bluuebunny/crossref_metadata_2025 huggingface dataset:
Singlemolecule Conductance of Porphyrin Arrays
Authors: Tamaki Takashi , Ohto Tatsuhiko , Yamada Ryo , Tada Hirokazu , Ogawa Takuji
Published: February 2020

Single molecule conductance of a series of porphyrin derivatives, whose porphyrin units are connected through a phenylene bridge that have one or two thiolate end groups, was measured by a scanning tunneling microscopic break junction technique. The observed conductance values were analyzed by partial transmission probabilities (T
i) for the molecular parts using the equation G = G
0×T1×T2×T3×... Unique combination of T
i was obtained, which indicates the validity of this analysis. Interestingly, the free-base porphyrin ring interacting with the gold electrode showed a greater transmission probability T
por-Au than that of the bridge between thiolate and the gold electrode (T
S-Au). This indicates that the porphyrin free base work as a good anchoring group to gold electrode.

Figure 1
Porphyrins As Photoredox Catalysts in Efficient C-C Bond Formation
Authors: Rybicka-Jasińska Katarzyna , Gryko Dorota
Published: February 2020

Porphyrins are natural functional dyes which are utilized by Nature as prosthetic groups of various enzymes not per se because of their coordination characteristic, but due to the combination of other properties with absorption of light (which translates to color) being the most important.

Efficient C−C bond formation in a green, nontoxic, and inexpensive way has always been a challenge and development of light-induced methodologies is one of the means to achieve such a goal.1 Photoredox catalysis is based on a photoinduced electron transfer process (PET) between a substrate and a photoredox catalyst, commonly Ru- or Ir-complexes.2 Though organic dyes have been well-known for their ability to participate in photoinduced electron transfer processes, their use as catalysts in such reactions has been less explored as the replacement of Ir- and Ru-complexes with known organic dyes is not always possible.3 We wondered whether simple porphyrins could be used as photocatalysts.

Herein, we demonstrate a successful application of these compounds as efficient photoredox catalysts for C-C bond forming reactions involving the reductive or oxidative quenching. Employing dual catalytic system – photocatalysis merged with enamine-iminium catalysis alkylation of aldehydes at the a position was accomplished (Scheme 1a).4

We have also found that porphyrins with tuned physicochemical properties, via tailoring various substituents at the periphery of the macrocycle, are also effective in catalyzing light-induced direct arylation of heteroarenes and cumarins with diazonium salts (Scheme 1b).5 The reaction afforded arylated products in good yields and tolerates a wide range of functional groups.

Scheme 1. a) Alkylation of aldehydes at the a-position b) Arylation of heteroarenes

References:

a) M. Fintecave, Angew. Chem. Int. Ed. 2015, 54, 6946. b) Bucker, J. W.; Stephenson, C. R. J. J. Org. Chem. 2012, 77, 1617. C) Skubi, K. L.; Blum, T. R.; Yoon, T. P. Chem. Rev. 2016, 116,10035.

Prier, C. K.; Rankic, D. A.; MacMillan, D. W. C.Chem. Rev. 2013, 113, 5322.

Nicewicz, D. A.; Nguyen, T. M. ACS Catal. 2014, 4, 355.

K. Rybicka-Jasińska, W. Shan, K. Zawada, K. M. Kadish, D. Gryko J. Am. Chem. Soc. 2016, 138, 15451-15458.

K. Rybicka-Jasińska, B. Konig, D. Gryko, Eur. J. Org. Chem. - submitted

Figure 1
Porphyrinoids for Molecular Photovoltaics
Authors: Torres Tomas , Carrascosa Hector , Lavarda Giulia , Medina Diana Paola , Ince Mine , Trukhina Olga , Fernández-Ariza Javier , Garcia-Iglesias Miguel , Zango German , Urbani Maxence , Rodriguez-Morgade M. Salome , Martínez-Díaz M. Victoria
Published: February 2020

In this contribution, hexachlorosubphthalocyanines SubPcCl6-X bearing different axial substituents (X) have been synthesized and used as novel electron acceptors in bulk-heterojunction organic solar cells. Solar cells with subphthalocyanines as the electron acceptors and PTB7-Th as the electron donor exhibit a power conversion efficiency up to 4% and an external quantum efficiency approaching 60% benefitting from significant photocurrent contribution from both electron donor and acceptor. These results indicate a promising prospect of developing non-fullerene acceptors based on subphthalocyanines and structurally related systems for highly efficient solution processed organic solar cells [1]. On the other hand, an unsymmetrical, push–pull porphyrazine derivative bearing an isoindole-4-carboxylic acid moiety (TT112) have been synthesized and incorporated in a dye-sensitized solar cell (DSSC). The device, which constitutes the first example of a porphyrazine-sensitized solar cell, exhibits a maximum power conversion efficiency of 3.4% [2].

Finally, easily accessible tetra-5-hexylthiophene-, tetra-5-hexyl-2,2’-bisthiophene-substituted zinc phthalocyanines (ZnPcs) have been employed as hole transporting materials (HTMs) in mixed-ion perovskite [HC(NH2)2]0.85(CH3NH3)0.15Pb(I0.85Br0.15)3
solar cells reaching the highest power conversion efficiency (PCE) reported so far for phthalocyanines. The resulting photovoltaic performance was strongly influenced by both, individual optoelectronic properties of ZnPcs and the aggregation of these tetrapyrrolic semiconductors in the HTM layer. The optimized devices exhibited a record PCE of 17.5% for tetra-5-hexylthiophene-based analogue under standard global AM 1.5 illumination. These results boost up the potential large-scale applications of solution-processed ZnPc derivatives as stable and economic hole-transport materials, opening new frontiers towards a realistic, efficient and inexpensive energy production [3].

