bluuebunny/crossref_metadata_2025 huggingface dataset:
(Invited) Innovative Approaches to Addressing the Fundamental Materials Challenges in Advanced Water Splitting Technologies for Renewable Hydrogen Production
Authors: Miller Eric Lars , Randolph Katie , Peterson David , Rustagi Neha , Klahr Benjamin , Lyubovsky Maxim , Cierpik-Gold Kim , Gomez J Carlos
Published: February 2020

The emergence of hydrogen and fuel cell technologies offers the world important and potentially transformative environmental and energy security benefits. In recent years, research supported by the U.S. Department of Energy’s (DOE) Fuel Cell Technologies Office has contributed substantially to the development of these technologies. The research investments to reduce costs in fuel cell stacks, for example, are clearly paying off, as commercial fuel-cell electric vehicles (FCEVs) are being rolled out by major car manufacturers today. With increasing market penetration of FCEVs, enabling technologies for the affordable and widespread production of clean, renewable hydrogen is becoming increasingly important. Long term commercial viability of renewable hydrogen in the commercial marketplace will rely on continued materials research on several important fronts. Examples include the discovery and development of efficient and durable materials, devices and systems for: (1) advanced electrochemical water splitting powered by renewable electricity sources; (2) direct low-temperature photoelectrochemical water splitting powered by sunlight; and (3) direct high-temperature solar thermochemical water splitting. Research innovations in macro-, meso- and nano-scale materials are all needed for pushing forward the state-of-the-art in these areas. Such innovations are being facilitated by the DOE Energy Materials Network (EMN) initiative which aims to accelerate materials research and development for clean energy applications through the streamlined utilization of advanced scientific resources in theory, computation, experimentation, analysis, and data informatics. The “HydroGEN” EMN consortium on Advanced Water Splitting Materials for renewable hydrogen production will be described and discussed.
Photoreduction of Carbon Dioxide By the Zinc Phthalocyanine Immobilized Titanium Dioxide
Authors: Endo Makoto , Ochiai Tsuyoshi , Nagata Morio
Published: February 2020

Carbon dioxide (CO2) photoreduction in artificial photosynthesis has a potential to be an effective technology for the energy resource depletion and environmental pollution. The metal complex catalysts required for the reaction, such as Ru-Re complex, have disadvantage of high cost although they enable efficient photoreduction performance. Therefore, a material-based development of an inexpensive catalyst that also holds acceptable efficiency is highly required. In this study, we have examined the potential of zinc phthalocyanine (ZnPc) and its combination with titanium dioxide (TiO2) as the new cathode material. As shown in the figure, ZnPc has porphyrin structure that is similar to the natural chlorophyll observed in plants. Using ZnPc/TiO2, CO2photoreduction in water was evaluated. In addition, performance on generation of formic acid and carbon monoxide (CO) was investigated as well.

Experiment was done as follows. ZnPc was immobilized on TiO2 surface in the following steps. First, the ZnPc was dissolved in 15 mL tetrahydrofuran (THF) in advance. Next, titanium dioxide (TiO2) particles were immersed in the prepared solution. Immersion was done in the shaker with slow movement and lasted for about 12 hours. Thereafter, the powder was removed from the suspension and dried by suction filtration. The obtained powder was used as the sample ZnPc / TiO2. Second, the 5% solution volume of triethanolamine (TEA) was mixed in 40 mL water as a sacrificial reagent. Solution was bubbled with CO2 for 30 minutes to make suspended ZnPc/TiO2. The suspended ZnPc/TiO2 was irradiated with visible light for 4 hours. Performance of CO2 photoreduction was evaluated using gas chromatography. Results of CO2photoreduction in 1, 2, 3 and 4 hours after visible light irradiation was compared and discussed.

As a result, generation of CO was confirmed using the proposed material. On the other hand, CO was not detected in the system using ZnPc only. This suggests the CO2 photoreduction using ZnPc/TiO2 in water was effective.

ZnPc/TiO2 was fabricated and its performance of CO2 photoreduction was evaluated using gas chromatography. As the sacrificial donor, water with triethanolamine (TEA) was used. As a result, carbon oxide (CO) was obtained as the reaction product, and hydrogen gas was obtained as the water decomposition product. As an overall result, surface modification using ZnPc had shown to enhance the CO2 photoreduction ability of the TiO2.

Figure 1
Photoconversion of Carbon Dioxide and Water to Formate on Copper and Iron Mixed Oxide Catalysts
Authors: Kang Unseock , Han Dong Suk , Yoon Sun Hee , Abdel-Wahab Ahmed , Park Hyunwoong
Published: February 2020

Solar conversion of carbon dioxide and water to value-added chemicals remains a challenge. A number of solar-active catalysts have been reported but still suffer from low selectivity, poor energy efficiency, and instability, and fail to drive simultaneous water oxidation. Herein, we report CuFeO2 and CuO mixed p-type catalysts fabricated via a widely employed electroplating of earth-abundant cupric and ferric ions followed by annealing under atmospheric air. The composite electrodes exhibited onset potentials at +0.9 V vs. RHE in CO2-purged bicarbonate solution and converted CO2 to formate with over 90% selectivity under simulated solar light (Air Mass 1.5, 100 mW×cm-2). Wired CuFeO2/CuO photocathode and Pt anode couples produced formate over 1 week at a solar-to-formate energy conversion efficiency of ~1% (selectivity >90%) without any external bias while O2 was evolved from water. Isotope and nuclear magnetic resonance analyses confirmed the simultaneous production of formate and O2 at the stand-alone couples.
Photoelectrochemical Reduction of CO2 to Ethylene Glycol on IL-SAM-Modified Au Electrodes
Authors: Sugano Yoshitsune , Tamura Jun , Ono Akihiko , Kitagawa Ryota , Yamagiwa Masakazu , Mikoshiba Satoshi
Published: February 2020

