bluuebunny/crossref_metadata_2025 huggingface dataset:
The Effect of Polypyrrole in the Capacity Retention of Fe3O4/Polypyrrole Composite Electrodes in Lithium-Ion Batteries
Authors: Bruck Andrea , Gannett Cara N , Bock David C , Smith Paul F , Marschilok Amy C , Takeuchi Esther S , Takeuchi Kenneth J
Published: February 2020

Future device applications will dictate increases in the energy density of batteries, which may be accomplished by incorporating high capacity electroactive materials into composite electrodes where all the electroactive material is electrochemically accessible and the mass and volume contributions of passive components are minimized. Electroactive materials are incorporated into batteries through the fabrication of composite electrodes, where several additives may be used to enhance conductivity and to mechanically bind the components. Typically, an electrically conductive carbon additive (e.g. acetylene black or graphite) and a polymer binder (e.g. PVDF and PTFE) are mixed with the electroactive material to form a composite electrode. Electrically conducting polymers are intriguing as composite electrode additives since conceptually they can fulfill the roles of both carbon and binder.

Magnetite is a naturally occurring mineral found in the earth’s crust; therefore, it is abundant, environmentally friendly, cheap, and non-toxic. Magnetite is also easy to synthesize and can be prepared through simple, non-hazardous techniques such as through a facile aqueous co-precipitation method. Complete reduction of magnetite involves the transfer of 8 electrons, providing opportunity for an impressive capacity of 925 mAh/g. Notably, the initial reactions are insertion reactions where the lithium ion can insert into the Fe3O4 structure with minimal structural distortion, while upon further reduction, a conversion reaction occurs generating Fe metal and Li2O as products of full discharge.

To further probe the role of the electrically conductive polymer in the mesoscale (bulk) properties of composite electrodes, this study focuses on the Fe3O4 conversion reaction and its relationship to the electrically conductive polymer binder, PPy, including a detailed study of composite electrodes with nanoscale Fe3O4 and PPy. Magnetite, Fe3O4, with 6% and 20% polypyrrole (PPy) was used to prepare composite electrodes with and without added carbon.

Galvanostatic cycling and Electrochemical Impedance Spectroscopy (EIS) measurements were used in tandem to determine delivered capacity, capacity retention, and the related impedance at various stages of discharge and charge. Further, the reversibility of Fe3O4 to iron metal conversion observed during discharge was quantitatively assessed, ex situ, using X-ray Absorption Spectroscopy (XAS). The Fe3O4 composite containing the largest weight fraction of PPy (20 wt%) with added carbon demonstrated reduced irreversible capacity on initial cycles and improved cycling stability over 50 cycles. This study illustrated the beneficial role of PPy addition to Fe3O4 based electrodes partially related to improved electrical conductivity and also to improved ion transport related to the formation of a more favorable surface electrolyte interphase (SEI).
Nickel Phosphides as Catalysts for Direct Electrochemical CO2 Reduction to Important Renewable Polymers
Authors: Calvinho Karin U. D. , Laursen Anders B. , Goetjen Timothy A. , Greenblatt Martha , Dismukes Gerard Charles
Published: February 2020

Copper1 and noble-metal alloys2 have been shown to catalyze the electrochemical reduction of CO2 to hydrocarbons such as methane (C1) and ethylene (C2). C1 and C2 hydrocarbons are the simplest building blocks for the synthesis of most industrial products and are therefore common chemical feedstocks. However, the production of hydrocarbons in aqueous solution is highly energy-consuming mainly due to the over-potential needed to overcome the transition states in C1 and C2 synthesis. In addition, there are significant efficiency losses due to the concomitant H2 production that is kinetically and thermodynamically favored under these conditions. As ethylene and methane from fossil source are comparatively cheap, the high cost of electricity makes the production of these simple hydrocarbons prohibitively expensive.

We have developed a noble metal free catalyst that is able to reduce carbon dioxide to hydrocarbons at lower over-potentials than copper (-0.6 V vs RHE), with significant suppression of the hydrogen production compared to the CO2 free environment. In addition, by changing the reactor configuration, CO2 may now be converted to a valuable polymer with composition akin to an aldehyde-carbonate co-polymer. This solid product can easily be de-polymerized to its parent monomers by changing pH. The resulting complex organic acids and aldehydes produced in at only -0.9 V vs RHE, have a significantly increased value to the simple hydrocarbons making this a very promising technology.

Supported by the BASF Corporation Catalysis Division Fellowship.

References:

(1) Hori, Y.; Kikuchi, K.; Suzuki, S. Chem. Lett.
1985, No. 11, 1695–1698.

(2) Kortlever, R.; Peters, I.; Balemans, C.; Kas, R.; Kwon, Y.; Mul, G.; Koper, M. T. M. Chem. Commun.
2016, 52, 10229–10232.
First-Principles Evaluation of the Catalytic Activity of Nanostructured Carbon for the Oxygen Reduction Reaction at Fuel Cell Cathodes
Authors: Hartmann Gregory Peter , Hwang Gyeong S
Published: February 2020

Carbon nanomaterials, including fullerenes, carbon nanotubes (CNTs), graphene, and their composites, have been actively studied as a potential candidate to replace platinum(Pt)-based ORR catalysts as fuel cell cathodes. These sp
2-bonded carbon nanostructures are inherently constituted by largely extended p-conjugation systems, making them essentially unreactive toward molecular oxygen (O2) in their pristine forms. However, the conjugated p-systems can be severely disrupted with localized p electrons through dopant incorporation, defect creation, and/or local lattice distortions. Doped, defective and distorted carbon structures are currently thought to be responsible for O2 adsorption/activation and thus ORR, but the active sites and the exact molecular mechanisms are still uncertain.

