and pH-universal ruthenium-based catalyst for the hydrogen evolution reaction. Nature Nanotechnology 2017, 12: 441.
(Invited) High Field THz Spectroscopy of Monolayer Graphene: Effect of Grain Size and Doping
Authors: Lim Seong Chu
Published: February 2020

Using a high terahertz electric field (E
THz), up to 282 kV/cm, the optical conductivity of monolayer graphene is studied as functions of grain size and doping concentration. In order to study the effect of the grain size on the optical conductivity, the graphene with three different grain size, small (5 μm), medium (70 μm), and large grains (500 μm), are prepared by controlling surface morphology of Cu substrates. The dominant carrier scattering source in large- and small-grained graphene differs at high field, i.e., optical phonon scattering for the large grained, but defect scattering for the small grained. The enhanced optical phonon scattering in high THz field from the large-grained graphene is caused by a higher optical phonon temperature, originating from the slow relaxation of accelerated electrons. Unlike the large-grained graphene, lower electron and optical phonon temperatures are found in the small-grained graphene, resulting from the effective carrier cooling through the defects, called supercollisions. In addition, the optical conductivity of graphene monolayer shows an opposite behavior between at high and low doping concentration of the graphene. At large Fermi energy > 110 meV, the conductivity reduced with increasing THz field, resulting from the emission of optical phonons by excited electrons. However, for ≤ 110 meV, electron–phonon scattering rate is suppressed owing to the diminishing density of states near the Dirac point. Therefore, E
THz continues to accelerate carriers without them losing energy to optical phonons, allowing the carriers to travel at the Fermi velocity. This leads to the enhanced optical conductivity of graphene when EF is low. The exotic carrier dynamics does not result from the massless trait, but the electron-optical phonon scattering rate that depends on Fermi-level in the graphene. Our observations provide insight into the application of graphene for high-speed electronics without degrading carrier mobility.
(Invited) Functionalization and Application of Carbon Nanostructures
Authors: Istif Akcan , Gajewska Agnieszka , Carini Marco , Armuzza Valentina , Gonzalez Dominguez Jose Miguel , Hadad Caroline , DaRos Tatiana
Published: February 2020

Since from the discovery of the new allotropic forms of carbon, their potential applications in many different fields appeared to be very interesting. The increasing of components in the Carbon NanoStructure (CNS) family is still widening these potentialities. However, in the majority of the cases, a chemical functionalization of these derivatives is needed and results to be challenging.

We will survey the recent years’ achievements in this field on various CNSs.
Vertically Oriented MoS2 with Spatially Controlled Geometry on Nitrogenous Graphene Sheets for High-Performance Sodium-Ion Batteries
Authors: Jeong Jong Yeob , Park Jong Hyeok
Published: February 2020

Lithium-ion battery (LIB) has been a tremendous success for decades. As the demand for rechargeable batteries surges, a need has arisen for low-cost secondary batteries. Among various studies, sodium-ion battery (SIB) is the most promising secondary batteries due to its similar working principles and the abundance of sodium in the natural world. Among many anode materials for SIB, MoS­­2 has attracted attention because it can intercalate sodium ions in its layered structure. However, in the repeated intercalation of Na+
, MoS2 suffers from collapse of its layered structure.

Herein, we present vertically grown MoS2 on nitrogenous reduced graphene oxides (N-RGO) with controlled sheet density and height of MoS2 sheets as SIB anode active material. The MoS2 materials are synthesized by gel-precursor based method. By adjusting the nucleation and growth processes, we controlled the height and density of MoS2 sheets to find optimal condition that show great performance and high stability. Control of the partial geometry can achieve these improved property because the high sheet density can prevent additional SEI layer and the shortened sheet length reduces the resistance of Na+ diffusion. It shows remarkably high reversible discharging capacity of 255mAh/g at 1C and 245mAh/g at 5C discharging with a capacity reduction of 5.35% after 1300 cycles. And closely packed MoS2 sheets shows specific capacity of 254, 243, 153, 86 mAh/g at 0.2, 2, 10, 50A/g current density, respectively. Furthermore, vertically grown MoS2 is paired with Na3V2(PO4)3 to fabricate SIB full cell, and the full cell shows a specific capacity of 262mAh/g (based on the mass of anode material) during 50 cycles.