As civilization continues to evolve, fossil resources are depleting and carbon dioxide (CO2) emissions are increasing. Recently, the conversion of CO2 to fuels has attracted much attention as one of the solution for resolving the above problems. Among them the conversion technologies powered by solar energy are expected to be clean methods, and some carbon compounds are generated with <10% conversion efficiencies.  However, all these compounds have only one carbon atom, and compounds with a C-C bond have not been reported. Recently, our group found that the imidazolium ion-terminated self-assembled monolayer (IL-SAM)-modified electrodes promote electrochemical conversion of CO2 to ethylene glycol with high selectivity (the Faraday efficiency is >80%) in an aqueous electrolyte solution.[1] Here we report that the SAM-modified electrodes promote the solar energy conversion to ethylene glycol from CO2.

The activity of photoelectrochemical CO2 reduction was investigated in a two-compartment cell with an anion exchange membrane. We utilized a two-wired photovoltaic (PV) cell system, wherein a four series-connected crystal silicon PV and platinum were used as the photoelectric conversion element and anode, respectively.  The cathode was synthesized by a similar method as described previously.[1] The reaction was performed by irradiation of simulated solar light, and the light intensity and the acceptance surface area of the PV were regulated so as to keep the applied potential of cathode at -0.58 V (v.s. RHE). Potassium bicarbonate dissolved in an aqueous solution was used as an electrolyte. During the reaction, CO2 was bubbled through the cathode solution, and the catholyte was periodically drawn into a syringe and directly analyzed by gas chromatography.

Initially, a high reaction current was obtained due to the electrical double layer and other effects, but several minutes later the value became approximately constant. The production rate of ethylene glycol at 3 h was 1.8 μmol and solar-to-ethylene glycol conversion efficiency was 0.16%. In this reaction, CO2 initially interacted with the C-2 ring position of the electrochemically deprotonated imidazolium, and produced a carboxylate species. The adjacent two imidazolium carboxylate species formed a dimer followed by the generation of oxalate, leading to further reduction to ethylene glycol on the imidazolium catalysts of the SAM. From this research, we achieved the photoelectrochemical conversion of CO2 to ethylene glycol with a C-C bond structure.

[1] J. Tamura, A. Ono, Y. Sugano, C. Huang, H. Nishizawa, S. Mikoshiba, Phys. Chem. Chem. Phys.
2015, 17, 26072.
(Invited) Solar Synthesis of C1-C4 Chemicals from Carbon Dioxide and Water
Authors: Park Hyunwoong
Published: February 2020

There is renewed interest in the photoelectrochemical conversion of CO2 into value-added chemicals using various semiconductor particles and electrodes. Common CO2 reduction products are C1 chemicals (CO, HCOOH, CH3OH, and CH4) in aqueous media, while the production of C2-C4 hydrocarbons (e.g., C2H6 and C3H8) has also been reported. A number of solar-active materials have been reported, but they still suffer from low selectivity, poor energy efficiency, and instability, while failing to drive simultaneous water oxidation. This talk presents our recent studies on the solar CO2 conversion to value-added chemicals while using water as an electron donor in various photo-systems [1-5].

[1] S.K. Choi, U. Kang, S. Lee, D.J. Ham, S.M. Ji, and H. Park, Sn-coupled p-Si nanowire arrays for solar formate production from CO2, Advanced Energy Materials 4 (2014) 1301614.

[2] H. Park, H.-H. Ou, A.J. Colussi, and M.R. Hoffmann, Artificial photosynthesis of C1 to C3 hydrocarbons from water and CO2 on titanate nanotubes decorated with nanoparticle elemental copper and CdS quantum dots, Journal of Physical Chemistry A 119 (2015) 4658.

[3] U. Kang, S.K. Choi, D.J. Ham, S.M. Ji, W. Choi, D.S. Han, A. Abdel-Wahab, and H. Park, Photosynthesis of formate from CO2 and water at 1% energy efficiency via copper iron oxide catalysis, Energy & Environmental Science 8 (2015) 2638.

[4] H. Park, H.-H. Ou, U. Kang, J. Choi, and M.R. Hoffmann, Photocatalytic conversion of carbon dioxide to methane on TiO2/CdS in aqueous isopropanol solution, Catalysis Today 266 (2016) 153

[5] N.C.D. Nath, S.Y. Choi, H.W. Jeong, J.-J. Lee, and H. Park, Nano Energy, revised.
Probing the Surface Oxidation of III-V Photoelectrodes with First-Principles Simulations and in Situ Experiments
Authors: Pham Tuan Anh , Zhang Xueqiang , Wood Brandon C. , Ptasinska Sylwia , Ogitsu Tadashi
Published: February 2020

While photoelectrochemical (PEC) cells based on III-V semiconductor photocathodes have been demonstrated to achieve highly efficient solar-to-hydrogen conversion, photocorrosion of the electrodes in electrolyte solution remains a significant challenge. In order to improve durability while retaining high solar conversion efficiency of these devices, fundamental knowledge of chemical processes at the electrode-electrolyte interface, and their correlation with electronic properties is essential. One such process is surface oxidation which occurs natively and is thought to be connected to device stability and performance.

