bluuebunny/crossref_metadata_2025 huggingface dataset:
Bulk Silicon/Graphite Alloy Anode Material for High Energy Density Li-Ion Batteries
Authors: Lee Myongjai , Feng Peter , Mahajan Vishal , Dahlberg Kevin , David Lamuel , Albano Fabio
Published: February 2020

Silicon anodes are an optimum alternative to traditional graphite anodes because of their higher lithium ion storage capacity. However, the massive first cycle capacity loss and large fade during cycling have hindered its commercialization. Here we present a solution for these issues in the form of commercial grade silicon/graphite alloy. A silicon-carbon alloy structure with carbon-coated silicon nanoparticles gives an ability to buffer volume changes and retain the silicon amorphous phase. The material achieved a first cycle reversible capacity of over 480 mAh/g when cycled between 0.01-1.5V at a c-rate of 0.05C, with first cycle efficiency of close to 95%. The capacity of the silicon alloy was ~30 mAh/g even at 10C after cycling, and recovered to 480 mAh/g at 0.05C. We performed further studies using galvanostatic intermittent titration (GITT) technique which showed the diffusion coefficient to be 10-9 to 10-12 cm2/sec. Nyquist plots were obtained using electrochemical impedance spectroscopy (EIS) at every 5%SOC. 95x64 mm pouch cells (2Ah) with the silicon alloy coupled with high capacity NMC cathode had impressive long term cycling, over 500 cycles, at a high c-rate (1C/1C), and stable c-rate performance at 10C. The cells were disassembled after cycling to study the SEI formation, electrode expansion and coating stability. Physical measurement of electrodes and SEM analysis of active materials showed that even after long term cycling, the coating was intact without minor cracks or paste delamination.
Precision Engineering of Co-Laminar Flow Cells for Electrochemical Energy Conversion
Authors: Goulet Marc-Antoni , Kjeang Erik
Published: February 2020

Most electrochemical cells used for energy conversion utilize a physical separator such as an ionomer membrane to keep reactants separated and prevent a mixed potential from reducing energy efficiency. A new class of electrochemical cell achieves this separation by design of channel dimensions such that reactant flows remain laminar.  These co-laminar flow cells (CLFC)1,2, which include both fuel cells and flow batteries, are generally microfluidic and constrained in operation by the diffusion time of reactants across the channel. Due to their small scale and lack of a membrane, these co-laminar flow cells are both simpler and lower cost devices which make them well suited as an experimental platform for understanding electrochemical energy conversion.  The cells in this study are based on flow-through porous carbon electrodes with vanadium redox reactants dissolved in sulfuric acid as both fuel and oxidant.  This presentation reveals some of the advancements made with these cells over the past year and the lessons learned which may be applied to larger scale conventional flow batteries and fuel cells. 

Some of the topics to be discussed include electrode enhancement to improve the limiting reaction rate, supported by both ex situ and in situ characterization of the flow-through porous electrodes. Reaction kinetics are studied using a custom-developed three-electrode analytical cell for electrochemical analysis of flow-through porous electrodes. Multiphysics modeling work based on this characterization provides insight into some of the design principles which can be used to maximize the power density of these devices.

Acknowledgements

Funding for this research provided by the Natural Sciences and Engineering Research Council of Canada (NSERC), Canada Foundation for Innovation, and British Columbia Knowledge Development Fund is highly appreciated.

References:

1. Goulet, M.-A. & Kjeang, E. Co-laminar flow cells for electrochemical energy conversion. J. Power Sources
260,186–196 (2014).

2. Kjeang, E. Microfluidic Fuel Cells and Batteries. (Springer, 2014).
A Novel Titanium/Manganese Redox Flow Battery
Authors: Dong Yong-Rong , Kaku Hirokazu , Hanafusa Kei , Moriuchi Kiyoaki , Shigematsu Toshio
Published: February 2020

Toward the realization of a low-carbon society, renewable energies such as wind and solar power have been promoted rapidly around the world. Since such renewable energies have a fluctuating power output due to the variability of weather, the increasing amounts of such energy sources will bring stability problems to conventional power system. Electrical energy storage systems are expected to solve these problems, and large-scale batteries attach more attention than ever. Redox flow (RF) batteries have several advantages comparing to solid batteries, such as easy to capacity scale up, long cycle life, real time state of charge (SOC) monitor, which make them the most suitable for power network stabilization.

RF batteries have been enthusiastically developed worldwide, since its principle was publicized in the 1970s by NASA[1], all vanadium system as a representative of them has been put in practical applications[2]. To meet the growing demand for electrolytes, it is generally desired that active metals should be lower cost, higher electrode potential and stable supply than vanadium. Mn(II)/Mn(III) redox couple as a positive active material meets the requirements mentioned above. However, Mn(III) ion is chemically unstable and tends to disproportionate to Mn(II) ion and MnO2 oxide, which make it difficult to be used in flow batteries.

We found that the precipitation of MnO2 can be effectively suppressed by containing Mn ions as well as Ti(IV) ions in positive electrolyte. We gained a very good cycle charge-discharge performance in a cell test, even at SOC in a range of more than 100%, in this case SOC is calculated on Mn(II)/Mn(III) one-electron reaction. It considered that Ti(IV) ions exiting in positive electrolyte suppress the Mn(III) disproportion reaction, as well as particle growth of MnO2. The theoretical energy density of positive Mn and negative Ti electrolytes RF battery is around 26kWh/m3, which is comparable to that in all vanadium RF battery.

