bluuebunny/crossref_metadata_2025_split huggingface dataset:
Strained-Induced Oxygen Non-Stoichiometry on La0.5Sr0.5Mn0.5Co0.5O3-Δ Thin Films
Authors: van den Bosch Celeste Anna Maria , Katcho Nebil , Cazorla Claudio , Santiso Jose , Carrasco Javier , Aguadero Ainara 
Published: February 2020

The control of defect structure and surface composition is of great importance to achieve performance improvements of a wide variety of materials for electrochemical applications. Effects of temperature, PO2 and bias have been widely studied. However, the potential of strain-induced oxygen non-stoichiometry requires further study to obtain a deeper understanding of the effects on controlling oxygen stoichiometry and modifying surface characteristics. In this work strained epitaxial thin films were investigated as a method to design the defect structure and surface characteristics of the La0.5Sr0.5Mn0.5Co0.5O3-δ (LSMC) perovskite. This perovskite was chosen due to its ability to accommodate a wide variety of oxygen stoichiometries1. Thin films of LSMC were grown using pulsed laser deposition on substrates with lattice mismatch of +0.46%, between SrTiO3 and the bulk reduced La0.5Sr0.5Mn0.5Co0.5O2.38(2) resulting in tensile strain, and -1.50%, producing compressive strain between LaAlO3 and the bulk oxidised La0.5Sr0.5Mn0.5Co0.5O2.98(2). Crystal lattice volumes of the thin films were determined by X-ray diffraction and confirmed that fully strained (00l) epitaxial films were achieved. Low energy ion scattering (LEIS) was used to probe both surface and sub-surface composition of the thin films. LEIS analysis confirmed that whilst both tensile and compressively strained films were A-site terminated, with strong strontium dominance, there was cobalt enrichment of the sub-surface layer which was more prominent in films under tensile strain. Density functional theory calculations show that the vibrational contribution to the vacancy free energy, i.e. thermal effects, strongly depends on the strain. In particular, the computational investigation demonstrated that the equilibrium oxygen vacancy concentration increases (decreases) under tensile (compressive) strain compared to the bulk LSMC case.
1 A. Aguadero, H. Falcon, J. M. Campos-Martin, S. M. Al-Zahrani, J. L. G. Fierro and J. A. Alonso, Angew. Chem. Int. Ed. Engl., 2011, 50, 6557–61.
(Invited) Effect of Fast Mass Diffusion Regime on Defective Ceria Mechano-Chemo-Electrical Properties
Authors: Esposito Vincenzo 
Published: February 2020

Ceria and ceria based compounds are a key materials in several energy related technologies. As cerium oxide (e.g. in acceptor doped CeO2-δ), the material presents distinctive mechano-chemo-electrical properties related to high oxygen defect concentration, fast defect mobility and large chemical expansion. In this work we show that cations diffusion and net fast mass diffusion mechanisms can be triggered at relatively low temperatures (T > 800 °C) under low oxygen partial pressure (pO2 < 10-12 atm) conditions. Such effects are promoted by coupling high content of oxygen defects and cation size changes from Ce4+ to Ce3+, activating fast densification, low viscosity mass flow, and unexpected microstructural evolution of the compound. On the other hand, in composites and at soli-solid interfaces with other metal oxides, ceria leads fast chemical transformations and phase changes. A detailed analysis of these phenomena indicated that tuned chemo-thermal conditions can be designed in treatments at controlled pO2 conditions and temperatures, resulting in novel ceria-based compounds and enhanced electrochemical properties.
(Invited) Microstructural Degradation in Rechargeable Batteries
Authors: García R. Edwin 
Published: February 2020