In this talk, we investigate oxidation processes of two representative III-V semiconductor electrodes, i.e. GaP and InP, at the interface with water using a combination of first-principles and experimental techniques. We show that coupling first-principles molecular dynamics simulations with advanced electronic structrure methods beyond DFT, and ambient-pressure XPS experiments allows one to link electronic properties with local interfacial chemistry, and to probe chemical and morphological changes of photoelectrode surfaces in contact with water. We demonstrate how subtle features in the surface mophology can significantly affect the band edge positions of the semiconductors due to the change in the surface polarization. We show that non-dissociated and dissociated adsorbed water coexist on the GaP/InP surface, leading to a surface hydroxyl coverage of 0.55 ML and 0.75 ML for GaP and InP, respectively. Implications for the efficiency and stability of the III-V semiconductor photoelectrodes will be discussed.

This work was supported by the U.S. Department of Energy at the Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.
Solar Water Splitting Photoelectrodes Structured By Laser Interference Lithography
Authors: Kriegel Herman , Schieda Mauricio , Herrmann-Geppert Iris , Voronov Dmitry L. , Olynick Deirdre L. , Klassen Thomas
Published: February 2020

One of the most environmentally friendly ways to produce hydrogen is by electrochemical splitting of water, using only sunlight as an energy source. In a photoelectrochemical cell with a semiconductor photoanode, water oxidation takes place on the surface of the electrode, at the interface between semiconductor and electrolyte. While photoelectrodes with structured surfaces tend to outperform planar ones, an increased surface area can be accompanied by enhanced surface recombination, which is deleterious to photoelectrode performance. Furthermore, the geometry of the surface structuring can influence light absorption and transport processes, and consequently the water splitting efficiency.

In order to investigate the effect of surface structuring on water splitting performance, model photoelectrodes are needed, where the geometry and aspect ratio of the surface features can be controlled. In this work, we report on the use of laser interference lithography to generate precisely defined surface patterns on n+Si substrates. The geometry and aspect ratio of the surface features is determined during a reactive ion etching step. After etching, the samples are conformally coated with TiO2 by atomic layer deposition. Photoelectrochemical characterization of the electrodes is complemented by extensive physicochemical studies in an effort to identify the structural parameters with highest impact on performance in the photodriven water oxidation reaction.

Figure 1
Integrated Anion and Cation Capture Agent for Use in Lithium Sulfur Batteries
Authors: Perdue Brian Robert , Wheeler David R. , Apblett Christopher A.
Published: February 2020

In recent years, tremendous effort has been invested into researching energy storage chemistries that will replace lithium ion. New strategies with higher capacities must be considered, such as a chemical conversion cathode. The lithium sulfur chemistry is a promising candidate as it uses earth abundant, inexpensive, high capacity sulfur as its cathode. Conversion cathodes like sulfur are much more challenging as a secondary battery, and behave differently than intercalation cathodes. One of the main issues with the sulfur chemistry is the loss of sulfur inventory do to the high solubility of polysulfides in the DOL:DME electrolyte. To address this issue an integrated anion and cation capture agent was synthesized and incorporated into the cathode to prevent inventory loss by means of lowering the free polysulfide concentration. This molecule has two separate functional groups capable of sequestering both Li ions and polysulfides. Conducting carbon was first modified with the integrated anion and cation capture agent then incorporated into cathode slurries to be coated for use in full cell experiments. The presence of the agent was confirmed with vibrational spectroscopy and XPS. The effectiveness agent was measured with visible and vibrational spectroscopy. Discharge capacity, coloumbic efficiency, and capacity retention data were also measured. Results will be discussed
Synthesis, Crystal Structure, and Electrochemical Properties of the New Alluaudite-Type Compounds Ag2-Y
Na
Y
M3(XO4)3
(M= Mn, Fe; X= V, P)
Authors: Ben Yahia Hamdi , Essehli Rachid , Belharouak Ilias , Shikano Masahiro
Published: February 2020

Abstract

In recent years, sodium batteries have raised interest as cheap rechargeable batteries for large format rechargeable battery applications such as the grid storage. A number of promising cathode materials has already been tested. Among the materials crystallising with the alluaudite-type structure, only phosphates such as Na2
M
2Fe(PO4)3 (M = Mn, Fe, Co, and Ni) [1-3] or sulfates such as Na2+x

M
2-y
(SO4)3 (M = Mn and Fe) [4,5] were studied. To our knowledge no alluaudite vanadates were reported so far as electrodes for Li- or Na-ion batteries. Herein, we report on for the first time the synthesis, the crystal structure, and the electrochemical properties of the Ag2-y
Na
y

M
3(XO4)3 (M= Mn, Fe; X= V, P; 0 ≤ y ≤ 2) compounds.

The new compounds Ag2-y
Na
y

M
3(XO4)3 (M= Mn, Fe; X= V, P) were synthesized by solid state reaction route, and their crystal structures were determined from single-crystal X-ray diffraction data [6,7]. The physical properties were characterized by Mӧssbauer and electrochemical impedance spectroscopies, galvanostatic cycling and cyclic voltammetry. These materials crystallize with a monoclinic symmetry, space group C2/c and the structure

can be considered as a new member of the AA’MM’
2(XO4)
3
alluaudite family. The A, A’, M, and X sites are fully occupied by Ag+/Na+, Mn2+, and P5+/V5+, respectively; whereas a Mn2+/Fe3+ mixture is observed in the M’ site. The Mӧssbauer spectra confirm that iron is trivalent. The impedance measurements indicate that the silver vanadate phase is better conductor than the sodium one.  Furthermore, these vanadate phases exhibit ionic conductivities two order of magnitude higher than the homologous phosphates. The electrochemical tests prove that the new Na2
M
3(XO4)3  (M= Mn, Fe; X= V, P) materials, which are reported for the first time, are active in sodium-ion batteries.The electrochemical performances will be detailed during the presentation.