[1] C. Duan, G. Zango, M. García Iglesias, F. J. M. Colberts, M. M. Wienk, M. V. Martínez-Díaz, R. A. J. Janssen, T. Torres, Angew. Chem. Int.. Ed. Engl.
2017, in press.

[2] J. Fernández-Ariza, M. Urbani, M. Grätzel, M. S. Rodríguez-Morgade, M. K. Nazeeruddin, T. Torres, ChemPhotoChem
2016, DOI: 10.1002/cptc.201600004

[3] K. T. Cho, O. Trukhina, C. Roldán-Carmona, M. Ince, P. Gratia, G. Grancini, P. Gao, T. Marszalek, W. Pisula, P. Y. Reddy, T. Torres, M. K. Nazeeruddin, Adv. Energ. Mat.
2016, in press
Highly Efficient ( >8%) Porphyrin-Based Bulk Heterojunction Organic Photovoltaics
Authors: Cuesta Virginia , Vartanian Maida , Arrechea Susana , de la Cruz Pilar , Singhal Rahul , Sharma Ganesh , Langa Fernando
Published: February 2020

Solution-processed organic solar cells (OSC) are a topic of current scientific interest as a complementary photovoltaic technology to current silicon solar cells owing to their solution processability, potential low cost of fabrication, light weight and high transparency. Now, the power conversion efficiency (PCE) of solution-processed organic solar cells based on a single BHJ active layer using a low-band-gap small molecule has exceeded 10%, which is comparable to those of polymer counterparts.

Porphyrins, which are synthetic analogues of natural chlorophylls, are of special interest, because they are known to be a natural choice as light-harvesting antenna systems that are involved in energy and electron transfer processes. In recent years, there has been a great focus of interest on the field of solution-processed BHJ organic solar cells using porphyrin derivatives as donors, which resulted in PCEs up to 9.06 %. [1]

Here, we will present the synthesis, optical, electrochemical and photovoltaic properties of new porphyrin A-D-A and D-A-D derivatives used as donor, in BHJ solar cells, with PC71BM as acceptor reaching excellent efficiencies, higher than 8%.

References

[1] K. Gao, J. Miao, L. Xiao, W. Deng, Y. Kan, T. Liang, C. Wang, F. Huang, J. Peng, Y. Cao, F. Liu, T. P. Russell, H. Wu, X. Peng. Adv. Mater. 2016, 28, 4727.

[2] G. Morán, S. Arrechea, P.de la Cruz, V. Cuesta, S. Biswas, E. Palomares, G. D. Sharma and F. Langa, J. Mater. Chem. A,
2016, 4, 11009.

[3] S. Arrechea, A. Aljarilla, P. de la Cruz, E. Palomares G. D. Sharma, F. Langa. Nanoscale2016, 8 , 17953.

[4] V. Cuesta, M. Vartanian, P. de la Cruz, R. Singhal, G. D. Sharma and F. Langa, J. Mater. Chem. A,
2017 (in press) DOI: 10.1039/C6TA09408B.

Figure 1
A Bio-Inspired Approach Towards NIR Emissive Ytterbium(III) Complexes
Authors: Ning Yingying , Zhang Jun-Long
Published: February 2020

Design of near infrared (NIR) emissive lanthanides such as ytterbium (Yb), erbium (Er) and neodymium (Nd) attracts considerable attentions for the potential applications in telecommunications, optical materials and biological imaging. Exploring an appropriate antenna ligand with the lowest triplet excited state (T1) to efficiently sensitize Ln emission plays a central role to overcome the forbidden f-f transition. To address this issue, natural light harvesting system sets a golden standard for harnessing sunlight power and energy transfer process with molecular precision. A prominent example is given by chlorophylls b, d, f widespread in land plants and cyanobacteria and algae of ocean, respectively, with gradually red shifted Q bands mainly differing from β-formyl substituent orientation. In contrast to modeling studies on deciphering how chlorophylls confer light harvesting function, much less has been reported regarding the application of such insights in designing luminescence materials.1-4 In this work, we reported the significant effect, arising from subtle structural changes, on tuning energy transfer process from the triplet state (T1) of ligand to Yb(III). Minor β-substituent orientation change in Yb cis/trans-porphodilactones (Yb-1 and Yb-2) significantly influences their NIR emissive properties that Yb-1 presented significant enhanced NIR luminescence and high thermo-sensitivity compared to Yb-2 (> 10 times). Combining with spectroscopy studies, we found strong back energy transfer process in Yb-1 but ineffective T1 → Ln* energy transfer in Yb-2. The strategy learning from nature should open a new method for designing NIR functional lanthanide complexes.

1. X.-S. Ke, Y. Chang, J.-Z. Chen, J. Tian, J. Mack, X. Cheng, Z. Shen* and J.-L. Zhang*, J. Am. Chem. Soc., 2014, 136, 9598-9607;

2. X.-S. Ke, H. Zhao, X. Zou, Y. Ning, X. Cheng, H. Su*, and J.-L. Zhang* ,J. Am. Chem. Soc., 2015, 137, 10745-10752;

3. X.-S. Ke, B.-Y. Yang, X. Cheng, S. L.-F. Chan, and J.-L. Zhang, Chem. Eur. J., 2014, 20, 4324-4333;

4. X. S. Ke, J. Tang, J. J. Chen, Z. Y. Zhou, J.-L. Zhang*, ChemPlusChem, 2015, 80, 25, 237-252;

Figure 1
Supramolecular Assemblies of a Water-Soluble Diprotonated Porphyrin and Heteropolyoxometalates
Authors: Kojima Takahiko
Published: February 2020

Photocatalytic oxidation of organic substrates has been of great interest in terms of utilization of photon energy to produce useful materials from abundant feedstock. As a photocatalyst that can mediate electron transfer (ET) from an oxidation catalyst to an oxidant upon photoexcitation, porphyrins can be useful in light of the strong visible-light absorption and clear redox behavior. Although porphyrins have been used as photocatalysts for reduction of organic substrates, photocatalytic oxidation of organic substrates has been seldom reported by using porphyrins as photocatalysts.

