bluuebunny/crossref_metadata_2025 huggingface dataset:
Mechano-Chemical Coupling in Double Perovskites As Energy Related Materials
Authors: Zuev Andrey Yu. , Tsvetkov Dmitry S. , Ivanov Ivan L. , Sereda Vladimir V. , Malyshkin Dmitry
Published: February 2020

Double perovskites RBaB2O6-δ and Sr2BMoO6, where R=rare-earth element and B=3d-transition metal, with A-site and B-site, respectively, cation ordering are very promising materials for a variety of different devices for moderate high temperature applications such as solid oxide fuel cells (SOFCs) and mixed ionic and electronic conducting (MIEC) membranes. The unique feature of the oxides is their ability to undergo both thermal strain and that induced by the defects of oxygen nonstoichiometry in the oxide lattice. The latter is called as chemical or defect-induced strain. This property was shown recently to be anisotropic unlike that of a perovskite with pseudo-cubic structure. The crystal lattice of a double perovskite expands along
a
axis and simultaneously contracts along
c
axiswith the decreasing lattice oxygen content. Expansion along
a
axis was found to obey the model for pseudo-cubic oxides proposed by us earlier and based on relative change of mean ionic radius. The possible reasons for lattice contraction along
c
axis are discussed as well.
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
Poisoning Effects of Sulfur on Emergent and Current Heterogeneous Electrocatalysts: Susceptibility of Molybdenum Disulfide and Correlation to Platinum Hydrogen Evolution Kinetics
Authors: Tan Shu Min , Sofer Zdenek , Pumera Martin
Published: February 2020

Transition metal dichalcogenides have been widely researched as promising heterogeneous materials to substitute the archetypal platinum noble metal electrocatalyst in electrochemical hydrogen production reaction. Considering the escalating interest in the development of transition metal dichalcogenides for hydrogen evolution reaction (HER), and the well-established vulnerability of Pt HER electrocatalyst towards sulfur poisoning, we are inspired to examine the impacts of poisoning by sulfur on both emergent and current electrocatalysts. A comparative investigation into the effects of sulfur poisoning on MoS2 and Pt/C revealed that, contrary to initial expectations, MoS2 is not completely invulnerable to poisoning. Moreover, with the use of X-ray photoelectron spectroscopy, correlations between the atomic percentages of Pt–S bonds and normalized Tafel slope and potential at –10 mA cm–2 have also been determined. This study is imperative for the assessment of functionality of various materials for potential hydrogen evolution catalysis.
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
Electrochemical Studies of L-Cysteine
Authors: Cheek Graham T. , Worosz Matthew A.
Published: February 2020

Introduction

     L-Cysteine is an important amino acid because of its role in various biochemical pathways (1).  Considering that L-cysteine is one of the few amino acids with significant redox characteristics, it was considered worthwhile to investigate its electrochemical behavior in various media and electrode surfaces.

Experimental

    L-Cysteine was obtained from Sigma-Aldrich.  Electrochemical experiments were carried out using a Gamry Interface 1000 potentiostat and Gamry Framework software.  Potentials are referenced against a Ag/AgCl reference electrode.  Platinum and glassy carbon electrodes were obtained from BASi.

Results and Discussion

    At a platinum electrode, L-cysteine in aqueous 0.10 M KNO3  produced a cyclic voltammogram with two merged oxidation processes (Figure 1), which were much more clearly resolved using differential pulse voltammetry. Preparative electrolysis at the potential of the first oxidation process (+0.80 V) resulted in the precipitation of cystine, which is the coupling product formed as a result of one-electron L-cysteine oxidation.  The current for the reduction peak at -0.60 V (dotted line in Figure 1) increased during the electrolysis, suggesting that this reduction process is related to cystine formation.  Similar results, including cystine formation, were also obtained in aqueous phosphate buffer at pH 7.  It is likely that the platinum oxide layer on the electrode surface plays a role in L-cysteine oxidation under these conditions (2).  The results of additional studies of L-cysteine oxidation in other media, particularly dimethylsulfoxide (DMSO), are also planned for presentation.

References

C. K. Mathews, K. E. Van Holde, D. R. Appling, and S. J. Anthony-Cahill, Biochemistry, 4th Edition, Pearson Canada, Toronto, 2013.

J. Koryta and J.  Pradac, J. Electroanal. Chem., 17, 185-189 (1968).

Figure 1.  Cyclic voltammogram of 10 mM L-cysteine at platinum in aqueous 0.10 M  KNO3. 100 mV/s.

                First sweep (solid line),  second sweep (dotted line).

