bluuebunny/crossref_metadata_2025_split huggingface dataset:
Molybdenum Disulfides and Diselenides By Atomic Layer Deposition
Authors: Sopha Hanna , Zazpe Raul , Prikryl Jan , Krbal Milos , Ng Siowwoon , Bures Filip , Macak Jan M. 
Published: May 2020

The success of graphene opened a door for a new class of chalcogenide materials with unique properties that can be applied in the semiconductor technology [1]. Monolayers of two-dimensional transition metal dichalcogenides (2D TMDCs) possess a direct band gap [2] that is crucial for optoelectronic applications. Additionally, the direct band gap can be easily tuned by either chemical composition or external stimuli. Next to the optoelectronic applications, where a monolayer planar structure is necessary to employ, a layer of standing flakes, which possesses a large surface area, can be used for hydrogen evolution [3] a photodegradation of organic dyes [4] or as electrodes in Li ion batteries [5].
In principle, TMDCs can be prepared by various top-down (e.g. exfoliation) and bottom-up techniques, such as chemical vapor deposition (CVD) and atomic layer deposition (ALD) growth techniques [1]. MoS2, a typical representative of TMDCs, has been widely studied for many applications. Recently, the possibility to employ ALD as a technique to grow MoS2 has been reported. In these works (CH3)2S2 [6] or H2S [7, 8] were used as the S precursor and Mo(CO)6 [6], MoCl5 [7] or Mo(thd)3 [8] as the Mo precursors. From the practical point of view, MoSe2 is even more interesting than MoS2 since MoSe2 possesses a higher electrical conductivity than MoS2 [9, 10]. Recently, we have shown that ALD deposition of MoSe2 [11] or Mo-O-Se [12] using ((CH3)3Si)2Se as the Se precursor and the MoCl5 or Mo(CO)6, respectively, as the Mo precursors is feasible.
The presentation will focus on the synthesis of MoS2 and MoSe2 by ALD, their characterization and applications in various fields. Experimental details and some recent results for photocatalytic, battery and hydrogen evolution applications will be presented and discussed.
References:
[1] A. V. Kolobov, J. Tominaga, Two-Dimensional Transition-Metal, Dichalcogenides. Springer Series in Materials Science, Springer International Publishing AG, Switzerland 2016

[2] B. Radisavljevic, A. Radenovic, J. Brivio, V. Giacometti, A. Kis, Nat. Nanotechnol. 2011, 6, 147.
[3] L. Wang, Z. Sofer, J. Luxa, M. Pumera, Adv. Mater. Interfaces
2015, 2, 1500041
[4] Y. Wu, M. Xu, X. Chen, S. Yang, H. Wu, J. Pan, X. Xiong, Nanoscale
2016, 8, 440
[5] D. Ilic, K. Wiesener, W. Schneider, H. Oppermann, G. Krabbes, J.Power Sources
1985, 14, 223
[6] Z. Jin, S.Shin,D.H.Kwon, S. J.Han,Y. S.Min,Nanoscale
2014, 6, 14453.
[7] L. K. Tan, B. Liu, J. H. Teng, S. Guo, H. Y. Low, K. P. Loh, Nanoscale
2014, 6, 10584
[8] M. Mattinen et al., Adv. Mater. Interfaces
2017, 4, 1700123.
[9] D. Kong, H. Wang, J. J. Cha, M. Pasta, K. J. Koski, J. Yao, Y. Cui, Nano Lett. 2013, 13, 1341.
[10] A. Eftekhari, Appl. Mater. Today
2017, 8.
[11] M. Krbal et al., Phys. Stat. Sol. RRL,
2018, 12, 1800023
[12] S. Ng et al., Adv. Mater. Interfaces
2017, 1701146.
(Invited) Multi-Level Non-Volatile Memory in Au/Monolayer MoS2/Au Structures
Authors: Bhattacharjee Shubhadeep , Caruso Enrico , McEvoy Niall , Coileáain Cormac Ó , Ansari Lida , Nagle Roger , Cherkaoui Karim , Gity Farzan , Hurley P. K. 
Published: May 2020