First principles computational methods are well suited to study in detail reactions at the surface of a heterogeneous catalyst and through these methods we explored the mechanisms by which modification can activate graphene for the adsorption and reduction of oxygen, with an aim to define design guidelines for carbon ORR catalysts. Using density functional theory (DFT) calculations, we have identified a novel method for the activation of graphene while establishing a computational scheme for the study of electrocatalysis by carbon. An important component of our methodology is the application explicitly solvated system to model the ORR at the solid-liquid interface with aqueous solvent. Many previous DFT studies were modeled in the gas phase where O2 adsorption is consistently predicted to be endothermic on carbon. Our study clearly demonstrates that a more accurate description of interactions at the graphene-solvent interface is necessary to properly describe O2 adsorption, which appears strongly influenced by solvation. Ab-initio MD simulations were performed with the explicit solvent model to outline a full reaction mechanism including novel elementary reaction steps. Another unique approach taken in our studies is the use of detailed electronic structure analysis to determine the factors influencing overpotentials in the course of the ORR.

In this presentation, we will focus on introducing the computational scheme that we have developed for the investigation of molecular mechanisms underlying the ORR on carbon catalysts and the synergetic effects of doping, defect creation, and lattice distortions on their catalytic performance for oxygen reduction. We will also discuss the key guidelines for the rational design and development of high-efficiency, cost-effective carbon-based ORR catalysts for fuel cell applications.
Redox-Active Hybrid Materials for Pseudocapacitive Energy Storage
Authors: Boota Muhammad , Gogotsi Yury
Published: February 2020

We aim to show the exciting development of sustainable pseudocapacitive hybrid materials for small and large scale electrochemical energy storage systems.1–5 In our approach, we combine redox-active organic molecules with suitable carbon nanostructures and/or highly conductive metal carbides (MXenes) to improve the conductivity of organic materials. These combinations result in high energy and power density pseudocapacitive electrodes with improved cyclability. Using experimental and simulation techniques, we will discuss the interfacial organic-inorganic interactions, charge storage mechanisms, and preferred molecular orientations of organic molecules at the interface. We will also highlight the remaining challenges and future opportunities for improvement in nanostructured hybrid materials for the electrochemical energy storage.

1. M. Boota et al., Adv. Mater., 28, 1517–22 (2015)

2. M. Boota, K. B. Hatzell, E. C. Kumbur, and Y. Gogotsi, ChemSusChem, 8, 835–843 (2015).

3. M. Boota, C. Chen, M. Bécuwe, L. Miao, and Y. Gogotsi, Energy Environ. Sci., 9, 2586–2594 (2016).

4. M. Boota et al., ChemSusChem, 8, 3576–3581 (2015)

5. K. B. Hatzell, M. Boota, and Y. Gogotsi, Chem. Soc. Rev., 44, 8664–8687 (2015)
Zinc-Ferricyanide: A Model-Validated Cost-Effective Flow Battery for the Grid
Authors: Ma Rose Xiaoya , Yan Yushan
Published: February 2020

The world’s electrical grid is increasingly powered by renewable sources, with wind and solar at the helm; indeed, these two renewables are expected to see the foremost and second-most capacity additions into the next decade1,2. Further deployment, however, is still checked by the intermittency of their supply. There is then urgent need for complementary storage technologies that are sufficiently economical, so as not to impinge upon the competitiveness of variable renewables and historically low cost of electricity2.

As RFBs approach the market, quantitative methods are needed to assess their efficacy and economy for grid-scale applications. To this end, we prescribe an objective for global optimization within a generalized electrochemical and economic model3. Performance characteristics, robustly scalable, can be validated even at laboratory scales, then combined with bulk pricing for required components into capital cost. To determine pareto optimal design and operating conditions at the desired application scale, we implement a genetic algorithm. This optimization not only simulates costs and efficiencies associated with scale-up of novel batteries, but also enables fair comparison between batteries that may have significantly different performance characteristics and cost structures (Figure 1).

The results for state-of-the-art RFBs indicate that model and experimental performance are in agreement, and that zinc-ferricyanide should outshine other RFBs in utility-scale applications. This expeditious integration of experimental and theoretical analyses can thereby help the RFB community to inform the truly cost-effective path forward.

References:

International Energy Agency. World Energy Outlook 2016 (WEO-2016). 2016.

U.S. Energy Administration. Annual Energy Outlook 2016 (AEO-2016). 2016.

Ma RX et al. In preparation.

Holland JH. Adaptation in Natural and Artificial Systems. 1975.

You D, Zhang H, Chen J. Electrochim. Acta
2009; 54:6827.

Zhao P, Zhang HM, Zhou HT, Yi BL. Electrochimica Acta
2005; 51:1091.

Gu S, Gong K, Yan EZ, Yan YS. Energy Environ. Sci.
2014; 7:2986.

Gong K, Ma RX, Conforti KM, Kuttler KJ, Grunewald JB, Yeager KL, Bazant MZ, Gu S, Yan YS. Energy Environ. Sci.
2014; 7:2986.

