bluuebunny/crossref_metadata_2025 huggingface dataset:
Automotive Pouch Cell Performance: Effect of Silicon Loading, Binder, and Additives
Authors: Karulkar Mohan , Wen Hao , Blaser Rachel , Kudla Robert , Drews Andy
Published: February 2020

As the auto industry looks towards increased electrification, there is a clear need for higher energy density batteries to increase vehicle range. One of the most promising next-gen anode materials is silicon, and indeed it is already being implemented in consumer electronic cells. [1] The first use in automotive cells will likely be lower-loading silicon in graphitic anodes. In anticipation of silicon incorporation in automotive applications, it is important to consider volume expansion of such cells. Existing automotive battery designs cannot accommodate significant volume expansion. There are also continuing concerns about cycle life and first cycle capacity loss. Factors like binder, electrolyte additives, and silicon content strongly affect performance metrics. [2]

To address these issues, 2 Ah and 4 Ah pouch cells were fabricated with NMC cathodes and various anode formulations, including 5% and 10% silicon in graphite, CMC/SBR and PAA binders, and with electrolytes containing 10% and 25% FEC additive. These cells were fabricated at the University of Michigan battery lab, and tests were conducted in-house. Design constraints, which will be discussed in this talk, limited N:P ratios to relatively high values (>1.5), which highlights challenges to designing full cells with high-SEI forming materials. PAA was found to produce 20% better capacity retention at 100 cycles, though that advantage lessened with continued cycling beyond 250 (Figures 1 and 2). Electrolyte with 10% FEC produced markedly better performance (40% + better retention) for the 5% silicon anodes. 25% FEC electrolyte produced better performance for higher-silicon anodes with 10% silicon. Volume expansion depended strongly on silicon content, but in no cases did cells swell by more than 2%, which is within current tolerances for pack design (Figure 3). The results point to future work with increased silicon content and more optimized N:P ratios that approach unity.

[1] X. Zuo, J. Zhu, P. Müller-Buschbaum, Y. Cheng, J. Power Sources, 31, 113-143 (2017).

[2] M. Karulkar, H. Wen, R. Kudla, R. Blaser, ECS Transactions, 72, 197-206 (2016).

Figure 1
Chemically Coupled Conducting Complex Framework Materials (C4FMs) As Sulfur Hosts in Lithium – Sulfur Batteries
Authors: Murugavel Shanthi Pavithra , Jampani Hanumantha Prashanth , Wang Louis S. , Gattu Bharat , Datta Moni Kanchan , Velikokhatnyi Oleg I , Kumta Prashant N
Published: February 2020

Abstract

Ever increasing demand for efficient portable energy storage systems has directed researchers towards finding alternatives for the conventional insertion – based lithium-ion battery cathodes. Sulfur, with a theoretical specific capacity of 1672 mAh/g is a promising candidate for high energy density lithium battery cathodes1, 2. Low cost and ease of availability further adds to the advantages of sulfur over hitherto transition metal – based cathodes.

However, elemental sulfur has very low electronic conductivity (~10-15 S/cm)3 at room temperature which restricts the active material utilization in Li – S battery. The formation of soluble non – intercalation based polysulfide intermediates (Li2Sn; n = 2 – 8)4 during electrochemical cycling further results in active material loss by coating onto the anode leading to eventual battery failure.

Embedding sulfur into porous materials have shown considerable reduction in polysulfide dissolution by preventing direct contact with the liquid electrolyte5-7. However, inability to precisely control porosity and lack of chemical interaction between these porous structures and the entrapped sulfur greatly limits the efficiency of this approach. To completely prevent polysulfide dissolution, sulfur hosts with tunable, engineered porosity and increased affinity for polysulfide needs to be engineered.

In this work, chemically coupled conductive complex framework materials (C4FMs) with nanoporous structure were used as hosts for sulfur in Li – S battery. Introduction of special functional groups improves the affinity of these structures towards polysulfide. The frameworks were synthesized using microwave assisted hydrothermal synthesis and then infiltrated with sulfur using vapor infiltration techniques. These sulfur – hosted cathodes showed a stable electrochemical performance with an initial discharge capacity of ~1620 mAh/g which stabilized at 1100 mAh/g to100 cycles (Figure 1).

Acknowledgements: The authors acknowledge the financial support of DOE grant DE-EE 0006825, Edward R. Weidlein Chair Professorship funds and the Center for Complex Engineered Multifunctional Materials (CCEMM).

References

1. J. R. Akridge, Y. V. Mikhaylik and N. White, Solid State Ionics, 2004, 175, 243-245.

2. M. M. Thackeray, C. Wolverton and E. D. Isaacs, Energy & Environmental Science, 2012, 5, 7854-7863.

3. M. Edeling, R. W. Schmutzler and F. Hensel, Philosophical Magazine Part B, 1979, 39, 547-550.

4. S. S. Zhang, Journal of Power Sources, 2013, 231, 153-162.

5. S.-R. Chen, Y.-P. Zhai, G.-L. Xu, Y.-X. Jiang, D.-Y. Zhao, J.-T. Li, L. Huang and S.-G. Sun, Electrochimica Acta, 2011, 56, 9549-9555.

