bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of Using Fluorinated Ether and Sulfone As Electrolyte Solvents for Lithium Ion Batteries with Lithium Rich Layered Cathode and Silicon Oxide Anode
Authors: Noguchi Takehiro , Hasegawa Takuya , Yamauchi Hideki , Yamazaki Ikiko , Utsugi Koji
Published: February 2020

Introduction

Li rich layered cathode is one of the candidates for next generation cathode active material of Lithium ion batteries, because of large capacity more than 250 mAh/g. On the other hand, because of the higher potential than conventional cathode active materials, Li rich layered cathode has the problem of the capacity fading and gas emission. We have studied fluorinated electrolyte solvents for high voltage operation batteries with LiNi0.5Mn1.5O4 cathode1) 2), and we have reported that fluorinated ether and fluorinated phosphate were effective to reduce gas emission in high voltage operation cells at elevated temperature. In this report, we examined fluorinated ether and sulfone as electrolyte solvents for Lithium ion batteries with Li rich layered cathode and SiO anode.

Experimental

Li(LixNiyMn1-x-y)O2 was used as a cathode active material, and SiO was used as an active anode material. The discharge capacity as a function of cycle number was tested using stack type laminated cells with these active materials. Ethylene carbonate (EC), diethyl carbonate (DEC), DES (Diethyl sulfone) and 1,1,2,2-tetrafluoroethyl 2,2,3,3-tetrafluoropropyl ether (FE) were used as electrolyte solvents. EC/DEC (30/70 v/v) and EC/DES/FE (x/(30-x)/70 v/v/v (x=0,5,10)) were used as electrolyte solutions. The volume of the cells was measured by the Archimedes method before and after initial 3 charge discharge cycles between 4.5 V and 1.5 V. After that, cycle tests were performed between 4.5 V and 1.5 V at 45 ºC.

 

Results

Figure 1 shows discharge capacity retention as a function of cycle number for Li(LixNiyMn1-x-y)O2/SiO cells with electrolyte solutions of EC/DEC (30/70 v/v) and EC/DES/FE (5/25/70 v/v/v). Capacity retention of EC/DES/FE after 200 cycles was larger than that of EC/DEC. DES and FE seem to have higher oxidation resistance than DEC and to have the effect of cycle life improvement. Figure 2 shows the volumes increase of cells after initial 3 charge-discharge cycles at 45 °C. The cause of volume increase is gas emission. The volume increase of the cell with EC/DEC (30/70 v/v) was larger than that with EC/DES/FE (x/(30-x)/50 v/v/v). Gas volume increased with amount of EC in electrolyte of EC/DES/FE. This result shows that the cause of gas emission at initial charge-discharge process seems to be due to the reaction between electrolyte solvents and cathode. EC is considered to be the cause of gas emission in initial charge discharge cycles.

References

T.Noguchi, M.Uehara, Y.Katoh, K.Utsugi, PRiMe 2012 Abstract, No.824 (2012)

T.Noguchi, Y.Katoh, K.Utsugi, 228th ECS Meeting Abstract, No.358(2015)

Figure 1
A Detailed-Electrochemistry Model of an LiFePO4/Graphite Lithium-Ion Cell Capturing Abuse and Aging Phenomena
Authors: Kupper Christian , Rißmann Sascha , Bessler Wolfgang G.
Published: February 2020

Numerical simulations are an important corner stone for the development of lithium-ion batteries as they can save expenses in time and cost for a large number of series of experiments. Empirical models have the advantage of a fast development and a low computational effort, but their predictions are only valid within the range of experimental data used for fitting. In contrast, physically-based models allow a deeper understanding and increase the applicability to different scenarios and the credibility of the model predictions.

We present a multi-scale modelling approach coupling a 1D thermal cell-level (macro-scale) model, a 1D electrode-pair level (micro-scale) model, and a 1D particle-level (nano-scale) model (Figure 1) 1. A particular feature of the model is detailed electrochemistry, capturing multi-step main and side reactions occurring during ageing or thermal runaway. The model is parametrized to commercial lithium iron phosphate cells. We assume solid electrolyte interphase (SEI) formation at the anode as dominant aging mechanism, which is known to be the main contributor to calendaric aging 2. By capturing the nonlinear feedback between electrochemistry and transport, the model is able to simulate cell behavior not only within recommended operating conditions, but also during cell abuse, for example, due to external short circuit, and during long-time operation.

Simulations of short time (external short circuit) and long time (lifetime estimation) scenarios are presented (Figure 2,3). These different events are compared and interpreted, for example in terms of reaction limitation or transport limitation. The sensitivity and reassessment of the model parameter is discussed, and the model as a comprehensive copy of the real battery is verified. Thereby insights into the battery which are experimentally hard to obtain, like concentration and temperature gradients or the distribution of lithium in the active material (Figure 4), are more justified than before.

