bluuebunny/crossref_metadata_2025_split huggingface dataset:
Modification of the Electronic Structure and Surface State of LaFeO3 for Improved Visible Light Photoelectrochemical Water Oxidation
Authors: Peng Qi , Wen Yanwei , Shan Bin , Chen Rong 
Published: February 2020

Photocatalytic hydrogen generation by solar energy is a promising approach to clean energy resource and has attracted great attention over the past decades. [1] Perovskites ABO3 structures provide the basic stable framework to both crystal and electronic structures modification, which have found extensive applications in photocatalysis, solar cells and photoelectrochemical (PEC) water splitting. [2] LaFeO3 has a suitable band gap of 2.07eV [3, 4] and exhibits excellent visible light photocatalytic performance. However, the poor charge transport and slow reaction kinetics at the surface [3, 4] are the main factors limiting its further improvement on photocatalytic application.
To overcome these obstacles, transition metals (Mn, Co, Cu) are introduced into LaFeO3 and the photocurrent of 10% Cu doped sample is improved by three times than that of LaFeO3. The reduced charge transport resistance owing to the Fe3+ discharge is identified to benefit the PEC performance improvement after TM doping. On the other hand, the surface state of LaFeO3 is modified by electrodepositing of amorphous cobalt-phosphate (Co-Pi). It shows that the presence of Co-Pi down-shifts the onset potential by ~ 560 mV for anodic photocurrent and the improvement can be attributed to the enhanced water oxidation due to the CoII/CoIII-OH discharge on Co-Pi decorated layers. The transition anodic photocurrent is improved by about six times after Co-Pi coating under visible light at 0.50 V vs. Ag/AgCl and the electrochemical impedance spectroscopy certifies the enhanced charge transfer, which contributes to the meliorative anodic photocurrent. The incident photon-to-current conversion efficiencies of LaFeO3 can be promoted from 1.37% to 2.14% at 400 nm after Co-Pi coating. Our results demonstrate that modification of the electronic structure (TM doping) and surface state (Co-Pi coating) are the promising way to promote the photoconversion efficiency of LaFeO3-based PEC cells under visible light.
References:

X. Lu, S. Xie, H. Yang, Y. Tong, H. Ji, Chem. Soc. Rev., 43, 7581 (2014).

Z. G. Yi and J. Ye, Appl. Phys. Lett., 91, 254108 (2007).

K. M. Parida, K. H. Reddy, S. Martha, D. P. Das and N. Biswal, Int. J. Hydrogen Energy, 35, 12161 (2010).

Q. Peng, B. Shan, Y. Wen and R. Chen, Int. J. Hydrogen Energy, 40, 15423 (2015).
Synthesis of Gallium Nitride Photocatalysts By Reaction of Solution Synthesized Gallium Oxide and Solid Nitrogen Sources
Authors: Sugiura Takashi , Sano Tatsuya , Manseki Kazuhiro 
Published: February 2020

Solar energy-driven water splitting is receiving considerable interest in hydrogen production as a renewable energy source. Various semiconductor materials for the photodecomposition of water have been investigated for solar energy conversion such as TiO2, TaON and BiVO4. GaN, GaN : ZnO and GaN : InN solid solution are also considered as the photoelectrochemically active material for solar energy-driven water splitting. And its band gap can be controlled by the composition of these solid solutions. We have reported a new technique to synthesize low cost GaN powder under moderate condition, Li3N or LiNH2 were used as a high reactive solid nitrogen source to improve the reaction rate and lowering the reaction temperature. A high yield and high purity GaN with wurtzite structure was synthesized [1, 2]. In this report we studied the method to synthesize GaN powders by the reaction of solution synthesized Ga2O3 powder with solid nitrogen sources. In previous reports commercially available Ga2O3 powder was used. When commercial Ga2O3 powder was used, by the inhomogeneous size, the reaction occurred partially and the yields became small. So the gallium oxide powder with homogeneous size was synthesized by the use of solution process. The photoelectrochemical properties of particulate electrode with synthesized GaN powder were also investigated.
The GaCl3 was dissolved in 2-buthyl alcohol under stirring. Then the purified water was added gradually to the Ga containing solution to get the white precipitate. XRD analysis demonstrate that the synthesized powder is Ga2O3. The crucible with starting materials, Ga2O3 and Li3N were put into a sealed stainless steel reaction vessel and it was set vertically in an electric furnace. Then it was heated at 550 – 700°C, 2 hours in N2 atmosphere. After the reaction, the products were washed by alcoholic HCl solution and distilled water.
Crystalline wurtzite GaN powder with several hundred nanometer size was successfully synthesized. The reaction yield for the GaN synthesis with solution processed Ga2O3 is higher than that with commercial Ga2O3 powder. Anodic photocurrent was clearly observed for the paste electrodes with GaN and this observation indicates that the GaN synthesized in this study shows n-type semiconductivity.
GaN : InN solid solution was also successfully synthesized by the reaction with GaCl3, InCl3 and LiNH2. Photo-electrochemical properties of its paste electrode was also studied.
References