6. Z. Gong, Q. Wu, F. Wang, X. Li, X. Fan, H. Yang and Z. Luo, RSC Advances, 2016, 6, 37443-37451.

7. J. Jin, Z. Wen, G. Ma, Y. Lu and K. Rui, Solid State Ionics, 2014, 262, 170-173.

Figure 1
Structural Hybrid Supercapacitor
Authors: Wang Yuchen , Qiao Xiaoyao , Zhang Chen , Zhou Xiangyang
Published: February 2020

Supercapacitors (SCs) have attracted tremendous attention due to their high specific power and long cycle life. The two major issues with SCs are low specific energy and self-discharge. The benefits of doping mediators or redox species in electrolytes include: 1) providing extra pseudocapacitance out of bulk of electrode materials, 2) increasing the electronic and ionic conductivities of electrolyte in the composite electrodes; and 3) releasing the ions into electrolyte to promote the capacity of electrolyte. Redox species or mediators as dopants in electrolytes are reported to realize the specific capacitance up to 400-500 F/g and the specific energy up to 30-50 Wh/kg. For the issue of self-discharge, adding primary cell materials into the mediator SC is proposed because the materials can provide a micro-current to compensate the self-discharge current. In this research, Cu powder/CuSO4 and Zn powder/ZnSO4 were added into the positive and negative electrodes respectively. The positive electrode also contained PVDF/LiTFS polymer electrolyte doped with K4Fe(CN)6 as mediator whereas the negative electrode contained PVDF/LiTFS doped with (VO)SO4 as mediator. A mixture of epoxy/PVDF/LiTFS thin film was used as the separator between the electrodes also to provide adhesion. Figure 1 shows the galvanostatic charge/discharge (GCD) curves of a structural hybrid SC. A cyclic voltammetry (CV) curve obtained at a scan rate of 10 mV/s of this hybrid SC is illustrated in Figure 2. The broad peak from 0.4V to 0.8V is an indication of pseudocapacitance behavior related to the redox reactions of the mediators. The asymmetric shape of CV curve is related to the electrochemical reactions of Cu and Zn during charging/discharging. It was found that the voltage of the SC can be withheld at 1V for more than 3 months. The mechanical strength of the SC was tested using a MTS machine. It was found that the elastic constant as 20 MPa and ultimate tension strength was 2 MPa.

Figure 1
Electrochemically Mediated Ion Transport in Layered Materials
Authors: Takeuchi Esther S , Takeuchi Kenneth J , Marschilok Amy C
Published: February 2020

Layered materials are desirable for energy storage as they offer opportunity for facile ion transport in two dimensions. In some cases, interlayer spacing can change significantly upon ion insertion and deinsertion, while in others the material structure can be largely maintained during the discharge and charge process. Progress involving synthesis, characterization and electrochemical investigation of select examples from the families of vanadium, iron, and manganese oxide systems will be discussed.
(Invited) Separation and Photophysical Properties of C84 Minor Isomer D2d(I)
Authors: Booth Eric , Yoshida Sanichiro , Jin Yao , Mitchell Mandy , Chou Ju
Published: February 2020

Higher fullerenes such as C84 present a rich variety of photophysical properties, due to their abundance of distinct geometric isomers. However, this multitude of isomers, along with their similar chromatographic properties, also creates difficulties in purifying and characterizing specific species of C84. In this paper, we present the application of an alternating-column HPLC technique to resolve C84 isomers. We find that this technique presents markedly higher separation efficiency than the recycling HPLC method. Subsequent photophysical analysis of a previously uncharacterized isomer of C84, D2d(I), shows its transient absorbance properties clearly differ from those of other C84 isomers, in terms of both its spectral features (with maxima at 620 and 840 nm) and lifetime (ca. 45.6 μs). Singlet-oxygen quenching experiments demonstrate that the T1 energy of D2d(I) lies below 7880 cm-1. Finally, the ground-state absorptivity of the D2d(I) isomer has been characterized via quenching experiments with palladium octaethylporphyrin, showing an ε = 21,400 M-1 cm-1 at a local maximum of 590 nm.
2D Water-Coupled Metallic MoS2 with Nanochannels for Ultrafast Supercapacitor
Authors: Zhu Hongli , Geng Xiumei
Published: February 2020

MoS2 is a promising electrode material for energy storage. However, the metallic, intrinsic multilayer, and pure MoS2 (M-MoS2) has not been investigated for use in supercapacitors. Here, an ultrafast rate supercapacitor with extraordinary capacitance using a multilayer M-MoS2-H2O system is first investigated. Intrinsic M-MoS2 with a monolayer of water molecules covering both sides of nanosheets is obtained through a hydrothermal method with water as solvent. The super conductivity of the as-prepared pure M-MoS2 is beneficial to electron transport for high power supercapacitor. Meanwhile, nanochannels between the layers of M-MoS2-H2O with a distance of ~1.18 nm are favorable for increasing the specific space for ion diffusion and enlarging the surface area for ion adsorption. By virtue of this, M-MoS2-H2O reaches a high capacitance of 380 F/g at a scan rate of 5 mV/s and still maintains 105 F/g at scan rate of 10 V/s. Furthermore, the specific capacitance of the symmetric supercapacitor based on M-MoS2-H2O electrodes retain a value as high as 249 F/g under 50 mV/s. These findings suggest that multilayered M-MoS2-H2O system with ion accessible large nanochannels and efficient charge transport provide an efficient energy storage strategy for ultrafast supercapacitors.
Novel Lead-Graphene Positive Grids for a Motive Power Lead-Acid Battery
Authors: Dai Guiping
Published: February 2020

As a result of scientific and technological innovation over past decades, the number of graphene-based products is growing rapidly throughout the world. Lead-acid is the most widely employed rechargeable system with a 65% share of the market. Although the battery was invented over 150 years, research continues to enhance its performance in terms of rate capability, stability, cycle life and durability [1]. The use of graphene is envisaged to offer further benefits given that it has high intrinsic electrical conductivity and also is extremely lightweight, chemical inert and flexible with a large surface area. The presence of graphene in the electrodes improves the electrical conductivity between the particles of the active mass through preventing thickening and the growth of large lead sulfate particles [2]. This feature is attributed to the formation of a stable and conductive matrix that enables homogeneous delivery and distribution of current to all parts of the active material. By enabling a uniform current distribution, and subsequently well distributed electrochemical redox reactions throughout the electrode matrix, arrested the formation of too large lead sulfate particles. The addition of graphene is also considered to increase both the mechanical stability and electrical integrity of the electrodes and to induce uniform changes in the active mass during charge-discharge cycling. This presentation discusses the commercial application of novel lead-graphene positive grids in a motive power lead-acid battery designed for e-bike duty. The composite grids have been produced by Chaowei Power Ltd. And to date have been used successfully in over 30 million e-bike batteries. Graphene-lead composites have higher hardness, shorter ageing time and greater corrosion resistance compared with lead-calcium alloys presently employed in lead-acid batteries and thereby show promise for a new-generation of positive grids.

