bluuebunny/crossref_metadata_2025_split huggingface dataset:
In Situ Investigation on Spatiotemporal Changes of SEI Properties By SECM
Authors: Bülter Heinz , Peters Fabian , Schwenzel Julian , Wittstock Gunther 
Published: February 2020

In our society Li-ion batteries are widely used, especially for small-scale devices. During the first charging process the solid-electrolyte-interface (SEI) between the electrode and electrolyte is established. This layer passivates the surface against electron transfer reaction but allows transfer of Li-ions. In order to realize high-energy Li-ion batteries in conventional carbonate-based electrolytes, the formation of the SEI is required.[1]

Content and structure of the SEI are highly discussed.[2, 3] The SEI represents a complex chemical system, where several solid, liquid and gaseous compounds establish interdependent equilibria. Characterization of the SEI is a difficult challenge, because of the similar chemical identity of SEI components and electrolyte molecules. Furthermore, ex situ analysis of the SEI requires separation and isolation of the SEI, which may change the content and the structure of the SEI.[3]
In situ analysis is highly sought after to circumvent this problem.
In our approach we use the scanning electrochemical microscopy (SECM) to investigate in situ the electron transport across the SEI. For this purpose, a redox mediator is added to the electrolyte, which communicates between the battery electrode and the positionable ultra-microelectrode (UME). Our results by SECM demonstrate the dynamic of SEI formation and dissolution. Furthermore, the swelling behavior of practical graphite anodes in standard battery electrolytes is characterized.
References
[1] J. B. Goodenough, K.-S. Park, J. Am. Chem. Soc.
2013, 135, 1167.
[2] V. Etacheri, R. Marom, R. Elazari, G. Salitra, D. Aurbach, Energy Environ. Sci.
2011, 4, 3243.
[3] P. Verma, P. Maire, P. Novak, Electrochim. Acta
2010, 55, 6332.
New Synthetic Methodology of Hybrid Materials for Energy-Related Applications
Authors: Herreros Lucas Carlos , Khlobystov Andrei N , Gimenez Lopez Maria del Carmen 
Published: February 2020

New hybrid nanomaterials are strictly required to meet the future energetic demand. In this context, supercapacitors are proposed as the ideal candidate to fill the energetic gap between batteries and conventional capacitors, showing higher power and energy density respectively [1]. Supercapacitos are based on two storage mechanism: i) electrochemical double layer, which relay on electric charge storage and ii) pseudocapacitance, which is associated with the surface redox processes at electrode materials. As the former has high cycling stability while the latter present higher capacitance, research is focused on combining materials which present both mechanisms.
Nowadays, the widely used conventional approach is based on a physically mixture of both materials. Carbon nanostructures are currently the most used support material for electrochemical applications mainly due to their low cost and high surface area, directly related to electrochemical double layer. Thus, pseudocapacitance materials such as metal oxides nanoparticles are the active material combined with the carbon support, leading to a much better distribution and also increment of the electrochemical properties. However, simple mixing these two nanocomponents affords limited interactions between them, leaving a significant portion of the material electrochemically inactive. Therefore, new synthetic procedures must be developed if new hybrid materials want to be achieved [2,3]
Here, we report a novel one-step methodology for preparing hybrid metal-carbon nanostructures by using pre-treated carbon nanofibers as templates for directing the in-situ syntehsis of surfactante-stabilised manganese oxide nanoparticles selected as model system for studying the structure-energy storage capacity relationship of the obtained hybrid nanostructure by electrochemical means.
[1] Simon, P. et al., Nature Materials, 2008. 845(7): p. 275709. [2] Gimenez-Lopez M. C. et al., Angew Chem. Int. Ed. Engl., 2013. 52(7): p. 2051-4. [3] La Torre, A., et al., ACS Nano, 2012. 6(3): p. 2000-2007.
Porous SiC/Graphene-on-Wafer Electrodes for Supercapacitors
Authors: Ahmed Mohsin , Khawaja Mohamad , Notarianni Marco , Wang Bei , Goding Dayle , Gupta Bharati , Boeckl John J. , Takshi Arash , Motta Nunzio , Saddow Stephen E. , Iacopi Francesca 
Published: February 2020