References

[1] N. H. Hagedorn, NASA Redox Storage System Development Project Final Report, DOE/NASA/12726-24, NASA TM-83677(1984)

[2] T. Shigematsu, Redox Flow Battery for Energy Storage, SEI Technical Review, Number 73, (October, 2011)
Non-Destructive High-Resolution Conductivity Mapping of Thin-Film Battery Electrodes
Authors: Riet Adriaan A , Sedgewick J Scott , Vogel John E , Clement Derek , Cutler Andrew D , Mazzeo Brian A , Wheeler Dean R
Published: February 2020

Accurately determining electronic conductivity of thin-film battery electrodes is not trivial, especially with the metallic current conductor still attached. A fast and reliable method would be of use for quality control and optimization purposes in battery manufacture, and would provide insight into the effects of changes in the fabrication process on the electrode structure.

We report a four-line probe that has been used to make high-resolution maps of local electrode conductivity on the micron scale. A computer-controlled apparatus allows precise control of pressure on the sample and positioning of the probe. A significant part of the work was developing a novel hybrid numerical-analytical model to invert the experiment, allowing a separate determination of film conductivity and contact resistance at the current collector in real time on a desktop computer. We will discuss the amount of local conductivity variation within representative electrode films.

This work was supported by the U.S. Department of Energy through the BMR program.

Figure 1
Co9S8@MoS2 Core-Shell Structures Formed on Carbon Nanofibers As Switchable Electrocatalyst for H2 and O2 Evolutions
Authors: Zhu Han , Du MingLiang
Published: February 2020

The production of hydrogen and oxygen through water splitting are promising and appealing solution for developing clean-energy technologies. However, how to design a kind of catalyst for simultaneously generating H2 and O2 is still a challenging and crucial issue for improving the overall efficiency of water electrolysis. To optimize and enhance electrocatalysts performance and durability for the hydrogen and oxygen evolution reactions through electrolysis, we describe a new class of core-shell structures formed on carbon nanofibers with cubic cobalt sulfide as cores and layered molybdenum disulfide as shells. The core-shell design of these nanostructures allows us to combine the advantages of cobalt sulfide and molybdenum disulfide, serving as switchable electrocatalyst for H2 and O2 evolutions. The unique core-shell nanostructure can serve as electrode for HER and OER and display excellent stability. These advantages can generate strong electron transfer between Co and Mo through the intermediate sulfur atoms bonded to both metals, leading to the promising promoted electrocatalytic activity. These approaches open new opportunities for exploring overall water splitting catalysts.
Forced Air-Cooling Strategies for Lithium-Ion Batteries Using Integral Wake Splitters and Flow Guide-Vanes
Authors: Ismailov Kiarat , Adair Desmond , Massalin Yerzhan , Bakenov Zhumabay
Published: February 2020

Thermal management of lithium-ion battery modules needs to be an integral part of the design process to guarantee that temperatures remain within a narrow optimal range. A well designed thermal management system will ensure good battery performance, safety and higher capacity. Many methods have been used, including air, liquid (direct and indirect), insulation, phase-change material, passive (ambient) or active (heaters, air-conditioning), or, a combination of these various approaches. In addition to regulating the module within a given temperature range, it is also important to minimize uneven distribution of temperature throughout the module. To not do so would decrease battery life cycle, and, charge and discharge performances.

This paper explores the use of surfaces extended into the near-wake of cylindrical lithium-ion cells, here termed integral wake splitters, and, of placing flow guide vanes also placed in the vicinity of the near-wakes. The numerical experiments are carried out in the Reynolds number range 102 - 103. After initially simulating flow and thermal characteristics in the vicinity of an isolated Li-ion cell, which includes optimizing the wake splitter length (L) - to - cell diameter (D) ratio, and, the gap (W
g)  between flow guide vanes in the wake and their placement distance downstream of the cell (W
d) , the study expands to examining the effect of using cell arrangements on the thermal characteristics within a given module with optimized splitters and flow guide-vanes in place (Figure 1a and Figure 1b).

When using the integral wake splitters it is found that the local Nusselt numbers in the very near wake of a single cylindrical battery are depressed. Similar effects are found to occur when the battery cells are in formation. The use of flow guide vanes was found not to be as effective, but their use did contribute to a depressed Nusselt number.

Figure 1 Illustrations of the splitter plates (a) and flow guide vanes (b)

Figure 1
Simulation and Modelling of the Solid Electrolyte Interphase with Varying Porosity
Authors: Single Fabian , Karaca Erkmen , Horstmann Birger , Latz Arnulf
Published: February 2020

Continuous capacity fade during the lifetime of lithium ion batteries is mainly attributed to the growth of the solid electrolyte interphase (SEI). This layer forms on the negative electrode and consists of electrolyte reduction products. Active lithium that is consumed in this reduction reaction is no longer available for the primary battery function, leading to capacity fade. By preventing direct electrolyte/electrode contact, the SEI layer can suppress the electrolyte reduction reaction to a large degree. However, capacity fade and SEI growth still continue with a decreasing speed [1,2]. The fundamental mechanisms behind this continuous SEI formation are still subject of active research.

Numerous models attempt to describe this effect [2-4]. They typically assume that the formation rate is limited by a single transport mechanism that allows one reactant to cross the SEI layer. While most of these models predict the experimentally observed SEI thickness and capacity decay, they remain inconclusive with respect to the limiting transport process. We present and evaluate the results of a new model to describe the SEI growth. Our model instead is based on two rate limiting processes and contains a spatially-varying porosity. This novel approach allows us to track the growth of the SEI morphology distribution.

