bluuebunny/crossref_metadata_2025_split huggingface dataset:
(Invited) Kinetics of Photocatalytic Multielectron Transfer By Nanoparticles of Bare or Catalyst-Loaded Titania
Authors: Ohtani Bunsho , Takeuchi Shugo , Takase Mai , Takashima Mai 
Published: February 2020

For heterogeneous photocatalysis, it is well known that photocatalytic oxidation of water into oxygen (O2) is induced by particulate photocatalysts in the presence of electron acceptors. This reaction has been presumed to proceed through a four-electron (hole) process, and therefore it is expected that reaction rate depends on light intensity and particle size of photocatalyst, which influence the number of photons absorbed by one photocatalyst particle. However such dependences have rarely been reported and discussed so far. In this study, we report light-intensity and particle-size dependences of rate of oxygen evolution from suspensions of commercial titania samples using iodate (IO3
-) and iron(III) (Fe3+) ions as an electron acceptor under intense UV-LED irradiation (365 nm; < 300 mW).
Figure 1 shows the light-intensity dependence of rate of O2 evolution from a suspension of rutile (Tayca MT-150A; 13 nm) with Fe3+. A higher-order non-linear dependence was observed in the relatively lower (< 190 mW = threshold intensity, I
thr), while the rate was almost proportional to the intensity (with slope, a) in the higher intensity range, and those dependences could be reproduced by second and first-order equations, respectively. Similar bimodal dependences, with different a and I
thr, were also observed when the other titania samples were used in the presence of IO3
- or Fe3+. Assuming a kinetic model (Scheme 1) in which second-photon absorption by a one photon-absorbing particle (TiO2(h+)) within its lifetime leads to oxygen evolution, a rate equation (eq. 1) was derived using parameters of lifetime of TiO2(h+), secondary photon-absorption efficiency and rate constant of oxygen evolution by a two-photon absorbing particle(TiO2*), and further derivation for lower and higher intensity limits to eqs. 2 and 3, respectively, reproduced the bimodal light-intensity dependences. Threshold intensity (I
thr) at which order of light-intensity dependence formally changes from second to first is defined as intensity for the equal rates of eq. 1 and 2 are equal. Differences in I
thr and a depending on the kind of electron acceptors, crystalline structure (anatase or rutile) and particle size are discussed.

Figure 1
(Invited) ­­­Stable and Durable CH3NH3PbI3 Perovskite Solar Cells at Ambient Conditions
Authors: Sunkara Mahendra Kumar , Kumari Sudesh , Vendra Venkat Kalyan , Druffel Thad , Spurgeon Joshua M , Lavery Brandon Wayne 
Published: February 2020

Organic-inorganic halide perovskites have created a breakthrough in the field of solar cells because of their low cost, low temperature processibility and excellent optoelectronic properties. However, the instability of organic-inorganic halide perovskites to moisture is currently a huge challenge in the field of perovskite solar cells and needs to be addressed to translate the perovskite technology from the laboratory bench to large scale industrial practice. Currently, all the lab scale perovskite cells are fabricated in controlled glove box atmosphere with less than 1 % relative humidity to prevent their deterioration under moisture.
In this work, a novel concept of protecting the perovskite using a highly conductive composite of a layered material and a hole transporting polymer is presented. The excellent charge transport properties of the composite coating allow the use of thick coating on the perovskite, creating extremely high length scales for moisture diffusion through composite. The composite coating developed in our work, could be extended to lead-free organometallic perovskites that are both moisture and oxygen sensitive. The deposition of gold as a counter electrode for the lab scale perovskite cells is usually performed by thermal evaporation in a bell jar evaporator. This process is time consuming, energy intensive and not viable to scale up. Our approach involving lamination of individual electrodes, enables a much facile low cost process for fabricating perovskite solar cells.
Our results and observation on polymer composites as protective coatings for perovskite and on laminating electrodes show high promise for the scalability and low cost fabrication of perovskite cells under atmospheric conditions (60 -70 % relative humidity). In addition, the degradation mechanisms involving both moisture and oxygen in the presence of UV light irradiation will be discussed.
(Invited) How Beneficial Is Reduced Graphene Oxide (RGO) for Long-Term Photo Generated Charge Transport in Inorganic Oxide - Rgo Nanocomposites? a Case Study of Bismuth Titnate - Rgo Films?
Authors: Selvaraj Josephine , Gupta Satyajit , Fiechter Sebastian , Subramanian Vaidyanathan 
Published: February 2020