Figure 1
Atomic Layer Deposition (ALD) of Transparent and Conducting Ta-Doped ZnO Thin Films
Authors: GAO Zhengning , Myung Yoon , Huang Xing , Mishra Rohan , Kanjolia Ravi , Park Jeunghee , Banerjee Parag
Published: February 2020

ZnO based transparent conducting oxides (TCOs) offer earth abundant alternatives to conventional indium tin oxide (ITO) films. At the same time, ALD enables discretized doping of substitutional cations at a monolayer level, providing fine and exquisite control over dopant concentration and resultant properties. In this work, we present the ALD of tantalum (Ta) doped ZnO (TZO) films. Compared to dopants such as Al3+ and Ti4+, a Ta cation exists in +5 oxidation state and thus, can ideally transfer 3 electrons by substitutionally doping a Zn2+ site. We show that 30 nm TZO films with 2 at% Ta provides a minimum resistivity of 4 mW.cm at room temperature and optical transmissivity of > 86% in the visible range.

The precursors used for Zn, O and Ta are diethyl Zn (DEZ), H2O and pentakis-dimethylamido Ta (PDMAT). The targeted % Ta is varied from 2 to 20% by introduction of PDMAT pulse between DEZ and H2O pulses. The electron concentration and the mobility are measured using Hall measurements. A minimum resistivity of 4 mW.cm with carrier density of 9.0x1019 cm-3 and a mobility of 17.7 cm2/V-sec is observed at 2 at% Ta at room temperature. UV-Vis spectroscopy indicates a monotonic increase in bandgap of TZO from 3.2 to 3.4 eV upon addition of Ta. Photoluminescence (PL) shows a quenching of the green band emission of ZnO associated with oxygen defects upon the addition of 2 at% Ta. Upon further Ta addition, a red shifted defect peak appears which is attributed to formation of new Zn vacancies. This data is supported by X-ray photoelectron spectroscopy (XPS), showing removal of O vacancies and a clear Ta-O-Zn bond formation for higher Ta doping. The conductivity of ZnO and 2% Ta doping ZnO behave differently as a function of temperature. TZO have different activation energy compare to pure ZnO. X-ray Diffraction (XRD) and Transmission Electron Microscope (TEM) indicate the crystallinity change with the Ta doping. The results provide a clear understanding on the mechanism of Ta doping in ZnO and its direct impact on vacancies and resulting electronic and optical properties.

Finally, ALD TZO is deposited on flexible glass substrates and inside nanoporous anodic alumina templates to demonstrate formation of transparent conducting electrodes, conformally on a variety of platforms of relevance to electrochemical research.
Synergistic Effect of Acid Treatment and Metal Oxide Co-Catalyst Loading on Inactive Rutile TiO2 Nanorods for Enhanced Photocatalytic Degradation of Orange (II) Dye
Authors: Dhandole Love Kumar , Mahadik Mahadeo A , Kim Su-Gyeong , Cho Min , Chung Hee-Suk , Ryu Jung Ho , Jang Jum Suk
Published: February 2020

Transition metal oxides (MnO, NiO, Co2O3 and CuO) 1 w % loaded on acid treated TiO2 nanorods were successfully prepared by chemical treatment and wet impregnation method. The catalyst were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), X-ray photoelectron spectra (XPS), Fourier transform infrared spectroscopy (FT-IR) and UV-visible diffuse reflectance spectroscopy (UV-DRS). FT-IR results confirmed the presence of H2O and OH groups on the surface of acid treated photocatalyst and TEM and XPS results confirmed the fine dispersion of metal and their oxide on TiO2 nanorods. The photocatalytic activity of as-prepared, acid treated, metal oxide loaded and metal oxide loaded on acid treated nanorods were compared and rate constant values were determined from kinetics of the degradation of Orange (II) dye. Cobalt oxide 1w% loaded on 1.0 M acid treated TiO2 nanorods exhibited the higher photocatalytic Orange (II) degradation efficiency 98.57% (within 120 min) than as-prepared and metal loaded acid treated samples under the solar irradiation. The synergistic effect of cobalt oxide 1w% loaded on 1.0 M acid treated TiO2 nanorods over Orange (II) degradation is considered due to fine dispersion of metal oxides on the OH rich surface of acid treated TiO2nanorods. The mechanism of enhanced photocatalytic activity and photoelectrochemical analysis of photocatalyst also studied.

Key words: TiO2rutile nanorods; acid treatment; wet impregnation; transition metal oxides, dye degradation; synergistic effect

Acknowledgments

This research was supported by the BK21 plus and Basic Science Research Programs (2012R1A6A3A04038530) funded by the Korean National Research Foundation (NRF).
Redox Responsive Fluorescent Probe Development for Super Resolution and Fluorescence Lifetime Microscopy
Authors: Woodcock Jeremiah , Choudhary Eric , Jones Brynna , Marr James , Kumar Abishek , Gilman Jeffrey W. , Stranick Stephan J. , Liddle J. Alexander , Szalai Veronika Ann
Published: February 2020