T. Zhang, A. Mabuchi, T. Sugiura, H. Minoura, Trans. Mater. Res. Soc. Jpn., 33(4), 1277-1280 (2008).

T. Zhang, A. Kouyama, M. Miura and T. Sugiura, Trans. Mater. Res. Soc. Jpn., 36(3), 513-516 (2011).
Tuning V Redox Couple By Metal-Ion Substitution in Na3V2(PO4)3 Cathode Material for High Energy Density Na-Ion Batteries
Authors: Sohn DongRak , Lim Sung-Jin , Nam Do-Hwan , Hong Kyung-Sik , Kim Tae-Hee , Kwon HyukSang 
Published: February 2020

Recently, the demand for renewable energy has raised with the increase of environmental issues and exhaustion of crude oil. To acquire efficient utilization of the renewable energy, large-scale energy storage systems (ESSs) are necessary that balance the discrepancy between production of and the time required to consume renewable energy. Li-ion batteries have been considered as candidates for large-scale ESSs because they provide high energy density and a long cycle life. However, due to the lack of Li reserves in the Earth and the corresponding growing cost problems, Na-ion batteries have been received great attention as alternative candidates for Li-ion batteries. The Na-ion batteries can replace the Li-ion batteries in the aspects of abundant Na resources, low cost, and easily accessible reserves. Furthermore, the similarity of the electrochemical reaction mechanisms of Na-ion batteries to that of Li-ion batteries has accelerated the development of the Na-ion batteries; thus, various research studies have been conducted to find proper electrode materials for Na-ion batteries.
Among various cathode materials of sodium-ion batteries for large-scale applications, NASICON-Na3V2(PO4)3 is an attractive candidate for the cathode material of Na-ion batteries due to its thermal and structural stabilities. Also, Na3V2(PO4)3 shows 117.6 mAh·g-1 theoretical capacity at 3.4 V vs. Na/Na+ using the V3+/4+ redox couple. However, the operating voltage of Na3V2(PO4)3 should be improved to replace the conventional Li-ion battery cathode materials. If V4+/5+ redox reaction, which utilizes higher operating voltage, can be employed in this material, higher operating voltage could be achieved. Herein, we suggest a simple method to enhance the operating voltage of Na3V2(PO4)3.
In this work, non-transition metal ions are substituted for V-ions in Na3V2(PO4)3 to utilize V4+/5+ redox reaction. During the (de)intercalation of Na-ions, the oxidation state of the non-transition metal ions is not changed. Hence, some V3+ ions in Na3V2(PO4)3 should be oxidized until V5+ instead of non-transition metal ions while two Na-ions are extracted. Therefore, some part of capacity reacts at 3.4 V using V3+/4+ redox couple and the other part reacts at voltage higher than 3.4 V using V4+/5+ redox couple. Through the tuning of V redox couple, not only the enhancement of energy density of the cathode material but the cost reduction of expensive V source also is possible. The figure shows the initial charge profiles of Na3V2(PO4)3/C and metal-ion substituted Na3V1.5M0.5(PO4)3/C. In case of Na3V1.5M0.5(PO4)3/C, a high voltage V4+/5+ redox reation was clearly observed as the cell was charged above 3.5 V vs. Na/Na+. In the presentation, the detailed structural analyses and electrochemical performance of the materials will be shown.