Our simulations agree nicely with experiments [2] after adjusting the limiting transport parameter. Most importantly, the SEI thickness shows the characteristic √t growth behavior. The porosity inside the SEI is found to be constant. We derive analytic expressions for the thickness evolution and the attained porosity. These well justified estimates are in very good agreement with simulations.

[1] A.J. Smith, et al, Journal of the Electrochemical Society, 158 (2011), A447.

[2] M.B. Pinson, et al., Journal of the Electrochemical Society, 160 (2012), A243-A250.

[3] H.J. Ploehn, et al., Journal of the Electrochemical Society, 151 (2004), A456.

[4] J. Christensen, et al., Journal of the Electrochemical Society, 151 (2004), A1977.

Figure 1
(Invited) Pluse Plating for Compound Semiconductor Electrodeposition
Authors: Stickney John Lewellen , Czerniawski Justing , Zhang Xiaoyue , Bui Nhi , Shen Sheng
Published: February 2020

Work in this group has mostly involved development of the electrochemical version of atomic layer deposition (E-ALD) over the last many years.  ALD refers to is a group of methods for the formation of materials an atomic layer at a time using surface limited reactions.   E-ALD achieves atomic level control during electrodeposition by alternating solutions and using underpotential deposition (UPD) to limit deposits to an atomic layer each cycle. It has been shown to form high quality deposits for a range of materials central to thin film photovoltaic formation, including: CdTe, CdS, CIS, and CIGS.  Growth chemistry for a family of absorber materials referred to as CZTS, or Cu2ZnSn(S,Se)4 is presently being investigated.  The primary advantages of CZTS for PV are that they are made from nontoxic earth abundant elements.  The primary advantage of an E-ALD process would be atomic layer control and conformal deposition. The main disadvantage would be the time it takes to grow a µm thick absorber layer.  The rate of growth is presently limited by the time it takes to alternate solutions.

Recently, efforts by this group have involved development of a variant of E-ALD based on potential changes (pulses), rather than solution exchanges, greatly increasing the rate of deposition.   Presently, this group refers to this method as potential pulse ALD (PP-ALD).   Preliminary results on the formation of Cu2Se and other components of a CZTS absorber layer will be discussed.
Electrochemical Oxygen Separation Using Layered Double Hydroxides As Hydroxide Ion Conductor
Authors: Tadanaga Kiyoharu , Arishige Yuji , Hayashi Akitoshi , Tatsumisago Masahiro
Published: February 2020

Oxygen separation membranes using oxide ion conducting materials have been studied for oxygen separation from air.  However, the membrane can effectively separate oxygen from the air only at high temperatures higher than several hundred degrees, because the oxide ion conductor shows high ionic conductivity at only elevated temperatures.

On the other hand, we have been studied layered double hydroxide (LDH) as a hydroxide ion conducting material [1-3].  LDHs are consisting of positively charged metal hydroxide layer and interlayer anions for charge compensation of cationic layer. The general formula for LDHs is [MII
1−x MIII
x(OH)2][(An−)x/n • mH2O], where MII is a divalent cation such as Ni2+, Mg2+, Zn2+, etc., and MIII is a trivalent cation such as Al3+, Fe3+, Cr3+, etc., and An− is an anion such as CO3
2−, Cl−, OH−, etc.  We have recently reported that LDHs intercalated with CO3
2- showed high ionic conductivity of the order of 10-3 S cm-1under humidification, and the LDHs are solid hydroxide ion conductors [1-3]. 

Here we report the development of an electrochemical oxygen separation process using a hydroxide ion conductor [4].   The electrochemical oxygen separation cell consists of pelletized OH− conductive solid electrolyte and electrodes.  At the air feed side, oxygen in air, H2O and electrons produces OH- ions at the electrode with the electrochemical oxygen reduction reaction.  At the same time, oxygen, H2O and electrons are generated from OH− ions at the other electrode with the electrochemical oxygen evolution reaction. Since H2O will easily be separated with O2, oxygen separation will be achieved.

In this study, Ni-Fe LDH intercalated with CO3
2− (Ni-Fe CO3
2− LDH) was used as a hydroxide ion conductive material.  The pellet of Ni-Fe CO3
2− LDH as an electrolyte was sandwiched with electrodes using Pt/C as a catalyst and Ni-Fe CO3
2− LDH as an ionomer. The oxygen concentration at the O2 product side was determined using a gas chromatography system.  The electrochemical oxygen product flow was confirmed to be proportional to the external current density at 50oC under 70% of relative humidity, indicating that the membrane functioned as electrochemical oxygen separator.

[1] K. Tadanaga, Y. Furukawa, A. Hayashi, M. Tatsumisago, Adv. Mater., 22 (2010) 4401-4404.

[2] Y. Furukawa, K. Tadanaga, A. Hayashi, M. Tatsumisago, Solid State Ionics, 192(2011) 185-187.

[3] D. Kubo, K. Tadanaga, A. Hayashi, M. Tatsumisago, J. Electroanal. Chem., 671 (2012) 102-105.

[4] Y. Arishige, D. Kubo, K. Tadanaga, A. Hayashi, M. Tatsumisago, Solid State Ionics, 262 (2014) 238-240.