Figure 1
Low Cost 3D Printed Biosensor Arrays for Biomedical Diagnostics
Authors: Kadimisetty Karteek , Rusling James F , Malla Spundana , Satterwhite Jennifer E
Published: February 2020

Development and fabrication of bioanalytical devices by 3D printing offers revolutionary new routes to low cost clinical diagnostic devices for molecular measurements. Relevant to future protein-based cancer diagnostics, we describe  here our development of prototype protein immunoarray devices using desktop Fused Deposition Modeling (FDM) and stereolithographic 3D printers. All these system feature sensitive electro-optical detection by a method called electrochemiluminescence (ECL). Our first 3D-printed immunoarray features screen-printed sensors in which manual manipulations enable gravity flow reagent delivery for measurement of 3 proteins at detection limits of 0.3 to 0.5 pg/mL. ECL detection is achieved in an open channel on integrated disposable screen-printed sensor elements. We then address the issue of printing and processing optically clear plastic using a stereolithographic printer to build a closed ECL detection chamber. Finally, we describe a prototype 3D-printed microprocessor-controlled enclosed microfluidic ECL immunoarray featuring reagent reservoirs, micropumps and clear plastic detection chamber with printed nanowells for ECL emission.
Ti/TiO2 as an Alternative Substrate Material for Impedance Biosensors
Authors: Liu Donghao , Rose Peter , Plunkett Kyle Newton , Suni Ian Ivar
Published: February 2020

Impedance biosensors have been widely studied for applications to biomedicine, environmental monitoring, food, and agriculture.  The most common format for AC impedance biosensors involves surface immobilization of an antibody, receptor protein, DNA strand, or other species capable of bio-recognition, and AC impedance detection of the binding event. 

One obstacle to application of impedance biosensors is the stability and reproducibility of protein immobilization. Alkane-thiols deposited on gold (Au) electrodes or alkenes deposited on silicon (Si) electrodes were used as impedance biosensors previously. However, Au-thiol bonds are unstable, so proteins are only stable atop such interfaces for days to weeks. While Si sensor electrodes are more stable, gradual oxidation of Si eventually displaces the polymer-protein film. Ti/TiO2 is an attractive alternative substrate material for impedance biosensors due to the biocompatibility of Ti, and the self-limiting thickness of TiO2. 

Sputtered Ti films are first cathodically stripped of the Ti native oxide, and then galvanostatically anodized in 1.0 M H2SO4.  Following anodization, nitrogen doping is accomplished by annealing at 600°C in NH3/N2 in a tube furnace.  A bifunctional reagent was synthesized with a carboxylate group at one end, and a phosphonate group at the other terminal end that could bind to hydroxyl groups on the surface of TiO2.  This reagent is used to attach mouse monoclonal antibodies to the TiO2 surface though amide bond formation using EDC/NHSS. Peanut protein Ara h1, an allergenic food protein, can then be detected at the Ti/TiO2 sensor electrodes. The response as a function of Ara h1 concentration follows the Langmuir adsorption isotherm, as expected.
Silk-Derived Graphene-like Carbon Material with High Electrocatalytic Activity for Oxygen Reduction Reaction
Authors: Zhang Junfeng , Wang Qingfa , Zhang Xiangwen , Wang Li , Du MingLiang , Zhu Han
Published: February 2020

Natural silk-derived, graphene-like carbon fiber (GF) assisted by K intercalation shows high catalytic activity for the oxygen reduction reaction (ORR). The enhancement in ORR activity results from the formation of a porous structure composed of nitrogen-containing graphene, which not only increases the specific surface area but also leads to more active nitrogen species within the carbon network being exposed to the electrolyte.
Techniques to Improve the Efficiency of Bulk Heterojunction Polymer Solar Cells
Authors: Ogundana Ifedayo Joseph , Foo Simon Y. , Yu Zhibin
Published: February 2020

Polymer solar cells (PSCs) have attracted much attention recently because of their high flexibility, lightweight, low cost, cheap processing technique and future promise of higher power conversion efficiency. With the realization of photo-induced electron transfer from a conjugated polymer to fullerene component, the bulk heterojunction PSC has become the most successful device structure developed in the field of organic solar cells till present day. The efficiency of bulk heterojunction (BHJ) solar cells has increased steadily over the last decade, currently reaching over 10%. The bulk heterojunction solar cells consist of a phase-separated blend of organic electron donor and acceptor components, where the donor component is a conductive polymer and the acceptor component is a fullerene derivative. In order to achieve high performance and efficiency in BHJ PSCs, a wide range of visible light wavelength needs to be absorbed by the electron donating conjugated polymer and at the same time, the conjugated polymer must possess a characteristic good hole mobility. Recent studies have shown new ways and control mechanisms to improve the efficiency of organic PSCs. This study reviews the various techniques used to improve polymer solar cell technology, the device operation mechanism, and the material design requirements. Potential future applications of this technology in flexible and portable devices are also discussed.