Figure 1
A New Concept of Flexible Electrodes for Lithium/Sulfur Batteries
Authors: Park Jin-Woo , Choi Sun-Hwa , Kim Hui-Hun , Kim Ki-Won , Ahn Jou-Hyeon , Cho Gyu-bong , Ahn Hyo-Jun 
Published: February 2020

According to the progress of electronics industry, electronic devices have been diversified to various forms such as roll-up displays, smart cards, and wearable devices. Flexible electronic devices are demanding has various properties such as lightweight, ultrathin, and flexibility. Therefore, batteries as their power sources are required to have same properties. In addition, high energy density and operational safety are needed. Until now commercial lithium-ion batteries (LIBs) are the only viable candidates for flexible devices.
Recently, the flexible lithium/sulfur (Li/S) battery has been proposed with a high theoretical energy density of 2600 Wh kg-1. As most active materials considered in these studies are rigid and brittle, flexible cathodes were achieved by the physical combination of rigid active materials with flexible current collectors such as carbon-based materials or polymers. This integrated design has two inevitable disadvantages; (1) during deformation the active material can detach from the current collector; (2) the capacity per electrode is reduced by the presence of electrochemically inactive materials such as current collector, binder and conducting agents. Therefore, there is a strong need for a new approach to the flexible cathode which consists of only active material without a separate current collector.
Sulfurized polyacrylonitrile (SPAN) composite could be a good candidate due to its good electric conductivity, high sulfur utilization, and stable cycle life. In addition, it can be fabricated as either particle or nanofiber. However, the SPAN electrodes reported so far were prepared by mixing SPAN, conductive agent, and binder which were pasted on metallic current collector.
In carbon nanotube paper and graphene paper, it is well-known that the strain during deformation decreases with the diameter of the fiber. Therefore, in this work, the SPAN nanofiber web cathode which does not include conductive agent, binder, as well as current collector was fabricated from PAN nanofiber web and sulfur by heat treatment process. Also, pre-lithiated carbon felt was used as anode in order to make all flexible full cell and investigated its electrochemical properties.
Developing Li-Metal Alloy Batteries with High Cyclability and Rate Capability
Authors: Niu Junjie 
Published: February 2020

The development of high-energy density and high-power density lithium ion batteries (LIBs) for portable electronics, electric vehicles, and other large-scale energy storage devices over the last decade has led to continual search on new electrode candidates. The cost-effective, chemically stable (safe), and highly conductive metal as anode electrode that is capable of high capacity due to the large Li stoichiometric ratio, has recently stimulated enormous attention. There have been many efforts to increase the capacity using group IV elements Sn, Ge, Pb, Si and Mg, Al, Ga, Zn, and Bi thus far. Sn, another group IV element, is a promising alternative anode material, as its bulk phase is known to have a higher theoretical capacity of 990 mAh/g (Li4.4Sn) compared to 370 mAh/g of commercial graphite. Sn is also less toxic and less expensive, but huge volume changes up to 300% during Li insertion and extraction limit the energy capacity and cycle lifetime in LIBs. In addition to the volume factor, another obstacle lies in the naturally formed oxide layer, which introduces a non-reversible capacity, although some researchers have found that an ultrathin coating on electrodes could enhance the performance of lithium-ion batteries. To maximize the electrochemical performance of Sn, a well-desired configuration that can efficiently prevent the chemo-mechanical failure must be developed.
Here we present a novel sub-100nm Sn nano-cage (Sn-NC) comprising an industrially available, pure metal Sn and a conductive oxide surface (not SnOx). The protection of the rigid oxide surface and the adjustable interspace can prevent the pulverization and oxidation of the metal while supplying a fast Li+/e- pathway. The coin/punch cell assembled using Sn-NCs as anode provides a high capacity (>600 mAh/g) with a long cyclability (>500 cycles) at a high charge/discharge rate. The synthesis of Sn-NCs is scalable thus indicating a potential on industrial commercialization.
Enhanced β"-Alumina Solid Electrolytes for Lower Temperature Operating Planar Sodium Beta-Alumina Batteries (LT-NBBs)
Authors: Lee Younki , Park Yoon-Cheol , Son Sori , Jung Keeyoung 
Published: February 2020