References

1. C. Kupper and W. G. Bessler, J. Electrochem. Soc.,
164(2), A304-A320 (2017).

2. H. Zheng, L. Tan, L. Zhang, Q. Qu, Z. Wan, Y. Wang, M. Shen and H. Zheng, Electrochim. Acta,
173, 323–330 (2015).

Figure 1
Flexible, Solid-State, Ion-Conducting Membrane with 3D Garnet Nanofiber Networks for Lithium Batteries
Authors: Fu Kun , Gong Yunhui , Wachsman Eric D. , Hu Liangbing
Published: February 2020

Beyond state-of-the-art lithium-ion battery (LIB) technology with metallic lithium anodes to replace conventional ion intercalation anode materials is highly desirable because of lithium’s highest specific capacity (3,860 mA/g) and lowest negative electrochemical potential (∼3.040 V vs. the standard hydrogen electrode). In this work, we report for the first time, to our knowledge, a 3D lithium-ion–conducting ceramic network based on garnet-type Li6.4La3Zr2Al0.2O12 (LLZO) lithium-ion conductor to provide continuous Li+ transfer channels in a polyethylene oxide (PEO)-based composite. This composite structure further provides structural reinforcement to enhance the mechanical properties of the polymer matrix. The flexible solid-state electrolyte composite membrane exhibited an ionic conductivity of 2.5 × 10−4 S/cm at room temperature. The membrane can effectively block dendrites in a symmetric Li | electrolyte | Li cell during repeated lithium stripping/plating at room temperature, with a current density of 0.2 mA/cm2 for around 500 h and a current density of 0.5 mA/cm2 for over 300 h. The presentation will focus on our recent development of 3D garnet nano structured solid-state electrolyte membrane for Li metal batteries.

Figure 1
Enhanced Electrochemical Performance of Fe-Sn Alloy with Cu Additive As Anode in Lithium-Ion Batteries
Authors: Xin Fengxia , Zhou Hui , Ji Dongsheng , Wang Xiaoya , Ding Jia , Shi Yong , Omenya Fredrick , Chernova Natasha A. , Whittingham M. Stanley
Published: February 2020

Tin based alloys have attracted much attention as one of the promising anode materials because of their higher gravimetric/volumetric capacity and safer thermodynamic potential for next generation lithium-ion batteries. Ultrasmall Fe-Sn alloy with Cu additive (Fe-Sn-(Cu)) was synthesized using Sn nanoparticles as template by modified polyol method. Compared with Fe-Sn alloy, the cycling performance and rate capability were largely enhanced when Fe-Sn-(Cu) alloy was used as anode with the average loading weight of 1.5 mg/cm2. It could deliver 465 mAh/g after 200 cyclesat the C/2 rate, corresponding to an average capacity loss of only 0.08% per cycle. The calculated volumetric capacity was more than 1.5 times of commercial carbon. It also has exceptional rate capability, delivering 91.9%, 82.6%, 74.4%, 63.5% of the 0.1C capacity (557 mAh/g) at 0.2C, 0.5C, 1C and 2C, respectively. Fe-Sn-(Cu) alloy with higher capacity and enhanced cycling performance may become a potential candidate as anode in lithium-ion battery. This work is supported by the U.S. Department of Energy’s Office of Energy Efficiency and Renewable Energy (EERE) program under Award No. DE-EE0006852.
Electronic Structures and Optical Properties of Al, Cu and Ag in Bulk, Thin Film and Nanoparticle Forms
Authors: Mishra Kailash C. , Piquette Alan , Schmidt Peter C. , Johnson Keith H
Published: February 2020

The electronic structures of aluminum, copper, and silver were investigated in bulk, thin-film and nanoparticle forms using first-principles band structure methods. The density of states (DOS) and partial density of states (PDOS) were also calculated. The calculations show the progression from continuous bands to subbands to discrete states as spatial confinement is imposed by going from bulk to thin film to particle forms. The choice of metals in this study allows for the comparison of the degree of localization of the d-electrons on inter-band transitions, which, in part, governs the optical properties of the metals.

The associated optical properties described by the imaginary component of the dielectric function, ε2(ω), were also investigated. The interband contributions to ε2(ω) were calculated from the band structure, while the intraband contributions were calculated using the Drude theory for free electrons. Both contributions to ε2(ω)are needed to understand the optical properties of metals and to interpret their reflectance spectra. The interband transitions need to be considered to explain reflectivity at energies lower than the plasma frequencies, but not all interband transitions result in reflectance peaks since they are significantly weaker compared to the intraband contributions at lower energies.

We have studied the dependence of the DOS, PDOS and ε2(ω) on the choice of exchange potentials by comparing results obtained using the generalized gradient approximation (GGA) and the Heyd-Scuseria-Ernzerhof (HSE) hybrid functional. In copper, where ultraviolet photoelectron spectroscopy data are available, the HSE potential leads to better agreement with the experiment than when using the GGA potential, and HSE reproduces correctly the variation of binding energy of the d electrons as spatial confinement is imposed. The corresponding dependence of exchange potential for silver exists, but is less severe.
(Invited) Upconversion: Photoswitching, Photocleavable
Authors: Capobianco J. A.
Published: February 2020

Research on light controlled drug delivery release systems has shown great potential in biomedical applications. However, in general the photo response of molecules is based on UV excitation. In biomedical applications longer wavelength NIR light is preferable since it shows deeper tissue penetration and is less detrimental to tissue. We report on the synthesis of LiYF4:Tm3+/Yb3+ functionalized(UCNP) with a lipid bilayer and azobenzene. The nanoconstruct synthesised is hydrophilic shows excellent colloidal stability and biocompatibility. The nanocomposite can be used as a drug delivery system making use of NIR light excitation (980 nm) to induce the multiphoton process known as upconversion. The LiYF4 Tm3+/Yb3+ nanoparticles emit in the UV, visible and/or near-infrared. Fluorescence energy transfer (FRET) from the upconverting nanoparticles (UV emission) to the azobenzene triggers the photoswitching of the azobenzene from the trans to the cis. The photoswitching of the azobenzene molecules disrupts conformation of the supported lipid bilayer thus releasing the drug.