The charge/discharge microstructural conditions that lead to mechanical failure, salt precipitation, and lithium dendrite formation in rechargeable lithium-ion batteries are explored. By starting from high resolution X-ray tomography, three-dimensional representations of porous microstructures from commercially batteries are used to simulate its local electrochemical and chemo-mechanical behavior and identify those microstructural features that will favor failure and heterogeneous lithium nucleation. The analysis demonstrates that spatial variation in porosity, particle roughness and morphology significantly alter the local intercalation kinetics, state of charge, mechanical stability, and dendrite formation. Based on this analysis, the thermodynamic conditions that will enable current density-controlled failure, its macroscopic Weibull statistics, and a overpotential-controlled critical lithium electrodeposit to become energetically favorable are identified. We define several regimes of growth behavior and directly compare them against experimental data to propose: nucleation and growth regimes, where after a short incubation time nuclei will grow as a result of favored morphological instabilities and localized fields directly impacting the macroscopic response and long term useful life of the device.
Identifying the Link Between Li-Ion Particle Fracture and Impedance Growth
Authors: McGrogan Frank P , Bishop Sean R. , Chiang Yet-Ming , Van Vliet Krystyn J. 
Published: February 2020

It is well established that lithium-ion batteries (LIBs) exhibit reduced performance with increasing electrochemical cycles (quantified as capacity fade or impedance growth), and it has also been demonstrated that the electrochemical driving forces for ion insertion and removal from the active electrode materials cause mechanical strain that can even lead to fracture of the active, brittle particles. In other words, battery storage capacity fades over repeated electrochemical cycles, and cathode particles can exhibit fracture over repeated cycles. However, the direct correlation between fracture events due to electrochemomechanical coupling and the performance reduction of LIB cathodes has not been established fully. Thus, although the fracture mechanics of electrode materials have been modeled extensively, it is not well understood whether, when, and how fracture initiates and progresses to result in changes in late-life performance of LIBs. Here, we monitored acoustic emission events during repeated cycling of LiMn2O4 and LiNi0.5Mn1.5O4 electrodes to consider the temporal correlations of electrode particle fracture and changes in capacity and impedance. We varied the electrochemical cycling rate to intensify fracture driving forces, and thus identified any temporal correlations between fracture, capacity fade, and impedance growth as a function of cycle characteristics. We analyzed performance degradation using electrochemical impedance spectroscopy, including the dependences on temperature and state-of-charge. Such analysis of how fracture relates to capacity fade and impedance growth in this class of brittle ionic conductors informs the design of Li-ion batteries with increased durable useful lifetimes.
Novel Diffusion Layers with Patterned Wettability: Measurement of Capillary Pressure Characteristic with Neutron and Synchrotron Imaging
Authors: Forner-Cuenca Antoni , Manzi-Orezzoli Victoria , Biesdorf Johannes , Lamibrac Adrien , Büchi Felix N , Gubler Lorenz , Schmidt Thomas J. , Boillat Pierre 
Published: February 2020

The gas diffusion layers (GDLs) play several important roles in polymer electrolyte fuel cells (PEFCs): conduction of heat and electrons, mechanical integrity and opposite-direction transport of gases and liquid water. This liquid product water is transported by capillary forces [1] throughout the GDL, forming tortuous pathways. State-of-the-art GDLs do not provide optimal characteristics for simultaneous water permeability and oxygen diffusivity. To address this issue, we are developing new GDLs with patterned wettability [2]. These materials provide low-resistance straightforward pathways for liquid water and dry low mass transport regions for the diffusion of gases [3].
In order to understand capillary transport in diffusion layers, Gostick et al. [4] developed an ex-situ experiment which allows obtaining saturation versus capillary pressure curves. This characteristic provides a very useful tool for designing optimized GDLs. We have used the same principle adapted for imaging (neutron radiography and X-ray tomography). In a recent publication [3], we demonstrated the capability of these materials to have water filled patterns at low capillary pressures (around 10 mbar), while significantly higher pressures (around 40-50 mbar) were needed to fill the hydrophobic regions (Figure 1).
In a more recent work, we have used two water injection strategies. The first consists in injection from a channel in the center of the GDL area and provides information about in-plane transport. The second brings the water equally distributed all over the area using a hydrophilic membrane [5], simulating a “cathodic” water transport situation, where water is produced all over the electrode.
In this presentation, we will show our latest results regarding parametric studies on differently treated GDLs. The effect of the following parameters on the capillary pressure characteristic has been investigated: type of carbon substrate (Toray, SGL and Freudenberg), coating load, hydrophilic monomer grafted (acrylic acid or n-vinylformamide), and width/separation of the patterns.
[1] U. Pasaogullari, et al., Int. J.Electrochem. Soc., 151(2004), 399.
[2] P. Boillat, et al., Patent Application EP14184065.2(2014).
[3] A. Forner-Cuenca, et al., Adv. Mater., 27, (2015), 6317.
[4] J. Gostick et al., J. Power Sources, 156(2006), 375.
[5] A. Lamibrac, et al., ECS 228th Meeting Abstract (2015), MA2015-02 1539.
Figure captions:
Figure 1: Local water thickness measured with neutron radiography at different capillary pressures: 0, 10, 20, 40 and 50 mbar (top). Curves at different capillary pressures of water thickness and saturation as a function of the position is represented in the bottom graphic.