The sodium beta-alumina battery (NBB), which employs molten sodium as an anode and sodium-ion conducting β"-alumina as a solid electrolyte, is an attractive device for grid scale energy storage thanks to its long lifetime with negligible self-discharge and potentially low cost by use of naturally abundant elements. Commercialized NBBs, such as sodium sulfur (Na/S) and sodium nickel chloride (Na/NiCl2) batteries, are typically being operated at 280~350oC in order to facilitate ionic conduction through the solid electrolyte. However, this high operation temperature disturb additional cell cost reduction, which is continuously exacted by demanding forecast, since it is difficult to replace conventional expensive sealing technologies (such as glass sealing, thermal compression bonding, electron beam welding and so on) with lower cost substitutes. If the cell operation temperature is lowered down to below 200oC, a wider range of choices for sealing technology can be considered such as inexpensive polymer sealing. Suppressed cell degradation at lower temperatures would be another important benefit.
However, a number of hurdles need to be overcome in order to lower the cell operation temperature. One of the most difficult challenges to make it is an issue regarding the exponential resistance rise of the solid electrolyte with decreased temperature, which can result in substantial performance loss. One can consider that reducing the thickness of the β"-alumina solid electrolyte (BASE) may resolve the issue. However, as the BASE thickness decreases below 1.5~2.0 mm, its flexural strength becomes not acceptable to be used in cell fabrication. Therefore, our target has set to develop a BASE (1) to be thin to compensate the resistance increase at lower temperatures, (2) with enhanced mechanical properties to minimize unwanted cell failure. The target can be achieved by fabricating highly toughened thin composite electrolytes. In this presentation, our on-going efforts on developing thin composite electrolytes made of β"-alumina and oxygen conducting oxides. Results showed that the flexural strength of this novel electrolyte could be greatly increased maintaining its area specific resistivity (ASR) as low as that of a conventional BASE.
Enhancing Electrochemical Performance By Coating Al2O3 on Na0.6Mn0.66Ni0.22Co0.11O2 cathode in Sodium-Ion Batteries
Authors: Nguyen Ngoc Anh , Kim Kyuman , Cho Inseong , Ryou Myung-Hyun , Lee Yong Min 
Published: February 2020

Rechargeable sodium-ion batteries (SIBs) have recently attracted much attention as an alternative electric energy storage device to lithium-ion batteries (LIBs) because of the availability and low cost of sodium. However, the cycle performance of SIBs is not comparable to LIBs due to the side reaction between electrode and electrolyte as well as the structural instability and transition metal dissolution into electrolyte. In order to solve these problems, various surface coating techniques have been used to coat oxides on the cathode active material surface before making the electrode. However, additional coating process causes the price increase, and they have not been applied for SIB cathodes.
Herein, an Al2O3 thin film was directly deposited on the surface of Na0.6Mn0.66Ni0.22Co0.11O2(NaMNCO2) cathode by a radio-frequency magnetron sputtering. Only 4 min coating of Al2O3 upon the NaMNCO2 could improve the specific capacity from 134.6 to 146.4 mA h g-1 in a voltage range of 2.1 to 4.3 V. In addition, the cycle performance was also enhanced to deliver 49.7 mA h g-1 even after 200 cycles. In case of high voltage operation up to 4.5 V, the discharge capacities of pristine and Al2O3-coated electrodes are 150.6 and 160.1 mA h g-1, respectively.

Acknowledgement

This work was supported by the Human Resource Training Program for Regional Innovation and Creativity through the Ministry of Education and National Research Foundation of Korea (NRF-2014H1C1A1066977).