The intensive research on epitaxial 3C SiC/Si wafers has opened up a new era for the micro-fabrication industry and led to the direct growth of high quality and large area graphene layers on the device location for on-chip applications.[1] This new technology to grow graphene on silicon possesses various advantages over the conventional methodology, such as eliminating the complex and unreliable process of transferring graphene flakes and replacing expensive SiC wafers, and also prompts the use of graphene for energy storage, e.g. as supercapacitors, at wafer level. However, morphology control of the graphene layers on silicon remains a challenge to further enhance the performance of supercapacitors, which mainly relies on the surface area of the active graphene layers through an electrochemical double layer mechanism. To address this issue, we demonstrate, for the first time, creating porosity on the graphene surface. The growth of porous graphene on wafers in our work presents a facile, highly reproducible and low-cost approach to obtain highly continuous graphene layers with extremely low sheet resistance. Our preliminary electrochemical investigation indicates that the porous SiC/graphene-on-wafer electrode can deliver typical supercapacitive behaviours and the porosity we create on the graphene surface can facilitate the electrochemical performance by providing more accessible surface area. Graphene prepared via this routine can also be employed to fabricate micro-supercapacitors in an interdiginated pattern for future on-chip integration and energy storage.
[1] B.V. Cunning, M. Ahmed, N. Mishra, A.R. Kermany, B. Wood, F. Iacopi, Nanotechnology, 25 (2014) 325301.
Molecular Engineering of Zinc Phthalocyanine Sensitizers for Efficient Dye-Sensitized Solar Cell
Authors: Kimura Mutsumi 
Published: February 2020

Dye-sensitized solar cells (DSSCs) have been expected as low-cost, lightweight, and flexible energy conversion devices. To date, the highest conversion efficiency above 12 % has been achieved with p-conjugated macrocyclic zinc porphyrin sensitizer YD2-o-C8 using cobalt polypyridine redox shuttles. Designed p-conjugated macrocycles such as porphyrins and phthalocyanines have attracted special attention as versatile molecular platforms of highly efficient dyes for DSSCs. While a lot of porphyrin-based sensitizers have been designed and synthesized to enhance the conversion efficiency in DSSCs, the efficiencies of DSSCs employing red/near-IR absorbing phthalocyanine-based sensitizers had not been impressive due to their strong tendency to aggregate and the lack of directionality of electron transfer in the excited states. To overcome these drawbacks of phthalocyanine-based sensitizers, several approaches such as steric suppression of aggregation, electronic push-pull structures through asymmetrical substitutions, and optimization of adsorption sites have been reported. Recently, we showed that the structural modification of peripheral bulky substituents and adsorption site around the phthalocyanine core induced the improvement of incident photon-to-current efficiency (IPCE), and thereby achieved a solar-to-electric power-conversion efficiency (PCE) of 5.9% from solar cells employing PcS18 under one sun condition. However, while the maximum value of IPCE was more than 80 %, the values around 520 nm was about 30 %. Since the absorption coefficient of the sensitizers at the wavelength is very low, in order to increase the efficiency, higher dye adsorption density is desired. This can be done by decreasing the molecular size. In addition to IPCE spectrum, open circuit voltage of the PcS18 cell was not high. This could be improved by modifying the size of peripheral substituents attached to the phthalocyanine core to cover the TiO2 surface by the dye molecules. In this presentation, we examine the effect of the length and number of alkoxy groups around the phthalocyanine moiety on the photovoltaic properties. We now expect the alkoxy groups to have three functions, preventing aggregation, filling the space among dyes on TiO2 surface and increasing dye adsorption density. We found that an asymmetrical zinc phthalocyanine (ZnPc) PcS20 bearing propoxy groups in the 2 and 6 positions of peripheral phenoxy units showed a record PCE value of 6.4 % under simulated air mass 1.5 global sunlight.
Facile Synthesis of Meso-Aminoporphyrins and Their Oxidative Oligomerization
Authors: Yamashita Ken-ichi , Shouichi Takeuchi , Motoko Asano , Sugiura Ken-ichi , Kataoka Kazuyuki 
Published: February 2020

