bluuebunny/crossref_metadata_2025_split huggingface dataset:
(Invited) Delayed Fluorescence from Single-Walled Carbon Nanotubes Induced By Energy Transfer from Singlet Oxygen
Authors: Bachilo Sergei M. , Lin Ching-Wei , Weisman R. Bruce 
Published: February 2020

Semiconducting Single-Walled Carbon Nanotubes (SWCNT) have small bandgaps between the ground state and the lowest singlet excited state. Such a low singlet-state bandgap will also result in even a smaller triplet bandgap between the ground state and the lowest triplet state. Due to big variations in singlet bandgaps with the nanotube diameter, it is possible to expect that some small-diameter SWCNT species will possess triplet states above the singlet oxygen level, corresponding to ~1270 nm wavelength, and some larger-diameter SWCNTs will be below. Correspondingly, smaller-diameter SWCNT may generate excited singlet oxygen if their triplet state will be quenched by molecular oxygen, while other may be efficient quenchers of singlet oxygen. Both processes are highly important for different photochemical and photophysical effects.
In the presented work we have discovered and investigated fluorescence of SWCNTs resulting from interaction of their water-based and toluene-based dispersions with singlet oxygen generated by sensitizers. Applying chopper-offset and photon-counting time-resolved techniques has allowed us to obtain luminescence spectra and kinetic dependencies for SWCNT and also for singlet oxygen. Among other observations we have determined a cut-off for energy transfer from singlet oxygen to SWCNT triplet, corresponding to approximate equality between the triplet state energy in SWCNT species (7,6) and the singlet oxygen energy. Nanotubes of smaller diameters have triplet states above the singlet oxygen level, but those of larger diameters – below it, and, correspondingly, can generate or quench singlet oxygen. While a direct triplet state lifetime for SWCNT was not possible to resolve in these experiments because it was shorter that the singlet oxygen lifetime, the data indicate it is on the order of a microsecond and decreases with the SWCNT bandgap. For some SWCNT species, especially (8,6), the delayed luminescence after triplet formation is rather efficient and its intensity could be compared with prompt fluorescence with direct excitation.
Thermal activation is the main mechanism for the conversion to a SWCNT excited singlet state after formation of its triplet state by energy transfer from singlet. This is not a surprising result because of rather small (~ 1000 wavenumbers) singlet-triplet splitting between the lowest excited singlet and triplet states, as determined here. However, triplet-triplet annihilation and some other photophysical and photochemical processes also influenced the intensities and kinetic traces of the delayed fluorescence. No SWCNT phosphorescence (emission from the triplet states) was observed, as consistent with usual properties in other organic molecules.
Three-Dimensional Ordered Nanoporous Nickel Electrode for Oxygen Evolution Reaction: Toward Highly Efficient and Ultra-Stable Water Electrolysis
Authors: Kim Sungsoon , Cho Yoonjun , Park Jong Hyeok 
Published: February 2020

Hydrogen generation by water electrolysis has been comprehensively studied for several decades, although it still faces many difficulties in commercialization due to low efficiency. Even though IrO2 and RuO2 have superior activities to oxygen evolution reaction (OER), such novel metal catalysts still need high overpotential compared to hydrogen evolution reaction. To overcome the limitation of OER, former researches have been studied with various materials which are cheaper and perform better than the novel metal-based electrocatalysts. Among them, nickel is considered as the best catalyst candidate due to hydroxide state transformation between Ni(OH)2 and NiOOH during the surface reaction.
Apart from the intrinsic properties, the morphology construction to the nanoscale structure is another useful way to enlarge the surface area, which is directly correlated to the overpotential decrease. Nanostructuring can inhibit continuous growth of bubbles on the surface and detach much easily. The bubble blocking effect on the electrode surface has been deeply studied within mechanical category but this effect has been poorly regarded for enhancement of the OER activity of the electrode. Also, the bimetallic system of nickel/iron chosen in this research enables great improvement for OER.
Herein, we synthesized three-dimensional ordered nanoporous mesh-like (3D-NM) nickel electrode by the photolithography method, which outperforms conventional porous nickel electrode. Successfully synthesized ordered nanoporous mesh-like structure provides highly extensive surface area within thickness of only 5 μm. In addition, we investigated that fast bubble formation/detachment from the pore can reduce the bubble blocking effect, which disturbs supply of electrolyte to the catalyst surface. 3D-NM nickel electrode only generates 12 times smaller extraordinary small bubbles compared to the typical bubbles in basic electrolyte. In line with the size of bubbles, impedance during the OER with 3D-NM nickel electrode smoothly undergoes while the nickel foam shows unstable graph.
Owing to the enlarged surface area and the fast bubble formation/detachment effect, overpotential measured at 10 mA cm-2 was 372 mV and the calculated Tafel slope was 94.4 mV dec-1. Through the unique nanoporous structure of nickel electrode, outstanding stability for 50 hours was achieved. To further improve the OER activity of as-prepared 3D-NM nickel electrode, the decoration of nickel and iron was conducted. The final 3D-NM NiFe electrode showed 261 mV of overpotential at 10 mA cm-2 with 43.8 mV dec-1 of Tafel slope.