References

[1] Detchko Pavlov, Lead-acid batteries: science and technology (Book), Elsevier 2011.

[2] Mo Shi, Guiping Dai, et al., Synthesis of Graphene and application in lead-acid battery, Chinese LABAT Man, 2015; 52(3): 142-145.
Electrochemical Regeneration of Reduced Graphene Oxide - Metal Oxide Composite Adsorbents
Authors: Roberts E.P.L. , Sharif Farbod
Published: February 2020

Reduced graphene oxide (RGO) has been demonstrated to be an excellent adsorbent for many aqueous contaminants, including dissolved organics1. A challenge for practical application remains the disposal of the loaded adsorbent, with regeneration the most desirable outcome. Anodic electrochemical regeneration has successfully been applied for graphite flake adsorbent for organic contaminants2, however oxidation of the graphite has been observed3. In this study, anodic electrochemical regeneration of RGO and RGO metal oxide composites has been evaluated. Rapid corrosion of RGO was found occur during electrochemical regeneration, so that the reuse of the RGO was not possible after only a few cycles. The addition of metal oxide nanoparticles of metal oxides to the RGO surface was found to lead to more efficient oxidation adsorbed contaminants and almost no corrosion of the RGO was detected.

References

Hongmei Sun, Linyuan Cao, Lehui Lu (2011) Nano Research
4, pp 550-562.

SN Hussain, EPL Roberts, HMA Asghar, AK Campen, NW Brown (2013) Electrochimica Acta
92, pp 20-30.

K Nkrumah-Amoako, EPL Roberts, NW Brown, SM Holmes (2014) Electrochimica Acta
135, pp 568-577.
(Invited) Processing and Applications of Monodisperse Two-Dimensional Nanomaterial Inks
Authors: Hersam Mark C.
Published: February 2020

Two-dimensional nanomaterials have emerged as promising candidates for next-generation electronics and optoelectronics [1], but advances in scalable nanomanufacturing are required to exploit this potential in real-world technology. This talk will explore methods for improving the uniformity of solution-processed two-dimensional nanomaterials with an eye toward realizing dispersions and inks that can be deposited into large-area thin-films [2]. In particular, density gradient ultracentrifugation allows the solution-based isolation of graphene [3], boron nitride [4], montmorillonite [5], and transition metal dichalcogenides (e.g., MoS2, WS2, ReS2, MoSe2, WSe2) [6,7] with homogeneous thickness down to the atomically thin limit. Similarly, two-dimensional black phosphorus is isolated in organic solvents [8] or deoxygenated aqueous surfactant solutions [9] with the resulting phosphorene nanosheets showing field-effect transistor mobilities and on/off ratios that are comparable to micromechanically exfoliated flakes. By adding cellulosic polymer stabilizers to these dispersions, the rheological properties can be tuned by orders of magnitude, thereby enabling two-dimensional nanomaterial inks that are compatible with a range of additive manufacturing methods including inkjet [10], gravure [11], screen [12], and 3D printing [13]. The resulting printed two-dimensional nanomaterial structures show promise in several applications including photodiodes [14], anti-ambipolar transistors [15], gate-tunable memristors [16], and heterojunction photovoltaics [17,18].

[1] D. Jariwala, et al., ACS Nano, 8, 1102 (2014).

[2] E. B. Secor, et al., Journal of Physical Chemistry Letters, 6, 620 (2015).

[3] A. A. Green, et al., Nano Letters, 9, 4031 (2009).

[4] J. Zhu, et al., Nano Letters, 15, 7029 (2015).

[5] J. Zhu, et al., Advanced Materials, 28, 63 (2016).

[6] J. Kang, et al., Nature Communications, 5, 5478 (2014).

[7] J. Kang, et al., Nano Letters, 16, 7216 (2016).

[8] J. Kang, et al., ACS Nano, 9, 3596 (2015).

[9] J. Kang, et al., Proc. Nat. Acad. Sci. USA, 113, 11688 (2016).

[10] E. B. Secor, et al., Journal of Physical Chemistry Letters, 4, 1347 (2013).

[11] E. B. Secor, et al., Advanced Materials, 26, 4533 (2014).

[12] W. J. Hyun, et al., Advanced Materials, 27, 109 (2015).

[13] A. E. Jakus, et al., ACS Nano, 9, 4636 (2015).

[14] D. Jariwala, et al., Proc. Nat. Acad. Sci. USA, 110, 18076 (2013).

[15] D. Jariwala, et al., Nano Letters, 15, 416 (2015).

[16] V. K. Sangwan, et al., Nature Nanotechnology, 10, 403 (2015).

[17] D. Jariwala, et al., Nano Letters, 16, 497 (2016).

[18] T. A. Shastry, et al., ACS Nano, 10, 10573 (2016).
Ionic Solutions of Two-Dimensional Materials
Authors: Cullen Patrick Linden , Cox Kathleen M , Bin Subhan Mohammed K , Picco Loren , Payton Oliver D , Buckley David J , Miller Tom , Hodge Stephen A , Skipper Neal T , Tileli Vasiliki , Howard Christopher A
Published: February 2020

Typical methods for forming liquid dispersions of nanoparticles rely on physical forces being applied to a system in which the reaggrigation is minimised through surface modification. Here we present a scalable method for synthesising undamaged two-dimensional nanosheets in solution. This is done by first intercalating a layered material with alkali metals to form layered material salts, that when simply added to polar solvent, form ionic solutions. The nanosheets made in this gentle manner maintain the morphology of the starting material, are stable against reaggregation and can create liquids containing exclusively monolayers. Electroplating allows for the removal of the charge from the anionic nanosheets and allows for controlled deposition upon the electrode. This method allows for the scalable production and controllable manipulation of 2d nanosheets.
Nanowire Templated Growth of Three-Dimensional Fuzzy Graphene
Authors: Cohen-Karni Tzahi , Garg Raghav , Rastogi Sahil , Nuhfer Thomas
Published: February 2020

Graphene, a two-dimensional (2D) hexagonal arrangement of sp2
carbon, is gaining popularity as a material for electrochemical sensors. Graphene outstanding electrical properties has led researchers to develop three-dimensional (3D) atomic layer graphene materials with increased surface area as more efficient electrodes. Although 3D graphene materials such as foams and multilayered carbon nanowalls have already been synthesized, synthesis of 3D vertical atomic layer graphene still remains a challenge.