Figure 1
(Invited) Uranium-Based Endohedral Fullerenes: Mono-, Di-Metallic and Cluster Compounds
Authors: Echegoyen Luis , Chen Ning , Fortier Skie , Cai Wenting , Murillo Jesse , Gomez Maria
Published: February 2020

After our recent successful synthesis, isolation and complete characterization, including single crystal X-Ray diffraction, of 3 mono-metallic uranium endohedrals (U@D3h
-C74, U@C
2(5)-C82, and U@C
2V(9)-C82) has led us to continue exploring new U-based endohedral compounds. At the time this abstract is being written a total of 37 compounds have been detected: U@C2n (2n=74, 80, 82, 86, 88, 90, 92, 94, 98, 100, 102, 104; U2@C2n (2n=72, 78, 80); U2O@C2n (2n=72, 74, 76, 78, 80); U2N@C2n (2n=72, 74, 76, 78, 80); U2S@C2n (2n=74, 76, 78, 80, 82, 84, 86); U2C@C2n (2n=72, 78, 80); and USc2C@C80 and USc2N@C80. We have isolated several of these compounds, such as U@C76, U@C84, U@C86, U2O@C80 as well as others and their structures and bonding are being studied. An update of what we learn from these will be presented and discussed.
(Invited) Subphthalocyanine-Fullerene Ensembles As Light Harvesting Systems
Authors: Torres Tomas , Martínez-Díaz M. Victoria , Zango German , González Delgado José Antonio , Mariñas Víctor , Labella Jorge
Published: February 2020

A multi-SubPc hybrid comprised of a perfluorinated SubPc fused dimer (syn or anti topoisomer) axially functionalized with unsymmetrical octylthio-substituted SubPcs linked through their periphery by ethynyl linkers to the boron atoms of the dimer has been prepared. Electrochemical and steady state photophysical studies of the syn hybrid suggest the existence of an electron transfer process from SubPc units to photoexcited SubPc dimer to generate a (SubPc•+-SubPc Dimer•-) radical pair. Furthermore, the disposition that the two axial SubPc units acquire in this assembly gives rise to unique supramolecular recognition sites suitable for the complexation of shape and size complementary fullerenes. Thus, the binding ability of this hybrid towards different fullerene derivatives, namely C60, C70, C60-PCBM and C70-PCBM, has been analyzed through UV-vis absorption, fluorescence and NMR titrations. It has been demonstrated that syn compound displays a unique fullerene complexation mode. Initially, the formation of a 1:1 supramolecular complex involving the axial octylthio-substituted SubPcs embracing a guest molecule with remarkable association constants of around 106 - 105 M-1 is observed. This well-defined cavity generated by the SubPc dimer and the axial SubPcs shows higher affinity for the C70 fullerene derivatives. Then, a secondary supramolecular recognition event between the curved perfluorinated SubPc syn dimer unit and another fullerene molecule occurs, with significant binding constants of 104 - 103 M-1, depending on the size and the host-guest electrostatic interactions, leading to the formation of the final 1:2 supramolecular ensemble.

Figure 1
(Invited) Chiral-at-Metal Fullerene Hybrids for Catalysis
Authors: Filippone Salvatore , Girón Rosa María , Vidal Sara , Martin Nazario
Published: February 2020

Fullerenes have found their main application in organic photovoltaic devices thanks to their ability to give rise a high efficient photo-induced electron transfer process and to their behaviour as n-type charge carriers.[1]

On the other hand, in face of the great interest for carbon based materials in catalysis, the use of fullerenes in this field has been completely neglected as probably due to the difficult to endow fullerene cages with suitable active sites. In this regards, as a first step to address this issue, we have reported recently a wide range of asymmetric metal mediated or organocatalytic methodologies for a precise stereocontrol in the fullerenes functionalizations.[2]

Herein, we present the enantioselective catalytic synthesis of fullerene hybrids where C60 is endowed with metal atoms such us iridium, rhodium and ruthenium with high enantiomeric excesses. A complete control on the stereochemistry of all the asymmetric centers was achieved, even on the stereogenic metal center.[3]

The catalytic and photo-electrocatalytic properties of these new fullerene derivatives will be discussed together with their ability to transfer chirality in hydrogen transfer processes.[4]

[1] (a) B. C. Thompson, J. M. J. Fréchet, Angew. Chem. Int. Ed.
2008, 47, 58; (b) J. L. Delgado, P.-A. Bouit, S. Filippone, M. A. Herranz, N. Martin, Chem.Commun.
2010, 46, 4853.

[2] (a) Maroto, E. E.; Izquierdo, M.; Reboredo, S.; Marco-Martínez, J.; Filippone, S.; Martín, N. Acc.
Chem. Res.
2014, 47, 2660. (b) Filippone, S.; Maroto, E. E.; Martín-Domenech, A.; Suárez, M.; Martín, N. Nat. Chem.
2009, 1, 578. (c) Maroto, E. E.; Mateos, J.; Garcia-Borràs, M.; Osuna, S.; Filippone, S.; Herranz, M. Á.; Murata, Y.; Solà, M.; Martín, N. J. Am. Chem. Soc.
2015, 137, 1190. (d) Marco-Martínez, J.; Reboredo, S.; Izquierdo, M.; Marcos, V.; López, J. L.; Filippone, S.; Martín, N. J. Am. Chem. Soc.
2014, 136, 2897. (e) Marco-Martínez, J.; Marcos, V.; Reboredo, S.; Filippone, S.; Martín, N. Angew. Chem. Int. Ed.
2013, 52, 5115.