Figure 1
Magnetic Property of Metallofullerenes within Metal-Organic Framework
Authors: Wang Taishan 
Published: February 2020

Endohedral fullerenes are formed by placing atoms or clusters in empty fullerene cages. Among them, magnetic endohedral metallofullerenes with unpaired electron spin have attracted many interests due to their potential application in quantum information processing (QIP), high-density data storage, and magnetoreception system. Notably, the arrangement of these magnetic endohedral fullerenes in solid state is essential for further applications. The metal-organic frameworks (MOFs) have been intriguing many interests due to their porous structures and excellent crystallinity. Particularly, the ordered nano-sized pores in MOF crystals make them good host for these metallofullerenes. In previous report of fullerene-containing host-guest complex, the fullerene carbon cages are always prone to interact with the planar aromatic motif of the host molecules through strong π-π interactions. In MOF structures, there are many similar planar aromatic contents. For example, MOF-177 has cage-shaped pore with two sets of parallel quasi-planar triphenylbenzene unit, 1.4 nm apart from each other. Therefore, the MOF-177 can well accommodate metallofullerenes and the ordered pores of MOF would lead to special solid state magnetic system.
Herein, we report the preparation and magnetic property of metallofullerenes (Y2@C79N, Sc3C2@C80, and DySc2N@C80) accommodating in MOF-177 crystal through a bottom-up approach. In Y2@C79N@MOF-177 complex, the Y2@C79N molecules tend to reside along the c-axis of MOF-177 crystal lattice under low temperature as disclosed by its axisymmetric electron spin resonance (ESR) characters. The confined effect of MOF’s pores plays a significant role in steering the electron spin on endohedral fullerene, leading to anisotropic paramagnetic solid system. In Sc3C2@C80@MOF-177 complex, it was disclosed that the ESR signals of Sc3C2@C80 can sense the tiny transformation of flexible pores under external stimuli. Furthermore, the changes of MOF-177 pores under different conditions exhibit reversible process as shown by Sc3C2@C80 EPR signals, which demonstrates the breathing of MOF-177 frameworks. In DySc2N@C80@MOF-177 complex, the magnetic properties of DySc2N@C80 can be effectively altered by means of imprisoning the molecule in MOF-177. Typically, its quantum tunnelling of magnetism (QTM) is suppressed through spin-phonon couplings.
Influence of Al-Zn Anode Alloy Composition on the Electrochemical Performance of Me–Air Batteries with Neutral Aqueous Solutions
Authors: Durmus Yasin Emre , Montiel Guerrero Saul Said , Tempel Hermann , Hausen Florian , Kungl Hans , Eichel Rüdiger-Albert 
Published: February 2020

Increased demand on resource efficient battery technologies and development of materials has urged an interest on Me–air batteries, such as Zn–air and Al–air, due to their high theoretical specific energies as well as using low cost, safe and abundant materials. In this regard, while employing pure metals as anode material is one line of development [1,2], modification of the electrode by alloying with other elements is also subject to recent investigations [3]. Up to now, the influence of the alloying on the electrochemical properties of the electrode, i.e. interactions between the microstructure constituents, impact on the potential, corrosion behavior as well as the electrolyte decomposition (water or oxygen reduction), have not been systematically investigated for alloys in the Al/Zi system.
The main objective of this work is to characterize the electrochemical properties of Al-Zn alloys in neutral aqueous solutions. Al-Zn alloys with six different compositions were prepared in a muffle furnace and shaped to anodes. Microstructure of the anodes in the initial state was analyzed with respect to the fractions of its constituents. The electrochemical characterization of the prepared alloy anodes encompass (i) open circuit potential, (ii) potentiodynamic polarization measurements and corresponding determination of corrosion parameters, (iii) galvanostatic discharge/charge experiments under various current densities. The potentiodynamic polarization results are further discussed with Evans diagrams considering on possible scenarios for the galvanic interactions of the different microstructure constituents. A comprehensive analysis of the surface characteristics of the alloys is also carried out after the electrochemical experiments in order to reveal the interactions during discharge. Based on the electrochemical results on potentials, charge/discharge and corrosion behavior, the Al/Zi alloys are evaluated with respect to their suitability for application in batteries.