Recently, photosensitive drug delivery systems, which make use of a nitrobenzyl-type ‘photocaged’ anticancer drug conjugated to another small or macromolecule. In each of these cases drug release from the conjugate was mediated by UV light. A major limitation of this approach for in vivo drug release is the low tissue penetration ability of UV light and inevitable DNA damage. A potential solution is afforded by UCNPs loaded with photocaged doxorubicin (DOX) onto the surface of the UCNPs via a photocleavable linkage.
Tb3+-Eu3+ Energy Transfer in Tb-Based Phosphates: A Comparison of Two Extreme Cases
Authors: Carrasco Irene , Piccinelli Fabio , Bettinelli Marco
Published: February 2020

Energy transfer processes involving trivalent lanthanide ions (Ln3+) are crucial for the development of innovative luminescent materials and devices such as phosphors, scintillators, materials for solar cells, nanothermometers or materials for optical bioimaging, among others.

In the case of the Tb3+→Eu3+ energy transfer in Tb-based materials containing Eu3+ as a dopant, different types of behaviour can be observed in different systems due to structural peculiarities of the host. These differences determine the emission colour of the material, since this is strongly related to the presence or absence of energy transfer (both Tb3+→Tb3+ and Tb3+→Eu3+).

In this contribution we present and discuss the luminescence properties of Ca9Tb(PO4)7 powders (whitlockite family, rhombohedral structure) and TbPO4 powders (tetragonal structure) doped with Eu3+. In the case of the Eu-doped TbPO4 powders, a very fast and efficient Tb3+→Eu3+ energy transfer is present upon near UV excitation in the Tb3+ ion. This changes the emission colour of the material from green to red even by addition of small amounts of europium ions. On the contrary, in the Eu-doped Ca9Tb(PO4)7 samples the Tb3+→Eu3+ energy transfer process is not efficient and the resulting emission colour of the Eu3+-doped materials appears to be yellow, even for high europium doping levels.
(Invited) Shedding Light in Nanothermometry
Authors: Carlos Luís D
Published: February 2020

Luminescent ratiometric thermometers combining high spatial and temporal resolution at the micro and nanoscale, where the conventional methods are ineffective, have emerged over the last decade as an effervescent field of research, essentially motivated by their potential applications in nanotechnology, photonics and biomedicine [1]. Among the distinct luminescent thermal probes, Ln3+-based materials play a central role in the field due to their unique thermometric response and intriguing emission features (e.g., high quantum yield, narrow bandwidth, long-lived emission, large Stokes shifts, and ligand-dependent luminescence sensitization).

One of the main challenge that is currently facing scientists in the field is to use luminescent thermometry for unveiling thermometers’ local surrounding properties, as, for instance, heat transfer in heater-thermometer nanoplatforms [2], the absorption coefficient and thermal diffusivity of tissues in small animals [3] and the measurement of the instantaneous ballistic velocity of Brownian nanocrystals suspended in both aqueous and organic solvents based on upconversion nanothermometry [4].

 This lecture presents a general revision of the work done in the last couple of years on ratiometric luminescent nanothermometers with foucus on recent examples in which the technique was used for unveiling thermometers’ local surrounding properties.

[1] C. D. S. Brites, A. Millán, L. D. Carlos, in Handbook on the Physics and Chemistry of Rare Earths, J.-C. Bünzli, V. K. Pecharsky, Eds., Amsterdam: Elsevier Science B.V., Vol. 49 (2016), 339.

[2] R. Piñol, C. D. S. Brites, R. Bustamante, A. Martínez, N. J. O. Silva, J. L. Murillo, R. Cases, J. Carrey, C. Estepa, C. Sosa, F. Palacio, L. D. Carlos, A. Millán, ACS Nano 9 (2015)3134

[3] E. C. Ximendes, W. Q. Santos, U. Rocha, U. K. Kagola, F. Sanz-Rodríguez, N. Fernández, A. da Silva Gouveia-Neto, D. Bravo, A. Martín Domingo, B. del Rosal, C. D. S. Brites, L. D. Carlos, D. Jaque, C. Jacinto, Nano Lett.
16 (2016) 1695.

[4] C. D. S. Brites, X. Xie, M. L. Debasu, X. Qin, R. Chen, W. Huang, J. Rocha, X. Liu, L. D. Carlos, Nature Nanotech.
11 (2016) 851.
Simulating a Potential Step Using Shareware
Authors: Haque Inam ul
Published: February 2020

Simulation of a potential step experiment of an electrochemical system in an infinite solution using explicit method [1] was done. Listing of program in Fortran was compiled using shareware program FORCE 2.0 FORTRAN compiler and editor [2]. Plot of potential step experiment for Z/Zc vs. X for L/n from above mentioned listing is shown.

Simulations done by transliterating Fortran [3] into Turbo Pascal will also be discussed. Symbols are as per [3].

[1] W. Breen and J. Cassidy, Simulation of dynamic electrochemical processes, Curr. Top. Electrochem., 9 (2003) p. 47

[2]www.igpp.ucla.edu/public/rwalker/ess261_2007_spring/Force/Force%20Fortran%20Compiler%20and%20Editor.htm

[3]A. J. Bard and L. R. Faulkner, Electrochemical Methods: Fundamentals and Applications, 2nd Edition, Wiley (2001) p. 793

Figure 1
Nitrogen-Doped Ordered Mesoporous Carbon/Graphene Framework As Dual Electrocatalyst for Oxygen Reduction and Evolution Reactions
Authors: Zhang Changlin , Wang Biwei , Dong Angang , Peng Zhenmeng
Published: February 2020

One important research topic in electrocatalysis is electrochemical redox between H2O and O2 for the design of regenerative electrochemical energy storage and conversion system, which involves oxygen reduction reaction (ORR) during discharging process and oxygen evolution reaction (OER) upon charging process. Thus, it is of great importance to develop a dual functional electrocatalyst which is active in both ORR and OER and can reduce the usage of noble metals.