 

Figure 1
(Invited) Advanced CMOS Device Technologies Discussed Also with Transition-Metal Di-Chalcogenide (TMDC) Channel
Authors: Wakabayashi Hitoshi
Published: February 2020

Abstract

Advanced CMOS device technology for a high-performance system-on-a-chip (SoC) LSI is firstly discussed by using benchmarking of published data [1-6], mainly-highlighted by a FinFET and beyond, as shown in Fig. 1. To enhance the performance of FinFET devices, a low-voltage operation less than 0.7 V with smaller variability of characteristics is highly required rather than an enlargement of channel width (Weff / Wfootprint). Here, Weff and Wfootprint mean effective and footprint channel widths. After that, higher-mobility channel devices are strongly needed with superimposed manner having an InGaAs high-electron mobility transistor (HEMT), InGaAs quantum well (QW), InAs QW, and InGaAs MISFET having an appropriate smaller bandgap. In this case, smooth thin-channel is promising to suppress the variability of characteristics. Therefore, an atomically-consistent semiconductor material such as a graphene and transition-metal di-chalcogenide (TMDC) are favorable candidates. Although the graphene has a zero band-gap, the TMDCs have superior properties such as an appropriate bandgap, for example, 1.2 eV in single-layer MoS2 film. Furthermore, they also yield higher mobility, transparent and mechanical robustness.

In our experiments, a higher Hall mobility of electron with 28 cm2/Vs in 10-nm-thick MoS2 film is achieved even by using a magnetron sputtering process with MoS2 target for channel formation [7]. This might be caused by a suppression of carrier scattering due to contaminations such as alkali metals of sodium and potassium, impurities, crystal defects, and film roughness in the MoS2 film.

In conclusion, the TMDC-channel MISFET could be suitable for high-performance SoC LSIs as not only advanced CMOS devices but also monolithic transistor to enhance the functionalities per chip area. Furthermore, it has a strong possibility achieving not only more-Moore and more-than-Moore but also more-comfort properties for high-performance human-interface (I/F) devices such as a transparent and flexible display.

Acknowledgements

This work was partially supported by JSPS Grant-in-Aid for Scientific Research on Innovative Areas: Grant Number 26105014, and the Center of Innovation Program from Japan Science and Technology Agency, JST.

References

[1]     C.-H. Jan, et al., in IEDM, p. 44, 2012.

[2]     S. Natarajan, et al., in IEDM, 3.7, p. 71, 2014.

[3]     M. Radosavljevic, et al., in IEDM, p. 319, 2009.

[4]     Alireza Alian, et al., in IEDM, p. 437, 2013.

[5]     S.W. Chang, et al., in IEDM, 16.1, p. 417, 2013.

[6]     J. A. del Alamo, et al., in IEDM, p. 578, 2014.

[7]     Takumi Ohashi, Hitoshi Wakabayashi, et al. “Multi-layered MoS2 film formed by high-temperature sputtering for enhancement-mode nMOSFETs,” in 2015 Jpn. J. Appl. Phys. 54 04DN08, doi:10.7567/JJAP.54.04DN08.
(Keynote) Heterogeneous Integration of MEMS by Adhesive Bonding
Authors: Esashi Masayoshi , Tanaka Shuji
Published: February 2020

Technology called microsystems or MEMS (micro electro mechanical systems) has been developed and applied as value added devices for systems. It is based on semiconductor microfabrication integrating not only circuits but also sensors, actuators and microstructures.

MEMS as switches and filters fabricated on CMOS LSI are needed for future multi-band wireless systems, in which good mechanical properties or piezoelectric materials are required for the MEMS and state of the art for the LSI. Such heterogeneous integration can be performed by transferring MEMS devices fabricated on a carrier wafer to a LSI wafer by adhesive bonding (Figure). Wafer level selective transfer from one carrier wafer to multiple target wafers are needed for cost-effective integration of different size chips. The selective transfer technology was applied to multiple SAW (surface acoustic wave) resonators on LSI and tunable SAW filter having variable ferroelectric capacitor.

Distributed tactile sensors are needed on the skin of robots to ensure their safety in nursing care robots. A tactile sensor network acquires sensing data from each tactile sensor element by autonomous data transmission (event driven). Capacitive tactile force sensors were formed on a communication LSI by adhesive bonding.

An electron emitter array integrated with a 100×100 active-matrix driving LSI has been developed using the adhesive bonding. Massive parallel EB (electron beam) exposure systems for maskless lithography (digital fabrication of LSI) are under development. A nc (nanocrystalline)-Si emitter consists of cascaded tunnel junctions can be controlled at low voltage (10V). Resist patterning by the emitted electron was successfully confirmed.

Amperometric biosensor in which 20×20 boron doped diamond electrode array are formed on LSI using the adhesive bonding. Distribution of chemicals like neurotransmitter can be detected owing to a wide potential window of the diamond electrode.

Cost effective development is required for micro systems because they are versatile and not standardized. A hands-on access fabrication facility in our University is reuse of a production line for power transistor and donated equipments. Companies can easily access and utilize for their prototyping or small-volume production. It is equipped with 4 and 6 inch facilities. The users are charged depending on their amount of usage. They can access a lot of technology and know-how accumulated and can be assisted by skilled engineers. More than 150 companies are using this facility and it is allowed to sell produced small volume devices.