References:

[1] Sumboja, A., Ge, X., Zheng, G., Goh, F. W. T., Hor, T. S. A., Zong, Y., Liu, Z., Journal of Power Sources 332, 330–336 (2016).

[2] Fan, L., Lu, H., Leng, J., Electrochimica Acta 165, 22–28 (2015).

[3] Pino, M., Herranz, D., Chacon, J., Fatas, E., Ocon, P., Journal of Power Sources 326, 296–302 (2016)
Current Density Improvement for Vanadium Redox Flow Cell Having Interdigitated Flow-Field
Authors: Mushtaq Kashif , Monteiro Ricardo , A. Zaidi Asad , Delgado Nuno , Mendes Adelio 
Published: February 2020

Tuning of operational conditions and by using pre-treatment of electrodes can lead to the increase in performance of Vanadium redox flow cell (VRFC) as evident through our published article [1]. This work reports the tuning of operational conditions of a VRFC having impregnated graphite bipolar plate with interdigitated flow-field as compared to conventional flow-field. The schematic is shown in figure 1.
The as-received Fumatech FAP-450 anion exchange membrane (AEMs) were used without any treatment. All membranes were cleaned in 1M H2SO4 solution at 80 oC until all vanadium stains were removed and stored in deionized water before being used again. The electrolyte consisted of a commercially available 4 M sulfuric acid-based vanadium solution (1.6 M V3+/V4+ 50:50 M ratio, GfE Metalle und Materialien GmbH, Germany) and it was used without further treatment or purification. Graphite felt electrode (GFE) of thickness 4.6 mm was used with compression ratio of 25%. GFE were boiled in 1M H2SO4 for 12 hours and then left for another 12 hours inside the same solution. Then, GFE are washed with DI water and dried at 100 oC in oven. Afterwards, GFE are thermally treated at 390 oC for 12 hrs inside the furnace injected by air and then cooled down in the furnace upto room temperature. These arrangements allowed to reach higher current density at lower flowrate than used in published article [1].
Charge discharge cycling was done at 40ml/min using current densities of 120mA/cm2, 150mA/cm2, 170mA/cm2, 190 mA/cm2 and 210 mA/cm2. Results of efficiencies (%), energy density (Wh/L) and capacity (mAh) are shown in attached figure 2,3 and 4 respectively. Electrochemical impedance spectroscopy (EIS) is carried out to measure the contribution of Area Specific Resistance at 40 ml/min which is 1.36 Ωcm2 for interdigitated flow-field. EIS results are further fitted using equivalent circuits to determine the contribution of each component.
As per the previous article [1], in the absence of flowfield, it was observed that increase in flowrate is feasible to increase the energy efficiency. But, current work highlighted the significance of using flowfields as an efficient way is to decrease the pressure drop to avoid continous increase in flowrate. This approach helps to reach higher current densities at much lower requirement of pumping flowrate.
Energy efficiency start decreasing significantly with increment in current density. Only voltaic efficiency is effected whereas columbic efficiency remain around 98% at all current densities. More research efforts are required to optimise the treatment of electrodes and also flowrate distribution to get higher efficiency at higher current density.
Reference:
[1] R. Monteiro, J. Leirós, M. Boaventura, and A. Mendes, "Insights into all-vanadium redox flow battery: A case study on components and operational conditions," Electrochimica Acta, vol. 267, pp. 80-93, 2018.