Porphyrins and their metal complexes have been attracting significant attentions due to their characteristic chemical, or physicochemical properties derived from their 18π aromaticity. Recently, nitrogen-based substituents (e.g., amino, amido, imido, imino, and azo groups) have been energetically introduced on the porphyrin periphery because of their strong influence of the p-electron system of the porphyrin. Among them, meso-aminoporphyrins are the simplest nitrogen-substituted porphyrins. Because of a wide variety of reactivities of the amino groups, meso-aminoporphyrins have been utilized as useful precursors for other nitrogen-substituted porphyrins. Despite their synthetic usefulness, there have been only a few practical methods for the preparation of meso-aminoporphyrins.
In this presentation, we present a facile and efficient synthetic method for meso-aminoporphyrins from meso-bromoporphyrins.1 This method involves the aromatic nucleophilic substitution (SNAr) of a bromo group with azide2 and the following in-situ reduction of the introduced azide group by sodium ascorbate. A simple treatment of 10 equiv. of sodium azide and sodium ascorbate with meso-bromodiarylporphyrins affords the corresponding meso-aminoporphyrins almost quantitatively. This reaction is easily scalable up to a gram scale without the decrease of the product yield.
We also performed the oxidative oligomerization of meso-aminoporphyrins to afford the polyaniline-like π-conjugated oligomers.3 We will also report the synthesis, structural characterization, and redox behavior of the obtained oligomers.

References

(1) K. Yamashita, K. Kataoka, S. Takeuchi, M. S. Asano, K. Sugiura, in preparation.
(2) K. Yamashita, K. Kataoka, M. S. Asano, K. Sugiura, Org. Lett.
2012, 14, 190–193.
(3) K. Yamashita, S. Takeuchi, M. S. Asano, K. Sugiura, in preparation.

Figure 1
Supramolecular Assembly of Helical Porphyrin Nanostructures on Single Stranded DNA Via Directional Hydrogen Bonds
Authors: Balaz Milan 
Published: February 2020

Chiral nanomaterials and metamaterials have great potential for applications in plasmonics, biological sensing, labelling, chiral memory, data storage, and optical communication. Porphyrins’ modular photophysical and structural properties, high stability, and accessible synthetic routes make them one of the most commonly utilized functional building blocks in molecular engineering. Single stranded DNA (ssDNA) represents a versatile supramolecular template, since its nucleotide sequence and structure can be easily copied into newly formed periodically arranged helical nanostructures. This lecture will present the synthesis of porphyrin-purine conjugates and their assembly into helical supramolecular porphyrin and metalloporphyrin nanostructures formed on a single stranded oligothymidine template via directional hydrogen bonding (see Figure).[1,2] We will describe how the helicity of ssDNA-templated porphyrin and metalloporphyrin nanoarrays can be controlled and switched using external stimuli to preferentially prepare left-handed and right-handed nanoassemblies. We will also present external stimuli induced, reversible switching of helical twist of ssDNA-templated porphyrin nanoassemblies. Time-dependent density functional theory (TD DFT) simulations of UV-vis and circular dichroism (CD) spectra for model porphyrin nanostacks have been used to confirm the origin of observed chiroptical properties and to assign the handedness of porphyrin nanoassemblies. We will also discuss successful use of dialysis to separate porphyrin nanoassemblies from porphyrin monomers. The chiral DNA-templated multiporphyrin nanostructures exhibited high thermal and acid/base stability: the helicity was fully preserved up to +85 °C and pH between 3 and 12. High resolution transition electron microscopy (HRTEM) has showed formation of metalloporphyrin nanoassemblies and their assembly into helical fibrils with micrometer lengths.[2]

1. G. Sargsyan, B. M. Leonard, J. Kubelka, M. Balaz, ‘Supramolecular ssDNA templated porphyrin and metalloporphyrin nanoassemblies with tunable helicity.’
Chem. Eur. J., 2014, 20, 1878-1892 (VIP)
2. G. Sargsyan, A. A. Schatz, J. Kubelka, M. Balaz, ‘Formation and helicity control of ssDNA templated porphyrin nanoassemblies.’
Chem. Commun.
, 2013, 49, 1020-1022

Figure 1
Can Heme Modes be Influenced By Protons?
Authors: Schünemann Volker 
Published: February 2020