Figure 1
Non-Stechiometric Titanates Embellished with a Catalyst and Employed for Visible-Light Water Splitting
Authors: Bienkowski Krzysztof , Kulesza Pawel J
Published: February 2020

Titanates are known from their photocatalytic properties, but they need additional catalysts to work efficiently also they have very high electronic conductivity when they are prepared under reducing conditions in the hydrogen flame or under thermal oxidation in high temperature. We prepared these non-stechiometric titanates as materials for visible-light water and/or small organic molecules oxidation.  Specific conditions of synthesis of non-stechiometric titanates, created by oxidation of the metal at high temperature in oxygen flow, allowed to get unique properties of such films like: large surface area, high conductivity, red-shift in the absorption spectrum and stability over large range of pHs. Adding to these properties, the affinity of polyoxometalate (POMs) species to the formed structures,  and their ability to catalyse the water oxydation reaction, the system of TiO2-x – POM  seems to be suitable for water splitting purposes under visible light irradiation. Morover, these sub-stoechiometric titanium dioxide / titanes films exhibited red-shifted IPCE photo-action spectrum. These results demonstrated the possibility to form defective TiO2 through thermal oxidation of the titanium metal as alternative to the reduction by H2.
Scanning Electrochemical Microscopy: A Tool to Study the Biomediated Calcification Process By Sporosarcina Pasteurii Biofilm
Authors: Harris Dustin , Ummadi J Ganesh , Koley Dipankar
Published: February 2020

Sporosarcina pasteurii, are known to perform CaCO3 precipitation by hydrolyzing urea and increasing the local pH, in presence of the Ca2+ rich brine solution. We have developed a new electrochemical probes for scanning electrochemical microscopy (SECM) to study this calcification process in real time. We have used the newly developed ultramicrosensors, such as pH, Ca2+, and redox sensors, to monitor a real-time, bacteria-mediated urea hydrolysis process and subsequent changes in morphology due to CaCO3 precipitation. We observed a rapid local (500 μm above the biofilm) pH change from 7.4 to 9.2 within 2 min of addition of urea, whereas the bulk pH remains constant at 7.5.  Similar Ca2+ profile was also recorded locally where the  Ca2+ concentration above the biofilm depleted from 170 mM to 1 mM. Recent developments regarding the real-time live biofilm morphological change correlated with the chemical (Ca2+ and pH) information will be presented in the meeting.
Evaluation of Co-Adsorption Effect on Performance and Outdoor Stability of Organic Dye-Sensitized Solar Cells By Electrochemical Impedance Spectroscopy
Authors: Nguyen Hoang Thai , Tran Linh Thi Phuong , Nguyen Thoa Thi Phuong
Published: February 2020

The dye-sensitized solar cells (DSCs) based on an organic sensitizer with trade name RK1 were fabricated by new fabrication procedure. The fabrication procedure that performed in inert gas atmosphere using a glove box includes: (i) assembling sandwich cells from preparative FTO/TiO2 and FTO/Pt electrodes; (ii) filling the cells with RK1 (10 mM)/DMF solutions containing 0–10 mM chenodeoxycholic acid (CDA) and keep still for 4 hours; (iii) filling the electrolyte; and (iv) sealing the cells. In high humidity environment this new proposed procedure has proved to prevent the water uptake into the cell.

In comparison with co-adsorbate free DSCs, the energy conversion efficiency (η) of DSCs with presence of co-adsorbate was improved. However, the photo-activation effect (slight increase of η) observed during first weeks of outdoor test for DSCs with CDA co-adsorbate is lesser than that of co-adsorbate free DSCs. From 14th day of outdoor test the cell efficiency began slightly decrease, and reached the initial value after 21-day-exposure. Meanwhile for the co-adsorbate free DSCs these dates are 30th and 100th, respectively.

The electrochemical impedance spectroscopy (EIS) technique was successfully applied to study electronic and ionic processes in DSC, and consequently, to evaluate the effect of co-adsorbate on cells performance and outdoor stability. The impedance data measured at open circuit voltage (Voc) under illumination were well fitted with the equivalent circuit Rs(RPtCdl)G(CdRd), in which Rs – electrolyte solution resistance, RPt and Cdl describe the modeled charge transfer resistance and capacitance at the counter electrode. The electron transport in the titanium dioxide (TiO2) film and the back reaction at the TiO2/electrolyte interface were modeled by a Gerischer element (G), revealed by an arc at the intermediate-frequency region. The RdCd circuit elements describe the  ion diffusion in the electrolyte.