Figure 1
Novel Polymer Gel Electrolytes for Facile Fabrication of Efficient and Durable Electrochromic and Photoelectrochemical Devices
Authors: Lee Ji-Eun , Kang Bo-Sung , Kim So-Eun , Song Hyeon-Bee , Kim Do-Hyeong , Kang Moon-Sung 
Published: February 2020

Polymer gel electrolytes (PGEs) have been widely investigated and utilized in various electrochemical applications such as lithium secondary batteries and dye-sensitized solar cells because they possess moderate ion conductivity and high physical stability. They have also been developed for the application to electrochromic devices (ECDs). Recently, ECDs have been attracting much attention owing to their use as a smart window. A smart window or a smart glass can effectively control the light transmission properties for the purpose of proper lighting or heating etc. The PGEs as one of the key components of the ECDs can dominate the major characteristics of transmittance and colored time etc. Especially, the ion conductivity and volatility of the PGEs should be optimized for the fabrication of efficient and durable ECDs. In addition, efficient injection process of highly viscous PGEs during the fabrication of large area ECDs should also be considered. In this work, therefore, we have developed the PGEs which can be easily loaded as a film and then in-situ polymerized through UV irradiation. The PGEs have also been applied to photoelectrochemical cells (i.e. dye-sensitized solar cells) for the efficient energy harvesting from solar irradiation.
Acknowledgments:
This work was supported by a grant (No.2017000140002/ RE201702218) from the Environmental Industry Advancement Technology Development Project of Korea Environmental Industry & Technology (KEITI) funded by Korea Ministry of Environment (MOE).
Understanding the Scales Formation Inhibition Mechanism on C-Steel in a Sour media
Authors: Al-Qahtani Noora , Qi Jiahui , Abdullah Aboubakr Moustafa , Laycock Nick , Ryan Mary P 
Published: February 2020

Corrosion control in sour environments is a serious challenge for oil and gas industry. One of the approaches to mitigate such problem is to use corrosion inhibitors (CI). The selection of a single or a mixture of CIs for a particular oil or gas production, transportation or storage facility depends on different parameters e.g. the ratio between carbon dioxide and hydrogen sulfide, pH, pressure, temperature, and brine chemistry where different kinds of iron sulfide and/or iron carbonate layers can be formed. To select the right corrosion inhibitor/s, it is highly crucial to understand the mechanism of corrosion of C-steel and its inhibition in H2S systems in absence and presence of CIs [1,2].
In this work, the electrochemical behavior of C-steel in (i) deionized water (DIW) and (ii) different NaCl solutions were examined in an H2S system. A series of experiments were conducted at different temperatures and two concentrations of inhibitors (A and B). The corrosion behavior of C-steel was investigated by measuring the open circuit potential (OCP), linear polarization resistance (LPR), and potentiodynamic polarization (PDP) in addition to scanning electron microscopy (SEM) coupled with an energy dispersive X-ray (EDX) besides Raman spectroscopy (RS). The results have shown that the corrosion rate of C-steel gradually decreased then stabilized with time in the inhibited solutions. The inhibition efficiency was found to increase in the presence of both types of inhibitors with temperatures. Surface analysis shows that no film of corrosion products existed. In fact, CIs controlled the corrosion process and prevented passive film formation (iron sulfide), even in the presence of H2S in all tests. 2.5.0.0 2.5.0.0
The Underoil Droplet Corrosion Behavior of X100 Pipeline Steel
Authors: Liang Hongxing , Liu Jing , Schaller Rebecca Filardo , Asselin Edouard 
Published: February 2020

