bluuebunny/crossref_metadata_2025_split huggingface dataset:
Perovskite Solar Cells with Two Dimensional Materials As Hole Extraction Layer
Authors: Kim Soo Young , Kim Yu Geun , Oh Jeong Hyeon 
Published: February 2020

Organometallic halide perovskites have attracted much attention as a promising material for high-efficiency absorber in photovoltaic devices. It is based on organic-inorganic light absorbing semiconducting material with a perovskite polycrystalline structure, CH3NH3PbX3, where X is halogenatoms (Cl, Br, I, or combination of some of them). The poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) was usually used as a hole extraction layer in planar type perovskite photovoltaic cells. However, PEDOT:PSS showed several disadvantages such as hygroscopic properties and a highly acidic suspension, which result in poor stability in air.
In this respect, we have investigated the possibility of two-dimensional materials including MoS2, WS2, and graphene oxide (GO) as a hole extraction layer in perovskite photovoltaic cells. MoS2 and WS2 layers with a polycrystalline structure were synthesized by a chemical deposition method using uniformly spin-coated (NH4)MoS4 and (NH4)WS4 precursor solutions. GO was made by following Hummer’s method. Raman spectra, transmission electron microscope image, and x-ray diffraction data confirmed the well-synthesis of two-dimensional materials. The device structure is indium tin oxide/PEDOT:PSS or MoS2 or WS2 or GO/CH3NH3PbIxCl3-x/bathocurione/LiF:Al. The PCE values of PEDOT:PSS, GO, MoS2 and WS2-based one are measured to be 9.93, 9.62, 9.53 and 8.02 %, respectively. These result indicated that two-dimensional materials could replace the PEDOT:PSS layer for the improvement of device stability.
(Invited) Predictive Modeling in 2D Materials: Morphology, Defects, Synthesis
Authors: Yakobson Boris I. 
Published: February 2020

It is of great interest and importance for materials design to uncover, through computational and theoretical modeling, the following relationships: {basic atomic interactions → structure/morphology → functionality (including electronic)}. We will discuss recent examples from low-dimensional materials, where we seem to achieve satisfactory degree of understanding, mostly focusing on nucleation and islands shapes [1], grain boundaries and dislocations [2], heterojunctions [3], catalysis [4], and even predictive synthesis [5].
[1] V. Artyukhov et al. Phys. Rev. Lett. 114, 115502 (2015); V. Artyukhov, Z. Hu et al. unpublished.
[2] X. Zou et al. Nano Lett. 15, 3495 (2015); A. Aziz et al. Nature Comm. 5, 4867 (2014); Y. Liu et al. Nano Lett.14, 6782 (2014).
[3] Y. Gong et al. Nature Mater. 13, 1135 (2014); A. Kutana, H. Yu et al. unpublished; F. Xu, et al. Nano Lett. DOI: 10.1021/acs.nanolett.5b02430 (2016).
[4] Y. Liu et al. Phys. Rev. Lett. 113, 028304 (2014); X. Zou et al. Acc. Chem. Res.48, 73 (2015).
[5] Y. Liu et al. Angew. Chemie, 52, 3156 (2013); Z. Zhang et al., Angew. Chemie, 54, 13022 (2015).
(Invited) Direct Template-Less Synthesis of Oriented Sub-10 Nm Semiconducting Graphene Nanoribbons with Smooth Armchair Edges on Ge(001)
Authors: Arnold Michael S 
Published: February 2020