Figure 1
Electroreductive Coupling Reactions Using a Microflow Reactor
Authors: Lam Chiu Marco , Little R. Daniel 
Published: February 2020

The construction of carbon-carbon bonds remains central to organic chemistry. The electroreductive cyclization (ERC) and the electrohydrocyclization (EHC) reactions provide a convenient method for the construction of a sigma bond between two formally electrophilic carbon centers.[1] They occur under mild, metal free conditions and can be achieved using both direct and mediated protocols. Yet, the need to use large quantities of supporting electrolyte can lead to problems during the isolation process and to the formation of significant amounts of waste.[2]
To address these issues, we have explored the use a microflow reactor. The small distance between the electrodes reduces the ohmic drop, and the large ratio of the electrode surface area-to-solution volume facilitates electron transfer. As a result, less supporting electrolyte is needed. Using our apparatus, we have achieved yields comparable to those reported in the literature while significantly reducing the amount of supporting electrolyte. In addition, recycling provides a convenient way to increase the reaction scale and to optimize yields.
References:
1. Miranda, J. A.; Wade, C. J.; Little, R. D. J. Org. Chem. 2005, 70, 8017-8026.
2. Moëns, L.; Baizer, M. M.; Little, R. D. J. Org. Chem. 1986, 51, 4497-4498.
Electrochemical Amination of Non-Activated Arenes Using Boron-Doped Diamond Electrodes
Authors: Herold Sebastian , Möhle Sabine , Zirbes Michael , Richter Frank , Nefzger H. , Waldvogel Siegfried R. 
Published: February 2020

The synthesis of organic compounds by electric current serves as an environmentally friendly and sustainable approach as it avoids the generation of reagent waste and may facilitate unusual reaction-pathways as well.[1] The direct electrochemical C,H amination of activated aromatic compounds was first reported and elaborated by the Yoshida group in 2013.[2]The introduction of an amino moiety is performed via anodic pyridination of the corresponding methoxy substituted aromatic compounds followed by ring-opening of the obtained pyridinium intermediates. We successfully applied this state-of-the-art amination method to less activated aromatic substrates e.g. alkylated arenes. However, using carbon felt anodes only moderate yields were obtained. Therefore, boron-doped diamond as anode material that shows a higher performance at more positive potentials was used.[3] In initial findings, this novel and innovative electrode material has demonstrated an outstanding performance in electrochemical amination reactions of simple alkylated arenes. Materials like platinum and glassy carbon show no performance at all. We present the scope and CV studies of this interesting electrosynthetic method.
References:
[1] a) B. A. Frontana-Uribe, R. D. Little, J. G. Ibanez, A. Palma, R. Vasquez-Medrano, Green Chem.
2010, 12, 2099-2119; b) J. I. Yoshida, K. Kataoka, R. Horcajada, A. Nagaki, Chem.
Rev.
2008, 108, 2265-2292.
[2] T. Morofuji, A. Shimizu, J. I. Yoshida, J. Am. Chem. Soc.
2013, 135, 5000-5003; S. R. Waldvogel, S. Möhle, Angew. Chem. Int. Ed.
2015, 54, 6398-6399.
[3] B. Elsler, D. Schollmeyer, K. M. Dyballa, R. Franke, S. R. Waldvogel, Angew. Chem. Int. Ed.
2014, 53, 5210-5213.