Here we demonstrate a novel synthesis of high density single to few layer vertical graphene on semiconductor nanowire mesh templates. The presence of graphene on the nanowires was confirmed by Raman spectroscopy. The progression of the templated growth of the 3D graphene flakes was verified by using scanning electron microscopy. Moreover, the growth of single to few layer crystalline graphene flakes that are vertically orientated with respect to the nanowire axis was validated by transmission electron microscopy. The sheet resistance of the new hybrid nanomaterial decreased with an increase in graphene flake size and density. Lastly, high electrochemically active surface area of the material was ascertained by cyclic voltammetry. These results pave way for the use of 3D vertical atomic layer graphene on nanowire mesh templates as electrodes for electrochemical sensing of biomolecules, quantification of fast-electron transfer reactions, and energy harvesting in fuel cells.
Excitonic Properties and Ultrafast Carrier Dynamics in 2D Hybrid Organic-Perovskites
Authors: Abdelbaki Katia , Diab Hiba , Lédée Ferdinand , Garrot Damien , Deleporte Emmanuelle , Lauret Jean-Sébastien
Published: February 2020

Due to their high potentiality for photovoltaic applications or coherent light sources, a renewed interest in hybrid organic perovskites (HOPs) has emerged since 2012. HOPs can be arranged in such a way that carriers are free to move at 3D or at 2D. At 3D, the exciton binding energy has been shown to be of the order of tenth of meV. When they are arranged in two dimensions, these materials can be considered as hybrid multi-quantum wells [1], that lead to strong light-matter coupling regime when they are embedded in an optical microcavity [2-9]. Moreover, both quantum and dielectric confinement lead to a huge exciton binding energy of several hundreds of meV [1].

In this talk, we will focus on the excitonic properties of 2D HOP. In particular, we will report on ultrafast pump-probe experiments performed on (C6H5C2H4NH3)2PbI4 thin layers at room temperature [10]. The exciton dynamics is fitted with a bi-exponential decay with a free exciton life-time of ∼100 ps. The presence of a long tail in the pump/probe signal is attributed to trapped excitons on dark states, while an ultrafast intraband relaxation (tintra ≤ 150 fs) is reported. The analysis of the transient broadening and loss of oscillator strength demonstrates that 2D-HOPs share common behaviours with standard semiconductors quantum wells despite their huge exciton binding energy that is closer to the one reported for organic semiconductors.

References:

[1]K. Gauthron, JS Lauret, L. Doyennette, G. Lanty, A. Al Choueiry, S. J. Zhang, A. Brehier, L. Largeau, O. Mauguin, J. Bloch, and E. Deleporte, O Optic Express 18, 5912 (2010)

[2] A. Brehier, R. Parashkov, J.-S. Lauret and E. Deleporte, Appl. Phys. Lett. 89, 171110 (2006)

[3] G. Lanty, A. Bréhier, R. Parashkov, J. S. Lauret and E Deleporte New Journal of Physics 10, 065007 (2008)

[4] G. Lanty, J. S. Lauret, E. Deleporte, S. Bouchoule, and X. Lafosse Appl. Phys. Lett. 93, 081101 (2008)

[5] G. Lanty, S. Zhang, J. S. Lauret, E. Deleporte, P. Audebert, S. Bouchoule, X. Lafosse, J. Zuniga-Perez,

[6] F. Semond D. Lagarde, F. Médard, and J. Leymarie Phys. Rev. B 84, 195449 (2011)

[7] Zheng Han, Hai-Son Nguyen, Fabien Boitier, Yi Wei, Katia Abdel-Baki, Jean-Sébastien Lauret, Jacqueline Bloch, Sophie Bouchoule and Emmanuelle Deleporte, Optic Letters 37, 5061 (2012)

[8] Z. Han, HS Nguyen, F. Réveret, K. Abdel-Baki, J.S. Lauret, J. Bloch, S. Bouchoule, and E. Deleporte Appl. Phys. Express 6, 106701(2013)

[9] H. S. Nguyen, Z. Han, K. Abdel-Baki, X. Lafosse, A. Amo, J-S. Lauret, E. Deleporte, S. Bouchoule, and J. Bloch, Appl. Phys. Lett. 104, 081103 (2014)

[10] K. Abdel-Baki, F. Boitier, G. Lanty, K. Djemli, L. Galmiche, P. Audebert, E. Deleporte and J.S. Lauret

Journal of Applied Physics 119, 064301 (2016)
Effects of Regioisomers in Fullerene Derivatives on Photovoltaic Properties of Bulk Heterojunction Solar Cells
Authors: Imahori Hiroshi
Published: February 2020