The rational synthesis of graphene nanoribbons that are semiconducting with sub-10 nm width, controlled crystallographic orientation, and well-defined edges on non-metallic substrates has been a significant challenge. The growth of nanoribbons on metal substrates precludes their direct use in semiconducting electronics due to the conductive substrate, and the direct synthesis of nanoribbons in solution is complicated by challenges of their post-synthetic assembly.
In this talk, we demonstrate the direct, scalable synthesis of graphene nanoribbons via chemical vapor deposition (CVD) on Ge(001).[1] Low energy electron diffraction (LEED) and scanning tunneling microscopy (STM) show that the ribbons are self-orienting ±2.9° from the Ge[110] directions and are self-defining. The nanoribbons have predominately smooth armchair edges that give rise to electron interference patterns indicative of high quality edges. By tuning the precursor flux, growth time, and growth temperature, the ribbon anisotropy and growth kinetics can be tailored to yield ribbons with controlled width < 10 nm and aspect ratio > 60. Compared to previous low aspect ratio crystals of graphene obtained on Ge, we find that in order to realize high aspect ratio nanoribbons, it is critical to operate in a regime in which the growth rate is especially slow, on the order of 5 nm/h in the width direction.
This work is important because unlike continuous two-dimensional graphene, which is semimetallic, one-dimensional graphene nanoribbons can be semiconducting, allowing for the substantial modulation of their conductance and enabling their application in semiconductor logic, optoelectronics, photonics, and sensors. Moreover, the direct synthesis of ultranarrow and smooth graphene nanoribbons on Ge demonstrated here provides a scalable, high throughput pathway for integrating semiconducting graphene directly on conventional large-area semiconductor wafer platforms that are compatible with planar processing.
[1] Jacobberger RM, Kiraly B, Fortin-Deschenes M, Levesque PL, McElhinny KM, Brady GJ, Rojas Delgado R, Singha Roy S, Mannix A, Lagally MG, Evans PG, Desjardins P, Martel R, Hersam MC, Guisinger NP, Arnold MS, Direct Oriented Growth of Armchair Graphene Nanoribbons on Germanium, NATURE COMMUNICATIONS, 6, 8006 (2015)
(Invited) Liquid-Phase Exfoliated Two-Dimensional Nanosheets: From Large Scale Production to Energy Storage Applcations
Authors: Nicolosi Valeria 
Published: February 2020

Graphene has generated huge interest in recent years due to its unique physics properties [1]. We have shown that high-quality monolayer graphene can be produced at significant yields by non-chemical, solution-phase exfoliation of graphite in certain organic solvents. Until a few years ago the standard procedure used to make graphene was micromechanical cleavage [2], which is a very low yield production method. In order to fully exploit graphene’s outstanding properties, a mass production method was necessary and the development of a method to exfoliate cheap, commercial graphite in organic solvents down to large area single graphene flakes with high yield was one major achievement [3]. Recently this work has been extended to a wide range of two-dimensional inorganic nanomaterials [3,4]. These are potentially important because they occur in >100 different types with a wide range of electronic properties, varying from metallic to semiconducting. The liquid-phase exfoliation method has now been up-scaled to produce grams of a variety of exfoliated materials per day [5].
This talk will first discuss the galaxy of existent layered materials, with emphasis on synthesis and liquid-phase exfoliation to finish off with some key applications recently developed in our laboratories.

A. K. Geim, Science 324, 1530 (Jun, 2009).

S. Stankovich et al., Nature
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J. N. Coleman et al., Science,
331, pp. 568-571 (2011)

V. Nicolosi et al., Science, 340, 6139, 1420 (2013)

K. R. Paton et al., Nature Materials, 13, 6, 624-30 (2014)
Observation of Two Dimensional Metallic Surface States and Metal to Semiconductor Transition on Low Dimensional Polar Thin Films
Authors: Wu Fei , Faghaninia Alireza , Lo Cynthia , Banerjee Parag 
Published: February 2020