References

[1] Y.S. Jung, A.S. Cavanagh, A.C. Dillon, M.D. Groner, S.M. George, S.-H. Lee, J. Electrochem. Soc. 157 (2010) A75.
[2] Y. Huang, J. Chen, F. Cheng, W. Wan, W. Liu, H. Zhou, et al., J. Power Sources. 195 (2010) 8267–8274.
[3] D. Yuan, W. He, F. Pei, F. Wu, Y. Wu, J. Qian, et al., J. Mater. Chem. A. 1 (2013) 3895.
Thermally Reduced Graphite Oxide for Potassium Ion Battery Anodes
Authors: Jeong Jae Hyang , Pyo Myoungho 
Published: February 2020

Among the alkali metals, Li is considered as the best element in terms of the energy density due to the lightest atomic weight and the lowest standard potential. Because of this fundamental advantage, lithium ion batteries (LIBs) are now overwhelmingly used in portable device and transportation markets. In spite of technological settlement, however, the scarcity in reserves and the concomitant rise in cost of lithium urged researchers to shift their interest to other ion sources. Sodium and potassium ions are most promising candidates in that the knowledge accumulated from LIBs researches can be directly applied and the world-wide reserve is almost unlimited. Regarding sodium ion batteries (SIBs), the major current-huddle to commercialization is believed to be a lack of reliable anode materials. Graphite cannot be applied to SIB anodes because the ionic size is not comparable to an interlayer spacing of graphite (This size effect becomes more pronounced when the solvation sheath is considered together.). As a result, graphite can deliver only a small capacity (~35mAh/g) in SIBs. On the contrary, graphite is known to be active for potassium-ion intercalation, showing a reversible capacity of ~230mAh/g (i.e., formation of KC8 at -2.9 V vs SHE). Although K+ ion radius is larger than Na+, weak solvation of K+ makes possible the use of graphite in potassium ion batteries (KIBs). In this work, we studied reduced graphite oxide (rGTO) as a KIB anode. Graphite was mechanically pulverized, chemically oxidized, and finally subjected to a thermal treatment. The graphite oxide was heat-treated at various conditions and the relation between controlled interlayer distances and capability of K+ intercalation/deintercalation was investigated. We controlled d-spacing of rGTO by changing the thermal reduction conditions (heating and cooling rate, maximum temperature, etc.) and established the optimal experimental parameters. We also examined the various types of graphite (MCMB, flake types, etc.). Electrochemical studies revealed that rGTO has superior rate-performance when compared with pristine graphite. Further improvement of reversible capacity and cyclability is underway.
Short and Intermediate Range Ordering in Fast Cation Glasses for Battery Applications
Authors: Kassem Mohammad , Usuki Takeshi , Bychkov Eugene 
Published: February 2020

Lithium batteries provide the highest energy density which makes them ideal candidates for future generations of portable electronics (laptops, cellular, tablets, etc.) and hybrid electric vehicles for the time being. However, the increasing demand for lithium batteries will be limited by the fact that lithium is not an abundant material and its cost is expected to increase considerably in the coming years. In contrast, sodium resources are unlimited (fourth most abundant element in Earth’s crust) and from economic point of view, sodium batteries appear as good alternative to lithium devices, particularly for large-scale stationary applications. The ionic conductivity of chalcogenide and chalcohalide glasses is 2 to 3 orders of magnitude higher than that of oxide glasses with the same mobile ion content. This makes chalcogenide systems suitable for applications in power rechargeable systems.
Our studies are focused on the development of new Na+ion-conducting chalcohalide glasses combining sodium halides and sulfide-based glass network. Cation local environment and intermediate-range ordering in glasses are critically important to achieve fast ionic conduction. Usual structural hypothesis related to superionic glasses containing metal halides MY = LiI, NaBr, AgI, etc., implies the absence of chemical interactions between the host glass and metal halide. An expansion of the host network caused by large anions (I, Br) and related increase of the available free volume for fast cations, forming preferential conduction pathways, was considered to be the key parameter for glassy superionics. Nevertheless, recent studies of AgY and CuY crystalline coordination polymers show chemical interaction between metal halide and chalcogenide backbone giving rise to mixed M-centered polyhedra. The polyhedral connectivity was also found to be different, starting from isolated units and dimers and finishing by chains, 2D layers and tubes. Some characteristic types of MY-subnetwork are given in Fig. 1(a,b).
Using pulsed neutron and high-energy x-ray diffraction combined with Reverse Monte Carlo modelling, we examine cation local and intermediate range ordering in two glassy systems containing either silver iodide or sodium halides. Sodium chalcogenide glasses exhibit high ionic conductivity and seem to be promising for battery applications.

Figure 1