We report the synthesis of highly ordered N-doped mesoporous carbon/graphene frameworks (N-MCF/N-MGF), which possessed large surface area, high porosity, excellent internal diffusion property, and superior intrinsic conductivity and exhibited promising catalytic properties in both ORR and OER. As a dual catalyst, the N-MGF exhibited overpotential as low as 324 mV for harvesting 10 mA cm-2 OER current density, which was lower than most of previously reported carbon-based materials and were comparable with the benchmarking noble metal oxide catalysts. The catalyst was also durable under both OER and ORR conditions. These results presented a low-cost dual ORR/OER electrocatalyst with high activity and good durability as well as their negligible internal diffusion resistance, which could be potentially utilized and implemented in renewable energy techniques such as metal-air batteries, fuel cells, and water splitting devices.
Binary Molybdenum Borides Nanostructures As Novel Electrocatalysts for Hydrogen Evolution Reaction
Authors: Jothi Palani Raja , Fokwa Boniface P.T.
Published: February 2020

Molybdenum based materials have recently emerged as highly active non-noble metal electrocatalysts for hydrogen evolution reaction (HER) [1, 2]. Molybdenum borides in contrary have not been studied for their HER activity at the nanoscale, however, they were recently shown to be already efficient HER catalysts in the bulk [3]. In this study, we have successfully synthesized nanocrystalline molybdenum boride nanowires (MoB) and nanospheres (MoB2) using a simple, one-step, solid state reaction. The structural and morphological characterizations were studied using XRD, XPS and electron microscopy. The obtained molybdenum borides nanostructures were tested for their electrocatalytic activity for HER in acidic conditions. We found that, nanoscale MoB2 exhibits a low onset overpotential and low Tafel slope value compared to nanoscale MoB indicating a boron- and structural dependency of these nanoborides for the HER. Also, the onset overpotential and Tafel slope values obtained represent a significant improvement from those observed for the already highly active bulk borides [3], thus opening a new avenue for inexpensive nanoscale metal boride nanomaterials as highly efficient non-noble metal HER catalysts.

References:

H. Vrubel and X. L. Hu, Angew. Chem. Int. Ed.,
55 (2012) 12703-12706.

P. Xiao, M. A. Sk, L. Thia, X. M. Ge, R. J. Lim, J. Y. Wang, K. H. Lim and X. Wang, Energy Environ. Sci.,
7 (2014) 2624-2629.

H. Park, A. Encinas, J. P. Scheifers, Y. Zhang and B. P. T. Fokwa, Angew. Chem. Int. Ed.,
56 (2017) https://doi.org/10.1002/anie.201611756.
Electroless Platinum Deposition for in Situ Spectroelectrochemistry
Authors: Gobrogge Eric A. , Ren Xiaoming , Lundgren Cynthia A.
Published: February 2020

Over the last 40 years, surface enhanced spectroscopic techniques have been used to study low concentrations of molecular species at surfaces. Among the more common of these techniques is surface enhanced infrared absorption spectroscopy (SEIRAS). SEIRAS utilizes surface plasmon phenomena to generate an interfacial electric field stronger than that of the incident light. Surfaces capable of supporting surface plasmons are generally composed of roughened metal films, or metal films coating a roughened surface. This work represents a study of roughened platinum surfaces deposited from different techniques including metal sputtering, evaporation, and wet chemical deposition. Diagnostics such as conductivity, optical transmission, particle size, and CO adsorptive capability were used to determine the ideal deposition parameters for a given application. After preparation, these surfaces are used to demonstrate plasmonically enhanced infrared absorption capabilities which we use in situ to study the mechanisms of electrochemical reactions in energy conversion devices.
Observation of First-Order, Marcus Normal, Interfacial Electron Transfer at Dye-Sensitized TiO2 Interfaces
Authors: DiMarco Brian N , Troian-Gautier Ludovic , Sampaio Renato N , Meyer Gerald J
Published: February 2020

Dye-sensitized solar cells combine the robustness of nanocrystalline TiO2 with molecular dyes or “sensitizers” that absorb broadly across the visible. The surface anchored sensitizer undergoes a photo-induced electron transfer to the TiO2 acceptor states and is subsequently regenerated by a redox mediator present in the external electrolyte. Efficient light-to-energy conversion requires that the injected electron be transported to the external circuit prior to recombination with the oxidized redox mediator. Despite the importance of this unwanted recombination reaction the mechanism remains elusive. This is due in part to complex kinetics that usually cannot be described with first- or second order kinetic models, but satisfactory fitting instead require sums of exponentials or stretched exponential functions. The non-exponential kinetics are likely due to transport of the injected electron and/or the electron acceptor prior to recombination. Here we report charge recombination studies of charge recombination to a family of oxidized amines that provide compelling evidence for first-order kinetics with abstracted rate constants that show a driving force dependence.