Canadian natural bitumen production will reach a peak of 112 million barrels per day in 2078 [1]. Pipelines are primarily used to transport this bitumen. Bitumen must be diluted in order to be pumped through a pipeline effectively because it is otherwise too viscous to flow [2]. Underoil droplet corrosion of diluted bitumen (dilbit) pipelines may lead to the loss of pipe wall thickness, which deteriorates the structural reliability and increases the risk of leaking of pipelines. The current models for atmospheric droplet corrosion, where no limitation to oxygen access is imposed, cannot be applied to underoil droplet corrosion in dilbit pipeline conditions.
In this study, a NaCl droplet on X100 pipeline steel covered by paraffin oil is used to simulate the corrosive environment encountered in diluted bitumen pipelines. A new distinctive corrosion mechanism is proposed to explain the corrosion of X100 pipeline steel beneath an underoil salty droplet. This mechanism accounts for the depleted oxygen levels in the droplet environment. In the initial stage (1 h), the distribution of corrosion pits was heterogeneous with one area under the droplet presenting a higher pit density. As the corrosion proceeded (24 h), the localized corrosion was governed by pH development due to initial pit density. Regions of initially higher pit density switched to general corrosion, while regions with lower pit densities continued pitting.
The effects of droplet volume, chloride ion concentration, and temperature on the underoil droplet corrosion behavior of X100 pipeline steel were also studied by scanning electron microscopy, Raman spectroscopy, and profilometry. At 23 °C, lepidocrocite and hematite were observed in the region where pitting was initially prevalent. However, as this region switched to uniform corrosion, goethite, lepidocrocite, and hematite were formed. The same distribution of crystal structures was identified for the droplets with varying volume and chloride ion concentration. When the temperature was increased to 60 °C, hematite was detected in both regions. Decreased droplet volumes, increased chloride concentration, and raised temperatures increase corrosion penetration when uniform corrosion is prevalent. This study provides important findings to better understand the mechanisms behind droplet corrosion underoil and informs future predictions of the corrosion rate of pipeline steels.
References
[1] S. H. Mohr and G. M. Evans. Long term prediction of unconventional oil production. Energy Policy 2010; 38: 265−276.
[2] National Research Council of the National Academy of Sciences, Effects of diluted bitumen on crude oil transmission pipelines, in: Transportation
Research Board Special Report 311, Washington DC, 2013.
EIS Study on Effects of Inorganic Inhibitors on Localized Corrosion on Stainless Steels at PEFC Environments
Authors: Ueyama Meiko , Hoshi Yoshinao , Shitanda Isao , Itagaki Masayuki , Takata Satoshi , Kogure Tomonari 
Published: February 2020

Stainless steel is considered as a suitable material of PEFC metal separator because it has good durability, formability, chemical stability and reasonable price. Whereas, localized corrosion would occur on stainless steel due to potential and temperature change during PEFC operation because a metal separator contacts with acidic solution containing fluoride and chloride ions. It is generally known that a few percent of molybdenum as an alloy element inhibits localized corrosion. Hashimoto et. al.
1) proposed that dissolved molybdenum from stainless steel affected protection of steel surface. In previous study2), we discussed anti-corrosive effects of molybdate ions as an inhibitor in solution. In present study, we investigate inhibitor mechanisms of sodium molybdate, sodium tungstate and sodium phosphate for localized corrosion of stainless steel by electrochemical impedance spectroscopy.
In this study, measurement of polarization curve and electrochemical impedance were conducted by three electrode methods. The working electrode was S44700 (Surface area : 0.28 cm2). The counter electrode was platinum wire and the reference electrode was a saturated KCl/Ag/AgCl (SSE) electrode. The electrolyte solution simulating PEFC operation environment (PEFC simulating solution) was 1 mol/dm3 H2SO4 aqueous solution (pH 3) which contained 10 ppm NaCl and 30 ppm NaF. Furthermore, some inorganic inhibitors were added to PEFC simulating solution as follows: 1 mmol/dm3 sodium molybdate, sodium tungstate or sodium phosphate. Polarization curves were measured by scanning the working electrode potential at 100 mV min-1 from open circuit potential to 1.5 V vs. SSE. Impedance measurements were carried out at potentials in passive and transpassive regions. Imposed AC potential amplitude was 10 mV and frequency ranges were from 10 mHz to 10 kHz.
Figure 1 presents polarization curve and impedance spectra of S44700 in PEFC simulating solution. The polarization curve is composed of passive region from open circuit potential to 0.8 V vs. SSE and transpassive region from 0.8 V to 1.5 V vs. SSE. Impedance spectra show blocking behavior at passive region (0.7 V, 0.8 V vs. SSE) and inductive loops at transpassive regions (0.9 V, 1.0 V vs. SSE). In present study, we investigate inorganic inhibitors reducing transpassive dissolution current. Then, we propose inhibitor mechanisms of sodium molybdate, sodium tungstate and sodium phosphate by EIS.

References

1) K. Hashimoto, K. Asami, M. Naka and T. Masumoto, Corros. Sci., 19, 857 (1979).
2) M. Ueyama, C. Tsukioka, Y. Hoshi, I. Shitanda, M. Itagaki, S. Takata, and T. Kogure, C01 – 697, 232 nd ECS Meeting.

Figure 1