The wide range of electronic and optical properties exhibited by two dimensional semiconductors, and their variation physical thickness, opens up new possibilities to create ultra-short length transistors [1], steep-slope switches [2, 3], light detecting/emitting devices [4, 5] and chemical/physical sensors. Recently, it was demonstrated that monolayer 2D semiconductors can also display resistive switching [6]. In this work we demonstrate that a single layer of large area CVD-grown moly disulphide (MoS2) sandwiched between two metal electrodes can be tuned to exhibit multi-level non-volatile resistive memory, with resistance values separated by 5 orders of magnitude. The switching process is unipolar and thermochemically driven (TCM memory) requiring significant Joule heating in the RESET process. Temperature dependent electrical measurements will be presented which demonstrate the charge transport mechanism varies between the initial state (IS), the high resistive state (HRS) and low resistive state (LRS). The temperature dependent behavior of the SET, RESET process is consistent with the creation and passivation of sulfur vacancies in the MoS2 monolayer. Conductive AFM measurements confirm that the multi-filamentary resistive memory effects are inherent to a single crystalline MoS2 triangle and not necessarily dependent of grain boundaries. This work demonstrates that potential for 2 terminal, multi-state, resistive memories for next generation digital memory and neuromorphic applications.
[1] S. B. Desai et al., "MoS2 transistors with 1-nanometer gate lengths," Science, vol. 354, no. 6308, pp. 99-102, 2016.
[2] S. Bhattacharjee, K. L. Ganapathi, S. Mohan, and N. Bhat, "A sub-thermionic MoS2 FET with tunable transport," Applied Physics Letters, vol. 111, no. 16, p. 163501, 2017.
[3] D. Sarkar et al., "A subthermionic tunnel field-effect transistor with an atomically thin channel," Nature, vol. 526, no. 7571, p. 91, 2015.
[4] K. Roy et al., "Graphene–MoS 2 hybrid structures for multifunctional photoresponsive memory devices," Nature nanotechnology, vol. 8, no. 11, p. 826, 2013.
[5] X. Zhou et al., "2D Layered Material‐Based van der Waals Heterostructures for Optoelectronics," Advanced Functional Materials, vol. 28, no. 14, p. 1706587, 2018.
[6] R. Ge et al., "Atomristor: Nonvolatile Resistance Switching in Atomic Sheets of Transition Metal Dichalcogenides," Nano letters, vol. 18, no. 1, pp. 434-441, 2017.
Synthesis and Performance Evaluation of Exfoliated Graphene Nanoplatelet Hydrogels As Electrodes for Supercapacitors
Authors: Mypati Sreemannarayana , Sellathurai Andrew , Kontopoulou Marianna , Docoslis Aris , Barz Dominik P.J. 
Published: May 2020

Graphene is an excellent material because of its high electrical conductivity, high surface area, and superior mechanical properties. Stable dispersions of graphene nanoplatelets (GNPs) can be only achieved in organic solvents while in polar solvents the GNPs tend to agglomerate. Therefore, covalent and non-covalent functionalization of the GNP, or the use of surfactants, is required to formulate stable dispersions. Unlike GNP, Graphene oxide (GO) can be readily dispersed in aqueous media because of the hydrophilic oxygen groups on the basal plane and edges. Consequently, GO has amphiphilic material characteristics like a surfactant, and we use it as a dispersing agent for GNP in aqueous solutions.
In this work, we formulate highly-concentrated aqueous GO/GNP dispersions (5 mg/ml to 25 mg/ml). The stability of these dispersions mainly depends on the pH, concentrations of GO/GNP and lateral dimensions of the flakes. Stable dispersions are used to synthesize graphene hydrogels which are usually made from reduced graphene oxide (rGO), which is considerably more expensive than GNP obtained from mechanical/thermal exfoliation. Graphene hydrogels are a self-assembled microporous structure that incorporate a liquid phase. The graphene hydrogel matrix has a very high surface area, along with high electronic conductivity, which makes it a very suitable material for supercapacitor applications. The graphene hydrogels that we prepare from GNP, containing a small fraction of GO, are characterized by scanning electron microscopy, electrical conductivity measurements, X-ray diffraction, and Raman spectroscopy. The results indicate that a minimum GO/GNP ratio of 0.1 is required to stabilize the GNP flakes. The three-dimensional self-assembly is promoted due to the reduction of GO. The GNP hydrogels have better mechanical stability compared to a conventional rGO hydrogel; a 50 mg freeze-dried sample can sustain a load of 200 g of weight. A flexible supercapacitor is prepared from the GNP hydrogels. In detail, the symmetrical electrodes are prepared by pressing a 1 mm thick slice of hydrogel onto a carbon cloth current collector and two of these electrodes are separated by a filter paper soaked in a 2 M H2SO4 electrolyte. The supercapacitor is characterized by cyclic voltammetry, electrical impedance spectroscopy as well as galvanostatic charge and discharge measurements. The specific capacitance obtained at 1 A/g is 187 F/g, which is around 30% higher than that of comparable supercapacitor made from rGO hydrogels. Additionally, the specific capacitance and the coulombic efficiency at 10 A/g remains at almost 100% of the initial values, even after 3000 cycles.