Two dimensional (2D) metallic conductivity has been studied for more than a decade because the unusual surface metallic states of ultrathin films may result in applications for 2D superconductors, spintronics and optoelectronic devices. Surface metallic states were predicted on ZnO polar surfaces, which is caused by charge transfer from O-terminated (000-1) surface to Zn-terminated (0001) surface to stabilize the polar instability.1 This charge transfer in polar thin films was also found to cause abrupt phase transition (i.e. ferromagnetism,2 and semiconductor to semimetal transition3), opening a new way to design functional devices by engineering surface or interface of ultrathin films.
2D metallic conductivity on ZnO has not been previously demonstrated in experiments. The charge transport properties of 2D surfaces have proved to be difficult to measure because of the dominant effect of bottom, bulk conduction channels. In our study, we reduce the ZnO thickness to several nanometer to suppress the bulk conduction channels and first experimentally show 2D metallic states on polar ZnO surfaces through surface conductivity measurements on SiO2 substrates. Then, introduction of a high density of oxygen vacancies to the polar ZnO surfaces can cause metal to semiconductor transition. These experimental results are also confirmed by the first principle calculations.
[1] Wander, A.; Schedin, F.; Steadman, P.; et al., Phys. Rev. Lett.
2001, 86, (17), 3811-3814.
[2] Wang, X. R.; Li, C. J.; Lu, W. M.; et al., Science
2015, 349, (6249), 716-719.
[3] Kim, J.; Baik, S. S.; Ryu, S. H.; et al., Science
2015, 349, (6249), 723-726.
Oxygen Reduction Reaction Kinetics of PrBaCo2O5+
As SOFC Cathode
Authors: Zhang Nan , Li Wenyuan , Liu Xingbo 
Published: February 2020

PrBaCo2O5+
δ double-perovskite has been identified as promising cathode for intermediate temperature SOFC. Research has shown that oxygen diffusivity and surface defects sites that promote the surface reactivity can be greatly enhanced due to the ordered structure and non-stoichiometry of such material. However, there have been very few detailed investigations on the ORR mechanisms and kinetics of PrBaCo2O5+
δ, including identifying the rate-limiting steps. In this work, oxygen reduction reaction mechanisms of PrBaCo2O5+
δ cathode were studied. The ORR kinetics was evaluated through EIS toward the PrBaCo2O5+
δ /GDC/ PrBaCo2O5+
δ symmetric cell configuration. The complex nonlinear least square (CNLS) fitting results shows that oxygen reduction on porous PrBaCo2O5+
δ electrode is limited by surface chemical exchange and solid state diffusion not the traditionally TPB charge transfer process under the limit of semi-infinite electrode. According to the reaction order under different temperature and Po2, oxygen surface incorporation is supposed to be the main rate-limiting step for the overall reaction rate with the certain microstructure.
Chromium Poisoning Effects on Surface Exchange Kinetics of La0.6Sr0.4Co0.2Fe0.8O3-X
Authors: Huang Yi-Lin , Pellegrinelli Christopher , Xiong Chunyan , Wachsman Eric D. 
Published: February 2020

Solid oxide fuel cells (SOFC) have been demonstrated with high efficiency in energy conversion through electrochemical reactions. However, the durability of SOFC cathodes under real operating conditions is still an important issue for widespread implementation. Chromium-containing interconnect alloys have been reported to cause severe degradations and restrain cathode performance. Also, the presence of both chromium and water vapor have been shown to accelerate the degree of chromium poisoning. Therefore, fundamental understanding of chromium effects, as well as cross-contamination effects, on the oxygen reduction reaction (ORR) and the cathode degradation mechanism are important to preventing chromium poisoning. Here we utilize in-situ gas phase isotopic oxygen exchange to explore effect of chromium on the ORR mechanisms. Gas phase isotopic oxygen exchange is a powerful technique to investigate surface reaction kinetics and catalytic activity from a molecular point of view. To investigate Cr effects on the surface kinetics of cathodes, La0.6Sr0.4Co0.2Fe0.8O3-x (LSCF) powders had been aged in contact with Cr-containing alloy (Crofer APU 22) with the presence of water. Aged La0.6Sr0.4Co0.2Fe0.8O3-x (LSCF) powders were examined under different atmospheres and the effects of chromium on LSCF as a function of temperature with or without the presence of water vapor were explored. The use of gas phase isotopic oxygen offers separate examination of Cr effects on the surface dissociation step and the overall surface exchange on LSCF. The changes in active surface sites of aged LSCF could also be quantified. Cross-contamination and the lifetime of intermediate adsorbed species were further determined to elucidate multiple gas-gas and gas-solid reactions on cathodes. Results of surface kinetics show correlations with surface configurations of LSCF. A possible degradation mechanism has been proposed to illuminate chromium poisoning effects on the ORR.
Poisoning of Proton Conducting SOFC By Hydrogen Sulfide and Carbon Dioxide Fuel Contaminants
Authors: Sun Shichen , Cheng Zhe 
Published: February 2020