Redox-sensing in aqueous solutions using super resolution fluorescence or lifetime microscopy has been applied extensively to image metabolic events in biological systems. Typically, such probes are designed to fluoresce following reaction with (or capture of) a particular analyte, for example, reactive oxygen species or a redox-active metal ion. Using such probes as a guide, we have designed and characterized new redox-responsive fluorescent probes intended for fluorescence-based imaging of aqueous electrochemical systems. We present solution spectroelectrochemical characterization of the parent dye molecules as well as initial optical microscopy characterization of these redox-sensitive fluorophores attached to a thermally-responsive polymer gel. Using thermal-control of polymer matrix thickness, the surface density of dye on the electrode can be modulated and imaged using fluorescence lifetime with super resolution microscopy.
Dye - Sensitized Solar Cell Photoanode Based on Silver – Doped Titanium Dioxide Nanoparticles
Authors: Nguyen Hoang Thai , Vo Long Thanh , Nguyen Lan Thi Kim , Nguyen Hien Quoc
Published: February 2020

Silver - doped titanium dioxide (Ag-TiO2) nanoparticles were prepared from TiO2 (P25, Degussa) and silver nitrate (AgNO3) by gamma Co-60 irradiation method with various initial concentration of AgNO3 (0.1 – 0.75%, w/w). The formed silver nanoparticles and optical band gap of Ag-TiO2
films were investigated by XRD, XRF, TEM and UV-Vis spectrocopy. The silver nanoparticles with grain size about 17 – 20 nm are woven on TiO2 nanoparticles and decrease the optical bandgap of TiO2
film. Ag-TiO2 nanoparticles were used to fabricate photoanode in N719-dye-sensitized solar cells (DSCs). Under full sunlight illumination (1000 W/m2, 1.5 AM) the DSC assembled with Ag-TiO2
(0.75% AgNO3) photoanode has shown a 25% increase in energy conversion efficiency compared with the DSC using undoped TiO2 photoanode. The improvement of energy conversion efficiency was attributed to enhanced photocurent of the cell. The effect of silver dopant content on DSC performance was also studied by electrochemical impedance spectrocopy. The impedance arc at intermediate frequency region in Nyquist plots are reduced with the concentration of AgNO3 precursor, demonstrating that charge transfer at TiO2/dye interface was improved in the presence of silver dopant. The Ag- TiO2 nanoparticles synthesized by gamma Co-60 irradiation method have shown themselves as promising photoanode materials for DSCs. This work may inspire new ideas for constructing high-performance photoanodes for large scale DSCs
A Way to New Smart Materials – Hierarchical 3D Structures Produced Via Self-Organization of Nanowires
Authors: Strukova Galina , Strukov Gennadii
Published: February 2020

The beauty of these pictures is intriguing and fascinating by its asymmetric, exquisite and intricate pattern. What is it? Is it a product of a novel computer program or photographs of fine creations of nature? Neither statement is true. In fact, these are not pictures, but images of metal samples made with an electron microscope. Only some color is added to the images to emphasize their resemblance to natural objects of our macroworld: seashells, jelly-fish, leaves of exotic plants. The size of the samples is varied in micron scale. They are produced via self-organization of nano-sized (millionth of a millimeter) wires growing on porous membranes under the action of electric current pulses. This is how such volumetric (3D) sculptures are described in scientific journals [1- 3] along with the experimental conditions for their reproduction, i.e., the conditions of the process (electrolyte composition, porous membrane, pulsed current mode) are specified, when growing nanowires organize themselves in an inexplicable fashion into “sculptures” that show perfect resemblance to natural creations. The authors have managed to isolate and photograph them with a modern electron microscope. Besides, they have proved that the internal structure of this metallic “seashells” is a volumetric multilayer network woven by nano-sized wires. Such antenna-like samples are expected to find application in nanotechnology as new materials for different applications. Now we produce such “sculptures” from various metals “by order”, examine their magnetic properties, study their interaction with plasma and focused electron beam, look for a field of their application and admire their elegant forms. However, it is still a riddle. Why do they so closely resemble shells and leaves? Does this mysterious self-organization have anything in common with formation of plant leaves and seashells?

 [1] J of Bionic Engineering 10 (2013) 368–376

[2] Materials Today 16 (2013) 98–99 , [3] Materials Letters, 128 (2014) 212-215. 

Figure 1
A Study of the Conduction Processes in Organic Schottky Diodes
Authors: Raja Munira
Published: February 2020

Electrical conduction processes in semiconducting organic films has been a subject of great debate for a number of decades. There is a general agreement that the energy band models are inappropriate, for describing the electronic conduction in such materials. Several analytical transport models including the Gaussian disorder1, multiple trapping and release2, and variable range hopping3, have been proposed to describe the charge transport mechanism in organic semiconductors. Despite the differences in the analytical approaches, there is a general agreement that the charge carrier transport is governed by thermally assisted tunnelling or hopping between localised states. More needs to be done to unify the principle of electronic conduction in such materials, with the classical treatment of carrier flow in terms of carrier drift, diffusion and their relationships to Fermi and quasi-Fermi levels, and the slopes of these energies, which classically predict the flow of current in semiconductors and semiconductor devices. In this work, we present an analytical model, describing the conduction processes in disordered and polycrystalline organic Schottky diode, by employing the so-called Universal Mobility Law4-6, on the exponential distribution of the intrinsic and extrinsic density of states. The Schottky barrier is possibly the only electrical method, which allows the study of both intrinsic and extrinsic regions, since the applied voltage moves the dopant energy level to the top of the barrier. From the analysis of the measured current of the organic disordered and polycrystalline Schottky barriers, key parameters such as the effective temperature associated with the distribution of the intrinsic and extrinsic states, and subsequently the Meyer-Neldel energy are extracted, and compared to those obtained from temperature analysis. Moreover, from the Arrhenius plots of the forward currents, the activation energies of the disordered and polycrystalline organic semiconductors are determined. The development of such models is essential in generating accurate simulation of the properties of the organic semiconductor devices, which subsequently predicts the circuit performance for mixed signal applications.