References

1) Essehli, R.; Belharouak, I.; Ben Yahia, H.; Maher, K.; Abouimrane, A.; Orayech B.; Calder, S.; Zhou, XL.; Zhou, Z.; Sun, YK. Dalton Trans.
2015, 44, 7881-7886.

2) Essehli, R.; Belharouak, I.; Ben Yahia, H.; Chamoun, R.; Orayech, B.; El Bali, B.;  Bouziane, K.; Zhou, XL.; Zhou, Z. Dalton Trans.
2015, 44, 4526-4532.

3) Trad, K.; Carlier, D.; Croguennec, L.; Wattiaux, A.; Ben Amara, M.; Delmas, C. Inorg. Chem.
2010, 49, 10378-10389.

4) Barpanda, P.; Oyama, G.; Nishimura, S.-I.; Chung, S.-C.; Yamada, A. Nat.
Comm.
2014, 5, doi:10.1038/ncomms5358.

5) Dwibedi, D.; Araujo, R.B.; Chakraborty, S.; Shanbogh,   P.P.; Sundaram, N.G.; Ahuja, R.; Barpanda P.; J. Mater. Chem. A
2015, 3 (36), 18564-18571.

6) Ben Yahia, H.; Shikano, M.; Essehli, R.; Belharouak I. Z. Kristallogr.
2016 DOI: 10.1515/zkri-2016-45678.

7) Ben Yahia, H.; Shikano, M.; Tabuchi, M.; Belharouak I. Inorg. Chem.
2016 in press.
Calcium-Ion Intercalation Chemistry of the Hewettite for Rechargeable Calcium-Ion Batteries
Authors: Kwak Hunho H , Hong Seung-Tae
Published: February 2020

Calcium-based battery is a very attractive alternative to Li-ion batteries due to theabundance of calcium. The hewettite (CaV6O16·xH2O) has recevied an attention due to its typical two-dimensional layered structure consisting of V3O8 layers and the hydrated calcium ions occupied between those layers (Fig1.a). The hewettite was known to be synthesized by sol-gel, hydrothermal or ion-exchange methods with a high yield, but taking a long reaction time (several days) to synthesize. In this work, we have developed a quick synthetic method to prepare CaV6O16·xH2O from Na1.2V3O8, utilizing a relatively simple electrochemical reaction.

The electrodes of Na1.2V3O8 was first prepared, consisting of the active material (Na1.2V3O8), conducting carbon (super P) and binder (PVdF) with the weight ratio of 8:1:1, coated on stainless foil. Activated carbon (AC) was served as the counter and reference electrodes. The electrode was oxidized electrochemically by holding the voltage at 0.7V vs. AC for 24hr in 1M Ca(NO3)2 aqueous electrolyte, which resulted in formation of the hewettite (CaV6O16·xH2O) that was confirmed by powder XRD and elemental analyses (ICP, EDAX). The electrochemical properties of the obtained CaV6O16·xH2O electrodes were characterized with potentiostatic cyclic voltammogram (CV) (Fig1.b), galvanostatic discharge/charge cycles, powder XRD and elemental analyses. Reversible redox reactions were observed in CVs as well as the discharge/charge curves, which were responsible for the calcium-ion intercalation and evidenced by EQCM, elemental and structural analyses. The bond valence sum mapping (Fig1.c) showed the calcium-ion pathways in the crystal structure.

Figure 1
Gas Analysis Formed in Dual Carbon Battery Using LiPF6 in EC-Dmc
Authors: Inda Keisuke , Ishihara Tatsumi , Ida Shintaro , Kurihara Takuya
Published: February 2020

Lithium ion rechargeable battery has been used in various field including mobile device and the power source for electric cars. Because of the limited capacity and rate property, advanced type new battery with large energy density as well as rate property are required at present. Dual carbon battery consists of graphitic carbon for both anode and cathode, and charge and discharge is performed by intercalation of Li and PF6 for both cathode and anode. This battery has an advantage of high discharge potential like 5V and superior rate property and expecting as an advance type battery. However,　this battery has disadvantage of low coulomb efficiency and this may be related with decomposition of electrolyte. In this study, gas formation during charge and discharge in dual carbon battery was investigated by using mass spectrometry.

 Formation of gas from anode and cathode was analyzed by using H-type cell and for cathode and anode, graphitic carbon of KS-6 (TIMCAL) and MAG-D(Hitachi Kase) was used and stainless mesh was used for current corrector. Ar gas was used for carrier gas and part of carrier gas was introduced to vacuum line and analyzed with quadrupole mass spectrometer (MS).

From the result of MS analysis of the gases in DCB during charge and discharge, it was found that the formed gas in charge was mainly observed at potential lower than 4.5 V from anode and higher than 4.5 V from cathode in charging process. The formed gas was mainly assigned to C2H6, C2H4, and CO2 for both anode and cathode. Considering the potential, gas from anode seems to be assigned to formation of SEI layer and that from cathode was decomposition of electrolyte. Comparing with Li ion battery, gas formation amount is little larger in DCB and this mainly assigned to gas formation from cathode at higher potential. On the other hand, the amount of gas was strongly affected by conducting binder and electrolyte. Among the examined carbon binder, it was found that carbon black shows the smallest gas formation and so by using the carbon black, the amount of gas from cathode was suppressed. After second cycles, the amount of gas was greatly decreased and so this study revealed that gas formation is mainly observed at initial charge process.
Molecular Simulation of Decomposition of Li2O2 and Li2CO3 during Charging Process of Li-O2 Battery
Authors: Takaba Hiromitsu , Soeno Masahiro , Iso Syoujiro , Alam Md. Khorshed
Published: February 2020