It is well known that conventional solid oxide fuel cells (SOFCs) with oxygen ion conducting electrolyte and nickel (Ni) anode are susceptible to poisoning by trace amount of hydrogen sulfide (H2S) while not significantly impacted by presence of carbon dioxide (CO2) in the fuel stream. In comparison, the impacts of H2S and CO2 as fuel contaminants on proton-conducting SOFCs remain unexplored. Here we report our study aimed at revealing the poisoning behavior caused by H2S and CO2 for proton-conducting SOFCs. Anode-supported proton-conducting SOFCs with BaZe0.1Ce0.7Y0.1Yb0.1O3 (BZCYYb) electrolyte and Ni-BZCYYb anode and La0.6Sr0.4Co0.2Fe0.8O3 (LSCF) cathode were subject to ppm-level H2S or percentage-level CO2 as fuel contaminants in hydrogen fuel. The response in cell electrochemical behavior and the change in materials microstructure and composition are characterized. Preliminary results suggest that, contrary to conventional SOFCs that show “sulfur poisoning” and “CO2 tolerance”, such Ni-BZCYYb anode/BZCYYb electrolyte/LSCF cathode proton-conducting SOFC button cells show good tolerance to H2S up to ~5 ppmv while severe poisoning by CO2 at even low percentage level. Experimental results aimed at understanding such different electrochemical behaviors for proton-conducting SOFCs versus conventional oxygen ion conducting SOFCs will be presented and their implications on the fundamental mechanism for anode hydrogen electrochemical oxidation reaction in proton conducting SOFCs will be discussed.
Colloidal Syntheis of Ptzn Nanocrystals and Their Activity for Oxygen Reduction Reaction
Authors: Ye Youngjin , Lee Jinwoo 
Published: February 2020

Commercialization of a polymer electrolyte fuel cell (PEMFC) is confronted with insufficient activity and durability of Pt-based cathode catalyst. Therefore, catalyst development for oxygen reduction has been focused on the increase of the specific activity of Pt-based catalysts by alloying Pt with transition metals. Computationally based electrocatalyst screening has made it possible to reduce the efforts for finding cathode catalysts with high activity and durability. According to the computationally predicted oxygen binding energy for Pt-based alloys, Pt3Zn has the nearly optimal oxygen binding energy for oxygen reduction.1 However, there is still lack of information on Pt3Zn as a cathode catalyst in a PEMFC. Here, we synthesized uniform Pt-Zn nanoparticles in oleylamine that has an average size of 4 nm. After deposition of Pt-Zn nanoparticles on a carbon support, the resulting material was heat-treated at higher than 400 oC. The electrocatalytic properties of Pt-Zn nanoparticles and the heat-treatment effect will be presented.
[1] J. Greeley et al. Nature Chemistry
2009, 1, 552.
Synthesis of TiO2 Nanotubes By Ti Foil Electrochemical Dissolution
Authors: Nikoleishvili Paata , Kurtanidze Rusudan , Gorelishvili Giorgi , Kveselava Valentina , Sharabidze Davit , Gogoli Davit 
Published: February 2020