References

[1] H. Bassler, Phys. Stat. Sol., 175, 15 (1993).

[2] D. Emin, Phys. Rev. B 48, 13691 (1993).

[3] T Holstein, Ann. Phys. 281, 706 (2000).

[4] M. Raja et. al., J. Appl. Phys. 92(3), 1441 (2002).

[5] M. Raja et. al., IET Circ. Dev. Syst. 6(2), 122 (2012).

[6] M. Raja et. al., J. Appl. Phys. 112, 084503 (2012).
Developement of Printed OTFTs and Logic Circuits
Authors: Chu Ta-Ya , Dadvand Afshin , Graddage Neil , Christophe Py , Lang Stephen , Tao Ye
Published: February 2020

We report the development of inkjet-printed organic thin-film transistors (OTFTs), inverters and logic circuits on PET substrate. The mobility of 1 cm2/Vs and 0.1 cm2/Vs achieved on p-type and n-type printed OTFTs with an operation voltage of 15 V. The printed uniform and thin dielectric layer achieved by introducing coffee ring effect on printing process. A gain value of 24 obtained from the printed CMOS inverter and the device exhibits an excellent air-stability without encapsulation. Our results demonstrated the potential of the developed printed transistors for flexible electronics in the near future.
Investigation of Alternative Mixed-Conducting Oxides for SOFC Anode Applications
Authors: Sabolsky Edward M. , Liu Xingbo , Zondlo John W. , Qi He , Thomas Tony , Hart Richard , Jezek Erik
Published: February 2020

The solid-oxide fuel cells (SOFCs) may undergo unwanted redox cycles during application and this may cause dimensional instability for the anode electrode. The state-of-the-art Ni/YSZ anode experiences a linear expansion of up to 1% when oxidized causing an irreversible microstructural change. Researchers are focusing on the development of many new SOFC anodes for internal reforming, lower temperature operation, and poison resistance, but there is a lack of study on the redox stability of the materials. In this work, the redox stability and electrochemcial performance of various oxides synthesized by solid-state and sol gel processes. The work focussed on mixed-conducting oxides with the perovskite and layered-perovskite crystal structures, but other similar structure families were also evaluated. The redox stability was measured using a controlled-atmosphere dilatometer. Two examples of compositions studied were doped-SrTiO3 and doped-Sr2B'B"O6-δ materials, which were subjected to >5 hours redox cycles in air and forming gas. Their linear expansion at isothermal conditions were compared to commonly used anode materials like Ni/YSZ and GDC. The change in microstructure of these samples after redox cycling were also studied. The electrical performance was also measured by four-point conductivity as a funciton of atmosphere changes, and this information was related to the defect and microstructure. Finally, the compostions showing the highest promise were tested in symmetrical cell and full fuel cell configurations to quantify their polarization resistance. Apart from the above-mentioned compositions, the redox and electrochemical performance of other non-traditional compositions with various doping strategy were also evaluated and will be discussed in this work.
Metal-Organic Framework-Based Flexible Resistive Switching Memory Devices
Authors: Park Myung-Joo , Lee Jang-Sik
Published: February 2020

Metal-organic framework (MOF) which consists of metal ionic nodes and organic linkers has wide applications such as hydrogen storage, catalysts, and gas sensors due to its structural and chemical versatilities. On demand for currently increasing interests for flexible and wearable electronic devices, it is suggested that some MOF materials have electrical hysteresis phenomena which can be further utilized as data storage device. The hysteresis arises from redox-active behavior of organic molecules. By selecting proper substances, realizing MOF-based resistive switching memory device could be possible. In this work, we applied zeolitic-imidazolate framework (ZIF-8), one of MOF materials, which is composed of zinc ions and imidazole molecules, as the resistive switching layer on the plastic substrate. The ZIF-8 layer on the gold-coated polyethylene terephthalate substrate is deposited by simple solution processes. Flexible ZIF-8-based resistive switching memory possesses set/reset behavior consistent over several cycles with good mechanical flexibility. The resistive switching behavior of ZIF-8-based device is thought to be due to the changes of charge conduction mechanisms from electron hopping to transporting through conjugated organic molecules. Flexible resistive switching memory device with solution-processed ZIF-8 thin film could be a promising candidate for flexible and wearable memory devices.
Pulsed Photoinitiated Synthesis of Nanocrystalline Iron Oxides-Reduced Graphitic Oxides in-Situ Nanocomposite Thin Film As Anode Materials for Silicon-Based Micro-Supercapacitor
Authors: Luo Sijun , Oguntoye Moses , Zhang Song , Pesika Noshir , Chrisey Douglas
Published: February 2020