This work begins with a summary of the role of reduced graphene oxide (RGO) in promoting the photoactivity of oxides and chalcogenides. Initial indicators suggest that RGO is a good material for promoting charge speration over short time scales. However the story over long term illumination is different. This presentation delineates the results of a systematic analysis of the photoelectrochemical (PEC) and optical responses of RGO combined with a representative multimetal oxide – bismuth titanate (BTO) on films. We investigated the role of RGO as a promoter of charge separation and transport, by suppressing recombination loss of carriers in BTO. The micro-structure of the BTO/RGO composite observed using transmission, scanning electron, and atomic force microscopy, revealed a well-integrated, and highly porous morphology compared to pristine BTO film. The integration of BTO with RGO resulted in a ~ 7 fold increase in photocurrent density with an optimal RGO loading of 2 wt%. The performance of the BTO/RGO interface was further examined to obtain critical insights on: (i) how the electrolyte influences the stability of the BTO/RGO composite and (ii) what interactions prevail at the BTO/RGO interface, under long-term illumination to impact the RGO stability. This work assumes immediate significance because implementation of RGO as a charge transport agent in oxidative systems is heavily researched currently. Unless a mechanism to protect RGO is determined, its long-term stability, especially under oxidative conditions of any form, has to be thoroughly investigated on a case-to-case basis to ensure composite longevity.
Carbon Nitride (C3N4) Photocatalysts Synthesized from Different Methods for Photocatalytic Reaction Under Visible Light Irradiation
Authors: Hu Che-Chia , Wang Mao-Sheng , Guo Zheng-Wei 
Published: February 2020

C3N4 photocatalyst powders have generally been synthesized with a solid-state (SS) method, which formed a graphitic feature with tri-s-triazine (C6N7) units as elementary building blocks. The present work reports a solvothermal (ST) synthesis, in which the yellow powders were obtained as low as 150-220 °C using cyanuric chloride (C3N3Cl3) and sodium azide (NaN3) as the starting materials and acetonitrile as the solvent. X-ray diffraction analyses showed that the crystalline structure of ST samples changed from pseudocubic-C3N4 to beta-C3N4 with increasing the solvothermal temperature, and powders obtained from SS method displayed a graphitic-C3N4 structure with diffraction angles at ca. 13.1° and 27.5°. The two distinct diffraction angles represented (100) plane of tri-s-triazine units and (002) plane of stacking of the conjugated aromatic system, respectively. UV-Vis absorbance spectra showed that the band gap of SS was estimated to be 2.6 eV, and that of ST samples were estimated to be 1.9 to 2.45 eV, varied with solvothermal tempearture. To evaluate the visible-light-responded photocatalytic activity of the samples, degradation of methylene orange dyes was conducted using a 200 W Xenon lamp. ST samples showed a higher photocatalytic activity on degradation of methylene orange, which can be attributed to its larger light absorbance in the visible regime compared to that of SS ones.

Figure 1
(Invited) Bodipy Dyes for Solar Energy Conversion
Authors: He Hongshan , Klfout Hafsah A , Elkhalifa Mahmoud , Stewart Adam 
Published: February 2020

BODIPY, abbreviation for boron-dipyrromethene, is a class of fluorescent dyes. They exhibit several unique characteristics including tunable spectral coverage, high absorption capability, exceptional chemical and photo-resistance in solution and in solid state, very good solubility in organic solvents, and easy structural modification making them attractive for many applications. However, in the past thirty years, the research on BODIPY dyes is heavily focused on development of new molecules for imaging and labeling of biological substrates, and only a few reports are related to solar energy conversion. In this talk, I will present our recent studies on several functionalized BODIPY dyes with a donor-π-acceptor configuration for dye-sensitized solar cells. Those highly functionalized BODIPY dyes exhibit strong absorption in the visible region and very interesting photovoltaic and sensitization behaviors. Synthesis, single-crystal structures, photophysical and photovoltaic properties will be discussed. The findings from our study will be of great interests to researchers who are working in the fields of solar energy conversion.
(Invited) Molecular Mechanism of NO Reduction By Bacterial Nitric Oxide Reductases
Authors: Shiro Yoshitsugu 
Published: February 2020