During the last decade, bulk heterojunction (BHJ) polymer solar cells (PSCs) revealed rapid progress and achieved a power conversion efficiency (PCE) of 6-10%, owing to the development of new high-performance low-bandgap polymers as electron donors. Meanwhile, although new electron-accepting materials for PSC devices habe been explored, [70]fullerene derivatives are still prevalent as electron acceptors. An important aspect of [70]fullerene derivatives, which is always neglected in PSC applications, is that as-prepared [70]fullerene mono-adducts consist of a mixture of regioisomers due to the lower symmetry of rugby-ball shaped C70 over spherical C60. As contrasted with C60, C70 has four distinct types of [6,6]-bonds (a-, b-, e-, and k-type bonds), and thereby [70]fullerene derivatives including a prevalent, high-performance [6,6]-phenyl-C71-butyric acid methyl ester ([70]PCBM) have been employed as a regioisomer mixture in BHJ PSC devices. Considering that the miscibility with conjugated polymers and the molecular arrangement of [70]fullerene derivatives in the active layer have a large impact on charge separation and charge-transporting properties, pristine isomers of [70]fullerene derivatives rather than the isomer mixtures would yield a more desirable donor-acceptor network toward highly efficient BHJ PSCs. Indeed, the regioisomer separations of fullerene bis-adducts have been demonstrated to exhibit positive effects on BHJPSCs. In this study, the regioisomers of [70]fullerene mono-adducts have been separated for the first time to evaluate the pure isomer effect on the photovoltaic properties. To assess the substitution position effect on C70 accurately, first we designed new dihydronaphthyl-substituted [70]fullerenes with two butoxycarbonyl groups ([70]NCMA) as a simplified system. The symmetrical dihydronaphthyl group was selected as the substituent to eliminate the plausible isomers such as enantiomers and diastereomers. Then, we have further extended this strategy to separate the regioisomers of a prevalent, high-performance [70]fullerene mono-adduct acceptor, [70]PCBM, for the first time.

[1] S. Kitaura, K. Kurotobi, M. Sato, Y. Takano, T. Umeyama, and H. Imahori, Chem. Commun., 48, 8550-8552 (2012).

[2] R. Tao, T. Umeyama, K. Kurotobi, and H. Imahori, ACS Appl. Mater. Interface, 6, 17313-17322 (2014).

[3] R. Tao, T. Umeyama, T. Higashino, T. Koganezawa, and H. Imahori, Chem. Commun., 51, 8199-8388 (2015).

[4] R. Tao, T. Umeyama, T. Higashino, T. Koganezawa and H. Imahori, ACS Appl. Mater. Interfaces, 7, 16676-16685 (2015).

[5] T. Umeyama, T. Miyata, A. C. Jakowetz, S. Shibata, K. Kurotobi, T. Higashino, T. Koganezawa, M. Tsujimoto,
,
S. Gélinas, W. Matsuda, S. Seki, R. H. Friend, and H. Imahori, Chem. Sci., in press.
(Invited) An Investigation into the Local Optical and Electrical Response of Hybrid Perovskites for Solar Cell Applications
Authors: Draguta Sergiu , Kuno Masaru
Published: February 2020

Hybrid perovskite (MAPbI3, MA=CH3NH3) based solar cells have attracted great interest recently due their fast growing power conversion efficiencies. Over the last 5 years solar conversion efficiencies have risen from 3.8 to 22 %. To further increase these power conversion efficiencies, a better understanding of underlying charge recombination mechanisms in hybrid perovskite thin films is needed. The solution-based fabrication of hybrid perovskite-based solar cells additionally means that there can be significant spatial heterogeneities in the dominant charge recombination mechanism across films. This can translate into spatially-varying photovoltaic performance. To address these issues, we have therefore conducted spatially-resolved measurements of carrier recombination in MAPbI3 thin films. This has led to the observation of large variations in local carrier trap densities. These variations, in turn, directly impact local photoluminescence quantum yields as well as photovoltaic performance. We have also conducted work to better understand the optical response of mixed halide perovskite thin films, which undergo phase separation upon illumination.
Improved Performance and Stability of Inverted Planar Perovskite Solar Cells Using New Fullerene Layers
Authors: Castro Edison , Zavala Gerardo , Fernandez Olivia , Echegoyen Luis
Published: February 2020

The unique properties of organic-inorganic hybrid perovskite materials make them promising candidates for developing next-generation photovoltaic cells for commercial applications to compete with silicon solar cells. Inverted planar structure perovskite solar cells (PSCs), due to their low temperature precessing and lack of hysteretic problems, are attracting increased attention by researchers around the world. Fullerene derivatives are the most widely used electron transporting materials (ETMs) in inverted planar perovskite solar cells, especially [6,6]-phenyl-C61-butyric acid methylester (PC61BM), which exhibits very good performance. However, the influence of adducts on fullerene-based PSCs performance has not been fully explored to date. Here, new C60 and C70 fullerene derivatives were synthesized in high yields via Bingel reactions at room temperature and incorporated into CH3NH3PbI3 perovskite solar cells as electron transporting materials.

Figure 1. Synthesis of C60 and C70 fullerene derivatives via Bingel reaction.

Figure 1
(Invited) Sensitizing Charge Carrier Generation in a Conjugated Polymer Using a C70-Encapsulated Covalent Organic Polyhedron
Authors: Rumbles Garry
Published: February 2020

This presentation will report on the photophysics of a covalent organic polyhedron molecule (COP-5) that contains two porphyrin molecules in the cage structure and with an encapsulated C70 molecule bound in its core. The photo-induced electron transfer processes in this structure create anomalously long-lived charge-transfer states that also respond in an unconventional fashion to the dielectric constant of the solvent. Preliminary results on using this complex to sensitize the production of long-lived charge carriers in a conjugated polymer will also be reported, where the carrier yields and kinetics are tracked using time-resolved microwave conductivity.

The purpose of this work is to gain a better understanding of the nature of charge transfer (CT) and charge-separated (CS) states in the production of carriers in conjugated polymers blended with fullerenes.
(Invited) Synthesis, Structures, and Properties of Stacked Antiaromatic Porphyrins
Authors: Shinokubo Hiroshi
Published: February 2020

The stacking of antiaromatic compounds has not been well investigated. Theoretical calculations have proposed that staking of two antiaromatic systems lead to three-dimensional aromaticity, which results from mutual interactions between frontier orbitals of each π-system. However, there has been no experimental support for this interesting prediction.