The recombination reaction between nanocrystalline anatase TiO2 and a series of symmetrically substituted triphenylamine (TPA) redox mediators that possessed electron donating or withdrawing groups at the para-position of the phenyl rings was quantified on nanosecond and longer time scales. The groups utilized afforded an ~0.5 V change in TPA+/0 reduction potential. The nanocrystalline TiO2 thin films were sensitized by a ruthenium polypyridyl complex bearing either a carboxylic or a phosphonic acid functional group for surface anchoring. Pulsed light excitation of the film resulted in excited-state injection to yield TiO2(e-)|S+. Sensitizer regeneration and the subsequent charge recombination reaction TiO2(e-) + TPA+ → TiO2 + TPA were then monitored spectroscopically. Concentration dependent data revealed that recombination could be described by a distribution of first-order rate constants that became strictly first-order when the driving force was larger. The reaction rate increased with more positive TPA+/0 reduction potentials, consistent with electron transfer in the Marcus normal region. The recombination reaction was monitored as a function of temperature, and an Arrhenius analysis provided activation energies. Interestingly, the same activation barrier was abstracted for all the TPA derivatives, suggesting that a common rate limiting step exists for all these reactions. A model for recombination consistent with both the thermodynamics and activational parameters will be presented.
(Invited) Enhanced Photoelectrocatalytic Activity for Splitting Water Based on Heterostructured TiO2 Nanotube Arrays
Authors: Wu Zhi , Sun Lan , Ye Meidan , Lin Zhiqun , Lin Changjian
Published: February 2020

Photoelectrocatalytic water splitting is widely recognized as one of the most promising strategies to large-scale production of hydrogen for renewable energy. To further enhance the photoelectrocatalytic efficiency, severalheterostructures based on TiO2 nanotube arrays were developed in this work. (1) TiO2 nanotube arrays (TNTAs) were decorated with NiO nanoparticles via a sequential chemical bath deposition (CBD) approach to yield NiO@TNTA photoanodes. It demonstrated that the incident-photon-to-current-conversion efficiency (IPCE) and hydrogen production rate of the optimized NiO@TNTA reached 62.8% and 37.8 μmol.h-1.cm-2, respectively, approximately 5.0 times higher than pure TNTAs, which was attributed primarily to the efficient separation of photogenerated charge carriers at the p–n junction of p-type NiO and n-type TiO2. (2) CuxZn1-xIn2S4 ultrathin nanosheets on TiO2 nanotube arrays (CZIS@TNTAs) was successfully synthesized by solvothermal reaction. It found that the CuxZn1-xIn2S4 ultrathin nanosheets on TNTAs significantly enhanced visible light absorption and and a near 8.0-fold increase in photoelectrocatalytic hydrogen production rate was achieved compared to that of the blank TNTAs. The superior photoelectrocatalytic activity of CZIS@TNTAs heterostructured composite electrode was mainly due to enhanced light absorption and separation of photo-generated charges, and facilitating electron transport along the 1D TiO2 structure. (3) TiO2 nanotube arrays (TNTAs) sensitized by palladium quantum dots (Pd QDs) by a modified hydrothermal reaction. When Pd@TNTA nanocomposites were used as both photoanode and cathode in water splitting, the photon-to-current conversion efficiency of nearly 100% atλ=330 nm and a greatly promoted photocatalytic hydrogen production rate of 592 μmol·h−1·cm−2 under 320 mW·cm−2 irradiation were achieved. The synergy between nanotubular structures of TiO2 and uniformly dispersed Pd QDs on TiO2 facilitated the charge transfer from TiO2 nanotubes to Pd QDs and the high activity of Pd QDs catalytic center, thereby leading to high-efficiency photoelectrocatalytic hydrogen generation.
(Invited) Energy Transfer and Catalysis in Metal Organic Framework Arrays
Authors: Morris Amanda J
Published: February 2020

Metal Organic Frameworks (MOFs) provide a promising platform for the control of energy transfer within light-harvesting arrays. The efficiency of energy transfer is related to three major factors - the degree of spectral overlap between the donor (emission) and acceptor (absorption), the distance between donor and acceptor, and the orientation of the donor and acceptor in 3D space. Our group has pioneered work in the investigation in effects of separation distance and orientation on energy transfer in chromophore-modified MOFs. Given our results, design parameters for MOF energy transfer candidates will be provided. Additionally, we will explore the capability of MOF arrays to promote electron transfer catalysis. Our results indicate that MOFs promote various energy-related catalytic reactions including oxygen reduction, carbon dioxide reduction, and water oxidation. The mechanism of electron transport through these catalysts-modified MOFs is one of ambi-polar redox hopping. Through MOF incorporation, the current resultant under electrochemical conditions is increased by two orders of magnitude.
(Invited) On the Low-Cost Design, Performance and Stability of Advanced Electrodes for Photocatalytic (sea)Water Splitting
Authors: Vayssieres Lionel
Published: February 2020

The latest advances along with the overview of two decades of fundamental and applied research on low-cost metal oxide semiconductor aqueous design, electronic structure and applications for renewable energy systems [1] will be presented. It will include the design and fabrication strategies [2] as well as nanodevices fabrication for efficient low cost solar (sea)water oxidation without sacrificial agents [3]. Visible-light active photocatalyst heteronanostructures based on non-toxic and earth abundant materials engineered to efficiently drive aqueous chemical reactions at their interfaces will be demonstrated. Their surface chemistry [4], structural, optical, electrical [5], electronic structure [6], photoelectrochemical, and dimensionality/confinement effects [7] along with their efficiency have been thoroughly investigated at synchrotron radiation facilities as well as in our laboratories. The most promising structures including oxides, nitrides, sulfides and phosphides for low cost and large scale solar water splitting will be discussed along with the atomic-scale origin of their performance and stability [8].