Figure 1
Effects of Composition and Size of Active Metal Particles on Electrochemical Performance and Characteristics of Sodium Metal Chloride Rechargeable Batteries
Authors: Choi Joon-Hwan , Ahn Cheol-Woo , Kim Mangi , Choi Jong-Jin , Kim Jong-Woo , Yoon Woon-Ha , Ryu Jungho , Hahn Byung-Dong , Lee Heesoo
Published: February 2020

Because of the limitation of lithium resources, sodium-based rechargeable batteries started to emerge as potential candidates for medium and large-scale stationary energy storage system (ESS) again. Na-S batteries have been used for large-scale stationary ESS but intrinsically have a risk for explosion. Sodium metal chloride batteries based on Na-NiCl2 chemistry, however, are consisted of safer electrode configuration with nickel, NaCl and NaAlCl4 as cathode ingredients than the Na-S batteries. The Na-NiCl2 batteries offer many attractive properties such as high cell voltage, high theoretical specific energy, and broad range in operating temperature. The nickel chloride electrode plays an important role in the cell performance. A qualitative and quantitative understanding of the electrochemical and morphological properties of the active metals, therefore, is very important. This paper will describe effects of iron addition to cathode side as an active material and size of the active metal particles on electrochemical performance and characteristics of the sodium metal chloride batteries.
Synthesis and Electrochemical Characterization of a Sodium Manganese Oxide By Facile Reduction Reaction for Sodium Ion Batteries
Authors: Song Jinju , Gim Jihyeon , Kim Sungjin , Jo Jeonggeun , Alfaruqi Muhammad Hilmy , Park Sohyun , Yang Juhyun , Kim Jaekook
Published: February 2020

A non-stoichiometric composition of sodium manganese oxide (NaxMnO2+δ) cathode useful for sodium batteries was synthesized by an ambient temperature strategy that involves the facile reduction of aqueous sodium permanganate in sodium iodide and subsequent heat treatment at 600 °C.  A combined powder X-ray diffraction (PXRD) and synchrotron X-ray diffraction (SXRD) analyses confirmed the annealed sample to belong to a NaxMnO2 phase with a P2-hexagonal structure. The ICP results confirmed the stoichiometry of the sample to be Na0.53MnO2+δ. Electron microscopy studies revealed the particle size of the electrode to be in the range of a few hundred nanometers. The Na0.53MnO2+δ cathode delivered average discharge capacities of 170 mAhg-1 with a stable plateau at 2.1 V for the initial 25 cycles versus sodium. Ex-situ XANES studies confirmed the reversible intercalation of sodium into Na0.53MnO2+δ and suggested the accommodation of over-stoichiometric Mn4+ ions to contribute towards electrode performance.

Figure 1
(Invited) Integration of 2-D Materials for Electronic Device Application
Authors: Jia Jianyuan , Jeon Jaeho , Park Jin-Hong , Lee Sungjoo
Published: February 2020

In this work, we present our recent progresses on the integration of 2-d materials (TMD, BP, TMC) for the electronic device application.

In spite of the recent heightened interest in molybdenum disulfide (MoS2) as a two-dimensional material with substantial bandgaps and reasonably high carrier mobility, a method for the layer-controlled and large-scale synthesis of high quality MoS2 films has not previously been established. Here, we demonstrate that layer-controlled and large-area CVD MoS2 films can be achieved by treating the surfaces of their bottom SiO2 substrates with oxygen plasma process. In addition, by using various polymers, we present that the doping level of MoS2 layers can be controlled for realization of electronic devices.

Black phosphorous (BP) is known as a most stable allotrope of phosphorous. Recent studies have shown that BP is an elemental layered material, making it possible to obtain layered structures through mechanical cleavage. In this study, we report the preparation of thickness-controlled few-layer black phosphorus (BP) films through the modulated plasma treatment of BP flakes. Not only does the plasma treatment control the thickness of the BP film, it also removes the chemical degradation of the exposed oxidized BP surface, which results in enhanced field-effect transistor (FET) performance.
ZnCdSe-Sensitized WO3 and TiO2 based Photoelectrodes: A Comparative Study
Authors: Gakhar Ruchi , Chidambaram Dev
Published: February 2020

After about four decades since Honda and Fujishima’s electrochemical photolysis report using TiO2(1), intensive research is still ongoing to identify efficient and cost effective semiconductor materials to be integrated in a photoelectrochemicalsystem. The ultimate goal is to have such a design that can simultaneously drive, both the hydrogen evolution and water oxidation reactions. Among all candidate materials, inexpensive metal oxides have been the primary choice due to their stability and excellent corrosion resistance.(2) However, the major drawback is their poor optical absorption that restrains solar-to-hydrogen efficiency to only few percent (3).

The best research strategy is to focus on a thermodynamically stable system with appropriate absorption properties and then attempt to improve its absorption, transport and catalytic properties. A stable tungsten based material with appropriate band edge alignment was chosen and the change in its band gap in the presence of a transition metal dopant was theoretically calculated. Based on the preliminary calculations, an optimal concentration of dopant was chosen and the material was synthesized via spray deposition. Surface morphology of the films (before and after sensitization) was examined using scanning electron microscope.Composition of substrate and oxidation state of elements was analyzed using X-ray diffraction and X-ray photoelectron spectroscopy. Absorption characteristics were determined using UV-Visible spectroscopy. Photoelectrochemical measurements (photocurrent/ photovoltage versus time and I-V characteristics) were undertaken to depict the photoconversion efficiency of designed photoanodes. The correlation of morphological changes with photoelectrochemical response of doped-oxide nanostructures will be discussed. Stability studies of the oxide films, conducted using ICP-OES, will also be presented.