[3] J. Marco-Martínez, S. Vidal, I. Fernández, S. Filippone and N. Martín, Angew.
Chem. Int. Ed., 2017, 56, 2136.

[4] R. Maria Giron, J. Marco-Martinez, S. Bellani, A. Insuasty, H. Comas Rojas, G. Tullii, M. R. Antognazza, S. Filippone and N. Martin, J. Mater. Chem. A, 2016, 4, 14284.

Figure 1
(Invited) Bodipy-Nanocarbon Hybrids for Mimicking Early Events of Natural Photosynthesis
Authors: D'Souza Francis
Published: February 2020

Mimicking the early events of natural photosynthesis, and utilizing that information to build energy harvesting devices is considered one of the avenues to tap into the vast amount of solar energy. Research performed on this topic by scientists across the globe has been highly promising and has strengthened our fundamental understanding of natural and artificial photosynthesis. In the process of mimicking the early events of photosynthesis, excitation transfer and electron transfer in a sequential fashion, similar to what happens in the antenna and reaction centre of natural photosynthesis, are deemed to be of paramount interest. Accordingly, supramolecular donor-acceptor systems capable of performing these photo processes are considered very important. Although several donor-acceptor systems are known to undergo either energy transfer or electron transfer or simultaneous occurrence of these two photo processes in competition upon photoexcitation, there are not many systems where energy transfer and electron transfer in a sequential route have been reported.

Nanocarbons such as fullerenes, single wall carbon nanotubes, graphene oxide, and graphene have been widely used in the construction of such multi-modular donor-acceptor systems. Porphyrins and phthalocyanines are class of widely used photosensitizers. In recent years, application BF2-chelated dipyrromethene (BODIPY) and BF2-chealted azadipyrromethene (azaBODIPYs), in building artificial photosynthetic models have witnessed a rapid growth. This is primarily due to the synthetic versatility of these sensitizers to couple with nanocarbons to modulate their photo- and redox properties to promote efficient photoinduced energy and electron transfer processes. In few instances, accomplishing the combined ‘antenna-reaction center’ functionality of photosynthesis has been possible. The present contribution summarizes recent progress made in our laboratory in this area of research.
(Invited) Gas-Phase Clusterfullerene Doping and Exohedral Modification By Laser-Based Methods
Authors: Dunk Paul W. , Mulet-Gas Marc , Marshall Alan G. , Hendrickson Christopher L. , Castro Edison , Echegoyen Luis , Abella Laura , Moreno-Vicente Antonio , Rodriguez-Fortea Antonio , Poblet Josep M.
Published: February 2020

We have observed new mechanistic insight into the formation of metallic nitride clusterfullerenes from doped graphite by use of laser-based plasma synthesis techniques, analyzed by ultrahigh resolution 9.4 tesla Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometry. These online chemical sampling techniques provide a route to investigate underexplored nanocarbon reactions that take place under the harsh conditions of metallofullerene synthesis, and are expected to be applicable to macroscopic production methods. Here, we report efforts to form various clusterfullerenes by laser vaporization and extend these techniques as new avenues for investigation of exohedral functionalization (e.g., fluorination of Sc3N@C80) and heteroatom-doping of endohedral fullerenes.

This work was supported by NSF Division of Materials Research through DMR-11-57490 and the State of Florida.
(Invited) Relative Stabilities for Isomeric and Non-Isomeric Endohedrals
Authors: Uhlik Filip , Slanina Zdenek , Akasaka Takeshi , Lu Xing
Published: February 2020

There are several stability problems important for fullerenic species, namely relative populations of (i) isomeric endohedrals, (ii) non-isomeric metallofullerenes differing in the number of the encapsulated metal atoms placed in still isomeric carbon cages, and (iii) monometallofullerenes with different metals encapsulated in one selected carbon cage. The related computational approaches are illustrated on endohedrals with encapsulated La and its congeners, evaluated using various density-functional theory (DFT) treatments or the second order Moller-Plesset perturbation theory (MP2). One of the illustrative examples treats encapsulations in the T_d IPR C76 cage using the metal series Al, Sc, Y, La, and Ac. Three formal reaction steps can be considered with the encapsulations: (i) double- (or triple-) ionization of the free metal, (ii) double (or triple-) charging of the empty cage, and (iii) placing the metal di- (or tri-) cation into the di- or (tri-) anionic cage. The (ii) energy change is identical for all members of the series, and the (iii) terms should be similar as they are controlled by electrostatics. Hence, only the (i) energy term comes as a differentiating factor. In other words, the free-metal ionization potentials should actually represent the critical yield-controlling parameter.The computed relative potential-energy changes upon encapsulation δE and the relative observed ionization potentials of the free atoms δIP should (according to the above three-step analysis) be correlated. Interestingly, Ac has the second best encapsulation energy after La in the series.
(Invited) Hierarchical Nanostructures in Multi-Functional Electrocatalysts for the Artificial Leaf
Authors: Valenti Giovanni , Marcaccio Massimo , Rapino Stefania , Iurlo Matteo , Prato Maurizio , Fornasiero Paolo , Paolucci Francesco
Published: February 2020

Nanomaterials are nowadays at the forefront of materials science research. The design and realization of hierarchical nanoarchitectures, in which selected components are arranged to leverage their expected mechanistic functions are obtaining a wide range of applications, from the aerospace industry to bio-medicine, and as benchmarks for many catalytic reactions.