References

[1]J.Z. Su and L.Vayssieres, ACS Energy Lett.
1, 121 (2016); Y. Tachibana et al, Nat. Photon.
6, 511 (2012); On Solar Hydrogen & Nanotechnology, L. Vayssieres Ed. (Wiley, 2010); L. Vayssieres et al, Pure Appl. Chem.
72, 47 (2000)

[2]L. Vayssieres, Appl. Phys. A
89, 1 (2007); Int. J. Nanotechnol. 4, 750 (2007); Int. J. Nanotechnol.
1, 1 (2004); Angew. Chem. Int. Ed.
43, 3666 (2004); Adv. Mater.
15, 464 (2003); J. Phys. Chem. B
107, 2623 (2003); Nano Lett. 2, 1393 (2002); Chem. Mater.
13, 4395 (2001); Chem. Mater.
13, 233 (2001); J. Phys. Chem. B
105, 3350 (2001)

[3] Y.K. Wei et al, Nano Res.
9, 1561 (2016); C.X. Kronawitter et al, Energy Environ. Sci.
7, 3100 (2014); Energy Environ. Sci.
4, 3889 (2011)

[4]L. Vayssieres, J. Phys. Chem. C
113, 4733 (2009); Int. J. Nanotechnol. 2,411 (2005)

[5]J. Engel et al, Adv. Funct. Mater.
24, 4952 (2014)

[6]C.X. Kronawitter et al, Nano Lett.
11, 3855 (2011); Phys. Rev. B
85, 125109 (2012); J. Phys. Chem. C
116, 22780 (2012); PhysChemChemPhys
15, 13483 (2013); F. J. Himpsel et al, J. Electron Spectrosc. Relat. Phenom. 190, 2 (2013); C. L. Dong et al, Phys. Rev. B
70, 195325 (2004); J.H. Guo et al, J. Phys. Condens. Matter
14, 6969 (2002)

[7]L. Vayssieres et al, Appl. Phys. Lett.
99, 183101 (2011); Adv. Mater.
17, 2320 (2005)

[8] M.G. Kibria et al, Adv. Mater.
28, 8388 (2016); J.Z Su et al, J. Phys. Chem. Lett. (2017), invited perspective
(Invited) Tuning the Selectivity of Carbon Dioxide Electroreduction Using Copper-Based Catalysts
Authors: Yeo Boon Siang
Published: February 2020

Currently, more than 80% of the world’s energy needs are met by burning fossil fuels. Supplies of these fuels are intrinsically limited and will eventually run out. Combustion of fossil fuels also generates carbon dioxide, whose rapidly increasing atmospheric concentration is suspected to be an accelerant of global warming. One solution for reducing atmospheric CO2 levels is carbon capture and sequestration. Another is to electrochemically reduce the CO2 into chemical feedstocks and fuels. If the energy used for these processes is generated from renewable sources such as solar and wind, we can envisage a chemical production cycle that is closed-loop with net zero carbon emission.

In this talk, we shall share our recent works related to the development of copper-based catalysts (including Cu single crystal surfaces, doped Cu, etc.) for the selective electroreduction of CO2 to compounds such as formic acid, ethylene, ethanol and propanol. We shall discuss factors that gave Cu2O-derived Cu catalysts the ability to selectively reduce CO2 to ethylene. We shall show that this ability can be correlated to the crystallite sizes of the Cu2O-derived Cu particles. We shall also present a new class of CO2 reduction catalysts made from Cu and Zn, which is highly selective towards the formation of ethanol. A two-site mechanism to rationalize the selectively is proposed. Finally, we present an overview of our recent efforts to couple photovoltaics to an electrocatalytic cell for the solar-driven reduction of carbon dioxide.

References:

Yun Huang, Albertus Denny Handoko, Pussana Hirunsit and Boon Siang Yeo. Electrochemical Reduction of CO2 Using Copper Single-Crystal Surfaces: Effects of CO* Coverage on the Selective Formation of Ethylene. ACS Catal., 2017, 7, 1749-1756.

Dan Ren, Bridget Su-Hui Ang and Boon Siang Yeo. Tuning the Selectivity of Carbon Dioxide Electroreduction towards Ethanol on Oxide-Derived CuxZn Catalysts. ACS Catal. 2016, 6, 8239-8247. 

Albertus D. Handoko, Cheng Wai Ong, Yun Huang, Zheng Guang Lee, Liyi Lin, Grace B. Panetti, and Boon Siang Yeo. Mechanistic Insights into the Selective Electroreduction of Carbon Dioxide to Ethylene on Cu2O-Derived Copper Catalysts. J. Phy. Chem. C
2016, 120, 20058-20067.