So far, we have established the utility of diprotonated porphyrins as electron acceptors in photoinduced ET.1 On the basis of the concept, we prepared a water-soluble and saddle-distorted porphyrin, which can act as an electron acceptor in photoinduced ET upon diprotonation. The porphyrin (H2P4+) possesses four N-methylpyridinium-4-yl substituents at the para positions of the four meso-phenyl groups of dodecaphenylporphyrin. We observed proton-coupled electron transfer processes of the diprotonated form of H2P4+, H4P6+, in water to establish the Pourbaix diagram of H4P6+. We also determined the pKa value of the first protonation/deprotonation equilibrium to form the monoprotonated H3P5+ (pKa1 = 4.04) and that of the second one to afford H2P4+ (pKa2 = 7.83).

The highly positively charged H4P6+ was revealed to form supramolecular assemblies with negatively charged heteropolyoxometalates (POMs) in the ratio of H4P6+ : POM = 1 : 2 in water at pH 3 as indicated by Job's plots. Based on the redox properties of H4P4+ and the formation of supramolecular assemblies, we examined intra-supramolecular photoinduced ET from heteropolyoxometalates as electron donors to H4P6+ as an electron acceptor in water at pH 3 using femto-second laser flash photolysis upon photoexcitation at 393 nm. First-order rate constants of ET were analyzed on the basis of the Marcus theory of ET to determine the reorganization energy of ET to be 0.74 eV and the electronic coupling matrix element (V) to be 43 cm-1.

We also examined its application to photocatalytic oxidation of organic substrates in water, using H4P6+ as a photocatalyst, Na2S2O6 as an oxidant, and a Ru-substituted POM (RuPOM) as an oxidation catalyst, under the visible light irradiation. Preliminary results on the photocatalytic oxidation of benzyl alcohol were 560 turnovers for 4h; blank tests clearly suggest that H4P6+, RuPOM, the oxidant, and photoirradiation are all required to perform the photocatalytic reaction.

References

1. S. Fukuzumi, T. Honda, T. Kojima, Coord. Chem. Rev. 2012, 256, 2488-2508.
Supramolecular Chirogenesis in Bis- and Multi-Porphyrin Systems: Recent Developments and Further Perspectives
Authors: Borovkov Victor
Published: February 2020

Supramolecular chirogenesis is a fundamentally novel interdisciplinary field of research being a smart combination of supramolecular/nano chemistry and chiral science. Supramolecular chirogenesis deals with the phenomenon of “symmetry breaking” in achiral multi- or unimolecular host systems by chiral guests (and vice versa), and is achieved by the rational application of specific non-covalent interactions via a chirality information transfer mechanism.

Recently, we have discovered a novel and very efficient supramolecular chirogenic system based upon an achiral ethane-bridged bis(metallo- or free base octaethylporphyrin).1-6 Upon interaction with the corresponding chiral guests, there are ligand induced structural deformations in the achiral host, resulting in a asymmetric orientation of the two porphyrin units and subsequent pronounced and easily detectable spectral changes monitored by various spectroscopies. Particularly, through-space exciton coupling between the porphyrin electronic transitions induces bisignate Cotton effects in the circular dichroism (CD) spectra. Significantly, the sign of the observed CD couplet is unequivocally correlated with the absolute configuration of the chiral ligand used, allowing us to develop an absolute configuration sensor for enantiopure amines, alcohols, acids. This system possesses a high degree of chiroptical activity, which allows the differentiation of one of the smallest homologous elements of organic chemistry, i.e. the methylene subunit, such as between methyl and ethyl groups attached to the asymmetric carbon; further, it is able to sense a remote chiral center at a position beta to the binding group. It was also found that this system is highly sensitive to various internal and external controlling factors such as the structure of guest molecules, stoichiometry, number of binding sites, solvent, temperature and phase transition.

Further developments and prospects toward new chirogenic systems on the basis of heterometallic bis- and multi-porphyrin structures will be discussed.

V. Borovkov, Symmetry
2014, 6, 256.

V. Borovkov, Symmetry
2010, 2, 184.

V. Borovkov, Y. Inoue, Eur. J. Org. Chem.
2009, 189.

G. A. Hembury, V. V. Borovkov, Y. Inoue, Chem. Rev.
2008, 108, 1

V. V. Borovkov, Y. Inoue, Top. Curr. Chem.
2006, 265, 89.

V. V. Borovkov, G. A. Hembury, Y. Inoue, Acc. Chem. Res. 2004, 37, 449.
First Investigation of Single-Walled Carbon Nanotubes Handedness Chirality Utilized By Scanning Tunneling Microscopy
Authors: Ibrahim Ahmed , Liu Gang , Komatsu Naoki , Inose Tomoko , Handayani Murni , Chen Zhijin , Ogawa Takuji
Published: February 2020