Carbon-based nanomaterials have been the main actors of nanotechnology since their very first discovery, and their unique morphological/electronic properties are particularly suited to be used in electrocatalytic applications. CNTs and graphene are indeed ideal supports in catalysis as they have an optimal electronic conductivity and provide percolation routes for charge transfer reactions to occur. The integration of nanocarbons into hierarchical materials is an effective strategy to further boost the potentiality of nanostructured catalysts. The generation of multiple interfaces in such hierarchical assemblies is responsible for their exceptional activity, whose origin is however only rarely understood.

We will show that, once embedded within nanoarchitectures made of multi-wall carbon nanotubes or graphene and metal oxide shells, the catalytic properties of nanoclusters (1,2,5) and metal nanoparticles (3,4) can be dramatically enhanced according to mechanisms which likely involve the concerted and synergic participation of all component building blocks in the electrocatalytic steps.

References

(1) F.M. Toma et al., Nature Chemistry 2010, 2, 826

(2) M. Quintana et al. ACS Nano 2013, 7, 811–817

(3) R. Mazzaro et al. ChemistryOpen 2015, 4, 268 – 273

(4) G. Valenti et al. Nature Communications 2016, 7 DOI: 10.1038/ncomms13549

(5) A.B. Marco et al. Angew. Chem. Int. Ed. 2017, 56, 6946-6951
(Invited) Fullerene-Based Single Molecule Magnets: Bulk and Surface Magnetism
Authors: Popov Alexey A. , Krylov Denis , Chen Chia-Hsiang , Liu Fupin , Avdoshenko Stanislav , Brandenburg Ariane
Published: February 2020

Encapsulation of lanthanides ions inside a carbon cage gives a variety of structures with very different magnetic properties, including single molecule magnetism (SMM). When other non-metal ions (N, S, O) are encapsulated as well, short distance between metal ions and negatively-charged non-metal ions creates large single-ion magnetic anisotropy of encapsulated lanthanides. In such clusterfullerene SMMs, very large barriers of the relaxation of magnetization can be achieved.[1] Encapsulation of only two metal atoms gives a possibility to create unique 3-center spin systems comprising large localized magnetic moments of lanthanide ions and an unpaired semi-delocalized spin on the metal-metal bonding orbital. In such a system, giant exchange interactions emerge and couple magnetic moments of individual spins into a giant superspin structure featuring unusually high blocking temperatures of magnetization.[2] Importantly, slow relaxation of magnetziatin is preserved even when fullerene-SMMs are deposited onto metal substrates, which usually has a dramatic deteriorating effect on SMMs. This contribution will present an overview of the recent developments in the magnetism of EMFs in bulk samples as well as in submonolayers deposited on metallic substartes..

References

[1] D.S. Krylov, F. Liu, S.M. Avdoshenko, L. Spree, B. Weise, A. Waske, A.U.B. Wolter, B. Büchner, A.A. Popov, Record-high thermal barrier of the relaxation of magnetization in the nitride clusterfullerene Dy2ScN@C80-Ih
, Chem. Commun., 53 (2017) 7901-7904.

[2] F. Liu, D.S. Krylov, L. Spree, S.M. Avdoshenko, N.A. Samoylova, M. Rosenkranz, A. Kostanyan, T. Greber, A.U.B. Wolter, B. Büchner, A.A. Popov, Single molecule magnet with an unpaired electron trapped between two lanthanide ions inside a fullerene, Nat. Commun., 8 (2017) 16098.
(Invited) Synthesis and Stabilization of the Unstable Dimetallofullerenes
Authors: Liu Fupin , Spree Lukas , Popov Alexey A.
Published: February 2020

The metal-metal (M-M) bonding in dimetallofullerenes presents the peculiar electronic structures as well as the chemical and physical properties.[1-2] For Y and medium-size lanthanides (Gd, Tb, Dy), computations by Shinohara et al. showed that M2@C80 has one unpaired electron occupying the M–M bonding molecular orbitals, and the other electron is delocalized over the carbon cage (Figure 1a).[3] Such molecules are unstable radicals. Recently, we have succeeded in the capture of the elusive M2@C80 (M=Y, Dy) as benzyl derivatives (Figure 1b). The structure was unambiguously determined (Figure 1c, d).[4] In this contribution, the synthesis, separation, and structural characterizations of the elusive M2@C80 will be presented and discussed.