Bacterial nitric oxide reductase (NOR) catalyzes the NO reduction reaction (2NO + 2H+ + 2e- --> N2O + H2O) at its active site, which is a binuclear center comprised by heme (heme b
3) and non-heme iron (FeB). In the enzymatic reaction by NOR, three short-lived intermediates have been proposed for the coordination of two molecules of NO to the binuclear center; i.e., trans-, cis-heme b
3- and cis-FeB-coordinations. To establish the molecular mechanism of the NO reduction by NOR, we have been studying the time-resolved spectroscopies to characterize the coordination and electronic structures of the intermediates, which are appeared in the micro- to milli-second time region after the reaction of the ferrous enzyme with the NO molecule(s). On the basis of the time-resolved optical, ESR and IR spectral changes, we have proposed that the trans-mechanism seem favorable for the NO reduction mechanism by bacterial NOR. We will discuss the NOR reaction with referring their crystallographic structural data which we reported.
Scale-up of Rechargeable Mutivalent Batteries Via Pouch Cells Development
Authors: Ha Seungbum , Gallagher Kevin G. 
Published: February 2020

Lithium ion batteries are now deployed to various portable electric devices and electric vehicles. However, the energy density, especially the volumetric energy density of the battery does not reach ideal target from a consumer perspective. The multivalent metal batteries are one of the promising candidates as a beyond lithium ion battery with 2–3 times the energy density of what lithium ion can offer.
Among multivalent metals, magnesium provides double the volumetric capacity of lithium. However, the standard reduction potential of magnesium is 700 mV less negative than that of lithium. Therefore, the approach to increasing its operating voltage is very important to increase energy density of battery.
Due to the demand for high voltage operation, comprehensive efforts have been demonstrated for high voltage electrolyte. The oxidative stability of many magnesium electrolytes is reported to be over 3 V vs Mg when tested by cyclic voltammetry on a Pt working electrode. However, their window of operation when assembled in coin cells and operated at constant current using typical stainless steel current collector and case is rarely above 2.0 V.
We demonstrated assembly of pouch cells for multivalent metal batteries and performed electrochemical testing. Initial work to identify high-performing materials, composition, fabrication variables and cycling conditions is conducted in cyclic voltammetry and coin cell test. The resulting information is then used for the pouch cell demonstration.
Toward the Polysulfide-Shuttle-Free Lithium-Sulfur Batteries with Functionalized Polymer Electrolytes
Authors: Yu Xingwen , Jorseph Jorphin , Manthiram Arumugam 
Published: February 2020

The emerging secondary battery system with room-temperature lithium-sulfur (Li-S) chemistry is gaining much attention as a promising next-generation energy storage technology for a broad range of applications.1
,
2 However, this battery technology is currently facing a critical obstacle due to a so-called “polysulfide-shuttle” behavior during cell operation.3
,
4 Although a lot of efforts have been attempted to address such a challenge since it has been recognized many year ago, there is still a lack of reliable approaches that can fully prevent the polysulfide-shuttle without bringing any other negative effects to the Li-S cell system. For instance, attempts in the development of the advanced cathode matrices or structural configurations can alleviate the polysulfide diffusion to certain extent, but these approaches are not able to absolutely encapsulate the polysulfides in the cathode.5 Use of the Li+-ion conductive solid electrolyte can effectively prevent the migration of the polysulfide species through. But these approaches usually bring new problems due to the relatively low room-temperature conductivity of the currently available solid electrolytes and the brittleness of the ceramic materials.6

Herein we present an alternative strategy to suppress the polysulfide-shuttle in the Li-S batteries with functionalized polymer electrolytes. One example is the use of a lithiated Nafion membrane (Li-Nafion) as both the Li+-ion selective electrolyte and the electrically insulating separator. Upon lithiation, the non-porous Li-Nafion offers both a reasonable Li+-ion conductivity and remarkably reduced polysulfide-shuttle, attesting to great advantages over the traditional Celgard membranes in terms of retention of polysulfide species and cyclability enhancement of the Li-S batteries.
Another example is the modification of a traditional polypropylene (PP) separator to form a desired carboxyl functional group at the PP back-bone. With the resulting carboxyl-PP as the separator, the Li || carboxyl-PP || S battery shows significantly enhanced capacity retention ability in comparison to the cell with the unmodified PP separator.
A series of mechanistic studies have also been performed towards the understanding of the cation/anion transport behavior at the functionalized polymer interface. Relevant mechanism regarding the polysulfide retention by the functionalized polymer electrolyte/separator will be presented.