Our results show that the bandgap can be altered significantly by using different dopants.  Furthermore, for a given dopant, the synthesis parameters such as composition, film thickness, temperature, and dopant concentration play a significant role in determining the final characteristics.  

 

Acknowledgements: This work was funded by Department of Energy under contract DE-FC36-06-GO86066. Dr. David Peterson and Dr. Eric Miller act as the program manager and the technical manager, respectively.

 

References

1.             A. Fujishima and K. Honda, Nature, 238, 37 (1972).

2.             N. M. Gaillard, in Meeting Abstracts, p. 1741 (2012).

3.             N. Gaillard, Y. Chang, J. Kaneshiro, A. Deangelis and E. Miller, in SPIE Solar Energy+ Technology, p. 77700V (2010).
(Invited) Transistors without Semiconductors By Functionalized Boron Nitride Nanotubes
Authors: Yap Yoke Khin
Published: February 2020

The development of one- and two- dimensional (1D and 2D) electronics are still facing various materials challenges. For instance, the nanotube-based electronics is still hindered by the chiral-specific synthesis of semiconducting carbon nanotubes (CNTs). On the other hand, the zero band gap of graphene is preventing their use in digital switches. Likewise, the structurally analog boron nitride nanotubes (BNNTs) and boron nitride nanosheets (BNNSs) are insulators and not applicable for electronic devices [1, 2]. Apparently, further development of nanoscale electronics will continue to rely on semiconducting nanowires and 2D nanosheets.

In this invited talk, I will discuss about the discoveries of 1D and 2D electronics without using semiconducting nanomaterials:

1) First, the use of BNNTs functionalized with gold quantum dots (QDs-BNNTs) as room-temperature tunneling field effect transistors (T-FETs) will be reviewed [3].

2) Next, the perspective of using QDs-BNNTs as flexible electronics will be evaluated based on our latest study using in-situ scanning tunneling microscopy performed inside transmission electron microscopy (STM-TEM).

3) Finally, I will discuss about effective digital switching of graphene as functionalized with BNNTs.

Acknowledgement:

This work is supported by the U.S. Department of Energy, Basic Energy Sciences, Materials Sciences and Engineering Division (DE-SC0012762) and the Center for Nanophase Materials Sciences (Project CNMS2012-083).

[1]. (Review) J. Wang et. al, Nanoscale 2, 2028 (2010).

[2]. C. H. Lee, et. al, Chem. Mater. 22, 1782 (2010).

[3]. C. H. Lee, et. al, Advanced Materials 25, 2544 (2013).

[4]. (Review) J. A. Jaszczak et. al. MRS Proceedings, 1700, mrss14-1700-mm03-01 (2014).
(Invited) Low Dimensional Materials Used for Solar Cells
Authors: Li Meicheng
Published: February 2020

Low dimensional materials, including nanoparticles, nanowires and nanosheets have been widely used in the field of light harvesting, and energy conversion. Based on our work, we will introduce  several low dimensional materials, and their application in the device of energy conversion, especially in solar cells. Detail information will coming later.

The low dimensionall materials offer a viable pathway to reduce fabrication costs and material usage, their energy conversion efficiencies can still be improved significantly by enabling them to harness a larger fraction of the incident solar photons, using new antireflection surface structure and even some new concepts, which can dramatically boost the amount of light trapping and light absorption per unit volume of semiconductor materials. The structural design and fabrication of these nanomaterials are essential for the further exploration of their functions.
(Invited) Single Cell Detection Using Magnetic Zigzag Nanowire Biosensor
Authors: Huang Hao-Ting , Wei Zung-Hang
Published: February 2020

Among various types of biosensors, magnetoresistance-based biosensors possess several advantages including high sensitivity and being less interfered by the environment, and are therefore suitable for sensitive biodetection [1-4]. Besides, the magnetic is not shielded by chemical compounds, microstructures, or another biomaterials, so the signals detected by the magnetoresistance-based biosensors are not influenced by the surrounding objects. In this report we present wave Permalloy (Ni81Fe19) nanowires with various line widths as a biomolecular sensing device. In this design, the magnetic poles on the apexes and valleys of the wave Permalloy nanowires can actively attract the magnetic beads immobilized biomolecular onto the nanowires for detection.

Permalloy nanowires with line widths 300 and 500 nm deposited onto wave silicon grooves were designed as biosensing devices of nano magnetic beads, which modified by biomolecule. Figure 1 shows the SEM image of the wave ferromagnetic nanowires. We applied a magnetic field along x axis, and measured the magnetoresistance curves of the nanowires before and after the attachment of magnetic beads by four-probe method. The stray field generated by the magnetized beads are against the magnetic moments of the wave sheet surfaced film, therefore making it harder for the switching process to occur. It was observed that the sensitivity 43.29% in switching field variation after magnetic beads were attached can be obtained when the field was applied perpendicular to the plane of the 300 nm wide nanowire. The sensitivity 45.78% in magnetoresistance variation occurred in the 500 nm wide nanowire for the same field direction.

Further work, we will focus on different wire width (150, 300, 500, and 800 nm) before and after attaching nano magnetic beads on the nanowires, when magnetic fields were applied in various directions,x, y, and z (out-of-plan) axes.