[1] A. A. Popov, S. Yang, L. Dunsch, Chem.
Rev.
2013, 113, 5989-6113.

[2] A. A. Popov, S. M. Avdoshenko, A. M. Pendas, L. Dunsch, Chem. Commun.
2012, 48, 8031-8050.

[3] Z. Wang, R. Kitaura, H. Shinohara, J. Phys. Chem. C
2014, 118, 13953-13958.

[4] F. Liu, D. S. Krylov, L. Spree, S. M. Avdoshenko, N. A. Samoylova, M. Rosenkranz, A. Kostanyan, T. Greber, A. U. B. Wolter, B. Büchner, A. A. Popov, Nat. Commun.
2017, 8, 16098.

Figure 1
(Invited) The Effect of Nitrogen Source on the Production of Uranium Metallofullerenes Possessing Non-IPR Cages
Authors: Cai Wenting , Murillo Jesse , Torres Maria A Gomez , Chen Ning , Echegoyen Luis
Published: February 2020

After our recent successful synthesis of the mono-uranium EMF species U@D3h
-C74, U@C2(5)-C82, U@C2v
(9)-C82, and U@C1(11)-C86 when using the gasses O2, SO2, and CO2 have been studied, the role of nitrogen source in accelerating the generation of mono-uranium EMFs possessing non-IPR cages will be discussed. Different nitrogen sources (such as N2 or NH3) have been used to produce these species (Figure 1). Besides the IPR species, the most abundant non-IPR species produced by N2 was U@C80, followed by U@C76. In addition, mono-uranium EMF U@C94 was obtained with the help of NH3 as well as U2N@C78. The extremely short retention time of U@C94 on Buckeyprep column indicates the possibility of a non-IPR C94 cage. The detailed synthesis, separation and structure characterizations will be presented and discussed.

Figure 1
(Invited) Photovoltaic Performance and Stability of Fullerene/Cerium Oxide Double Electron Transport Layer Superior to Single One in P-I-N Perovskite Solar Cells
Authors: Xie Su-Yuan , Zhang Mei-Lin , Xiao Jun
Published: February 2020

Interface engineering that involves in the metal cathodes and the electron transport layers (ETLs) facilitates the simultaneous improvement of device performances and stability in perovskite solar cells (PSCs). Herein, low-temperature solution-processed cerium oxide (CeOx) films are prepared by a facile sol-gel method and employed as the interface layers between [6,6]-phenyl-C61-butyric acid methyl ester (PC61BM) and an Ag back contact to form PC61BM/CeOx double ETLs. The introduction of CeOx enables electron extraction to the Ag electrode and protects the underlying perovskite layer and thus improves the device performance and stability of the p-i-n PSCs. The p-i-n PSCs with double PC61BM/CeOx ETLs demonstrate a maximum power conversion efficiency (PCE) of 17.35%, which is superior to those of the devices with either PC61BM or CeOx single ETLs. Moreover, PC61BM/CeOx devices exhibit excellent stability in light soaking, which is mainly due to the chemically stable CeOx interlayer. The results indicate that CeOx is a promising interface modification layer for stable high-efficiency PSCs.
(Invited) Fullerene Nanostructures: Preparation and Application
Authors: Zheng Shushu , Lu Xing
Published: February 2020

During the past two decades, the self-assembly of spherical fullerene molecules has attracted intensive attention for their definite structures, high electronic affinity and three-dimensional (3D) electron transporting property. We report herein the systematical investigation of the self-assembly behavior of C60 molecules to form various polyhedron microstructures and well-aligned arrays together with their extraordinary optical properties.[
1
] Furthermore, a solution-processible co-assembly strategy taking advantage of charge-transfer interaction is developed to prepare C70/porphyrin supramolecular architectures, which possess excellent electrical conductivity and high thermal resistance, and charge separation characteristics.[
2,3
] More practically, porous carbon materials with abundant functional moieties are readily obtained by KOH activation of C70 microtubes, which exhibit excellent supercapacitor performances.[
4
]

References

[1] S. Zheng, et al., Carbon 201
8, DOI:10.1016/j.carbon.2017.10.012.

[2] S. Zheng, et al., Nano Res. 201
8, DOI:10.1007/s12274-017-1809-7.

[3] B. Wang, S. Zheng, et al., J. Am. Chem. Soc.
2017, 139, 10578.

