bluuebunny/crossref_metadata_2025_split huggingface dataset:
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.
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).
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.
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.