Nuclear Resonance Vibrational Spectroscopy (NRVS) –also called Nuclear Inelastic Scattering (NIS) - is a synchrotron based technique which uses a Mössbauer active nucleus -in most cases 57Fe- to characterize iron-ligand vibrations. This method does not depend on optical selection rules; any vibrational mode involving movement of the 57Fe is NIS-active and therefore this technique is complementary to other methods including IR or Raman spectroscopy. In order to explore iron ligand vibrations in heme systems we have investigated the vibrational properties of Fe(III) containing model hemes as well as the NO-adducts of the NO-transporter proteins nitrophorin 2 (NP2) [1,2] and nitrophorin 7 (NP7) [3]. Theoretical QM/MM-calculations have been performed to understand and assign all iron-related vibrational modes in the range starting from 20 cm-1 up to 600 cm-1. Interestingly the QM/MM-calculations do also show that protonation of the heme carboxylates significantly influences the Fe-NO stretching and bending modes of the heme-NO unit [3], an effect which can be related to a change of its electronic properties.
This work was supported by the research initiative NANOKAT and the German Federal Ministry of Education and Research under 05 K13UK2.
1. B. Moeser, A. Janoschka, J.A. Wolny, H. Paulsen, I. Fillipov, R.E. Berry, H. Zhang , A.I. Chumakov, F.A. Walker, V. Schünemann, J. Am. Chem. Soc. 134(9) (2012) 4216.
2. B. Moeser, A. Janoschka, J. A. Wolny, I. Filipov, A.I. Chumakov, F. A. Walker, V. Schünemann, Hyperfine Interact. 206(1) (2012) 19.
3. H. Auerbach, I. Faus, S. Rackwitz, J. A. Wolny, F. A. Walker, A. I. Chumakov, H. Ogata, M. Knipp, V. Schünemann, Hyperfine Interact. 226 (2014) 439.
Porpholactone and Metal Complexes: Effect of Lactonization of ß-Pyrrole
Authors: Zhang Jun-Long , Ke Xian-Sheng 
Published: February 2020

The development of “porphyrin-like” molecules (porphyrinoids) and related tetrapyrroles has attracted considerable attention for the potential as optical materials and photosensitizers for photodynamic therapy (PDT). Porpholactones (TPPLs) are an important but relatively unstudied class of tetrapyrroles, which combine some of the features of porphyrins and chlorins. To explore the effect ß-Lactonization on the electronic structures and spectral properties is of importance to expand the porpholactone chemistry. In recent years, we focused on the synthesis, characterization and the application of porpholactone and their metal complexes. Based on the skeleton of porpholactones, the β-lactone moiety provides an access to tune their NIR optical characteristics, amphilicity and cellular behaviour. More importantly, the relative orientation of the β-dilactone moieties significantly influences their electronic structures and photophysical properties, for example, the Qy band of trans-porphodilactone is red shifted 19 nm compared to that of the cis-isomer with a 2-fold increase in the absorption intensity. Trans-isomer exhibit much higher singlet oxygen quantum yield and the related PDT efficiency than cis-isomer upon irradiation at their Qv bands, respectively. Thus, these results reveal the importance of relative orientation of b-substituents on optical properties at NIR regions.
Mechanistic Understanding of Li Transport in Rechargeable Batteries
Authors: Shahbzian-Yassar Reza 
Published: February 2020

Electrodes in rechargeable batteries undergo complex electrochemically-driven phase transformations upon driving Li ions into their structure. Such phase transitions in turn affect the reversibility and stability of the battery. It is of prime importance to better understand how Li ions transport within the host electrodes and what phase transitions are triggered during such interaction. This presentation gives an overview of the PI’s research program on in situ transmission electron microscopy (TEM) of battery materials. Various anode materials including SnO2, Zn-Sb were subjected to lithiation process and the transport of Li ions was visualized within their atomic structure. For SnO2 nanowires, it was observed that the Li ion transport results in local strain development preferably along (200) or (020) plans and [001] crystallographic directions. Anisotropic plastic deformation was also observed along [010] directions of MnO2 nanowires. Zn-Sb alloys also exhibit a new cubic alloying phase Li2ZnSb that form by intermixing of the ABAB atomic ordering in hexagonal LiZnSb due to Li inclusion in their lattices.
Low Voltage Anodes for Lithium-Ion Batteries
Authors: Clark Steve , Armstrong Anthony Robert , Bruce Peter G 
Published: February 2020

Graphite has proved a highly successful anode for lithium ion batteries; however it is not without its limitations. There is intensive research to perfect silicon based anodes but important challenges still remain in the quest for high cycling efficiency and high cycle numbers. As a result, there remains much need for investigation of alternative anodes for lithium-ion batteries. Recently we investigated anodes based on LiVO2
1,2. Intercalation into this compound, which is isostructural with LiCoO2, occurs in a two phase process with the formation of hexagonal close packed Li2VO2.1 We have now extended these studies to related compounds, and solid solutions, and have identified anodes with a capacity of over 215 mAh/g at C rate, Fig. 1. The density of these materials is 3.34 g/cm3 resulting in a volumetric capacity of 718 mAh/cm3 at 1C. Volumetric capacity is important for applications such as electric vehicles. Detailed results of these investigations will be presented at the meeting.
References:
1) A.R. Armstrong, C. Lyness, P.M. Panchmatia, M.S. Islam, P.G. Bruce, Nat. Mater. 10 (2011) 223-228.
2) F.d.r. Pourpoint, X. Hua, D.S. Middlemiss, P Adamson, D Wang, P.G Bruce, C.P. Grey, Chem. Mater. 2012, 24, 2880−2893.