References

1. A. Manthiram, Y. Z. Fu, S. H. Chung, C. X. Zu and Y. S. Su, Chem Rev, 2014, 114, 11751-11787.
2. Y. X. Yin, S. Xin, Y. G. Guo and L. J. Wan, Angew Chem Int Edit, 2013, 52, 13186-13200.
3. A. Manthiram, S. H. Chung and C. X. Zu, Adv Mater, 2015, 27, 1980-2006.
4. D. Bresser, S. Passerini and B. Scrosati, Chem Commun, 2013, 49, 10545-10562.
5. C. J. Hart, M. Cuisinier, X. Liang, D. Kundu, A. Garsuch and L. F. Nazar, Chem Commun, 2015, 51, 2308-2311.
6. X. W. Yu, Z. H. Bi, F. Zhao and A. Manthiram, Acs Appl Mater Inter, 2015, 7, 16625-16631.
Core-Shell Structural Evolution of Crystalline Silicon Nanoparticles upon Lithiation/Delithiation By Ex Situ Raman Spectroscopy and Operando Synchrotron X-Ray Diffraction
Authors: Pavlenko Ekaterina , Quazuguel Lucille , Boniface Maxime , Tardif Samuel , Rieutord François , Marechal Manuel , Micha Jean-Sébastien , Mareau Vincent , Gonon Laurent , Lyonnard Sandrine 
Published: February 2020

Core-shell structural evolution of crystalline silicon nanoparticles upon lithiation/delithiation by ex situ Raman spectroscopy and operando synchrotron X-ray diffraction

Silicon has attracted substantial attention as an alternative anode material for next-generation Li-ion batteries (LiBs) as it has a high theoretical capacity of 3580 mA h g-1 that is about ten times that of the commonly used graphite. (1) Upon charging, Si and Li react via an alloying process with a sharp interphase separating the growing LixSi amorphous phase from the pristine crystalline Si. In case of spherical particles this leads to a core-shell structure captured in Figure1b and c. An enormous volume expansion of Si associated with alloying leads to cracking of the electrode material and rapid fading of its performance. This hinders Si from being widely used in LiBs. It has been reported that for Si nano-particles (diameter<150nm) volume expansion does not lead to cracking (2). To benefit from silicon unique properties and enable realization of smart electrode design, an enhanced understanding of structural evolution along charging/discharging is required.
In the present work we were able to evidence the gradual amorphisation of crystalline Si nanoparticles upon cycling using ex situ Raman spectroscopy. Furthermore we probed the resulting stresses found in cores of the core-shell structures of Si nanoparticles and their evolution along lithiation/delithiation. Operando synchrotron X-ray diffraction (XRD) has also been performed to monitor the changes of the crystalline lattice during the initial cycles and to further quantify the constrained/unconstrained state of the silicon core. By means of combined ex situ Raman spectroscopy and in situ XRD we were able to provide in-depth understanding of the nanoparticles evolution.

Figure
1
. Schematic representation of silicon electrodes: a) pristine b)
after 1 cycle lithiation
c)
after 100 cycles lithiation
d) corresponding Raman spectra. Black, blue and green, respectively.
(All spectra were normalized to the maximum of the c-Si peak)

1. Obrovac, M. N., and Leif Christensen. "Structural changes in silicon anodes during lithium insertion/extraction." Electrochemical and Solid-State Letters 7.5 (2004): A93-A96.
2. Liu, Xiao Hua, et al. "Size-dependent fracture of silicon nanoparticles during lithiation." Acs Nano 6.2 (2012): 1522-1531.

Figure 1
Advanced Processing and Electrochemical Analysis of Novel Sodium-Rich Anti-Perovskites Via Conventional Sintering and Spark Plasma Sintering Methods
Authors: Wu Erik , Nguyen Han , Hy Sunny , Yersak Thomas A. , Meng Ying Shirley 
Published: February 2020