Dan Ren, Nian Tee Wong, Albertus Denny Handoko, Yun Huang and Boon Siang Yeo. Mechanistic Insights into the Enhanced Activity and Stability of Agglomerated Cu Nanocrysals for the Electrochemical Reduction of Carbon Dioxide to n-Propanol. J. Phy. Chem. Lett.
2016, 7, 20.
Junction Electrochemistry of InGaN Anode Materials in Solar Energy Conversion
Authors: Parameshwaran Vijay , Sampath Anand V , Wraback Michael
Published: February 2020

The indium gallium nitride (InGaN) ternary alloy system offers an ideal semiconductor basis as a light absorber for driving chemical reactions such as the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER). It is a direct bandgap semiconductor whose energy can be tuned for optimal solar absorption and overcoming kinetic overpotential losses, it can be grown epitaxially as a single crystal for high material quality, and it exhibits relatively high corrosion resistance in aqueous solutions for a III-V material. In this work, we report on the design, synthesis, and photoelectrochemical studies of InGaN in an anode configuration with a goal of using this material as a light absorber basis for driving solar fuels reactions such as the OER and the HER. Studies are shown reporting on how reactive vapor synthesis of GaN and InN with different structuring affects the light conversion properties and band diagram electrostatics in an electrochemical junction with ferrocene and cobaltocene redox pairs. This structure is extended to thin films of GaN and InGaN grown by molecular beam epitaxy for high efficiency light conversion, with the resulting electrochemical junction also made with ferrocene and cobaltocene. The effects of ternary alloying, doping, and the two different c-plane polarities (III-polar and V-polar) on the junction are investigated using the same electrochemical junction to evaluate the light conversion properties in relation to the electrostatics; specifically, tuning the bandgap energy for optimal light absorption, determining the c-plane polarity configuration for the electric fields to have the correct band alignment, and incorporating silicon doping to create a conductive substrate. The combination of these engineering techniques extends the depletion region of the active layer for high efficiency light absorption as similarly demonstrated for epitaxial phosphide films [1], and is utilized toward the goal of high performance solar energy conversion.

[1] V. Parameshwaran, X. Xu, and B. Clemens, Journal of the Electrochemical Society, vol. 163, no. 8, pg. H714-H721 (2016).
The Role of Ionic Liquid Electrolytes in Li-S Batteries
Authors: Ueno Kazuhide , Yogo Hirotaka , Tsutsumi Hiromori , Dokko Kaoru , Watanabe Masayoshi
Published: February 2020

Much attention is being paid to high-energy density lithium batteries such as lithium-sulfur (Li-S) battery because its specific energy density is much higher than those for commercialized lithium ion batteries [1]. However, many challenges including insulating properties of active materials, sluggish electrochemical reactions, and dissolution of the sulfur species into electrolyte remain unresolved for practical application. Electrolyte properties are essentially concerned with the above serious issues of these batteries. Undesirable side-reactions between electrolytes and the reduction products (lithium polysulfides, Li2Sm) occur in some non-aqueous electrolytes. The dissolution of the sulfur species, volatility, and flammability of electrolytes have also to be addressed for long-life operation of the Li-S cells. Therefore, development of electrolytes is a key to establishing these batteries [2].

We have determined saturated solubility of Li2Sm and S8 in various type of electrolytes ranging from molecular solvents to aprotic and solvate ionic liquids to study factors that govern the dissolution of S8 and Li2Sm species into electrolyte. In terms of solvent parameters, the solubility of Li2Sm was well correlated with Gutmann’s donor number, whereas solubility of S8 was explained by Hildebrand solubility parameter. Although weakly coordinating solvents having low donor number could greatly suppressed dissolution of Li2Sm, supporting lithium salts (e.g., LiTFSA) were hardly soluble in such weakly coordinating solvents. An exception was ionic liquid-based electrolytes: ionic liquids having a weakly coordinating anion can dissolve the supporting salt while suppressing dissolution of Li2Sm. We show how the electrolyte properties of the ionic liquids link to the cell performance such as large capacity, high Coulombic efficiency, and good reversibility.

Reference

[1] P. G. Bruce, S. A. Freunberger, L. J. Hardwick, and J-M. Tarascon, Nat. Mater., 11, 19 (2012).

[2] M. Watanabe M. L. Thomas, S. Zhang, K. Ueno, T. Yasuda, K. Dokko, Chem. Rev., ASAP (2017).
Stationary Probe Rotating Disk Electrode for in Situ Dissolution Studies
Authors: Lopes Pietro Papa , Strmcnik Dusan , Stamenkovic Vojislav , Markovic Nenad M
Published: February 2020

The development of clean, reliable and cost-effective electrochemical processes must be guided by three equally important fundamental principles: improving the catalytic activity of electrode materials, increasing their long-term stability in harsh electrochemical environments and high selectivity for targeted products. Although our current understanding on the electrochemical interface has rendered great improvement in activities for a range of energy related processes, such as those involved in Fuel Cells and Electrolyzers, we still lack the same level of control over the stability and selectivity aspects of the catalysis. One of the limitations is the ability to measure in situ and in real time how species are being generated while the reactions are taking place, a key element for understanding the dynamics of the processes beyond steady-state conditions. For that, we developed a unique experimental setup that adds to the existing rotating disk configuration the capability to observe the species produced during catalysis. The Stationary Probe Rotating Disk Electrode (SPRDE) enables a seamless connection between electrocatalysis and high-end mass spectrometers that gives us the opportunity to measure with precision the dissolution rates of almost any element of the periodic table (combination with ICP-MS). This new methodology offers advantages over flow cell systems and it can be readily applied in understanding electrochemical dissolution processes that occur during fuel cell and electrolyzer catalysis, dealloying processes, corrosion, and battery research.
(Invited) In-Operando Synchrotron X-Ray Computed Tomography for Electrochemical Energy Conversion and Storage
Authors: Zenyuk Iryna V.
Published: February 2020

Understanding transport processes in thin and porous materials is critical for electrochemical energy applications. Tools that are designed for material characterization on a large scale are not always applicable for thin (< 500 um) layers and films. Specific care needs to be taken to design hardware to observe transport phenomena on micro- and nano-scales. To correlate transport and morphology on these minute length and time-scales synchrotron X-ray computed tomography (CT) is well fit due to its fast, non-intrusive measurements, bright energy sources and relatively large field-of-view to spatial resolution ratios 1, 2.