Figure 1
B12-TiO2 Hybrid Catalyst for Light-Driven Hydrogen Production and Hydrogenation of Carbon-Carbon Multiple Bonds
Authors: Shimakoshi Hisashi , Tian Hui , Hisaeda Yoshio 
Published: February 2020

Naturally-occurring B12(cobalamin)-dependent enzymes catalyze various molecular transformations that are of particular interest from the viewpoint of biological chemistry as well as synthetic organic chemistry and catalytic chemistry.1 For example, the B12-dependent enzyme catalyzes the rearrangement reactions and the methylation reaction as in the synthesis of methionine. All of these reactions are mediated by the cobalt alkylated complex which is generally formed by the reaction of the Co(I) state of the B12 with various electrophiles in vitro. Recently, we have reported the unique catalysis of the B12-titanium oxide (TiO2) hybrid catalyst in which the B12 complex, cyanoaquacobyrnic acid, is immobilized on the surface of TiO2 and the B12 complex is reductively activated to form the Co(I) species by electron transfer from TiO2 under UV-light irradiation.2 The hybrid catalyst mediated the dehalogenation of various organic halides and was applied to the radical-mediated organic reaction via an alkylated complex as a catalytic intermediate. The great advantage of the catalyst is the facile and efficent formation of Co(I) species by only UV light irradiation. This property prompted us to investigate further applications of the B12-TiO2 catalyst utilizing the high reactivity of the Co(I) species of the B12 complex. We now report the new catalysis of the B12-TiO2 for H2O reduction to form hydrogen. Cobalt complexes have been studied as excellent catalysts for hydrogen production, and the cobalt hydride complex is thought to be an intermediate for the reaction which could be formed by the reaction of Co(I) and a proton. As the metal hydride complexes are widely used for the reduction of unsaturated compounds, such as alkenes, an application of the B12-TiO2catalyst for the hydrogenation of C-C mutiple bonds was also investigated.
[1] a) K. ó Proinsias, M. Giedyk, D. Gryko, Chem. Soc. Rev. 2013, 42, 6605-6619; b) K. Gruber, B. Puffer, B. Kräutler, Chem. Soc. Rev. 2011, 40, 4346-4363; c) W. Buckel, B. T. Golding, Annun. Rev. Microbiol. 2006, 60, 27-49; d) K. L. Brown, Chem. Rev. 2005, 105, 2075-2149; e) T. Toraya, Chem. Rev. 2003, 103, 2095-2127, f) R. Banerjee, S. W. Ragsdale, Annu. Rev. Biochem. 2003, 72, 209-247.
[2] a) H. Shimakoshi, Y. Hisaeda, Angew. Chem. Int. Ed. 2015, in press; b) H. Shimakoshi, Y. Hisaeda, ChemPlusChem 2014,
79, 1250-1253; c) H. Shimakoshi, M. Abiru, S. Izumi, Y. Hisaeda, Chem. Commun.
2011, 6427-6429; d) S. Izumi, H. Shimakoshi, M. Abe, Y. Hisaeda, Dalton Trans. 2010, 39, 3302-3307; e) H. Shimakoshi, M. Abiru, K. Kuroiwa, N. Kimizuka, M. Watanabe, Y. Hisaeda, Bull. Chem. Soc. Jpn. 2010, 83, 170-172; f) H. Shimakoshi, E. Sakumori, K. Kaneko, Y. Hisaeda, Chem. Lett.
2009, 38, 468-469.