Figure 1
Liquid-Water Distribution in Compressed Gas-Diffusion Layers Using X-Ray Computed Tomography
Authors: Zenyuk Iryna V , Parkinson Dilworth Y. , Weber Adam Z 
Published: February 2020

Effective liquid-water management is essential for commercializing polymer-electrolyte fuel cells (PEFCs). At lower operating temperatures, there is a need to remove liquid water from the cathode electrode to ensure optimal reactant transport1. To achieve maximum water permeation, it is necessary to optimize the gas-diffusion layers (GDLs). Currently, there is a lack of understanding of water transport, especially under in-situ conditions wherein the GDLs are selectively compressed under lands to provide good electrical conductivity but remain uncompressed under the gas flow channels. In this study, we use synchrotron X-ray micro computed tomography (CT) to study the water distribution in commercially available GDL materials under various levels of compression. We correlate the GDL’s morphological properties such as local spatially-resolved porosity and void-size distribution to local liquid-water distribution and water-transport capability.
Water imbibition through the GDL driven by a static water column was imaged in a sample holder with a grooved stomp. Controlled levels of GDL compression were achieved by tuning an ultra-fine pitch threaded bolt on top of the stomp. Liquid-water profiles were resolved as local averages in in-plane and through-plane directions. Figure 1 shows local liquid-water distributions for three GDLs under different levels of compression as local averages through the GDL depth. Narrowing of the liquid front was observed with increasing compression (decreasing thickness), where most of the liquid is transported under the channel. It appears that at lower compressions the advance of the liquid front is uniform; this is due to uniform porosity and due to availability of void space at the GDL|injection plate interface that allows liquid-water redistribution. At high compressions, porosity and liquid saturation are directly correlated, something that was not observed for the uncompressed sample. This finding is relevant for the design of GDL architectures with modulated porosity, where liquid-water removal can be directed through controlled porosity levels.
Figure 1 Average YZ liquid saturation as a function of X position for three compressions at capillary pressure of 1.4 kPa Acknowledgement
This work was funded by Assistant Secretary for Energy Efficiency and Renewable Energy, Fuel Cell Technologies Office, of the U. S. Department of Energy under contract number DE-AC02-05CH11231. This work made use of facilities at the Advanced Light Source (ALS), supported by the Office of Science, Office of Basic Energy Sciences, of the U.S. Department of Energy.

References

A. Steinbach, “High Performance, Durable, Low Cost Membrane Electrode Assemblies for Transportation Applications”, DOE
Annual Merit Review (2014).

Figure 1
Insights into the Oxygen Reduction Reaction Activity of Pt/C and PtCu/C Catalysts
Authors: Coleman Eric J , Co Anne C. 
Published: February 2020

A mechanistic electrochemical study of the oxygen reduction reaction (ORR) on a carbon-supported PtCu core-shell catalyst is presented. The catalyst was prepared by galvanic displacement of nanoporous copper with Pt. The electrochemistry of the catalyst was explored at pH 1 and pH 13. Hydrogen peroxide reduction and rotating ring-disk electrode (RRDE) studies showed that the PtCu/C catalyst facilitates a 4e- direct or series reduction to water in alkaline electrolyte. Tafel data suggests that the ORR rate limiting step for PtCu/C does not change when the catalyst is subject to pH extremes. The ORR activity of the PtCu/C catalyst was found to be 2 to 3 times higher than the ORR activity of commercially available Pt/C (Johnson Matthey). Adsorption of OH- was quantified for PtCu/C and Pt/C, and PtCu/C was observed to have a reduced affinity towards OHads in both acid and alkaline electrolyte, which was found to promote the rate of the ORR relative to Pt/C. Based on this study, we propose that: 1) Pt-based catalyst has a unique rate of change of OHads coverage which is correlated to their ORR activity and 2) All Pt-based catalysts have the same rate of change of OHads coverage during irreversible oxide formation.

Figure 1