Norcorrole is a ring-contracted porphyrin, which shows distinct antiaromatic character. We have discovered that diphenylnorcorrole Ni(II) adopts a triple-decker π–π stacked structure in the solid state. A significant reduction of antiaromaticity of the norcorrole skeleton was observed.

Figure 1
(Invited) Influence of Nano-Structuring of Substrate Materials on Local Structure of Ionic Liquid
Authors: Imanishi Akihito
Published: February 2020

Ionic liquids (ILs) have attracted much attention as promising electrolytes for electrochemical devices due to their wide electrochemical window (stability) and negligible vaporization. For such applications, nanostructured electrodes have advantage on their large surface area leading to accumulation of large density energy at the interface. However, recent reports on IL/electrode interfaces revealed that quite strange structures can be formed and it is not clear how the interface forms and how it changes by forming the characteristic local structure. In this study, we investigated the local structure and physicochemical properties of the interfacial properties of nanostructured materials using XPS and electrochemical impedance spectroscopy (EIS).

Polystyrene beads were self-assembled in a close packed form on a gold substrate by dipping in polystyrene beads solution and rapid drying. Au electrodeposition on thus prepared surface followed by removal of the beads resulted in the fabrication of a nanostructured Au electrode with periodic 100 nm-sized Au dimples. Electrochemical behavior of a ferrocene dissolved ionic liquid (1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl) amide (BMI-TFSA)) at the nanostructured Au electrode was investigated by EIS. It is obvious that the capacitance of the nanostructured electrode was smaller than that of the flat electrode in the whole potential range. This result suggests that the thickness of the electric double layer formed in the nano-sized dimple is thicker than that formed on the flat surface. The dimple size dependence on the capacitance will also be discussed.

On the other hand, it is an interesting subject to study how ILs and solutes behave in the nano-micro sized pore. We investigated the properties of IL(BMI-TFSA) and solute ions (Au3+, Ag+, Mg2+ etc.) confined in the porous silica whose diameter was 1.8 nm using XPS, IR and TEM. It was revealed that the molar ratio of all the ions existing in the pore is largely different from that in the bulk. Interestingly, the molar ratio of Au3+ to BMI+ (or TFSA-) was very large comparing with that of as prepared BMI-TFSA solution. The result of N-1s XPS spectra revealed that cation and anion of IL were organized in the nanopores. Such characteristic local structure in nanospace may affect the catalytic reaction in the pore.
(Invited) Pseudomorphic Transformation of Nanocrystals By Element Replacement
Authors: Teranishi Toshiharu
Published: February 2020

Chemical conversion of inorganic nanocrystals (NCs) via element replacement reactions, such as ion exchange reactions and galvanic replacement reactions, can overcome the difficulties associated with controlling the size, shape, chemical composition and crystal structure in conventional syntheses. The retained shape of the parent-NCs in element replacement reactions provides an opportunity to obtain non-equilibrium unique structures and even new structures of inorganic NCs, these final structures being known as “pseudomorphs” [1-4]. Here I present the nano-pseudomorphic chemistry to give unique semiconductor [5] and metallic NCs [6].

[1] Saruyama, M.; So, Y.-G.; Kimoto, K.; Taguchi, S.; Kanemitsu, Y.; Teranishi, T. J. Am. Chem. Soc.
2011, 133, 17598.

[2] Kanehara, M.; Arakawa, H.; Honda, T.; Saruyama, M.; Teranishi, T. Chem. Eur. J.
2012, 18, 9230.

[3] Teranishi, T.; Samamoto, M. J. Phys. Chem. Lett.
2013, 4, 2867. (Perspective)

[4] Sakamoto, M.; Inoue, K.; Saruymama, M.; So, Y.-G.; Kimoto, K.; Okano, M.; Kanemitsu, Y.’ Teranishi, T. Chem. Sci.
2014, 5, 3881.

[5] Wu, H.-L.; Sato, R.; Yamaguchi, A.; Kimura, M.; Haruta, M.; Kurata, H.; Teranishi, T. Science
2016, 351, 1306.

[6] Sato, R.; Haruta, M.; Kurata, H.; Teranishi, T. to be submitted.
Earth Abundant Metal Corroles As Catalysts for Energy Relevant Processes
Authors: Gross Zeev , Mahammed Atif
Published: February 2020

We have recently introduced corrole metal complexes (metallocorroles) as catalysts for various energy-relevant reactions. This includes those that are of prime importance for water splitting into its elements, the hydrogen and oxygen evolution reactions, and also the oxygen reduction reaction for fuel cells. A careful choice of substituents on the corrole ligand and the kind of metal ion (all earth abundant) chelated by them allows for lowering of the electrocatalytic overpotential, increasing reactivity, and controlling selectivity.

An arsenal of electrochemical and spectroscopic methodologies, which in the case of metallocorroles is very rich, was applied for acquiring highly valuable information about the mechanisms of action such as characterization of a cobalt-dioxgen intermediate.

REFERENCES

“Cobalt Corrole Catalyst for Efficient Hydrogen Evolution Reaction from H2O under Ambient Conditions: Reactivity, Spectroscopy and DFT Calculations”, Inorg. Chem.
2013, 52, 3381-3387.

"The Cobalt Corrole Catalyzed Hydrogen Evolution Reaction: Surprising Electronic Effects and Characterization of Key Reaction Intermediates" Chem. Commun.
2014, 50, 2725-2727.

"Metallocorroles as photocatalysts for driving endergonic reactions, exemplified by bromide to bromine conversion", Angew. Chem.
2015, 54, 12370 –12373.

"Metallocorroles as Non-Precious Metal Catalysts for Oxygen Reduction", Angew. Chem.
2015
, 54, 14080 –14084.

“Metallocorroles as Non-Precious Metal Electrocatalysts for Highly Efficient Oxygen Reduction in Alkaline Media" ChemCatChem
2016, 8, 2832-2837.