Figure 1
Electrochemical Reduction of CO2 Using Cyclopentadienone Iron Complexes
Authors: Rosas Alonso , Junge Henrik , Beller Matthias , Francke Robert 
Published: February 2020

The generation of fuels and commodity chemicals by electrochemical reduction of the greenhouse gas CO2 can be considered as a promising approach towards a more sustainable economy.[1] In this context, the quest for selective and efficient noble metal-free catalysts poses one of the key challenges. Among the typical products of CO2 reduction, carbon monoxide is particularly attractive due to numerous possibilities for further processing as C1-building block. Due to the high overpotential and a variety of possible reaction pathways, a selective electroreduction of CO2 to CO is not trivial.[2] In this regard, considerable progress has been recently made with homogeneous electrocatalysts.[3-5] However, most of the methods reported so far require either precious metal centers such as Ru or Re, ligand-systems with limited availability such as porphyrine analogues and/or excess amounts of a proton donor such as trifluoroethanol or phenol.
Herein we report a highly active (cyclopentadienone)iron-tricarbonyl complex (see figure below) for the selective electroreduction of CO2 to CO in aprotic electrolytes. Using this robust and easy-to-synthesize system, the electrochemical generation of CO becomes feasible without addition of proton donor. Electroanalytical experiments were carried out in order to characterize the complexes and to evaluate their catalytic behavior. These experiments show high turnover frequencies and a remarkable influence of the ligand substitution and the solvent on the catalytic performance. The application in bulk electrolysis under optimized conditions rendered excellent Faradaic yields and turnover numbers. Along with the catalytic performance, possible mechanisms are discussed based on voltammetric data and spectroelectrochemical results.

References:

[1] J. Qiao, Y. Liu, F. Hong, J. Zhang, Chem. Soc. Rev.
2014, 43, 631.
[2] C. Costentin, M. Robert, J.-M. Savéant, Chem. Soc. Rev.
2013, 42, 2423.
[3] J. Agarwal, T. W. Shaw, C. J. Stanton III, G. F. Majetich, A. B. Bocarsly, H. F. Schaefer III, Angew. Chem. Int. Ed.
2015, 53, 5152.
[4] M.D. Sampson, A. D. Nguyen, K. A. Grice, C. E. Moore, A. L. Rheingold, C. P. Kubiak, J. Am. Chem. Soc.
2014, 136, 5460.
[5] E. A. Mohamed, Z. N. Zahran, Y. Naruta, Chem. Comm.
2015, 51, 16900.

Figure 1
(Spectro)Electrochemical Study of the Role of Electron Structure of Three Isomeric Benzendialdehydes on Their Reduction in Aprotic Media
Authors: Kantnerová Kristýna , Ludvík Jiří 
Published: February 2020

The presented work is dealing with electrochemical reduction of three isomeric benzene dialdehydes: orthophthalaldehyde (benzene-1,2-dicarboxaldehyde, OPA), isophthalaldehyde (benzene-1,3-dicarboxaldehyde, IPA) and terephthalaldehyde (benzene-1,4-dicarboxaldehyde, TPA) in aprotic media. Whereas their electrochemical reduction in aqueous buffered solutions is described and compared in the literature (together with their covalent hydration) [1-3], the reduction mechanism of the title compounds in non-aqueous and aprotic solvents has not been investigated up to now (with one exemption: OPA and TPA in methanol [4]).
The reduction was investigated by voltammetric methods, electrolyses, coulometry, UV-vis and EPR spectra in order to identify the primary radical intermediates as well as reduction products. OPA and TPA form stable radical anions after the first ET which were confirmed by the in-situ EPR spectroelectrochemical experiments. Using cyclic voltammetry the influence of the water content in dimethylformamide on the stability of radicals was followed. The first electroreduction step of IPA was irreversible, therefore the EPR spectra did not reveal any paramagnetic species. The differences were discussed and correlated with quantum chemical calculations.
Acknowledgement: The material support from the grant GACR No. 13-21704S and the institutional support RVO 61388955 are acknowledged.
[1] M. S. Baymak, E. Kulla and P. Zuman, J. Mol. Liq., 2007, 131-132, 24_28.
[2] M. S. Baymak, W. J. Bover, H. Celik and P. Zuman, Electrochim. Acta, 2005, 50, 1347_1359.
[3] M. S. Baymak, K. L. Vercoe and P. Zuman, J. Phys. Chem. B, 2005, 109, 21928_21929.
[4] D. Jannakoudakis and G. Kokkinidis, Chim. Chron., 1977, 6, 439_450.
Electrochemical Intramolecular C-H Amination of Aromatic Compounds
Authors: Shimizu Akihiro , Morofuji Tatsuya , Yoshida Jun-ichi 
Published: February 2020