Thin film-based micro-supercapacitors have great potential for energy storage application in portable electronics, microelectronics devices and microelectromechanical systems. Nanocomposites of transition metal oxides and carbon materials are preferable for electrode materials in electrochemical capacitors due to the combination of high capacitance and long cycle life. However, the cost-efficient manufacturing of nanocomposites thin film for integration with silicon has been a significant challenge for commercialization. Herein we report a novel approach to rapid (~80s) pulsed photoinitiated synthesis of iron oxides-reduced graphitic oxides in-situ nanocomposite thin film on nickel-coated silicon substrate through pulsed white light irradiation of photosensitive iron-organic precursor made by chemical solution deposition. The instantaneous photoinitiated pyrolysis of photosensitive precursor occurs in the first couple pulses of irradiation and results in iron oxides-graphitic oxides composite thin film with a 3-D nanostructure. Subsequent pulsed light irradiation improves the crystalline quality of iron oxides nanograins and leads to the reduction of graphitic oxides. The nanocomposite thin film with a thickness about 1 um shows a high performance in 2M KOH electrolyte measured in a three-electrode cell. The unoptimized specific areal capacity by discharge is as high as 100 mF/cm2 at 5 mA/cm2 within the potential range from -0.8 to -0.25 V after stable cycling more than 5,000 times. This straightforward and scalable nanotechnology opens a new pathway to the manufacturing and practical application of iron oxides-reduced graphitic oxides nanocomposite thin films as anode materials in silicon-based micro-supercapacitor for microelectronics devices and microelectromechanical systems.
A Novel Photodetector Based on Azo/SiO
x
/N-Si Heterojunction Structure
Authors: Tien Tsung-Cheng , Hsieh Tsung-Eong , Wu Bing-Chien
Published: February 2020

Recently, photodetector based on semiconductor-insulator-semiconductor (SIS) heterojunction structure which contains indium zinc oxide (IZO) as the transparent conductive oxide (TCO) layer was reported. In that work, IZO layer was deposited by pulsed laser deposition which is impractical to the large-area device production. Moreover, the IZO contains indium which becomes a scarce element due to the vast demand in solar cell and display industries in recent years. In order to overcome these difficulties, aluminum zinc oxide (AZO) was adopted to replace IZO as the TCO layer and the feasibility of AZO/SiO
x
/n-Si SIS structure to photodetection was investigated.

The SIS structure was prepared firstly by growing SiO
x
 layer with appropriate thickness (~1.8 nm) on n-type Si wafer substrate by dry thermal oxidation method. Radio-frequency sputtering was then adopted to deposit a 200-nm thick AZO layer on SiO
x
/Si substrate. Afterward, the 100-nm thick aluminum layers were deposited by e-beam evaporation to form the bottom electrodes on the backside of Si substrates and the top finger electrodes on AZO layer, respectively, to complete the SIS photodetector preparation.

Without applying external bias, the sample with quick photo-response time less than 10 msec and photoresponse (R) of 0.17, 0.67 and 0.22 AW-1separately under the 365-nm, 650-nm and 940-nm illuminations were achieved. The lower R value at short-wavelength illumination was attributed to the absorption of AZO layer since the photon energy of incident light is close to the absorption edge of AZO. The sample was further annealed at 300°C for 1 hr in air ambient and the improvement of R values, 0.27, 1.60 and 0.67 AW-1 under the 365-nm, 650-nm and 940-nm illuminations, was observed. The improvement of R values of the device was ascribed to the reduction of interface trap density (Dit
) at the AZO/SiO
x
 and SiO
x
/n-Si interfaces as revealed by the capacitance-voltage measurement. The annealing treatment reduced the 
Dit
 from 1.63×1012 to 2.80×1011 eV-1cm-2, which efficiently alleviated the carrier capture at interfaces and improved the photodetection properties of the sample.

Keywords
: Photodetector; Aluminum zinc oxide; Semiconductor-insulator-semiconductor heterojunction; interface trap density.
Production of Hydrogen through Photo-Electro-Catalytic Oxidation of Coal Using TiO2 Nanotube Arrays
Authors: Wang Ding , Mohanty Bobby , Wang Bonan , Eddings Eric
Published: February 2020

Due to global warming concerns, major efforts have been devoted to reducing CO2 emission by switching from the use of coal to other clean fuels, such as natural gas. However, since coal is the most abundant hydrocarbon resource, it would be helpful to develop a non-traditional approach for the utilization of coal that substantially reduces its climate impacts, e.g., electro-oxidation of coal.

Electro-oxidation of coal has been studied for many years. The basic concept provides for the production of gaseous pure hydrogen fuel (H2), along with a separate stream of CO2, and these products can be achieved at relatively mild reaction conditions as compared to conventional coal gasification. However, due to the formation of a diffusive barrier film at the coal surface during the oxidation reaction, sufficiently high kinetic rates leading to an acceptable level of conversion have not been achieved at atmospheric pressure. In addition, to obtain desired reaction rate and electrode stability, noble metal materials have to be used in this process, resulting in higher cost and a higher barrier for potential commercialization. To solve these problems, a modified electro-oxidation of coal concept has been developed, by combining pyrolysis and photo-electro-catalysis technology.