(n,m) chirality of single-walled carbon nanotubes (SWNTs) has been extensively identified as well as investigated and/or characterized using many spectroscopic techniques [1]. On the other hand, the identification of the absolute handedness chirality of SWNTs still big challenge to be achieved even though there are some attempts [2]. Hereby, we have distinguished the absolute handedness chirality of SWNTs for the first time by using scanning tunneling microscopy (STM). This can be accomplished by using supramolecular structures of some porphyrin derivatives i.e. 5,15-bisdodecylporphyrin (C12P) on the chital SWNTs surface. Two types of chiral SWNTs have been used in this study, right-handed helix
P
(or plus) type and left-handed helix
M
(or Minus) type [3]. As an exclusive finding, two opposite chiral supramolecular structures of C12P molecules have been observed on the chiral SWNT surface; reflecting the considerable effectiveness of the handedness chirality of SWNT on the supramolecular structures of organic molecules on its surfaces. This pivotal results directly open the gates towards the determination of the absolute handedness chirality of SWNT, as well as a key point for further understanding and building new supramolecular architectures on curved surfaces which can be used for designing and fabricating more advanced porphyrin-SWNTs based devices.

References

[1] N. Nakashima & F. Toshimitsu. Sci. Rep.
2015, 5, 18066; N. Nakashima & F. Toshimitsu. Nat. Commun.
2014, 5, 1; F. Wang et al.
Nanoscale
2011, 3,4117; H. Liu et al.
Nature communi.
2011, 2, 309; W. Xiaojun et al.
Nature communi. 2016, 7, 12899.

[2] H. Liu et al. Nano Lett.
2014, 14, 6237; S. Ghosh et al. Nat. Nanotechnol.
2010, 5, 443.

[3] N. Komatsu et al. Chem. Lett.
2010, 39, 1022; N. Komatsu et al. J. Am. Chem. Soc.
2010, 132, 10876; N. Komatsu et al. J. Am. Chem. Soc.
2013, 135, 4805; N. Komatsu et al.
J. Am. Chem. Soc.
2007, 129, 15947.

Figure 1
Study of Transport Properties of Polyelectrolyte-Cellulose Acetate Membranes
Authors: Hakanpää Janina , Yliniemi Kirsi , Wilson Benjamin Paul , Singer Ferdinand , Höhn Sarah , Kontturi Eero , Virtanen Sannakaisa
Published: February 2020

The rapid and uncontrollable corrosion of Mg and Mg based alloys is one of the main obstacles in the development of Mg based temporal implant materials1,2; the potentially harmful corrosion products leading to the increase of local pH and release of H2 gas to the surrounding tissues are especially problematic. Therefore, the control over the dissolution rate and release of corrosion products is of high importance if Mg based materials are to be used as temporary biomedical implants. Earlier, the authors have developed a weak polyelectrolyte-cellulose acetate membrane (poly(N,N-dimethylaminoethyl methacrylate)-cellulose acetate=PDMAEMA:CA membrane), which can simultaneously control the dissolution rate of Mg as well as protect the surrounding environment from the high pH increase and H2 gas3.

In the present study, scanning electrochemical microscope (SECM) was used to investigate the transport properties of these membranes in more details. The results show that the PDMAEMA content controls the permeability of the membrane but also, a surprising time-dependent behaviour was observed: the permeability of the PDMAEMA:CA membranes decreased as a function of time and ellipsometer results showed that this behaviour is not related to the swelling of the membrane. Instead, the time-dependent behaviour might be an indicator of the conformational change of PDMAEMA molecules – either due to the screening of charges or change in degree of ionisation - blocking the membrane pores and this results in a change in permeability as a function of time. A material with such a time-dependent behaviour is an extremely interesting candidate when designing smart and responsive coatings and membranes for temporal biomedical implants.

(1) F. Witte, N. Hort, C. Vogt, S. Cohen, K. U. Kainer, R. Willumeit, F. Feyerabend, Current Opinion in Solid State and Materials Science, 2008, 12, 63-72.

(2) S. Virtanen, Mater. Sci. Eng. B, 2011, 176, 1600-1608.

(3) K. Yliniemi, B. P. Wilson, F. Singer, S. Höhn, E. Kontturi S. Virtanen, ACS Applied Materials and Interfaces, 2014, 6, 22393-22399.
Initial Corrosion Study of Magnesium Alloys in Simulated Body Fluid By SECM
Authors: Mena Morcillo Emmanuel , Veleva Lucien Petrova , Wipf David O
Published: February 2020

Magnesium alloys have been proposed as suitable biomaterials for resorbable implant applications. Although a substantial amount of research has been performed on the use of Mg alloys for biomedical applications, there are few studies employing micro-electrochemical techniques for characterizing these materials in physiological environments. The unique capabilities of the scanning electrochemical microscope (SECM) make this a powerful tool for in situ study of the localized corrosion of Mg alloys in physiological fluids. The work presented will assess the initial stages of electrochemical corrosion attack of AZ31 and AZ91D Mg alloys, and compare their performance in simulated body fluid (SBF). SECM measurements in amperometric operation modes were carried out in order to characterize the alloys surface during corrosion. Substrate Generation/Tip Collection (SG/TC) mode was used to spatially resolve regions of hydrogen flux related to cathodic sites while Feedback mode was used to distinguish between conductive/insulating regions on the passive layer. These results show intensive electrochemical activity on substrate surfaces at short exposure times of up to one hour, demonstrating rapid pit nucleation and formation of nearby, surrounding corrosion products. These results provide useful information on the localized hydrogen evolution process at Mg alloy surfaces under physiologically relevant conditions.
Membrane-Based Electrochemical Sensor for Corrosion Monitoring in Natural Gas Pipelines
Authors: Beck Justin , Ziomek-Moroz Margaret , Lvov Serguei N.
Published: February 2020