The growing demand for environmentally clean energy because of depletion of fossil fuel resources and the issues of climate change, such as global warming, caused the need for environmentally stable sources of energy. Renewable energy can be obtained from stable resources. Solar energy has the large prospects as an alternative source of energy, because its feed is un-limited and free.
Goal of the project is the preparation of TiO2 nanoparticles for dye-sensitized photoelectrochemical solar cell. We propose a new method of TiO2 electro-generation. TiO2 nanoparticles have been obtained by Ti foil anodic dissolution in 0.1-1M HCl solution, where hydrogen peroxide solution (30%) drop by drop has been added, cathode was stainless steel foil, and current density in different tests has been changed from 0.2 A/cm2 to 1A/cm2, voltage has been changed from 8 V to12 V, respectively. Electrochemical processes have been carried out at 90oC at steering rate 800 rpm. TiO2 has been directly obtained in electrolyte solution. This method gives allows to control a size of generated TiO2 particles by changing current density and hydrogen peroxide addition rate. TiO2 nanoparticles have been identified by X-ray diffraction (XRD) and scanning electron microscope (SEM) with particle size 50-500 nm. Finally, dye-sensitized photoelectrochemical solar cell has been fabricated.
Electrochemical properties of the solar cell (i-V and I-P curves): open circuit voltage 0.63 V, short circuit current 12 mA/cm2, maximum power 4 mW/cm2 and current density at the maximum power - 7.5 mA/cm2, fill factor (ff) - 0.538, light energy conversion efficiency - 8.0%.
Fabrication and Electrochemical Properties of Highly Ordered Titania Nanotubes Modified with Boron Nanocrystalline Diamond
Authors: Bogdanowicz Robert , Siuzdak Katarzyna , Sobaszek Michal , Szkoda Mariusz 
Published: February 2020

Recently, we reported on the phenomena of the formation of the novel composite material based on titania nanotubes (TiO2 NTs) over-grown by thin boron-doped diamond (BDD) produced in microwave plasma enhanced chemical vapor deposition (MW PE CVD) [1,2]. Under microwave plasma treatment, the structure TiO2 NTs underwent transformation from stoichiometric anatase into non-stochiometric oxide with Ti(III) phase and some rutile phase arises. Furthermore, obtained material was characterized with a significantly enhanced conductivity and capacitance comparing to pristine titania. The electrochemical studies showed that the specific areal capacitance of TiO2/BDD raised up to 7.46 mF cm-2 whereas for the pure BDD it reached only 0.11 7.46 mF cm-2.
Because of such strong modification of titania and application potential in energy storage devices we decided to initiate growth of boron nanocrystalline diamond (B-NDC) on the highly ordered TiO2 nanotube arrays. TiO2 NTs are fabricated via two-step anodization of titanium metal plate followed by a short immersion in diluted HF in order to remove any surface debris [3]. Titanium plate covered by uniform titania nanotube layer provides a large specific surface area as well as a direct pathway for charge transport, thus holding promising capabilities of being support for another materials deposition. Afterwards, similarly to formation of TiO2NTs/BDD material, the deposition of boron nanocrystalline diamond will be also realized under microwave plasma conditions and Ti/TiO2 NTs will act as a substrate. The morphology and the structure of obtained composite material will be investigated using scanning electron microscopy and Raman spectroscopy. Electrochemical activity will be identified applying cyclic voltammetry and electrochemical impedance spectroscopy techniques performed in aqueous electrolyte. The influence of boron-doping level will be observed as a change in registered capacitive current and impedance behaviour.
References:
[1] K. Siuzdak, R. Bogdanowicz, M. Sawczak, M. Sobaszek, Enhanced capacitance of composite TiO2 nanotube/boron-doped diamond electrodes studied by impedance spectroscopy, Nanoscale 7 (2015) 551
[2] M. Sawczak, M. Sobaszek, K. Siuzdak, J. Ryl, R. Bogdanowicz, K. Darowiski, M. Gazda, A. Cenian, Formation of highly conductive boron-doped diamond on TiO2 nanotubes composite for supercapacitor or energy storage devices, J Electrochem Soc 162 (2015) A2085
[3] M. Szkoda, K. Siuzdak, A. Lisowska-Oleksiak, J. Karczewski, J. Ryl, Facile preparation of extremely photoactive boron-doped TiO2 nanotube arrays, Electrochem Comm. 60 (2015) 212
Financial support from the Polish National Science Center – under grant No. 2012/07/D/ST5/02269 and No. 2011/03/D/ST7/03541 is gratefully acknowledged.
Gold-Cobalt Deposited on Titania Nanotubes as Anode Catalyst for Direct Borohydride Fuel Cells
Authors: Santos Diogo M.F. , Balciunaite Aldona , Tamasauskaite-Tamasiunaite Loreta , Zabielaitë A. , Jagminienë A. , Stankeviciene Ina , Norkus E. 
Published: February 2020