Much attention has been given to Li-O2 battery due its high energy density compared to Li ion battery. However, charging voltage of Li-O2 battery is sometimes reported to be larger than the voltage during discharge. Therefore, the suppression of charging voltage is the subject for its practical applications. In this study we have applied a first principles molecular dynamics method for the analysis of the dynamics of electrochemical decomposition of Li2O2 and Li2CO3 in Li-O2 battery. Using the first-principles molecular dynamics we also estimated the free energy change for decompositions and the change of overpotential and its relationship with decomposition behaviour were calculated. The simulations of the decomposition reaction for both species have been successfully performed in vacuum and also for the cluster of Li2O2 and Li2CO3 placed on the carbon surface in consideration of the real system. In the case of Li2O2, our simulation results show that all the cases of Li2O2-carbon complexes Li2O2 first decompose into superoxide like LiO2 structure via the removal of lithium atoms. The decomposition pathway from our simulations has a good consistency with experimental findings that lithium superoxide is an intermediate in the formation of Li2O2 in the reduction reaction. The free energy profile of during the decomposition of Li2O2
at the applied potential U = 0 and U = 4 eV were calculated. The free energy change indicates that the system is capable to be charged when applying the potential of 4 eV. Experimentally, charging voltages as high as 4.0-4.5 V have been observed, which validates our simulation results. Our simulation results also show that the charging voltage increase when the interaction of decomposed species becomes large. In summary, our simulation results successfully reveal the decomposition path at the atomistic level as well as the free energy profile which was not clear from the experimental findings. We will discuss the results of decomposition process of Li2CO3 at the conference.
The Catalytic Activity and Electrochemical Performance of Flower-like PEDOT for Enhanced Air Electrode of Li-Air Batteries
Authors: Yoon Seon Hye , Park Yong Joon
Published: February 2020

Recently, the Li-air batteries have attracted a lot of attention as an alternative of lithium ion batteries (LIB), since they have higher capacity than LIB. An air electrode, a component of Li-air batteries, plays a key role in the electrochemical performance because the capacity and cycle life of Li-air batteries are highly dependent upon the air electrode. Generally, air electrode has been composed of porous carbon, oxide catalyst and binder. Among them, porous carbons act as sites for redox reaction and store the reaction products such as Li2O2 since they have large specific surface area. However, carbon in the air electrode activates side reaction caused by direct contact with electrolyte/Li2O2, which leads to accumulation of unwanted reaction products such as Li2CO3 and organic materials. These results lead to the increase of over-potential and limited cycle performance. In this study, PEDOT, a conductive polymer, was applied in base material for air electrode as an alternative to carbon. PEDOT has a catalytic activity and store the reaction products [1]. Moreover, introduction of PEDOT for base material of air electrode is expected to prevent the side reaction because it suppresses the direct contact between carbon and electrolyte/Li2O2. Specially, the PEDOT was prepared flower-like shape for enhance the active reaction area. Our approach may enhance the electrochemical performance of the air electrode due to reduction of side reaction and accumulated reaction products during cycling.

 

Reference

C. K. Lee, Y. J. Park, ACS Appl. Mater. Interfaces, 2016, 8 (13), pp 8561–8567
Relationship Between Discharge Profile and Pore Structure for Lithium-Air Secondary Battery
Authors: Matsuhashi Nozomi , Takeguchi Tatsuya , Kojima Miyuki , Ui Koichi
Published: February 2020

Introduction High-capacity next-generation secondary batteries have been desired to spread plug-in hybrid vehicles and electric vehicles. Lithium-air secondary batteries have attracted much attention as the large storage secondary batteries due to their high theoretical capacity (5200 Wh kg-1). However, the reversible capacity is limited because the discharge products block the oxygen diffusion path in air electrode. The influence of the pore structure of carbon materials on the deterioration of electrochemical performance is not clear, although the carbon materials are widely studied as air electrode for lithium-air secondary batteries. In this study, we have prepared the carbon electrodes using carbon materials (CNovel MH (MH) and ketjen black (KB)) with different pore volume, analyzed the discharge products and change of pore structure by discharging.

Experimental The carbon materials (MH and KB) were mixed with PVdF (carbon : PVdF = 93 : 7 wt. %). After coating on the carbon paper as a current collector (the loading of carbon material 1 mg, electrode area 2.0 cm2), it was dried overnight at 80 oC in a vacuum to obtain carbon electrodes. The CR2032 coin type cell was assembled in an Ar-filled glovebox. It consisted of the prepared carbon electrode as a cathode, lithium foil as an anode, 1 mol dm-3 LiCF3SO3/TEGDME as an electrolyte, and Whatman glass filter GF/A as a separator. The carbon electrodes were analyzed by using FE-SEM, EDX, XRD, and the nitrogen adsorption method. For the electrochemical measurements, the discharge-charge tests were carried out (current value: 100 mA, voltage range: 2.0-4.5 V, measured temperature: 25 oC, and atmosphere: dry air).

Results and Discussion From the discharge-charge tests, the MH electrode showed higher discharge capacity than the KB electrode. Fig. 1 shows SEM images of MH and KB electrodes before and after 6 h discharge. The MH electrode has much larger volume of micropore than the KB electrode, as shown in the pore size distribution. The spherical Li2O2 particles is deposited on the surface of the KB electrode after 6 h discharge, while they are not observed on the MH electrode. The micropore structures prevent growth of Li2O2 particles for MH. The mesopore structure of the MH electrode does not change by 6 h discharge, while mesopore volume of the KB electrode clearly decreases by 6 h discharge. From these results, it was found that the deposited spherical Li2O2 particles changed not only micropore structure but also mesopore structure of carbon electrode to affect the discharge profile.