[5] S. Zheng, H. Ju, X. Lu, Adv. Ener. Mater.
2015, 1500871.
The Catalytic Performance of Transition Metal Nitrides on Nitrogen Electroreduction and Hydrogen Evolution Reaction
Authors: Abghoui Younes , Skúlason Egill
Published: February 2020

Renewable electrocatalytic synthesis of ammonia by nitrogen reduction reaction (NRR) at room temperature and ambient pressure has attracted numerous attentions in order to find a promising alternative to the centralized, energy-intensive, and CO2 emitting Haber-Bosch process. Despite all the efforts that have been made in this regard, NRR has yet been plagued with low faradaic efficiencies (FE) and reaction rates under ambient conditions with hydrogen evolution reaction (HER) considered as an important competitive side reaction. Here with the use of density functional theory, we have investigated a wide range of transition metal nitride (TMN) surfaces for possibility of catalyzing the NRR at ambient conditions1–6. We explored the thermochemistry of the cathode reaction so as to construct the free energy profile and to predict the required onset potential for activation of nitrogen to ammonia. Some of these materials were found not suitable for catalyzing ammonia formation mainly due to either poisoning or decomposition in electrochemical environment. However, some of earlier TMNs are predicted to catalyze ammonia formation at small onset potentials (-0.5 to -0.75 V) with considerable selectivity, while some other favoring the HER. When comparing the activity and the onset potentials predicted on these TMNs, it is seen that the Mars van Krevelen mechanism should be more favourable mechanism for NRR compared to the conventional associative and dissociative mechanisms. We recently tested few of the DFT predicted TMNs in experiments, and preliminary results indicate proof of concept and interesting performance of these materials under operating conditions.

Reference:

(1) Abghoui, Y.; Garden, A. L.; Hlynsson, V. F.; Björgvinsdóttir, S.; Ólafsdóttir, H.; Skúlason, E. Enabling Electrochemical Reduction of Nitrogen to Ammonia at Ambient Conditions through Rational Catalyst Design. Phys. Chem. Chem. Phys.
2015, 17 (7), 4909–4918.

(2) Abghoui, Y.; Garden, A. L.; Howalt, J. G.; Vegge, T.; Skúlason, E. Electroreduction of N2 to Ammonia at Ambient Conditions on Mononitrides of Zr, Nb, Cr, and V: A DFT Guide for Experiments. ACS Catal.
2016, 6 (2), 635–646.

(3) Abghoui, Y.; Skúlason, E. Electrochemical Synthesis of Ammonia via Mars-van Krevelen Mechanism on the (111) Facets of Group III–VII Transition Metal Mononitrides. Catal. Today
2017, 286, 78-84.

(4) Abghoui, Y.; Skúlason, E. Onset Potentials for Different Reaction Mechanisms of Nitrogen Activation to Ammonia on Transition Metal Nitride Electro-Catalysts. Catal. Today
2017, 286, 69–77.

(5) Abghoui, Y.; Skulason, E. Computational Predictions of Catalytic Activity of Zincblende (110) Surfaces of Metal Nitrides for Electrochemical Ammonia Synthesis. J. Phys. Chem. C
2017, 121 (11), 6141–6151.

(6) Abghoui, Y.; Skúlason, E. Hydrogen Evolution Reaction Catalyzed by Transition-Metal Nitrides. J. Phys. Chem. C
2017, 121 (43), 24036–24045.
Methods for the Environmental Stability improvement of CoS2 as Thermal Battery Cathode
Authors: Cao Yong
Published: February 2020

The paper presented illustrates the environmental stability of CoS2 under varied conditions, and physical or chemical methods for its improvement. The results confirm: the decomposition rate of CoS2 increases with decreasing temperature, increasing water or oxygen partial pressure. Mixing with molten salt LiCl-KCl was adopted as the physical method to improve the environmental stability of CoS2, and good result was achieved, which was ascribed to the stronger ability of absorbing H2O in LiCl-KCl, and blocking the reaction of H2O and CoS2. Chemical route was also adopted, by forming a protect layer on CoS2. The protect layer was formed by using cation exchange method, with FeCl2 solution under specifically situation, and obvious improvement was observed. Fig. 1 shows the variety of decomposition rate of CoS2 with temperature in humid (pH2O~3x10-2 atm) air.

Figure 1
Performance Analysis of a 5 Kw/30 Kwh Residential Vanadium Redox Flow Battery System in Denmark
Authors: Pérez Martínez Luis Carlos , Hansen Mads Weiss , Madsen Morten Brun , Bentien Anders
Published: February 2020

The first residential vanadium redox flow battery system in Scandinavia was installed in Gladsaxe by Aarhus University and VisBlue Aps with support from the Energy Technology Development and Demonstration Program (EUDP) of Denmark. The flow battery has a nominal power output and capacity of 5 kW and 30 kWh respectively and is coupled to a 50 kW peak photovoltaic array. This solar plus storage system is integrated in a ten apartments building that already complies with the Danish Nearly Zero-Energy Building (NZEB 2020) energy performance requirements.

In this work, the performance of the vanadium redox flow battery system is reported for two periods, the first between February-December 2017 and the second between February-August 2018. Performance for different periods is analyzed based on the energy balance provided by the battery inverter and the data acquired from the flow battery. The energy balance is also used to map the consumer behavior in order to develop: 1) seasonal flow battery control strategies and 2) battery power and capacity optimal sizing methods. Since the flow battery operated intermittently during 2017 before final commissioning in February 2018, the photovoltaic array was coupled to a 7.4 kW lead-acid battery pack during specific periods. An overview of the lad-acid battery performance during these periods is also reported.