As a widely used photo catalyst, black TiO2 nanotube arrays (bTNA) have been intensively studied as the anode material in the area of photo-assisted water electrolysis. However, in nontransparent systems, use of this process is still a challenge. In this modified process, coal can be oxidized by bTNA with the aid of sunlight, with iron cations serving as the shuttle catalyst. Along with the development of this concept, a series of parameters (e.g., the reaction conditions and methods for electrode preparation) were also examined to facilitate higher kinetic rates, higher coal conversions and overall higher energy efficiency.
Bifunctional Ag Doped SnS2 Photocatlyst and Electrocatlyst for Solar Energy Appliations
Authors: Cui Xiaodan , Xu Wangwang , Xie Zhiqiang , Dorman James A. , Gutierrez-Wing Maria T. , Wang Ying
Published: February 2020

SnS2, as a mid-band-gap semiconductor shows a good potential as an excellent photocatalyst due to its low cost, wide light spectrum response and environment-friendly nature. At the same time, it is also considered as a prospective counter electrode (CE) electrocatlayst for dye-sensitized solar cells (DSSC) due to its good electrocatalytic property. However, to meet the demand of large-scale commercialization of both applications, SnS2 with superior properties are required. Doping is a facile method to manipulate the optical and chemical properties of semiconductor materials simultaneously. In this work, Ag-doped SnS2 samples with various doping amounts are prepared via a facile one-step solvothermal route. The product was characterized by XRD, SEM, TEM and UV-VIS spectrometry. The photocatalytic activity of the Ag-doped SnS2 is studied by degradation of methylene blue dye under solar light irradiation. It’s found increasing Ag dopant concentration can effectively increase solar light adsorption efficiency and accelerated heterogeneous photocatalysis. The optimal concentration of Ag dopant concentration was found to be 5 % with the highest rate constant of 1.8251 hour-1. It is also found that the DSSC based on 5% Ag-doped SnS2 CE demonstrates the best performance showing an impressive photovoltaic conversion efficiency of 8.70 % which exceeds the efficiency of Pt-based DSSC (7.88%) by 10.41%, while the DSSC consisting of undoped SnS2 only exhibits a PCE of 6.47%. Such enhanced efficiency of DSSC is attributed to the effectively improved electrocatalytic activity and mixed conductivity resulted from Ag dopant. Therefore, a proper amount of Ag doping can effectively increase the photocatalytic and electrocatalytic performance of SnS2 and may pave a new way for large-scale solar energy applications.
Mechanical and Durable Properties of Ni-YSZ Electrode Under High Temperature for Solid Oxide Electrolysis Stack
Authors: Jang Byung-Koog , Matsudaira Tsuneaki , Kim Sun-Dong , Woo Sang-Kuk
Published: February 2020

Many researches based on SOFC development and high temperature electrolysis (HTE) have been reported in the last couple of decades. HTE is one of the most clean and efficient technologies for manufacturing large amounts of hydrogen from water with oxygen. The processing and structure of HTE is closely related to the knowledge and concept of solid oxide fuel cells (SOFCs). Specially, it is very important to evaluate the durability’s properties of oxide electrolysis stacks under high temperature as well as steam environment to apply HTE. Unfortunately, no study has been reported the durable properties of oxide electrolysis stacks at high temperature as well as steam environment. For the reason, the aim of this work is to realize the durable properties (ex, high temperature strength fatigue and creep) at high temperature of 600°C~850°C for oxide electrolysis stacks which consists of 55%NiO-45%YSZ(8mol%Y2O3) composition. NiO-YSZ cathode supports were prepared in the shape of flat tubes by extrusion method. The pre-sintered NiO-YSZ flat tubes were dip-coated in YSZ slurry to secure the interconnector area with a masking fluid and then were sintered at 1400°C for 3h. The creep properties showed decreasing tendency with increasing applied load in range of 40~80MPa and temperature in range of 600°C~800°C. The life time of fatigue at 850°C under Ar-4%H2O environment was decreased with increasing applied load.
Novel Architecture of Air Cathode for Rechargeable Lithium-Air Batteries
Authors: Jiang Yuexing , Zou Lu , Cheng Junfang , Huang Yizhen , Chi Bo
Published: February 2020

As the increased demand of eco-friendly rechargeable batteries in recent years, aqueous/non-aqueous lithium-air batteries have been attached more and more attention because of their high specific energy density, 3-5 times higher than that of lithium-ion batteries1-2. As the key component, the structure of the air cathode should been optimized to improve the cycle performance during discharge and charge process3-4. In this work, polyaniline-assisted polyvinylidene fluoride film was synthesized coated on graphene sponge as flexible cathode for lithium air batteries. With the 3D inter-connected structure of the graphene sponge for the guidance of oxygen flows, the assisted polyaniline for enhanced electron transfer, as well as the polyvinylidene fluoride film for the prevention of electrolyte flooding, the reaction zone can be reserved extremely during oxygen reduction reaction and oxygen evolution reaction, which can then promote charge transfer, and result to the lower overpotential for both discharge and charge process. The detailed electrochemical performance will be analyzed in the following presentation.

References

[1] Bruce, P. G.; Freunberger, S. A.; Hardwick, L. J.; Tarascon, J. M. Li-O2and Li-S Batteries with High Energy Storage. Nat. Mater. 2012, 11, 19-29.

[2] Luntz, A. C.; McCloskey, B. D. Nonaqueous Li-air Batteries: a Status Report. Chem. Rev. 2014, 114, 11721-11750.

[3] Wen, Z.; Shen, C.; Lu, Y. Air Electrode for the Lithium-Air Batteries: Materials and Structure Designs. ChemPlusChem 2015, 80, 270-287.