References

1) Y. Gao et al., Int. J. Hydrog. Energy, 37, 12725 (2012).

2) T. Cetinkaya et al., J. Power Sources, 267, 140 (2014).

Acknowledgments

This research was partially supported by ALCA-SPRING, JST.

Figure 1
Applications of a Novel Multi-Parametric/Multimodal Spectroscopy Apparatus on Characterization of Functional Interfaces
Authors: Zhou Lang , Arugula Mary A , Simonian Alex
Published: February 2020

Multiparametric/Multimodal spectroscopy (MPMS), the integration of surface plasmon resonance, fluorescence, and electrochemistry based approaches provides new insights and complementary information about functional interfaces. In detection of biologically important analytes, MPMS is a promising tool, capable to provide a valuable cross-validated data in many important applications, and particularly in disease diagnosis. We have developed an integrated MPMS instrument and optical fiber spectral probe for simultaneous collection of all three parameters to quantify the components and kinetic parameters in the assembly of various functional interfaces, including covalent binding, layer-by-layer assembly, aptamer-based Electrochemical Proximity Assay (ECPA) and antibody-based ECPA. The instruments’ 3D printed flowcell integrated with multimode optic fiber, excitation laser sources (660nm), and sensing electrodes capable to record the SPR spectra, fluorescence and electrochemical data on the same platform. We have designed ECPA model system and obtained SPR signal that gives a comprehensive information about all steps of assembly, fluorescence signal corresponds specifically to the fluorophore labeled moieties, while electrochemistry will allow highly sensitive quantitative characterization of target analyte. This work not only provides quantitation information for protein targets, but allows a fundamental understanding of the kinetics in the formation of ECPA with an unprecedented level, which can overcome several key limitations of current, widely-used surface characterization technologies.
(Invited) Biomaterials Research Support at the National Science Foundation
Authors: Simonian Aleksandr
Published: February 2020

The NSF/DMR/BMAT perspective on biomaterials research and education will be presented, as well as a description of ongoing and forthcoming research funding opportunities. It will start by providing an overview of divisions and programs at the NSF where an applicant may consider submitting proposals for biomaterials related research. Additionally, an information about several priority areas where progress in basic research is vital to addressing key national challenges will be provided. This presentation will be particularly useful to early career researchers in the field of biomaterials and biosensors.

The Biomaterials program supports fundamental materials researchrelated to (1) biological materials, (2) biomimetic, bioinspired, and bio-enabled materials, (3) synthetic materials intended for applications in contact with biological systems, and (4) the processes through which nature produces biological materials.  Projects are typically interdisciplinary and may encompass scales from the nanoscopic to the bulk.  They may involve characterization, design, preparation, and modification; studies of structure-property relationships and interfacial behavior; and combinations of experiment, theory, and/or simulation.  The emphasis is on novel materials design and development and discovery of new phenomena.

General information on all the programs in DMR can be found on the DMR Web page: http://www.nsf.gov/div/index.jsp?div=DMR. In addition, attendees will have the opportunity to interact “one on one" with NSF BMAT Program Director.
Estimation of Gas Source Location from Fluctuating Readings of Gas Sensors and Anemometer on Mobile Robot in Outdoor Environment
Authors: Wada Yuta , Matsukura Haruka , Ishida Hiroshi
Published: February 2020

Here we report on a new method for robotic gas source localization. Research efforts are being made to develop mobile robots that can autonomously search for gas sources. The tasks envisaged for such robots include detecting gas leaks in industrial plants and exploring gas emissions in landfill sites. If a mobile robot is provided with gas sensors, it can detect the presence of a target gas drifting in the air. However, to find the location of the gas source is not a trivial task for the robot. Gas molecules released in the air are carried by the airflow and form a plume in the downwind direction. Since the airflow the robot encounters in gas source localization applications is almost always turbulent, the plume randomly meanders and comes to have a complicated patchy structure. Gas source localization in outdoor environments is especially challenging owing to the large fluctuations in the wind direction. In the method proposed in this series of work, a mobile robot equipped with gas sensors and an anemometer is used to measure the gas concentration and airflow direction at various locations in the area under consideration. The location of the gas source is estimated by applying a turbulent diffusion model of a gas plume to the sensor data collected by the mobile robot. Two different turbulent plume models were compared regarding the accuracy in the estimated gas source location. The results are presented to show that the proposed method can provide a map showing the area in which a gas source is likely to be found.
Bismuth-Activated Graphene Nanocomposite Modified Electrode for Electrochemical Determination of Trace Heavy Metals
Authors: Lee Sohee , Piao Yuanzhe
Published: February 2020

Heavy metals, such as Pb2+, Cd2+, and Zn2+, cause major public-health concerns due to their high stability and bio-accumulation. These heavy metals affect several human organs even at very low concentrations. Accordingly, developing simple, robust and highly sensitive analytical methods for assessing environmental pollutants in soil, water, and air samples to improve the quality of environment and human life is very important.

Graphene is an excellent nanomaterial for electrochemistry owing to its good electrical conductivity, low cost, excellent mechanical properties, and high specific surface area. To date, much research has been focused on their development for attractive applications in electroanalytical chemistry as a unique electrode material for manifolds. Moreover, chemical modification of graphene could further improve its electrochemical performance. The resultant activated graphene has a unique structure that makes it attractive as a potential material for the electrochemical determination of trace metal ions.