Interest in non-flammable solid-state battery electrolytes continues to grow as they hold promise for batteries with increased safety, reliability, and energy density. They are nonflammable, stable over a wide temperature range, have a large electrochemical window, and potentially allow for the use of metallic Li anodes [1].
One particular solid-state electrolyte is the Lithium-rich anti-perovskite (LiRAP) with the formula Li3OX where X is a halogen or a mixture of halogens. Conductivities of >1 mS/cm were previously reported [2]. Interest in the material grew as the conductivity varied with different processing conditions thus opening the door to improvement with structura tweaking and optimization [3].
Whenever new a lithium compound is discovered in the battery field, interest in a sodium analog also arises. Na-ion batteries are considered a possible lower-cost alternative to lithium ion batteries due to the abundance of sodium. The conductivity of various Na-rich anti-perovskite (NaRAP) compounds with varying halogens were also previously reported [4].
Here we compare different synthesis methods for the Na3OBr compound, namely conventional cold-pressed sintering and spark plasma sintering. Spark plasma sintering enables a shorter processing time and more tightly-packed, dense pellets [5]. We report that the Na ionic conductivity for Na3OBr remained at similar values regardless of the synthesis method.
Acknowledgements
This work was supported by the National Science Foundation under grant number ACI-1053575.
References
[1] Thangadurai, V., Pinzaru, D., Narayanan, S., Baral, A. “Fast Solid State Li Ion Conducting Garnet-Type Structure Metal Oxides for Energy Storage”. J. Phys. Chem. Lett., 2015, 6 (2), pp 292–299. doi: 10.1021/jz501828v
[2] Wang, Y, Richards, W. D., Ong, S. P., Miara, L. J., Kim, J. C., Mo, Y., and Ceder, G. “Design principles for solid-state lithium superionic conductors”. Nature Materials, 2015, 14, pp 1026-1031. doi: 10.1038/nmat4369
[3] Deng, Z., Radhakrishnan, B., Ong, S. P. “Rational Composition Optimization of the Lithium-Rich Li3Ocl1-xBrx Anti-Perovskite Superionic Conductors”. Chem. Mater.
2015, 27(10), pp 3749-3755. doi: 10.1021/acs.chemmater.5b00988
[4] Wang, Y., Wang, Q., Liu, Z., Zhou, Z., Li, S., Zhu, J., Zou, R., Wang, Y., Lin, J., Zhao, Y. “Structural manipulation approaches towards enhanced sodium ionic conductivity in Na-rich antiperovskites.” J. Power Sources
2015, 293, pp 735–740. doi: 10.1016/j.jpowsour.2015.06.002
[5] Sairam, K., Sonber, J. K., Murthy, T.S.R.Ch., Subramanian, C., Fotedar, R. K., Nanekar, P., Hubli, R.C. “Influence of spark plasma sintering parameters on densification and mechanical properties of boron carbide”. Int. Journal of Refractory Metals and Hard Materials, 2013, 42, pp 185-192. doi: 10.1016/j.ijrmhm.2013.09.004
Electrochemical Characterization of Advanced Sulfur Cathode Materials for Li-S Batteries
Authors: Nguyen Dan Thien , Hoefling Alexander , Lee Young Joo , Theato Patrick , Song Seung-Wan 
Published: February 2020

Lithium-ion batteries are promising energy storage systems for electric vehicles and smart-grid storage systems. However, the needs for new batteries with higher energy than that of the current lithium-ion batteries are increasing. Among many battery systems, lithium-sulfur (Li-S) batteries are one of the most attractive candidates for next-generation high-energy density batteries due to high theoretical capacity of sulfur of 1672 mAh/g.1 However, commercialization of Li-S batteries has been hindered by the issues such as the insulating nature of sulfur and lithium sulfide (Li2S) and polysulfide shuttle electrode-electrolyte interfacial instability. In order to achieve high performance Li-S batteries, much research efforts have devoted to solve those problems by preparing sulfur-based composite with porous carbon, and optimizing electrolyte composition and concentration and functional binder.2,3 However, report of the development of new sulfur material, and its electrochemical behavior and reaction mechanism, and correlation to the cycling performance of Li-S batteries is limited. Herein, we report on the improvement of electrochemical performance of an advanced sulfur cathode material by optimizing the cathode composition and electrolyte concentration. Correlation between the cycling performance and the changes in surface property and particle morphology of sulfur cathode material with cycling, which is obtained through ex situ X-ray photoelectron spectroscopy and scanning electron microscopy, would be presented in the meeting.

Acknowledgements

This work was supported under the framework of international cooperation program managed by National Research Foundation of Korea (2015K2A5A3000068) and German Academic Exchange Service (57141898).

References

1. Y.S. Su, Y. Fu, T. Cochell, and A. Manthiram, Nat. Commun., 4, 2985 (2013).
2. N. Jayaprakash, J. Shen, S. S. Moganty, A. Corona, and L. A. Archer, Angew. Chemie, 123, 6026 (2011).
3. S. Urbonaite, and P. Novák, J. Power Sources, 249, 497 (2014).