Analysis of impedance spectra indicated that the increase of electron injection via the effect of co-adsorption contributed to enhancement of photocurrent. This fact was revealed by the decrease of Gerischer impedance. Meanwhile the increase of photocurrent which caused the photo-activation of the cathode interface during first weeks of outdoor exposure was interpreted by the decrease of charge transfer resistance RPt. EIS data show that DSC performance declines under prolonged outdoor exposure. The DSC ageing resulted mainly from the decrease of electron injection in TiO2 film.
Insights to the Complex Role of Surface Oxide in the Oxygen Reduction Reaction
Authors: Coleman Eric J. , Zhang Fen , Co Anne C.
Published: February 2020

Currently our work is focused on understanding the effect of surface species including their interaction between each other and with the catalysts surface that influence the activity and selectivity of the electrocatalyst.  For example, highly efficient Pt-based catalysts are now able to deliver higher currents at lower overpotential.  In the case of the oxygen reduction reaction (ORR), catalysis at low ORR overpotential happens at a potential range where dynamic oxide growth is occurring on the underlying Pt and Pt alloy surfaces resulting in the catalyst becoming oxidized over periods of prolonged use which alters both the catalytic activity and selectivity with time.  In this paper, we report our recent analysis on decoupling electrochemical contributions from oxide growth vs. catalytic ORR.
Understanding the Effects of pH and Alkali Cations on Cyclic Voltammograms and the Hydrogen Oxidation Reaction on Transition Metal Catalyst Surfaces
Authors: McCrum Ian T. , Meduri Praveen , Hickner Michael A , Janik Michael J.
Published: February 2020

The electrochemical interface between a catalytic electrode surface and electrolyte is complex and its structure and composition have a direct effect on the rates and mechanisms of electrocatalytic reactions. For example, it has been found that the rate of the hydrogen oxidation reaction on a platinum electrode is strongly dependent on electrolyte pH, and this effect had tentatively been correlated to a shift in hydrogen binding strength with pH (beyond the expected Nernstian shift) as measured by cyclic voltammetry [1]. We used density functional theory (DFT) to calculate the thermodynamics of adsorption of hydrogen, hydroxide, water, and alkali cations on the low index facets of platinum to support prior work which has shown that the low potential peaks measured by cyclic voltammetry on Pt(100), Pt(110), and higher order facets containing 100 and 110 steps, actually correspond to the competitive and co-adsorption of hydrogen and hydroxide [2]. We further show that increasing pH leads to an increasing amount of specifically adsorbed alkali metal cation which weakens the binding of hydroxide, leading to the experimentally observed shift in the low potential peaks measured by cyclic voltammetry, as opposed to a strengthening of hydrogen binding [2]. Now that we understand the mechanism for these experimentally measured effects of pH and alkali cations, we use experiment and DFT to examine their effect on the rate of the hydrogen oxidation reaction, which we find, on a platinum electrode, to depend on cation identity. We also discuss this effect of pH and alkali metal cation on cyclic voltammograms and the hydrogen oxidation reaction across transition metal surfaces (Ru, Ir, Pt, and Au) as measured by Strmcnik et al. [3] and Durst et al. [4].           

[1] Sheng, W.; Zhuang, Z.; Gao, M.; Zheng, J.; Chen, J. G.; Yan, Y. Correlating Hydrogen Oxidation and Evolution Activity on Platinum at Different pH with Measured Hydrogen Binding Energy. Nat. Commun.
2015,
6:5848.

[2] McCrum, I.T.; Janik, M. J. pH and alkali cation effects on the Pt cyclic voltammogram explained using density funtional theory. J. Phys. Chem. C.
2016, In Press. DOI:
 10.1021/acs.jpcc.5b10979

[3] Strmcnik, D.; Uchimura, M.; Wang, C.; Subbaraman, R.; Danilovic, N.; van der, V.; Paulikas, A. P.; Stamenkovic, V. R.; Markovic, N. M. Improving the Hydrogen Oxidation Reaction Rate by Promotion of Hydroxyl Adsorption. Nat. Chem.
2013,
5, 300-306.