In this work, we developed a facile method for the preparation of a new and enhanced sensing platform based on bismuth and activated graphene. The activated graphene was prepared through chemical activation of graphene oxide with KOH to create nanopores. The surface morphology of the bismuth-activated graphene nanocomposite film modified electrode was investigated by using scanning electron microscopy and transmission electron microscopy. The electrochemical properties of the nanocomposite electrode were evaluated to examine the effects of experimental variables, such as deposition potential, deposition time, bismuth concentration, and stirring speed during pre-concentration, on the determination of trace metal ions. The bismuth-activated graphene nanocomposite electrode was applied for the simultaneous determination of trace zinc, cadmium, and lead by differential pulse anodic stripping voltammetry. The composite film integrates the unique properties of activated graphene and the advantages of bismuth electrodes, leading to enhanced sensitivity towards trace metal ions, especially zinc. The appearance of a zinc stripping peak reveals its superior sensitivity as compared to previous bismuth electrodes. The bismuth-activated graphene nanocomposite was also used as an electrode material for the sensitive determination of metal ions in a real sample. The limits of detection achieved are much lower than the guideline for drinking water quality provided by the World Health Organization. Thus, the proposed method facilitates the monitoring of trace heavy metals and can be expanded to detect other environmental pollutants.
4-(Trimethylsiloxy)-3-Pentene-2-One As a Novel Film-Forming Agent for High-Voltage LiNi0.5Mn1.5O4 Positive Electrode
Authors: Lee Tae Jin , Lee Jeong Beom , Jung Jiwon , Soon Jiyong , Ryu Ji Heon , Oh Seung M.
Published: February 2020

As an effort to improve energy density of lithium-ion batteries (LIBs), the nickel-doped manganese spinel (LiNi0.5Mn1.5O4, LNMO) has been projected as a high-voltage positive electrode. The high working voltage (> 4.6 V vs. Li/Li+) and outstanding structural stability are advantageous with respect to energy density and cycle life. This advantage is, however, offset by the oxidative instability of electrolytes (> 4.3 V), which is even more serious at elevated temperatures.1 The commonly used electrolytes decompose and surface films deposit on the positive electrodes to lead to capacity fading.2, 3

In order to prevent electrolyte oxidation and film growth, the LNMO electrode should be passivated. To this end, the film-forming agents are added into electrolytes, which electrochemically decompose prior to the carbonate-based electrolytes to form passivation layer on the positive electrode.

In this study, 4-(trimethylsiloxy)-3-pentene-2-one (TMSPO) was tested as a film-forming agent for LNMO electrode. TMSPO is oxidatively decomposed at 3.6 V (vs. Li/Li+) prior to the oxidation reaction of the carbonate-based electrolyte (1.3 M LiPF6 in EC : EMC : DEC = 3 : 2 : 5 (v/v/v)). The surface film derived from TMSPO shows good passivation ability to improve both Coulombic efficiency and cycle life of Li/LNMO cell (Fig. 1b). Electrolyte depletion and film growth are not serious in TMSPO-added cell. In contrast, the film derived from the carbonate-based electrolyte is poorly passivating. Cell polarization resulting from electrolyte decomposition/film deposition continues to cause capacity fading.

References

1 .J. B. Goodenough and Y. Kim, J. Power Sources,
196, 6688-6694 (2011).

2. T. Yoon, S. Park, J. Mun, J. H. Ryu, W. Choi, Y.-S. Kang, J.-H. Park, and S. M. Oh, J. Power Sources,
215, 312-316 (2012).

3. D. Aurbach, B. Markovsky, Y. Talyossef, G. Salitra, H.-J. Kim, and S. Choi, J. Power Sources,
162, 780-789 (2006).

Figure 1. (a); Differential capacity plot in the 1stcharging at 25℃, and (b) Coulombic efficiency and cycle performance at 60℃

Figure 1
Electrochromic Devices Fabricated with Electrolyte Impregnated on Porous Substrate
Authors: Lee So Hee , Park Su Mi , Kim Haekyoung
Published: February 2020

Electrochromic devices, which dynamically change colour under applied potential, are widely studied for use in energy-efficient smart windows. To improve the viability of smart windows, many researchers are utilizing nanomaterials, which can provide electrochromic devices with improved coloration efficiencies, faster switching times, longer cycle lives, and potentially reduced costs. The flexible electrochromic films are promising film for applications in automobiles, buildings, etc. Here, we synthesized nanostructured tungsten trioxide (WO3) particles for electrochromic materials. The thin layers with nanostructured materials of WO3 inks were coated on ITO glass at room temperature, solution-processed method. For comparing the effects of electrolyte, liquid electrolytes were used with/without a porous substrate. Porous substrates can be helpful in leakage issues of liquid electrolytes. The porosity and pore size of porous substrate were parameters for characterization of electrolyte. The coloration efficiencies and cycle performance will be discussed with characteristics of porous substrate.
In-Situ XAFS Measurement of K:MnO
x
Oxygen Evolution Catalyst
Authors: Yamamoto Futaba , Yoshida Masaaki , Kondoh Hiroshi
Published: February 2020

[Introduction]

Water splitting using solar energy is a promising approach to produce renewable hydrogen gas toward a sustainable society. For the realization of efficient photovoltaic and photoelectrochemical systems for water splitting, oxygen evolution reaction (OER) electrocatalysts have been used to catalyze water oxidation. Thus, the development of highly active OER catalysts has attracted considerable attention. Recently, manganese oxide electrodeposited in a potassium phosphate electrolyte (K:MnO
x
) was reported to function as an efficient OER electrocatalyst over a wide pH range.[1,2] Therefore, in this study, the K:MnO
x
catalyst was investigated by in-situ Mn K-edge XAFS measurements under potential control conditions.