C-H amination is a straightforward method to synthesize nitrogen-containing organic compounds. Electrochemical oxidation serves as a powerful method to functionalize C-H bonds of aromatic compounds. However, it often suffers from overoxidation when the product is easily oxidized compared to the starting material. Therefore, electrooxidative C-H amination of aromatic compounds has been difficult so far. To solve the problem, we have developed a new approach to the electrochemical intermolecular C-H amination of aromatic compounds via N-arylpyridinium ions, which can be converted to aromatic primary amines by a subsequent chemical reaction.
In this paper we report that the method can also be applied to the intramolecular C-H amination of aromatic compounds to give nitrogen-containing heteroaromatics. Benzoxazoles and benzothiazoles were successfully synthesized from phenols and thiophenols, respectively. The intermediacy of the electrooxidatively inactive cationic intermediates which avoid overoxidation is responsible for the success of the transformation.
Synthesis, Properties, and Theoretical Study of Extended Diynes and Their Analogs Bearing Two Amino Moieties
Authors: Mitsudo Koichi , Kamimoto Natsuyo , Nakamura Nariaki , Tsutsumi Akina , Suga Seiji 
Published: February 2020

Recently, π-conjugated compounds have received attention because they are known to be key building blocks for pharmaceuticals and potential candidates for electrochemical and optical materials. From this perspective, we have investigated the use of electrochemically assisted coupling reactions for the construction of π-conjugated compounds, and recently reported sequential coupling reactions including the Pd/Cu-catalyzed electro-oxidative homo-coupling of p-bromophenylacetylene (1) to give 1,4-bis(p-bromophenyl)-1,3-diyne (2) and subsequent Suzuki–Miyaura coupling with arylboronic acids leading to 1,4-bis(diaryl)-1,3-butadiynes 3 (Scheme 1).1 Two reaction sites of p-bromophenylacetylene, the terminal alkyne and Br group, could be almost completely discriminated by the on/off application of electricity, and we called the strategy as “Electrochemical Reaction Site Switching (e-RSS)”. Several arylboronic acids can be used in these reactions, which proceed selectively to give 1,4-bis(diaryl)-1,3-butadiynes in good to excellent yields.
During the course of our investigation, we found that 1,4-bis(diaryl)-1,3-butadiynes bearing two amino groups at the p-position of the terminal benzene rings exhibited solvatochromic fluorescence. There have been many reports on amines that exhibit solvatochromic fluorescence. Most of the known amines that exhibit solvatochromic fluorescence have a strong acceptor moiety. There have been a few reports on the solvatochromic fluorescence of diamines, which have a small dipole moment. This unexpected result encouraged us to gain deeper insight into this unusual phenomenon. This time, we synthesized their analog 4 which contains an alkyne, and 5 which does not contain a triple bond (Figure 1), and compared their properties with those of 1,4-bis(diaryl)-1,3-butadiynes bearing two amino moieties. To estimate the solvent effect, we also carried out DFT and TD-DFT calculations of their compound. The results of TD-DFT calculations in different solvents indicated that the excitations and the emissions were mainly due to the HOMO–LUMO transitions of these compounds.
(1) Mitsudo, K.; Kamimoto, N.; Murakami, H.; Mandai, H.; Wakamiya, A.; Murata, Y.; Suga, S. Org Biomol Chem
2012, 10, 9562-9569.

Figure 1