Although electrochemical sensors are widely used in many aqueous systems, their applications have been limited in environments where water is distributed within a bulk non-aqueous phase. One example is in transmission pipelines such as for natural gas. In these environments, the bulk phase is often not conductive enough to perform electrochemical measurements. We have investigated the use of ion conducting membranes of the type found in polymer electrolyte membrane fuel cells for preparing sensors to be used in high pressure gas pipelines. The membrane provides an electrolyte whose conductivity depends on the partial pressure of water vapor in the gas stream. Commercial Nafion™ 117 was used for the prototypes, and conductivity and corrosion measurements in gas streams up to 75 °C and 6.9 MPa (1000 psig) were conducted to determine the effectiveness of the sensor. Membrane conductivity data is reported for a range of water contents representative of gas transmission at 0.69 and 6.9 MPa (100 and 1000 psig) in nitrogen, methane, and a methane/carbon dioxide blend. Corrosion data collected from linear polarization resistance and electrochemical impedance spectroscopy measurements for carbon steel in simulated pipeline conditions are also presented.
A Study on the Interaction Between Rare Earth 4-Hydroxycinnamate and AS1020 and X65 Steel Microstructures in Carbon Dioxide Environment
Authors: Nguyen Nam Dang , Nguyen Vu Si Hoai , Tan Mike yongjun , Hinton Bruce , Forsyth Maria
Published: February 2020

The performance of rare earth 4-hydroxycinnamate (RE(4OHCin)3) inhibitor in CO2 corrosion has been studied by electrochemical and surface analyses. AS1020 and X65 steels with different microstructures have been used in a saturated CO2 0.01 M NaCl solution at room temperature and pH 4. The results showed that X65 steel has a better corrosion resistance than the AS1020 steel in saturated CO2 0.01 M NaCl solution. In contrast, RE(4OHCin)3 has more effective carbon dioxide inhibition for AS1020 compared with X65. The same inhibition mechanism has been proposed for the formation of protective inhibiting deposits at the active electrochemical corrosion sites in addition to a thinner surface film deposit on the surface and RE(4OHCin)3 mitigates corrosion by promoting random distribution of minor anodes.
Effect of Crevice Geometry on Corrosion Behavior of Carbon Steel in 5wt% NaCl Solution
Authors: Tada Eiji , Maeda Hatsumi , Nishikata Atsushi
Published: February 2020

Perforation corrosion of steel sheet lapped joints such as door hems is one severe corrosion type taking place on automobiles. This is because the lapped joints are exposed to a corrosive solution containing de-icing salt during driving and the solutions flowing into the crevice at the lapped joints, causing severe corrosion. Therefore, it is quite important to evaluate corrosion degradation of steel at the crevice of the lapped joints. In this study, effect of crevice geometry on corrosion behavior of carbon steel is investigated by immersion tests in 5wt% NaCl solution. In order to mimic steel sheet lapped joints, a block jig made of ABS resin having a cylindrical crevice former was prepared by a 3D printer. Crevice geometry on carbon steel such as a gap between a steel and a jig, and a diameter of the crevice former was changed by employing the jigs with different geometry. It was found from the results of the immersion tests that steel corrosion mainly took place below the crevice former and little corrosion was observed on the outer part of the steel apart from the crevice former. Furthermore, weight loss of the steel sheet during the immersion tests decreased with increasing the diameter of the crevice former. These results suggested that steel corrosion proceeds under the crevice former by the differential aeration inside and outside of the crevice, forming anode and cathode areas on the steel surface in the solution.
The Effect of Cations on Carbon Steel Corrosion in Chloride Media
Authors: Baranwal Prince Kumar , Das Sudip , Rajaraman Prasanna Venkatesh
Published: February 2020

The corrosion of carbon steel in chloride media has been investigated extensively in literature [1, 2]. However, the role of cations in carbon steel corrosion behavior is not widely reported. In the present work, the effect of Na+, K+ and NH4
+cations on the corrosion of carbon steel in chloride media is investigated via. potentiodynamic polarization, electrochemical impedance spectroscopy (EIS), and field emission scanning electron microscopy (FESEM) measurements. All the electrochemical measurements were carried out using a three electrode system, and after open circuit potential reaches a stable value. The carbon steel was used as working electrode. The reference and counter electrode were Ag/AgCl (3M KCl) and platinum wire respectively. The concentration of chloride is 10 wt.% for all the solutions. The polarization curves were obtained by scanning the electrode potential from -250 mV to 500 mV w.r.t OCP at a scan rate of 1 mV/s. The impedance spectra were obtained by applying an AC perturbation signal of 10 mV in the frequency range 100 kHz to 10 mHz.

The polarization measurements (Fig. 1) reveals that the corrosion rate is higher in case of ammonium chloride (NH4Cl) solution following the order NH4
+> K+ > Na+. Further, the polarization measurements, in case of chloride solutions containing Na+ and K+ cation shows the formation of passive layer on the carbon steel surface (the regime of insignificant current increase with potential) followed by breakdown of the same (the regime of increase in current) indicating susceptibility to pitting corrosion. While the anodic polarization curve in the presence of NH4
+cation does not show any sign of passivation. This implies that the carbon steel is more prone to uniform corrosion. These results suggest the formation of passive layer on the carbon steel surface and the mechanistic reaction pathway of carbon steel dissolution in chloride media is strongly influenced by the cations present in the solution.