[Experimental]

Electrochemical measurements were performed in a three-electrode Teflon cell equipped with a Pt counter electrode and an Ag/AgCl (saturated KCl) reference electrode. The K:MnO
x
catalyst was electrodeposited on a　gold-coated film in a 50 mM methanesulfonic acid electrolyte containing 0.5 mM MnCl2. In-situ XAFS spectra of the prepared samples were measured at various potentials in a 0.1 M potassium phosphate buffer electrolyte at BL 9A of the Photon factory and BL01B1 of SPring-8 as fluorescence excitation spectra.

[Result and discussion]

Figure 1 shows the Mn K-edge XAFS spectra for the K:MnO
x
catalyst at various electrode potentials between 0.2 and 1.0 V. At the potential of 0.2 V, the position of half edge energy for K:MnO
x
was observed at ca. 6549.3 eV, similar to those of the Mn3O4 and Mn2O3 references, which indicates that the electronic structure of Mn species in the K:MnO
x
is most likely the same as that of Mn3+. As the potential was changed from 0.2 to 1.0 V, the position of half edge energy gradually shifted to the higher energy around 0.6 V and then remained constant at 6552.3 eV up to 1.0 V, which shows that the Mn species in K:MnOx catalyst was oxidized from Mn3+ to Mn4+ by positive electrode potential. Figure 2 shows Fourier transformed extended X-ray absorption fine structure (EXAFS) spectra of the K:MnO
x
catalyst. The Mn-O and Mn-Mn peaks of the spectrum at 0.2 V were observed at the same positions with those of δ-MnO2, exhibiting that the structure of K:MnO
x
is similar to that of δ-MnO2. Moreover, those peaks increased when the electrode potential was changed to 1.0 V, which probably implies that the Jahn−Teller distortion with nonequivalent Mn−O and Mn−Mn distances was relaxed. Considering that the OER proceeds at higher electrode potential, the δ-MnO2 structure with lower distortion is likely to function as an active species for water oxidation catalysis.

In this presentation, we will discuss more detailed assignment for the XAFS spectra and relationship with the OER activity.

[1] Huynh, M.; Bediako, D. K.; Nocera, D., J. Am. Chem. Soc.,
2014, 136, 6002.

[2] Huynh, M.; Shi, C.; Billinge, S. J. L.; Nocera, D. G., J. Am. Chem. Soc. 2015, 2015, 137, 14887.

Figure 1
Synthesis of High Surface Area Magneli-Phase Ti5O9 from SiO2 Supported TiO2 Nanosheets
Authors: Toda Yosuke , Makino Sho , Ayato Yusuke , Mochizuki Dai , Tominaka Satoshi , Sugimoto Wataru
Published: February 2020

Magnéli phases are substoichiometric titanium oxides with oxygen-deficiency (Ti
n
O2n-1
n = 4~10), and shows good electronic conductivity and stability in acidic solution. Synthesis of Ti
n
O2n-1 is typically conducted by reduction of TiO2 with H2 at high temperature, thus making it difficult to prepare in nanoscale and high surface area reduction. In this study, TiO2 nanosheets were deposited on SiO2 particles in order to prevent sintering and aggregation during the reduction process at high temperature.

TiO2 nanosheet colloid was prepared by exfoliation of layered H2Ti4O9∙nH2O.2 The preparation process of the nano-sized Ti
n
O2n-1 is schematically shown in Fig. 1. TiO2 nanosheet lamellar structures were fabricated on spherical SiO2 by layer-by-layer (LbL) deposition using poly(diallyldimethylammonium chloride) (PDDA) as the polycation. Alternately-layered structures (TiO2ns/PDDA)10 were obtained on spherical SiO2 by repeating the process 10 times. (TiO2ns/PDDA)10 was treated under hydrogen flow at 950˚C for 7 hours.

After hydrogen treatment, the color of the (TiO2ns/PDDA)10 changed from white to black, indicating reduction. XPS measurement revealed that the average Ti valence was 3.6+, suggesting that the n = 5 phase Ti5O9 was synthesized. TEM images of (TiO2ns/PDDA)10 and Ti5O9 on SiO2 particles are shown in Fig. 2. (TiO2ns/PDDA)10 lamellar structures are observed on the surface of SiO2 particles (Fig. 2a). After reduction, Ti5O9 with particle size of ca. 30 nm was observed on spherical SiO2 (Fig. 2b). The particle size of the obtained Ti5O9 on SiO2 was smaller than other process such as UV-irradiation1 and H2 reduction3. Thus, sintering of Ti5O9 particles was effectively suppressed during the reduction process by using SiO2 particles.

Cyclic voltammogram of Ti5O9 on spherical SiO2 in 1.0 M H2SO4 is shown in Fig. 3. Assuming a double layer capacitance of 10 ~ 20 mF cm-
2 for Ti5O9, the surface area is estimated as 50~100 m2 g-1 which is in good agreement with the particle size. The good conductivity, high oxidation resistance, and high surface area of nano-size Ti5O9 may allow its use as a fuel cell catalyst support.

1) T. Ioroi, H. Kageyama, T. Akita, K. Yasuda, Phys. Chem. Chem. Phys., 12, 7529 (2010).

2) W. Sugimoto, O. Terabayashi, Y. Murakami, Y. Takasu, J. Mater. Chem., 12, 3814 (2002).

3) T. Ioroi, Z. Siroma, N. Fujiwara, S. Yamazaki, K. Yasuda, Electrochem. Commun., 7, 183 (2005).

Figure 1