Finally, several technical challenges including coupling the vanadium redox flow battery with the battery inverter, stack leaks and remote monitoring of critical operating parameters are briefly discussed.
Characterizing the Decay of Redox Flow Battery Materials Utilizing a Microelectrode
Authors: Kowalski Jeffrey A , Brushett Fikile R.
Published: February 2020

Redox flow batteries (RFBs) are a promising electrochemical technology for energy-intensive grid storage, but further cost reductions are needed for widespread adoption spurring research efforts into new redox chemistries and reactor designs1. Notably the recent emergence of redox active organic molecules offers intriguing new pathways to low cost energy storage through tunable molecular structure and inexpensive synthesis routes. While the rapid and continued advancement of these redox couples is exciting, iterative design-test-improve cycles are slowed as molecules become increasingly robust and failure modes become more subtle. Thus, there is a growing need for more advanced diagnostic techniques to evaluate materials performance, particularly stability2,3.

At present, common methods for characterizing the decay of RFB materials include extensive cycling in an electrochemical cell4 to correlate capacity fade to overall species decay or monitoring decay of a single reporter constituent (e.g. oxidized species) via different spectroscopy techniques (e.g. NMR3, EPR2, or UV-Vis5). However, these methods are challenged by, in the case of cell cycling, disambiguation of the sources of capacity fade, and, in the case of spectroscopies, issues operating under RFB relevant conditions (e.g. high concentrations of active species and supporting salt). Here, I will present a new technique to quantitatively probe active species stability in RFB-type electrolytes using a microelectrode. The talk will include discussion of underlying theory, systematic evaluation of sources of error, method validation using model compounds, and, finally, demonstration with several new redox couples.

References

M. L. Perry and A. Z. Weber, J. Electrochem. Soc., 163, A5064–A5067 (2016).

J. Huang et al., Sci. Rep., 6, 32102 (2016).

C. S. Sevov et al., J. Am. Chem. Soc., 139, 2924–2927 (2017).

J. Huang et al., J. Mater. Chem. A, 3, 14971–14976 (2015).

J. D. Milshtein et al., Energy Environ. Sci., 9, 3531–3543 (2016).
Towards a Generalized Phase Transforming Porous Electrode Theory
Authors: Campos Juan Alfonso , Battiato Ilenia , García R. Edwin
Published: February 2020

Traditional Porous Electrode Theory has provided an impressive amount of insight on the description of the intercalation kinetics of rechargeable batteries by describing the porous electrochemically active electrode as a diffusion and ohmic system with a spatial distribution of reversible interfacial reactions. Here, events such as phase transformations are fit into a curve by using the open circuit potential (OCP), and mass and interfacial reactions are described by starting from the classic reaction theory and fitted to experimental data. Recent experimental results highlight that the kinetics associated to phase transformations occurring during the intercalation/deintercalation process, are key to specifying battery performance and long term degradation. These kinetics, however, are theoretically and numerically complex to spatially resolve at a level that would make them practical to use in commercial applications. In this paper, we report on progress in the formulation of a coarse-grained description that naturally accounts for the volumetric electrochemical phase transformations and reactions in a porous rechargeable battery by starting from fundamental materials science principles.
Improved Cycling Performance of Intermetallic Anode By Minimized SEI Layer Formation
Authors: Kuwata Hiroko , Matsui Masaki , Sonoki Hidetoshi , Manabe Yusuke , Imanishi Nobuyuki , Mizuhata Minoru
Published: February 2020

Alloy anodes including intermetallic anode, such as Si, Sn, Sb or Al, have been widely studied to replace the standard graphite-based anode, because these anode active materials theoretically have much higher specific capacity than the graphite anodes. The biggest challenge of the alloy anode is its cycleability. Huge volume expansion/shrinkage during the lithiation/delithiation process leads the pulverization of the active material particles resulting in loss of the electric contact among active in the electrode.　Since the volume expansion/shrinkage also initiates formation/dissipation of electrode/electrolyte interphase, the SEI layer is supposed to have physical flexibility. However, the required physical properties of the SEI layer is not understood yet. We think the analogy of Mg-based system is useful, because the organohaloaluminate-based electrolyte solution of the Mg-based system does not form the typical SEI layer.