The EIS measurements performed at open circuit potential, shows two time constant for all the cations (Fig.2). However, for NaCl and KCl system, the two time constants are merged and appears to be a single capacitive loop. The impedance data is analysed by an appropriate electrical equivalent circuit (EEC) and the EEC parameters are retrieved. Impedance results also confirms that the corrosion rate is higher in NH4Cl solution while lower in NaCl solution. So the presence of cations affect both the corrosion rate and the corrosion mechanism.

Keywords: Carbon steel, cations, chloride media, polarization, EIS References

1. K. Toba, M. Ueyama, K. Kawano and J. Sakai, "Corrosion of carbon steel and alloys in concentrated ammonium chloride solutions," NACE Intl., 68, 1049 (2012)

2. O. Forsen, J. Aromaa and M. Tavi, "Corroison reistance of different materials in dilute ammonium chloride bearing environments," Corros. Sci., 35, 297 (1993)

Figure 1
(Invited) Progress in Flexible 2D Nanoelectronics
Authors: Park Saungeun , Zhu Weinan , Akinwande Deji
Published: February 2020

In the past decade, two-dimensional (2D) atomic crystals have stimulated great interest in the electronic device community for their interesting physics and diverse applications. With the rapid growing market of wearable electronics and internet-of-things (IoTs), flexible nanoelectronics with high operation speed and low power consumption has become one of the most researched topics. In this regard, 2D atomic van der Waals crystals has emerged as promising candidates for such applications owing to their compelling capabilities including ultimate thickness scalability, superior mechanical flexibility and highly tunable electronic performance. We describe state-of-the-art advancements in 2D flextronics based on chemical vapor deposition (CVD) monolayer graphene, CVD monolayer MoS2, and few-layer black phosphorus with specific emphasis on radio frequency (RF) applications.
A New Cathode Material for Potassium-Ion Batteries
Authors: Kim Haegyeom , Kim Jae Chul , Bo Shou-Hang , Shi Tan , Ceder Gerbrand
Published: February 2020

Lithium-ion batteries have succeeded in powering small portable electric devices due to their high energy density. However, it is still debatable whether mineral resources can meet the increasing demand associated with the growth of Li-ion into large scale energy storage systems. As a result, potassium- and sodium-ion batteries are considered alternative energy storage options because of the natural abundance of K and Na resources. Potassium’s standard redox potential is lower than that of Na and is even below Lithium’s potential in non-aqueous electrolytes (i. e. propylene carbonate (PC) and ethylene carbonate/diethyl carbonate electrolyte (EC/DEC)).1-3It is therefore likely that K ion batteries can deliver a high cell voltage as compared to Na and Li systems.

Only few cathode compounds are reported to date for K ion batteries. In this early stage, it is important to design cathode materials that can maintain their crystal structures during de/intercalation of large K ions. We develop a new cathode material for K ion batteries and investigate K storage mechanism in this new cathode compound by in-situdiffraction characterization combined with electrochemical measurements. Lastly, we further demonstrate the practical feasibility of K ion batteries by constructing full cells. We consider that this work can suggest a guideline to open up new research opportunities in the development of K ion batteries.

References

1. Eftekhari, A., Jian, Z. & Ji, X. Potassium Secondary Batteries. ACS Appl. Mater. Sci., (2016).

2. Marcus, Y. Thermodynamic functions of transfer of single ions from water to non-aqueous and mixed solvents: Part 3 - Standard potentials of selected electrodes. Pure and Applied Chemistry 57, 1129, (1985).

3. Komaba, S., Hasegawa, T., Dahbi, M. & Kubota, K. Potassium intercalation into graphite to realize high-voltage/high-power potassium-ion batteries and potassium-ion capacitors. Electrochem. Commun. 60, 172-175, (2015).
Light-Weight and Corrosion-Resistant Current Collector for Aqueous Li-Ion Batteries
Authors: Gheytani Saman
Published: February 2020

The use of low-cost and light-weight aluminium as current collectors in aqueous Li-ion batteries with water-based electrolytes is restricted by corrosion reactions caused by the aggressive ions in the aqueous environments. Here we report for the first time using highly corrosion-resistant Al foil with the chromate conversion coating (CCC Al) as current collector for cathodes in aqueous Li-ion batteries. Coating aluminium with chromium compounds is currently the most effective way to inhibit corrosion of aluminium and its alloys. The protection with the CCC is two-fold: (1) an impervious hydrated chromium(III) oxide serving as a physical barrier on the surface and (2) the chromium(VI) ions stored in the coating provide active corrosion protection.

We have experimentally demonstrated that CCC Al foil is resistant to corrosion when used as the current collector of LiMn2O4 electrodes. The cyclability of these electrodes are on par with or better than those observed for electrodes fabricated on stainless steel and titanium substrates. In contrast, electrodes fabricated on untreated Al foil saw serious corrosion of the substrate within the initial 10 cycles. Interestingly, CCC also effectively suppress oxygen evolution reaction at high potentials, leading to improved Coulombic efficiency of up to 99%. The increased overpotential for oxygen evolution was attributed to the occupation of active chemisorption sites and inhibition of electron transfer on the substrate surface by the chromium compounds. These results may open a new insight into the design of high performance and high-stability cathode electrodes for aqueous Li- and Na-ion batteries with a higher cell-level energy density.
High Capacity Electrolytes for Non-Aqueous Redox Flow Batteries – a Positive Focus
Authors: Kaur Aman Preet , Kowalski Jeffrey A , Casselman Matthew , Milshtein Jarrod David , Elliott Corrine F , Modekrutti Subrahmanyam , Zhang Naijao , Attanayake Harsha A , Risko Chad , Brushett Fikile R. , Odom Susan A
Published: February 2020