[1] B. Ilic, D. Czaplewski, H. G. Craighead, P. Neuzil, C. Campagnolo, and C. Batt, Appl. Phys. Lett. 77, 450 (2000).

[2] H. K. Kim, J. S. Hwang, S. W. Hwang, and D. Ahn, Nanotechnology 21, 465501 (2010).

[3] S. Tombelli, M. Minunni, and M. Mascini, Methods 37, 48 (2005).

[4] P. Kauffmann, A. Ith, D. O’Brien, V. Gaude, F. Boué, S. Combe, F. Bruckert, B. Schaack, N. M. Dempsey, V. Haguet, and G. Reyne, Lab Chip 11, 3153 (2011).

Figure 1
Sustainable Innovations Electrochemical Technologies
Authors: Molter Trent M.
Published: February 2020

We live in a world that demands innovation.  There is no way forward without a different way of thinking and doing.  Companies cannot sustain themselves, and the world cannot sustain us by conducting business as usual.  It’s time to become smarter about the way we do things.  Sustainable Innovations has developed a low-cost, fluids-flexible, scalable electrochemical platform based on the proton pumping capability of cation exchange membranes to meet near-term and emerging market needs.  Sustainable Innovations’ products serve global, high-value applications including: Hydrogen for industrial use, energy, and vehicle fueling; energy storage (regenerative fuel cells); and recycling CO2 into high-value fuels and chemicals. This paper discusses the key features of the common electrochemical platform as well as important differences in the hardware design elements and electrochemistry associated with each of these specific products that leads to important cost and performance benefits for end-users.
Doped and Decorated Graphene Foam Electrocatalysts
Authors: Lyth Stephen Matthew , Liu Jianfeng , Mufundirwa Albert , Sasaki Kazunari , Daio Takeshi
Published: February 2020

Graphene is an ideal material for electrochemical applications due to high electrical conductivity, large surface area, and stability over a wide electrochemical potential window. However graphene is expensive; it is difficult to control porosity (and thereby mass diffusion); and it is difficult to dope effectively. Simple carbon foams with large micron-scale pores, very thin walls, and very large surface area (e.g. 2500 m2/g) can be synthesized at low cost by thermal decomposition of sodium ethoxide.[1,2] 

Crucially, by decomposing nitrogen-containing alkoxides, nitrogen-doped graphene powders are made.[3] These do not contain transition metal contamination, as is the case with carbon nanotubes and carbon black. Therefore they can be used to probe the fundamental oxygen reduction reaction (ORR) activity of nitrogen-doped carbon in acid – a relatively under-represented research topic, plagued by contamination issues.[4,5] We record surprisingly high mass activity and onset potential for the ORR, with high electron transfer number (3.6). The negligible metal content was confirmed by ICP-AES. This work shows that 4-electron ORR is possible even in the absence of transition metals, most likely at (or adjacent to) tertiary nitrogen sites.[6]

The activity in alkaline medium is also of interest, due to the development of new alkaline ion exchange membranes and the faster ORR kinetics. The nitrogen-doped graphene foams presented here display negligible degradation in cyclic voltammograms over 60,000 load potential cycles, demonstrating the applicability of such metal-free non-precious electrocatalysts in application that require long lifetimes.[7]

[1] S. M. Lyth, H. Shao, J. Liu, K. Sasaki, Int. J. Hydrogen Energy, 2014, 39, 376

[2] J. Liu, D. Takeshi, K. Sasaki, S. M. Lyth, J. Electrochem. Soc. 2014, 161, F838

[3] S. M. Lyth, Y. Nabae, N. M. Islam, et al., eJournal of Surface Science and Technology, 2012, 10, 29-32.

[4] S. M. Lyth, Y. Nabae, N. M. Islam, S. Kuroki, M. Kakimoto, S. Miyata, J. Nanosci. Nanotechnol. 2012, 12, 4887

[5] S. M. Lyth, Y. Nabae, N. M. Islam, S. Kuroki, M. Kakimoto, S. Miyata, J. Electrochem. Soc. 2011, 158, B194

[6] J. Liu, D. Takeshi, D. Orejon, K. Sasaki, S. M. Lyth, J. Electrochem. Soc. 2014, 161, F544

[7] J. Liu, K. Sasaki, S. M. Lyth, ECS Trans. 2014, 64, 1161

Figure 1
3d and 4f Ions in Solids: Description and Understanding of Optical Properties
Authors: Brik Mikhail G. , Srivastava Alok M , Camardello Sam Jospeh
Published: February 2020

An overview of recent results on modeling of properties of optical materials doped with transition metal and rare earth ions is given. Studies of various groups of materials – pyrochlores, perovskites, garnets, spinels – are presented. Applications of several different approaches (e.g. crystal field theory, DFT-based computational techniques, configurational coordinate model etc) are discussed in details. Special attention is given to the positioning of impurity ions energy levels in the host band gap. It is shown that through the combination of the crystal field theory and ab initio methods of electronic structure calculations it is possible to build up the complete energy level scheme of a doped crystal, which includes the host’s electronic band structure and impurity ion energy levels superimposed onto it.

A new model that links together the energies of the spin-forbidden transitions of transition metal ions (Mn4+, Cr3+, Ni2+) with the covalent effects experienced by those ions is also outlined. Several recommendations on how to tune the emission wavelengths of the Mn4+
2Eg – 4A2g transition are outlined.