In the present work gold-cobalt catalysts deposited on titania nanotubes surface (denoted as Au(Co)/TiO2-NTs) were investigated as anode material in direct borohydride fuel cells (DBFCs). The catalysts were prepared by a simple and cost-effective galvanic displacement technique [1]. At first, the sub-layer of Co was deposited on the titania nanotubes surface via electroless deposition. The gold crystallites were then deposited on the Co/TiO2-NTs electrodes by their immersion into gold(III)-containing solution for different time periods. It has been determined that the Au loadings were in the range from 10 to 60 µg cm–2 in the Au(Co)/TiO2-NTs catalysts.
Field emission scanning electron microscopy (FESEM) and energy dispersive X-ray spectroscopy (EDXS) were used to characterize the surface morphology and composition of the samples, respectively. The activity of the Au(Co)/TiO2-NTs catalysts for borohydride oxidation reaction (BOR) was evaluated by cyclic voltammetry and chronoamperometry measurements.
The performance of a DBFC operating with 1 M NaBH4 + 4 M NaOH as fuel and 5 M H2O2 + 1.5 M HCl as oxidant, while employing Pt as the cathode catalyst and Au(Co)/TiO2-NTs with different Au loadings as the anode catalyst were investigated. Peak power densities up to 122 mW cm-2 were attained at 25 ºC. It was found that the highest specific peak power density of 9.6 kW g–1
Au was obtained when employing Au(Co)/TiO2-NTs with the Au loading of 10 µg cm–2as the anode catalyst.

References

[1] L. Tamašauskaitë-Tamašiûnaitë, A. Jagminienë, A. Balèiûnaitë, A. Zabielaitë, A. Þielienë, L. Naruškevièius, J. Vaièiûnienë, A. Selskis, R. Juškënas, E. Norkus. Int. J. Hydrogen Energy 38 (2013) 14232-14241.

Figure 1
(Invited) Functional Gradient Carbon-Sulfur Cathode for Rechargeable Li-S Battery
Authors: Liu Xingbo , Yan Jianhua , Yao Meng , Li Bingyun 
Published: February 2020

Lithium−sulfur (Li−S) battery is promising next generation rechargeable battery due to its potential high energy density. However, it suffers from major problems including poor cycle performance and low efficiency, mainly due to the high solubility of intermediate poly-sulfides and their side-reactions with the Li-anode. Recently, we have developed various open-structure functional gradient C-S composite cathodes with very high S-loadings that can utilize the high energy density of S-cathode while minimize the migration of poly-sulfide to anode side. We employed scalable and industrial viable method such as layer-by-layer nano-assembly technique that leads to a binder-free, three-dimensional porous cathode via electrostatic attraction and enables the fabrication of Li−S cells with remarkably improved performance including a long cycle life exceeding 600 cycles and a high Coulombic efficiency of 97.5% at the 1 C rate. Moreover, our Li−S cells have presented a high rate response up to 2.5 C with high sulfur utilization (a reversible capacity of 1100 mAhg−1, 900 mAhg−1, 700 mAhg−1, and 450 mAhg−1 of sulfur at 0.3, 0.6, 1, and 2.5 C rates, respectively). The results provide important progress toward the understanding of the role of multilayered cathodes and the realization of high-efficiency and long-term service life for Li−S batteries.