In the present study, electrochemical properties of bismuth composite electrode are investigated in magnesium and lithium system. The bismuth composite electrode shows good cycleability in a magnesium half-cell with an organohaloaluminate electrolyte solution, while sever capacity decay is observed in a lithium system with a conventional carbonate-based electrolyte solution. In the carbonate-based electrolyte solution, the bismuth composite electrode shows low coulombic efficiency of < 90% due to the formation of solid electrolyte interphase (SEI) layer, while the high coulombic efficiency is maintained in the magnesium system. The comparison of the two system suggests that the formation of the SEI layer accelerates the capacity fading. Another lithium-based electrolyte solution: 2M LiBH4 in THF is proposed as a minimized SEI formation electrolyte solution. The LiBH4-based electrolyte solution shows excellent cycleability with high coulombic efficiency. A spectroscopic study using in situ FTIR proved that the LiBH4-based electrolyte solution does not form the typical thick SEI layer.
Effects of a-Site Composition of Ru-Based Pyrochlore-Type Oxide on Catalytic Activity for Oxygen Reactions
Authors: Iketani Chinami , Kawaguchi Kenji , Morimitsu Masatsugu
Published: February 2020

A metal hydride (MH)/air secondary battery uses oxygen in air as the active mass of the positive electrode. The positive electrode’s reactions are oxygen reduction and evolution during discharge and charge, and the polarization of the positive electrode significantly depends on the bi-functional oxygen catalyst. In our previous work [1], one of pyrochlore-type oxides (general formula A2B2O7), Bi2Ru2O7-z, showed a good performance on bi-functionality for charge and discharge, while the overpotential was still high for the oxygen reactions. On the other hand, pyrochlore-type oxides are known to be able to substitute various elements in A and/or B site as A2-xA’xB2-yB’yO7-z. In this paper, we tried to prepare this type of catalyst by partly substituting Bi with boron group elements, A’, i.e., Bi1-xA’xRu2O7-z, and investigated the polarization behaviors for oxygen reduction and evolution in KOH solutions using rotating disk electrode (RDE).

The oxide catalysts were prepared by co-precipitation method, in which the calcination of the precipitates obtained by adding excess NaOH solutions into the metal salt solution containing Bi(III), A’(III) (A’ = Al, In, Ga or Tl) and Ru(III). The obtained oxides were characterized by XRD, SEM, and EDX. Electrochemical measurements were carried out using a three-electrode cell, of which the working electrode was RDE and the electrolyte was 0.1 mol/L KOH solutions. The substrate of RDE was a titanium disk and the oxide particles prepared were dropped and dried on the titanium surface. The anodic polarization measurement by linear sweep voltammetry was performed, and the cathodic polarization was also examined by linear sweep voltammetry in the solution under N2 or O2 bubbling. The oxygen reduction current was obtained by subtracting the measured current under N2 bubbling from that under O2 bubbling. The specific activity of the oxide catalyst was evaluated by the currents normalized with the amount of the loaded catalyst, i
w, or the double layer charge, i
c.

The results by XRD for Bi0.9A’0.1Ru2O7-z (A’ = Al, In, Ga or Tl) and Bi2Ru2O7-z revealed that these oxides contained no by-product. Oxygen evolution showed no significant difference in catalytic activity for the oxides, while Bi2Ru2O7-z was superior in catalytic activity than Bi0.9A’0.1Ru2O7-z, implying that the change of ionic radius of A-site can affect the overpotential for oxygen reduction. In this paper, more results for the effects of the composition of A-site on the catalytic activity for oxygen reactions will be presented.

This work was supported by “Advanced Low Carbon Technology Research and Development Program (ALCA)” of Japan Science and Technology Agency (JST).

Reference

[1] T. Hirai, M. Morimitsu, PRiME 2016, Abs#0064, Hawaii (2016).
Break-in Phenomena in Commercial Alkaline & Li-Ion Batteries through Acoustic and Impedance Measurements
Authors: Hodson Thomas , Knehr Kevin William , Steingart Daniel A
Published: February 2020

Alkaline batteries are a mainstay of the primary energy storage market, with LR6 (AA) batteries selling in the billions of cells per year. In addition, Lithium-Ion Batteries (LiBs) have become ubiquitous in modern technologies, such as in the burgeoning electric vehicle and consumer electronics markets. In both cases, the commercial cells undergo a “break-in” period after initial cycling period. In the case of alkaline cells, it has been noted that impedance changes drastically after initial discharge of a pristine cell [1]. After manufacturing the LiB, a period of break-in occurs wherein the battery experiences rapid changes in properties, such as capacity and stress [2], before leveling off to a stable value. Most research in these commercial cells analyze the full cycle life of the battery and have little regard for the initial break-in period. However, understanding and controlling break-in conditions could determine future performance of the cell. In this study, we use electrochemical acoustic and impedance spectroscopy measurements to analyze break-in of commercial AA and LiBs. We further analyze how break-in conditions, such as varying the rate of current, affect the overall performance of the battery.

[1] Hsieh, A.G. et al. “Electrochemical-acoustic time of flight: in operando correlation of physical dynamics with battery charge and health.” Energy Environ. Sci. (2015) 8, 1569-1577.

[2] Liu, Xinyi M., and Craig B. Arnold. "Effects of Cycling Ranges on Stress and Capacity Fade in Lithium-Ion Pouch Cells." Journal of The Electrochemical Society 163.13 (2016): A2501-A2507.