The development of low-cost, large-scale energy storage technologies is required for increased reliance on non-polluting, intermittent renewable energy sources connected to our electrical grid. Our research focuses on the development of organic materials for charge storage in non-aqueous redox flow batteries (RFBs). At present, most commercial RFBs contain aqueous, vanadium-based electrolytes, which have been demonstrated on scales as large as 1.5 MW. With non-aqueous electrolytes, a wider electrochemical window allows for 2-3 times higher operating voltages, while avoiding the use of corrosive electrolytes. Most of the organic species reported as electron donors are only stable in the neutral and singly oxidized states; removal of a second electron results in an unstable dication. Here we sought to increase the stability of dication species without significantly raising molecular weight, thus preserving atom economy. Considering phenothiazine donors, we found that the addition of certain substituents led to improved stability of the dication form; specifically, electron-donating methoxy groups (Figure 1) are more effective in stabilization than non-conjugated substituents. This presentation will include the synthesis of these materials, as well as electrochemical and spectroelectrochemical analysis. Furthermore, the results of density functional theory calculations will be presented to evaluate the design of a stable two-electron donor.

Figure 1. Structural representation of 3,7-dimethoxyphenothiazine derivatives (a) and cyclic voltammograms of N-ethyl-3,7-dimethoxyphenothiazine (DMeOEPT) showing reversible first and second oxidations (b).

Figure 1
Highly Stable Hydroquinone Ether-Based Catholyte for Non-Aqueous Redox Flow Batteries
Authors: Zhang Jingjing , Shkrob Ilya A , Tung Siu on , Duan Wentao , Hu Bin , Thompson Levi T , Wei Xiaoliang , Zhang Zhengcheng , Zhang Lu
Published: February 2020

Hydroquinone ethers are a key class of catholyte materials for non-aqueous redox flow batteries, showing high open-circuit potential, electrochemical reversibility and chemical tunability. However, the instability of many hydroquinone ethers, particular to electrochemical oxidation, limits their applicability. 2,5-dialkylation of the benzene core has been by far the only effective chemical approach to suppress the side reactions of the corresponding radical cations, restricting the chemical space of structures from which to choose. This talk will describe a bicyclo-alkyl substitution strategy that yields a hydroquinone ether with unprecedentedly high electrochemical stability. The influences of different substituents on the electrochemical properties are investigated. The electrochemical stability is determined via a full flow cell using a benzothiadiazole-based anolyte. In addition, the low impedance shown in the single electrolyte flow cell indicates its great promises as catholyte for high-performance non-aqueous redox flow batteries.
Redox Flow Batteries Based on Aqueous Soluble Organics and Mechanistic Diagnostics of Capacity Fading
Authors: Wei Xiaoliang , Wang Wei , Hollas Aaron , Li Bin , Nie Zimin , Vijayakumar Murugesan , Reed David , Sprenkle Vincent
Published: February 2020

Redox flow batteries have been considered as one of the most promising grid energy storage technologies. The unique cell architecture leads to an important advantage of decoupled energy and power, which offers very flexible designs and excellent scalability to meet different grid applications. State-of-the-art flow batteries based on inorganic redox-active materials (e.g. vanadium) have gained significant momentum and even commercialization offerings. However, the broad market penetration is hampered by limited energy density and/or high cost. This has driven the search for electrochemically active, cost-effective aqueous soluble organics (ASO) to enable competitive flow battery systems. Organic compounds have other advantages of molecular diversity and structural tailorability to enable high solubilities and desirable cell voltages.

Here we report the new development of high-performance ASO flow batteries at Pacific Northwest National Laboratory.1Materials discovery efforts have led to identification of promising ASO candidates, followed by structural tailoring to improve the solubilities, redox activity, and chemical stability. Electrolyte engineering was also carried out to improve the rate performance and cyclability of the ASO flow batteries. Finally, systematic spectroscopic analysis has revealed the mechanisms of capacity fading observed in these ASO flow batteries.

References

1. T. Liu, X. Wei, Z. Nie, V. Sprenkle, W. Wang. Adv. Energy Mater.
2016, 6, 1501449.

Figure 1. The ASO flow battery based on methyl viologen (MV) and 4-hydroxy-TEMPO (TEMPOL). The mechanistic studies of capacity fading will be discussed.

Figure 1
Macromolecular Design Strategies for Long-Lived and Energy Efficient All-Organic Redox-Flow Batteries
Authors: Helms Brett A. , Doris Sean E. , Ward Ashleigh L. , Frischmann Peter D. , Baskin Artem , Prendergast David , Gavvalapalli Nagarjuna , Chenard Etienne , Sevov Christo S. , Moore Jeffrey S
Published: February 2020

Scalable, low-cost, multi-hour electrochemical energy storage is critical to our efforts seeking to productively integreate renewable energy souces with the grid. Redox-flow batteries offer a solution. However, many suffer from rapid capacity fade and low energy efficiency due to the high permeability of redox-active species across the battery’s membrane. Here I will discuss how macromolecular design, applied to both the membrane and the active materials, uniquely addresses the crossover problem in these cells. In doing so, we identify the minimum size an active material must be to keep it isolated in its intended electrode compartment. We also identify the design rules governing the use of blocking membranes in these cells, particularly with respect to area-specific resistance in flow cells as it is dictated by polymer composition, membrane pore architecture, and electrolyte formulation. I will also discuss early successes in pairing optimized blocking membranes and oligomeric organic active materials in cross-over free redox-flow cells, which bode well for this technology development.
Zinc-Iron Flow Batteries with Common Electrolyte
Authors: Selverston Steven , Savinell Robert F. , Wainright Jesse S.
Published: February 2020