 [4] Durst, J.; Siebel, A.; Simon, C., Hasché, F.; Herranz, J.; Gasteiger, H.A. New insights into the electrochemical hydrogen oxidation and evolution reaction mechanism. Energy Environ. Sci.
2014, 7, 2255-2260.
Tolerance of Impurities in Bioethanol on Pd/C and Pdru/C Catalysts Toward the Ethanol Oxidation Reaction in Alkaline Media
Authors: Chen Rongrong , Qi Jing , Guo Junsong , Schubert Peter , Hyden Josh , Taylor E. J.
Published: February 2020

Although the uses of alternative energy sources have been increased greatly in recent years, current major energy demand is still supplied from conventional fossil fuels such as oil, coal and natural gas. Considering the inevitable depletion of the world’s energy supply and the release of green-house in the earth’s atmosphere, it is necessary to look for an alternative source of fuel. Alkaline-anion-exchange membrane direct alcohol fuel cells (AAEM-DAFCs) are among the promising candidates as alternative power sources for both stationary and portable power applications. Due to the facile kinetics at both the cathode and the anode in alkaline media, the use of non-noble and low-cost material catalysts become feasible, which makes the AAEM-DAFCs a potentially low cost technology compared with proton exchange membrane (PEM) based DAFCs working in acidic media.

Bioethanol has high energy density and is non-toxicity, easy to transport and can be distributed with the existing infrastructure. Bioethanol is a renewable bio-based liquid fuel that can be produced from several different biomass feedstock and conversion technologies. First generation bioethanol is produced by distillation from crops such as wheat, corn, sugar cane and sugar beet; however, this bioethanol production has limitation due to concerns about food price and land use impacts. Second generation bioethanol is produced from different types of lignocellulosic materials as substrate. Currently, only negligible amounts of second generation bioethanol are produced in several demo plants around the world that work industrially, but are not yet commercially feasible. In this work, the bioethanol was produced by diversity feed stocks, like food waste and cellulosic, away from expensive corn. The produced bioethanol may contain some impurities, such as acetic acid, lactic acid, phosphorus, maltotetraose (Dp4), glucose, maltose, fructose, glycerol, isomaltotriose (Dp3), sulfur and so on.

Pd/C was a promising catalyst for the ethanol oxidation reaction (EOR) in alkaline media. Our earlier work indicated that the PdRu/C catalyst exhibited much higher initiate activity toward EOR than the Pd/C catalyst in fuel cell operation conditions. Therefore, we further study the tolerance of impurities in bioethanol on Pd/C and PdRu/C catalysts toward EOR in alkaline media and demonstrate their performance and stability in AAEM-DAFCs using bioethanol as the fuel.

Acknowledgements

We acknowledge financial supports from the National Science Foundation Partnerships for Innovation: Building Innovation Capacity (Contract 1317731).
Exploring Extracellular Electron Transfer in Hyperthermophiles for Electrochemical Energy Conversion
Authors: Sekar Narendran , Wu Chang-Hao , Adams Michael W. W. , Ramasamy Ramaraja P.
Published: February 2020

Hyperthermophiles are microorganisms that thrive in extremely hot environment from 80 oC and upwards. They are the most primitive organisms evolved to survive in the early unhostile earth. The simplest and versatile respiratory electron transport chain of these hyperthermophiles made them suitable candidates for microbial fuel cells (MFC) anode catalysts to generate power at high temperatures. We explored the extracellular electron transfer ability of a hyperthermophilic archaeon called Pyrococccus furiosus (PF). PF is an aquatic anaerobe that grows optimally at 100 oC using a wide range of substrates such as carbohydrates and peptides1. The respiratory chain of PF is simple and unique that it does not require any terminal electron acceptor, rather reduces proton to H2 through membrane bound enzyme complex called hydrogenase2. Their ability to reduce the extracellular oxidants such as insoluble Fe(III) oxide and soluble Fe(III) citrate has been investigated. PF reduced Fe(III) oxide during its growth at 90 oC and the PF culture re-suspended in MOPS buffer (pH 7.5) was found to reduce Fe(III) citrate significantly using H2 as an electron donor. Further, low scan-rate cyclic voltammetry at 90 oC using potassium ferricyanide as a mediator showed greater mediated electron transfer by PF compared to the control without PF. The proof of concept study reported here reveals the potential of PF to generate electricity in MFCs at high temperature locations such as in solfataric fields or near hydrothermal vents. Moreover, such studies also help to advance our understanding in the field of biogeochemistry of the early hot environment and exobiology.

References:

S. D. Hamilton-Brehm, G. J. Schut and M. W. W. Adams (2005) J Bacteriol., 187(21): 7492–7499

S Mukund and M. W. W. Adams (1991) J. Biol. Chem., 266(22), 14208-14216. 

Figure 1