“Metallocorroles as Electrocatalysts for the Oxygen Reduction Reaction (ORR)", Israel J. Chem.
2016, 56, 756– 762.

 “Dioxygen bound Cobalt Corroles”, Chem. Commun. 2017, in press.
A New Mode of Action for Porphyrins – Nonplanar Porphyrins As Organocatalysts
Authors: Senge Mathias O.
Published: February 2020

Porphyrins are nature’s cofactors par excellence. Next to oxygen transport and storage, their role in electron transport and as photosynthetic pigments, they catalyze a multitude of chemical reactions. All these catalytic functions depend on the presence of a central metal which is intricately involved in the catalytic processes. Thus, all known catalytically active porphyrins are metalloporphyrins. However, we have discovered that, upon appropriate manipulation of the porphyrin macrocycle conformation, the core nitrogen atoms in free base porphyrins can be involved in catalysis as well.

Distorted porphyrins are able to activate small molecules via general base catalysis by participation of the imine groups or via hydrogen bonding catalysis involving the pyrrole units. To make the “active center” more accessible to substrates, the degree of outwards orientation of the pyrrole groups can be fine-tuned depending on the peripheral substitution pattern using peri-interactions or core substitution. Various distortion modes exist and saddle distorted porphyrins have been shown to have an increased basicity which qualifies these tetrapyrroles for catalytic screening. Additionally, it is possible to enhance the basicity via electronic modulation of the β- and meso-substituents through the introduction of electron-withdrawing groups. An extensive screening of a number of nonplanar porphyrins and substrates, as well as reaction conditions, has been used to evaluate the catalytic properties of planar and distorted porphyrins. Notably, certain free base porphyrins have been found to function as organocatalysts in Michael addition reactions indicating a new mode of catalytic action for porphyrins which does NOT require a central metal ion.
Synthesis and Properties of 10-Heterocorroles
Authors: Shinokubo Hiroshi
Published: February 2020

The properties of porphyrinoids are substantially affected by their skeleton and structural factors. In particular, inclusion of heteroatoms into the p-conjugation circuit of porphyrinoids induces dramatic change of their electronic structures. Recently, 10-heterocorroles has regained the spotlight as promising candidates for novel building blocks of molecular materials as electronically tunable porphyrin analogues.

We have explored the synthesis and properties of meso-aryl type 10-aza-, 10-oxa-, 10-thia-, and 10-silacorroles. These 10-heterocorroles can be efficiently prepared fro bis(dipyrrin) metal complexes as precursors. Optical and electrochemical properties of these compounds are heavily dependent on the introduced heteroatoms at the meso-positions. The energy level of HOMOs and LUMOs of these molecules can be effectively manipulated by the proper choice of the heteroatoms.

Figure 1
New Porphyrinoids through Palladium-Catalyzed Couplings
Authors: Anguera Gonzalo , Kauffmann Brice , Borrell José I. , Borrós Salvador , Sánchez-García David
Published: February 2020

Concise and versatile syntheses of oligopyrrolic derivatives are crucial for the preparation of macrocycles such as porphycenes, bronzaphyrins or cyclopyrroles. However, these precursors are usually obtained via long and tedious synthetic pathways. Besides, the key reactions of these procedures (i.e., Ullmann coupling, Stetter condensation) often hamper the preparation of functionalized macrocycles. As an alternative to these reactions, palladium-catalyzed couplings have emerged as promising synthetic methodologies.

Recently, our group has developed a new family of 2,2´-bipyrroles 1 that possesses a remarkable chemical stability, ascribed to the presence of electron withdrawing groups. This stability allows the preparation of α-brominated 2,2´-bipyrrole derivatives. With these halogenated 2,2´-bipyrroles in hand and using palladium-catalyzed cross-coupling reactions, such as the Suzuki coupling, a new family of chemically stable and easy-to-functionalize quaterpyrroles have been synthesized (2). A similar strategy has been applied to halogenated pyrroles to yield terpyrroles and related analogues (3). In this presentation, the preparation of such oligomers and their use to obtain new expanded porphyrins will be discussed.

Figure 1
Pyrazinacenes and Oxoporphyrinogens
Authors: Hill Jonathan P. , Miklik David , Svec Pavel , Matsushita Yoshitaka , Labuta Jan , Ishihara Shinsuke , D'Souza Francis , Ariga Katsuhiko
Published: February 2020

Porphyrins substituted with antioxidant 2,6-di-tert-butylphenol substituents have been shown to exhibit different conformations based on the oxidation state of those substituents leading to the oxoporphyrinogens.1,2 On the other hand, pyrazinacenes are obtained by synthesis of linearly-fused 1,4-pyrazine groups giving molecules with potential as semiconductors, proton conductors or fluorescent labels. We have investigated both classes of compounds for their potential applications3,4 Here, we will describe the results of these investigations including highlighting the different compounds obtained from the porphyrin system, synthesis and structure in the phthalocyanine,5 TPA and HPB systems,6 and an extensive crystallographic analysis of the resorcinarene system.7 We will also present synthetic aspects of the pyrazinacene system including new synthesis pathways for higher derivatives.8 Finally, a molecular switch based on mechanical extension of an oxoporphyrinogen molecule will be described.9