Aqueous hybrid flow batteries are being developed because of their high performance and low cost relative to other energy storage technologies. Zinc-bromine flow batteries, which use an acidic chemistry, have demonstrated high performance by many groups. However, their application has been limited by the safety concerns regarding bromine toxicity. Zinc-ferricyanide flow batteries, which operates in alkaline environment, have also been widely developed, but there have been reported challenges with the high membrane costs, precipitation of zinc oxides and the possibility of generating toxic gas in the event of electrolyte mixing with acid. In our lab, we are investigating a new type of zinc-iron chloride flow battery operating with the reactions given by:

negative Zn2+ + 2e- → Zn -0.76 V

positive Fe3+ + e- → Fe2+ +0.77 V

cell Zn2+ + 2Fe2+ ↔ Zn + 2Fe3+ 1.53 V

The key to making this work is to use the anomalous codeposition (ACD) of zinc from mixed ZnCl2-FeCl2 electrolytes. This effect prevents iron from electroplating during battery charging, so the negative electrode behaves similar to a normal zinc electrode. As with all-iron flow batteries, this type of flow battery also has an inherent crossover tolerance, which is important for long-term stability as well as operability using inexpensive microporous separators. Here, we report results from three-electrode studies of the anomalous codeposition as well as preliminary flow battery experiments.
Polyacrylonitrile-Based Membranes for Aqueous Redox-Flow Batteries
Authors: Karpushkin Evgeny A. , Klimenko Maria M. , Gvozdik Nataliya A. , Stevenson Keith J , Sergeyev Vladimir G.
Published: February 2020

Due to several advantages (independent power and energy sizing, long cycle life, fast response, and no self-discharge during storage), redox-flow batteries have been recognized as promising electrochemical energy storage devices. A crucial part of the redox flow-cell is the membrane separating the anolyte and catholyte containers (thus providing for charge carriers conductivity and preventing the cross-mixing of the redox-active components). For example, a membrane for vanadium redox-flow battery (VRB) should be stable against oxidation by VO2
+ cations as well as to reduction by V2+ cations and exhibit high proton conductivity to provide high voltage efficiency of the battery as well as low vanadium permeability to ensure high Coulombic efficiency.

Perfluorinated membranes such as Nafion® are currently the most widely used ion-exchange membranes for VRBs. However, the best-performance membranes recognized so far are generally expensive, and the crossover of vanadium species across the membrane is rather high. Therefore, if a cheaper alternative membrane material is found, the cost efficiency of the battery will be drastically improved.

In this contribution, we demonstrate the applicability of membranes based on polyacrylonitrile (PAN) in redox-flow batteries. Using VBR as a model system, we have shown that microporous PAN membranes provide the desired balance of proton conductivity and vanadium species permeability and are chemically resistant under the VBR operation conditions. The proton conductivity of PAN-based membranes is usually lower than that of Nafion® membranes, but the vanadium ions transport is significantly suppressed. This makes the overall energy efficiency of the VBR cell built using the PAN-based membrane comparable to that determined with Nafion® membranes. It is important to mention that porosity and hydrophilicity of PAN membranes can be easily tuned, enabling facile adjustment of its ion-conducting properties. We have studied the influence of the PAN membranes preparation conditions on their characteristics and elaborated the procedures of the membrane modification by introduction of hydrophilic nanoparticles and by heat treatment.

This work was financially supported by Russian Foundation for Basic Research (project no. 16-33-60185 mol_a_dk) and by Centre for Electrochemical Energy of Skolkovo Institute of Science and Technology.
Chronoamperometric Study of Ammonia Oxidation in a Direct Ammonia Alkaline Fuel Cell Under the Influence of Microgravity
Authors: Cabrera Carlos R , Acevedo Raul , Morales Camila , Echegoyen Luis , Martínez-Rodríguez Roberto Alexis
Published: February 2020

This is a study of the chronoamperometric performance of the electrochemical oxidation of ammonia in an alkaline fuel cell for space applications. Under microgravity the performance of a fuel cell is diminished by the absence of buoyancy since nitrogen gas is produced. The following catalysts were studied: platinum nanocubes of ca. 10nm, platinum nanocubes on carbon Vulcan and platinum on carbon nanoonion support of ca. 10nm. These nanomaterials were studied in order to search for catalysts that may reduce or counter the loss of ammonia oxidation current densities performance under microgravity conditions. Chronoamperometries at potential values ranging from 0.2 V to 1.2V vs. cathode potential (Breathing Air/300ml/min/12psi) in 1.0 M NH4OH (30ml/min in anode) were done during over 30 parabolas in the Zero G airplane. The current densities at 15s in the chronoamaperometric experiments showed diminishing values under microgravity and in some cases improvements of up to 92%, for Pt-carbon nanoonions, and over 70% for the three catalysts versus ground at potentials ranging from 0.2 to 0.4V after 5 minutes of chronoamperometric conditions. At higher potentials, 1.0V or higher, Pt nanocubes and Pt-carbon nanoonions showed enhancements of up to 32% and 24%, respectively. At these higher potentials we will have a contribution of oxygen evolution. The changes in current behavior are attributed to the sizes of the catalyst materials and the time needed for the N2 bubbles detachment from the Pt surface under microgravity conditions.