bluuebunny/crossref_metadata_2025_split huggingface dataset:
Electrochemical Synthesis of Tantalum Carbide in the NaCl-KCl-K2TaF7-K2CO3 Melt
Authors: Dolmatov Vladimir S. , Kuznetsov Sergey A. 
Published: February 2020

The goal of this study was electrochemical synthesis of tantalum carbide in the NaCl-KCl-K2TaF7-K2CO3 melt. It was shown that tantalum carbide can be synthesized from the abovementioned melt under the certain conditions.
Alkali metal carbonates are subjected to thermal decomposition and appearance of oxygen anions led to the formation of tantalum oxofluorides complexes. Therefore, for understanding of electrode reactions during synthesis of tantalum carbide electrochemical behavior of tantalum oxofluorides complexes in the NaCl-KCl melt was studied. The titration of the NaCl-KCl-K2TaF7 melt was carried out by oxide ions as a Na2O. Formation of tantalum monooxofluoride complexes TaOF6
3- was found at the molar ratio of O2-/TaF7
2- = 1:1 that can be interpreted by the following interaction:
TaF7
2- + О2- ↔ TaOF6
3- + F-

Potentiostatic electrolysis at discharge potentials of TaOF6
3- complexes led to the tantalum formation, and this process can be expressed by the following electrochemical reaction:
TaOF6
3- + 5e
–
→ Ta + O2- + 6F
-

Appearance of tantalum dioxofluoride complexes TaO2F4
3- was observed in the melt at the molar ratio of O2-/TaF7
2- = 2:1, and potentiostatic electrolysis of such melt resulted to the formation of mixture tantalum oxides and oxofluorides.
Discharge waves of TaOF6
3-, TaF7
2- complexes and CO3
2- -ions were observed on cyclic voltammograms after addition of potassium carbonate to the NaCl-KCl-K2TaF7 melt. However, the electroreduction wave of CO3
2- disappeared during 40-50 min after addition, which can be explained by the following interaction:
TaF7
2- + CO3
2- → TaOF6
3- + F- + CO2↑
Therefore, the joint electroreduction of tantalum and carbon leading to the synthesis of tantalum carbide TaC was possible under the following conditions: potentiostatic electrolysis at discharge potentials of CO3
2- - ions during 40-50 min after addition of K2CO3 and the molar ratio of K2CO3/K2TaF7 ≤ 1.0.
Chopped-Illumination Pulse Frequency Effect on the Product Selectivity of CO2 Reduction at Si Photocathodes
Authors: Kumar Bijandra , Brian Joseph Patrick , Spurgeon Joshua M 
Published: February 2020

The electrochemical carbon dioxide reduction mechanism is a complex reaction pathway dependent on the active catalyst surface and intermediate species binding energy, convoluted with the competing effects of kinetics and mass transport. The nature of the photoelectrochemical semiconductor/catalyst interface and the optical interactions occurring there provide a unique opportunity to possibly affect the carbon dioxide reduction mechanism and influence the reaction pathway. For CO2 reduction under continuous 1-Sun illumination, Cu-catalyzed p-Si photocathodes demonstrated the same general product faradaic efficiency trends as dark Cu electrocatalysts, but offset by the photovoltage of the photocathode. Under chopped illumination, however, the product distribution at a given potential changed significantly and depended on the chopping frequency. The results are discussed along with the proposed effects of the chopped illumination on mass transfer and on the electrode interface which lead to the observed mechanistic shifts.
(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
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