Water management is critical for polymer-electrolyte fuel cells (PEFCs), anion exchange membrane fuel cells (AEMFCs) and polymer electrolyte membrane (PEM) electrolyzers, as depending on a device, water is used as either a reactant or byproduct of electrochemical reaction and its location, as well as transport is critical for these devices operation. In PEFCs during start-up and operation liquid water formed as a byproduct of electrochemical reaction can block gas (reactant) delivery to a catalyst, resulting in flooding, mass-transport losses, and low cell power densities. For AEMFCs water is a reactant in the cathode and its transport from the anode is critical for the cell operation. Addressing and understanding water transport issues, is made possible by introducing the capabilities for in-operando X-ray CT. In this presentation a single serpentine channel, 1 cm2 active area fuel cell and electrolyzer operating at 30 and 60oC will be presented. Cells with Platinum-group medals (PGM) and PGM-free electrodes on either cathode or anode will be presented with examples of water distributions. It was observed that for PGM-free electrodes water accumulates at components interfaces, where large voids are present. For electrolyzers water distribution in the anode under 50 and 200 mA/cm2will be shown. Furthermore, application of nano- X-ray CT for in-operando PEFCs will be demonstrated, as well as micro-CT for in-situ batteries characterization.

References

1. I. V. Zenyuk, A. Lamibrac, J. J. Eller, D. Y. Parkinson, F. Marone, F. N. Büchi and A. Z. Weber, The Journal of Physical Chemistry C, 2016.

2. I. V. Zenyuk, D. Y. Parkinson, G. Hwang and A. Z. Weber, Electrochemistry Communications, 2015, 53, 24-28.
Developing Synthetic Routes to Magnesium Battery Cathodes
Authors: Wustrow Allison , Incorvati Jared T , Hancock Justin , Vaughey John T. , Poeppelmeier Kenneth
Published: February 2020

Magnesium batteries are one of the most promising topics for next generation energy storage chemistries owing to their high theoretical energy density and similarities in testing and evaluation to more commonly studied lithium-ion systems. However they remain a relatively underexplored area due to limitations in our understanding of the storage mechanism among available electrolytes and cathode materials. While magnesium cations have been shown to reversibly intercalate into many known materials, for example Mo6S8, V2O5 and Ti2S4, expanding this work has proved difficult owning to the lack of suitable analogous structures for further study. We recently have made several advances in developing an understanding of the role of oxide lattice stability and intrinsic conductivity in creating a new generation of higher voltage cathode materials when we reported on the layered molybdenum oxide fluorobronze Mgx[MoO2.8F0.2]. In this example by developing active materials with stronger metal oxide bonds, the storage mechanism shifted from irreversible MgO formation by oxide abstraction (seen in MnO2) to true reversible intercalation. Electrochemical experiments were made possible by a new lower temperature, phase pure synthetic route which allowed us to easily scale the reaction. This talk will focus on the importance of synthetic chemistry to the advancement of the field and highlight new routes designed to expand the number of active cathode materials designed for multivalent cations.
Bulk and Nanostructured Closo-Hydroborate Salts of Lithium and Sodium As Superionic Electrolytes for Solid-State Batteries
Authors: Stavila Vitalie , Dimitrievska Mirjana , Tang Wang Si , Talin Albert Alec , White James L. , Varley Joel , Shea Patrick , Wood Brandon C. , Skripov Alexander , Udovic Terrence J
Published: February 2020

Liquid organic electrolytes continue to dominate metal-ion battery technologies despite lingering concerns over safety, capacity loss due to parasitic side reactions, limited operating temperature range, and costly packaging needed to prevent electrolyte leakage. Although several solid-state electrolytes with ionic conductivity approaching that of liquid organic electrolytes have been recently demonstrated, including perovskites, garnets, and sulfides, challenges exist in integrating these into durable battery systems. The main issues of the existing solid electrolytes are their low ionic conductivity, low electrochemical stability and large interfacial resistance between the electrodes and the solid electrolyte. We propose a new class of superionic solid electrolytes based on closo-borate and carborate anions, such as B12H12
2-, CB11H12
-, B10H10
2-, CB9H10
-. The facile cation conduction pathways in these materials are enabled by the spacious, vacancy-rich, interstitial network afforded by a sub-lattice of large, orientationally mobile anions. Many of these materials display superionic conductivity in bulk, for instance a conductivity as high as 0.03 S cm-1 was achieved in NaCB9H10 at room temperature.

This talk will describe three strategies used to further improve the conductivities of bulk closo-hydroborate and carborate anions by 1) ball-milling to create vacancies and stabilize disordered phases, 2) anion mixing to create preferred pathways for facile cation diffusion, and 3) nanoconfinement of salts inside mesoporous silica or alumina with functionalized surfaces to enhance ion-transport through nano-channels. We will show examples where nanostructuring was efficient in increasing the Li and Na-ion conductivity, in some cases by two orders of magnitude compared to bulk. We will present results from neutron scattering and nuclear magnetic resonance techniques which provide invaluable insights into the dynamical nature of the reorienting anions. Finally, we will describe the remaining challenges and barriers which remain to be solved to enable the use of nanostructured electrolytes in all-solid-state batteries at device-relevant temperatures.