All shown examples are compared with the corresponding experimental results (whenever possible). Predictive potential of the presented models is discussed.
Enhanced Photo-Bioelectrochemical Energy Conversion By Genetically Engineered Cyanobacteria
Authors: Sekar Narendran , Ramasamy Ramaraja P.
Published: February 2020

Photosynthetic energy conversion using natural systems is increasingly being investigated in the recent years. Photosynthetic microorganisms such as cyanobacteria exhibit light dependent electrogenic characteristics in photo bio-electrochemical cells1 (PBEC) and/or photosynthetic microbial fuel cells2 (PMFC) that generate substantial yet lower photocurrents than their photovoltaics counterparts. Recently we demonstrated that a cyanobacterium named Nostoc sp. employed in PBEC could generate up to 35 mW/m2 even in a non-engineered PBEC.  With the insights obtained from our previous research2, a novel and successful attempt has been made in the current study to genetically engineer the cyanobacteria to further enhance its extracellular electron transfer. The cyanobacterium Synechococcus elongatus PCC7942 was genetically engineered to express a non-native outer membrane redox protein. The engineered S. elongatus exhibited very high extracellular electron transfer ability resulting in ~ 9 fold higher photocurrent generation on the anode of a PBEC than the corresponding wild-type cyanobacterium. This work highlights the scope for enhancing photocurrent generation in cyanobacteria thereby benefiting faster advancement of the PMFC technology.

References

J. M. Pisciotta, Y. Zou and I. V. Baskakov, PLoS One, 2010, 5, 10

N. Sekar, Y. Umasankar, R. Ramasamy Phys.Chem.Chem.Phys., 2014,16,7862

Figure 1
Fabrication of Low-Invasive Patch Glucose Sensors
Authors: Li Jiang , Hiura Kentaro , Yasuzawa Mikito , Fuchiwaki Yusuke
Published: February 2020

1. Introduction

Recently, implantable glucose sensors for continuous glucose monitoring (CGM) are provided significant advantage on diabetic health care, since it not only lower the physical and mental load on glucose measurement, but also present continuous glucose trend, which is useful for treatment evaluation. However, since the length of sensor device inserted in skin is about 1 cm, development of lower invasive CGM system is expected for the improvement of diabetic patients' quality of life.

In this study, a fine needle tube type glucose sensor, which has sensing region at the tip of a fine tapered electrode, was proposed. The schematic illustration of such glucose sensor is shown in Fig. 1. Since the sensing region is at the tip of tapered electrode, it only requires the sensor tip to be implanted in the tissue for glucose monitoring, which makes it possible to perform as a patch type sensor instead of implanting sensor. Fine platinum-iridium alloy wire was placed inside the tapered PEEK tube and glucose oxidase (GOx) was immobilized on the surface of platinum electrode by using the combination of electrodeposition and electropolymerization technique. Properties of the obtained sensor were evaluated mainly by in vitro measurement.

2．Experimental

Pt-Ir alloy wire (0.17 mm in diameter) was fixed in a PEEK tube (0.20 mm in inner diameter and 0.8 mm in outer diameter). The prepared assembly was mechanically polished to form a fine tapered needle structure. According to the procedure proposed by Wilson's group [1], the biosensor was prepared.

The amperometric responses of the prepared electrodes to glucose were examined at 40°C in a 0.1 M PBS (pH 7.4) containing 0.1 M NaCl, by measuring the electrooxidation current at a potential of 0.6 V (vs. Ag/AgCl).

3．Results

Current-time response of the prepared electrode was investigated. The response current increased with increasing concentration of glucose. Response current provided good linear relationship with glucose concentration. Variation of response in time on the prepared electrode was investigated for two weeks. The response of the electrode was measured at 40°C and stored in phosphate buffer at 4°C when not in use. After initial increase of response current for few days, the electrode provided stable response current.

(1) N. Matsumoto, X. Chen and G. S. Wilson, Anal Chem, 74, 368 (2002).

Figure 1
The Studies of Interfacial Property and Water Dynamic Process within Self-Humidifying Confined PFSA-Zeolite Composite Membrane
Authors: Sim Viola , Deng Ran , Han Wei , Yeung King Lun
Published: February 2020

Self-humidifying proton exchange membrane fuel cell (PEMFC) is important in the development of portable fuel cell devices as it avoids the need for bulky eternal humidification equipment. The use of inorganic additives and confinement of the perfluorosulfonic acid (PFSA) are shown to provide advantages in membrane hydration. More recently, we demonstrated that confinement of subnanoliter volumes of PFSA within zeolite coated walls enables fuel cell to operate at high temperatures and dry conditions. The resulting PEMFC delivered higher performances than those of fuel cells made with traditional PFSA membrane. It is believed that the narrow confinement of PFSA and its surface interaction with the zeolite influence the polymer chain conformation and therefore the transport pathway through the PFSA volume. Using focused ion beam under cryogenic conditions, the membrane dissected microscopically to reveal the structure and composition at the interfacial region between the PFSA and zeolite. Exfoliated sections were examined under high resolution electron microscopy. Water dynamics include water diffusion in PFSA matrix, its transport across the interface and reversible adsorption and retention within the zeolite. Real-time monitoring of water dynamics was carried out using quartz crystal microbalance at different water activities. The results indicate that the anchorage of PFSA polymer on zeolite intercrystalline pores and the oriented PFSA chain distribution within confined space increase mechanical and thermal stabilities of composite membrane, and accelerate water adsorption, exchange and transport processes.