[4] Wang, X.; Wen, K.; Song, Y.; Ye, L.; Zhang, K. H. L.; Pan, Y.; Lv, W.; Liao, Y.; He, W. Gas Transport Evaluation in Lithium–air Batteries with Micro/nano-structured Cathodes. J. Power Sources 2015, 274, 762-767.
The Effects of Redox Mediators and Water Content on Oxygen Evolution for Li-Air Batteries
Authors: Petrucco Enrico A.
Published: February 2020

Chemistries that can demonstrate tolerance to both moisture and atmospheric carbon dioxide have the power to advance the technology readiness level of non-aqueous lithium air batteries. Previously published results have found that lithium iodide as redox mediator in dimethoxyethane solvent containing high water content affords reversible cycling of a lithium oxygen battery via lithium hydroxide[1]. In collaboration with the authors of the previous work, this concept has been extended to explore additional redox mediators and alternative electrolyte mixtures. Quantitative oxygen evolution for the new chemistries was studied using continuous differential electrochemical mass spectroscopy. Oxygen evolution was found for some of the new chemistries employed. Faradaic efficiency for oxygen evolution and Tafel analysis shows complex behaviour. Discharge product analysis shows that some of the new chemistries which afford oxygen evolution also cycle via lithium hydroxide.

[1] Liu, et al. Science, 2015, 350, 6260, p530.
Pouch Type Cells for Practical Evaluation and Application of Large-Scale Li-Air Batteries
Authors: Kwak Won-Jin , Shin Hyeon-Ji , Aurbach Doron , Sun Yang-Kook
Published: February 2020

Thanks to high theoretical specific capacity and energy density, Li-air batteries are considered as candidates for next-generation battery systems in place of conventional Li-ion batteries for advanced applications such as electric vehicles (EV).1-3 However, low energy efficiency, poor cycle life and Li-metal safety issues make the use of Li-air batteries yet impractical. In addition, actual cell capacities are very low and, since only small-scale electrodes are currently tested, it is hard to predict the properties of large-size electrodes and cells, thus evaluating and judging real practical challenges related to this battery technology.

Here, we report on fabrication, operation and evaluation of pouch-type Li-air cells using 3×5 cm2 sized electrodes, in which we intend deal with higher capacity (mAh) of the electrodes, compared to most previous studies in the field. With the relatively large-sized cells, operating at high current density and capacity, we could recognize some remarkable problems that may not be significant in small cells.

In relatively large cells as those explored in this work issues related to non-uniform current distribution, mechanical and electronic integrity of electrodes are much more influencing compared to small cells. Hence, problems such as lithium dendrites formation and non-uniform deposition of oxygen reduction product become severe.

This study can help to determine which parameters are the most important for developing practical Li-air batteries.

 

References

1. K. M. Abraham, Z. Jiang, J. Electrochem. Soc.
1996, 143, 1.

2. H. G. Jung, J. Hassoun, J. B. Park, Y. K. Sun, B. Scrosati, Nature Chemistry
2012, 4, 579. 3.

3 M. M. O. Thotiyl, S. A. Freunberger, Z. Peng, Y. Chen, Z. Liu, P. G. Bruce, Nature Materials
2013, 12, 1050.
Effect of Water on the Product Distribution at the Cathode of Li-O2 Batteries
Authors: Tomita Kentaro , Noguchi Hidenori , Uosaki Kohei
Published: February 2020

Li-O2 secondary batteries are attracting much researcher’s attentions as a candidate for the post lithium-ion secondary batteries due to the superior theoretical energy capacity. Oxygen reduction reaction forming Li2O2 deposition takes place at the cathode of Li-O2 secondary batteries during the discharge process. The theoretical capacity of the Li2O2 electrode (8 kWh L-1) is comparable to the energy density of diesel fuel (9.7 kWh L-1). However, the mechanisms of the cathode reactions are complicated and are not well understood. The trace amount of water in electrolyte solutions is known to affect the reaction mechanisms1,2 but how water affect the reactions are still under discussions.

In this study, the effects of trace amount of water on the discharge product at gold electrode in the DMSO-based electrolyte solution are studied by using electrochemical quartz crystal microbalance (EQCM), rotating ring-disk electrode (RRDE) method, in situ surface enhanced Raman scattering (SERS) spectroscopy and other instrumental analysis. In situ SERS showed that ca.1000 ppm of water results in the decrease of crystal Li2O2 signal intensity and new peaks of LiHO2 and H2O2 at the initial stage of the discharge process. Application of negative potential, which causes surface mediated electrochemical reduction of LiO2 in the anhydrous electrolyte solution,3 results in the decomposition of DMSO forming Li2SO4 while amorphous phase of Li2O2 was formed in the anhydrous electrolyte solution. The series of decomposition reactions of DMSO induced by water clearly indicated by EQCM measurement as M/z = 55 g mol-1 corresponding to the formation of 1 mol of Li2SO4 by consumption of 2 mol of electron. These results show that effects of water should be considered when developing the better battery system utilizing water to change morphology of Li2O2 or converting Li2O2 to LiOH.1,2

References

 (1) D. G. Kwabi, T. P. Batcho, S. Feng, L. Giordano, C. V. Thompson and Y. Shao-Horn, Physical Chemistry Chemical Physics, 18, 24944 (2016).

 (2) F. Li, S. Wu, D. Li, T. Zhang, P. He, A. Yamada and H. Zhou, Nature Communications,
6, 7843 (2015).

(3) D. G. Kwabi, M. Tułodziecki, N. Pour, D. M. Itkis, C. V. Thompson and Y. Shao-Horn, Journal of Physical Chemistry Letters,
7, 1204 (2016).