References

(1) F. D’Souza, N. K. Subbaiyan, Y. Xie, J. P. Hill, K. Ariga, K. Ohkubo, S. Fukuzumi, J. Am. Chem. Soc. (2009) 131, 16138–16146. (2) J. P. Hill, I. J. Hewitt, C. E. Anson, A. K. Powell, A. L. McCarthy, P. Karr, M. Zandler, F. D’Souza, J. Org. Chem. (2004) 69, 5861–5869. (3) S. Ishihara, J. Labuta, T. Šikorský, J. V. Burda, N. Okamoto, H. Abe, K. Ariga, J. P. Hill, Chem. Commun. (2012) 48, 3933–3935 (4) A. Shundo, J. Labuta, J. P. Hill, S. Ishihara, K. Ariga, J. Am. Chem. Soc. (2009) 131, 9494–9495; J. Labuta, S. Ishihara, A. Shundo, S. Arai, S. Takeoka, K. Ariga, J. P. Hill, Chem. Eur. J. (2011) 17, 3558–3561. (5) J. P. Hill, N. K. Subbaiyan, F. D’Souza, Y. Xie, S. Sahu, N. M. Sanchez-Ballester, K. Ariga, Chem. Commun. (2012) 48, 3951–3953. (6) S. Jin, J. P. Hill, F. D'Souza, K. Ariga, (2016) in press. (7) D. Payne, J. P. Hill, F. D'Souza, K. Ariga, (2016) in press. (8) D. Miklik, P. Svec, J. P. Hill (2016) in press. (9) M. Perrin, J. P. Hill, D. Dulic, H. van der Zant, (2016) submitted.
Characterizing Reduction Reactions on Doped Titanium Oxides Using Intensity Modulated Photocurrent Spectroscopy
Authors: Policastro Steve A , Anderson Rachel , Hangarter Carlos
Published: February 2020

The oxide on titanium is generally considered to behave as a semiconductor with a band-gap of approximately 3.1 eV. The interface between the oxide and the electrolyte can be envisioned in the semiconductor energy level diagram in Figure 1 and semiconductor properties of the oxides, such as the band gap, the flat band potential, and the dielectric constant, can be obtained from electrochemical impedance spectroscopy and Mott-Schottky tests. However, kinetic information, especially regarding reduction reactions occurring at the oxide surface is missing from these measurements. One approach for probing the catalytic properties of the oxide is to use IMPS to excite photoelectrons and measure the resulting oxide electrochemical response.

A kinetic model of the oxide behavior in response to photo-excitation was developed following the Ponomarev-Peter approach and was used to predict charge transport in the oxide band structure. From the band diagram in Figure 1, it can be supposed that incident photons, with energy greater than the band gap, will excite electrons from the valence band into the conduction band, leaving positively charged holes behind. Once in the conduction band, some of the electrons recombine with the holesand are lost while the majority will be transported through the external circuit to the counter electrode. Only a few will be able to travel to the interface to participate in a reduction reaction. The valence band holes, on the other hand, have much lower mobility than the electrons and, those that are not extinguished due to recombination, will reach the oxide-electrolyte interface and help drive water oxidation or other available reactions. Fitting the model parameters to the measured photo-electrochemical responses of the oxides provides a way to compare the effectiveness of the oxides to catalyze reduction reactions.

Figure 1. Band energy diagram for TiO2 shows the valence and conduction bands and the band gap in the oxide, the interface with the electrolyte, and approximate density of states at the interface for selected redox reactions. The shaded regions represent occupied density of states.

Acknowledgments

This work was sponsored by the Office of Naval Research, ONR, under grant/contract number N0001415WX00948; the views and conclusions contained herein are those of the authors and should not be interpreted as necessarily representing the official policies or endorsements, either expressed or implied, of the Office of Naval Research, the U.S. Navy or the U.S. government.

Figure 1
Room-Temperature Atomic Layer Deposition of Al2O3 for Anticorrosion Coating on Metal Surfaces
Authors: Kanomata Kensaku , Ishikawa Makoto , Miura Masanori , Ahmmad Bashir , Kubota Shigeru , Hirahara Kazuhiro , Hirose Fumihiko
Published: February 2020

A room-temperature atomic layer deposition (RT-ALD) of Al2O3 as an anticorrosion coating for metal surfaces was developed using trimethylaluminum (TMA) and a plasma excited humidified argon. The schematic of ALD system is shown in Fig.1. TMA as the aluminum precursor was introduced with a mass flow controller. A remote plasma system generating excited humidified argon was installed to the ALD chamber. The source gas for the oxidizing gas is a mixture of water vapor and argon. The plasma was generated in a glass tube with an induction coil with a frequency of 13.56 MHz and a RF power of 100 W. For the Al2O3 deposition, we repeated the cycle of TMA saturation and oxidizing gas treatment at RT. The TMA exposure was set at 5.86×10-3 Torr×40 sec. The saturation of TMA on the hydroxylated surface was confirmed by the IR absorption spectroscopy. The plasma excited oxidizing gas was injected for 2 min.

As a result, we show the anticorrosion test of ALD coated metal in a HCl solution. We used SUS430 plates with a size of 20×50×0.5 mm3 as the sample. In this test, we used a not-attenuated HCl solution with a concentration of 35 %. All the samples were immersed in the HCl solution for a certain amount of minutes at room temperature and we observed its surface coloring. Fig.2 shows a picture of the tested samples. The not-treated SUS430 sample clearly exhibits a white stain by the HCl corrosion. On the other hand, the Al2O3 coated sample maintained a mirror surface, which indicates that the RT-ALD coated film works as the anti-corrosion film against the acid solution. In the conference, we discuss the applicability of the RT-ALD to the anticorrosion coating for metal components.

 

Acknowledgements

This work was partly supported by JST-CREST, JSPS KAKENHI Grant Numbers 15H03536 and 15K13299.

Figure 1
On-Line Atmospheric Corrosion Monitoring of Field-Exposed Steels Using a Electrochemical Probe
Authors: Xia Da-Hai , Song Shi-Zhe , Jin Wei-Xian , Li Jian
Published: February 2020

In this work, a new corrosion monitoring system for Q235B and T91 steels that exposed to Zhoushan offshore environment was established by using a portable EN monitoring system based on CompactRIO and atmospheric-corrosion-monitoring probes. Noise resistance was calculated and used as an indicator of corrosion resistance. A 20-day continuous monitoring result indicated that noise resistance correlated well with weight loss data. Wavelet analyses results of EN data indicated that Q235B undergone uniform corrosion and T91 suffered from localized corrosion, which was further confirmed by the surface observation.

Figure 1 EN measurement system for field test

Figure 1