Figure 1
An Artificial Interface (AI) to Open the Window for Aqueous Electrolytes
Authors: Olarte Marco , Menu Marie-Joelle , Simon Patrice , Gressier Marie , Taberna Pierre-Louis 
Published: May 2020

Devices with high power density which can store energy with a fast rate charge-discharge, the supercapacitors are suitable in different applications where high power is needed. That because it stores charge by fast surface process, i.e. ion adsorption of an electrolyte into the electrochemical double layer at the electrode/electrolyte interface. Nevertheless, in order to extend their autonomy beyond few seconds, its energy density has to be increased. For this aspect, in recent years many teams around the world have set up different strategies as a combination of a carbon electrode with a faradic type electrode (battery electrode or pseudocapacitive) or through the development of new active materials, including the development of new electrolytes. The main significant achievements are more on the active material side. Even though some works have been successful in increasing the cell voltage, thanks to the use of new ionic liquids, they are still room for improvement regarding the increase of the cell voltage.
To address this point, we have targeted to obtain an aqueous-based high voltage supercapacitor. Our strategy consists in using an Artificial Interface (AI) by depositing an ionogel onto a carbon electrode, the AI is composed of an inorganic matrix and an ionic liquid, in order to form a passivation layer at the electrode/electrolyte interface; a better electrochemical and thermal stability of this interface is thus expected. The IA has got to be electronically insulating but ionic conductive, limiting or even preventing the transfer of electronic charge to the electrode / electrolyte interface.1,2

First things first, the study have been carried out on glassy carbon where AI has been deposited and the linear sweep voltammetry tests in an aqueous electrolyte based on EMI+ HSO4
- and H2SO4 indicate, in both cases, an increase in the potential window: the onset potential for water reduction is shifted toward more cathodic potentials. Going further, tests in the presence of a redox probe (Ferri-Ferro potassium cyanide) demonstrate the absence of electron transfer at the electrode/electrolyte interface. On the other hand, it appears, thanks to measurements carried out by electrochemical impedance spectroscopy, since within the IA is embedded EMI+ TFSI-, better ionic conduction is obtained when the electrolyte is made of EMI+ HSO4
-, sharing the same cation than the one of IA. As we will be showing, a better transference number is achieved for EMI+ cations than for H+ still further works are needed to improve the selectivity of the IA to improve its stability over cycling.
1. Z. H. Zhang et al., Sci. Rep., 8, 1–12 (2018).
2. M. D. Elola and J. Rodriguez, J. Phys. Chem. C, 123, 3622–3633 (2019).
Integration of Thermo-Electrochemical Conversion into Forced Convection Cooling
Authors: Ikeda Yutaka , Fukui Kazuki , Murakami Yoichi 
Published: May 2020

In our present civilization, forced convection cooling is used in wide-ranging situations from cooling of microprocessors in data centers to that of power turbines and automobile engines. Active cooling is essential in such situations. However, active transfer of heat or thermal energy across a large temperature difference promptly destroys the free-energy component of the thermal energy called “exergy”. This issue has remained unaddressed despite widespread use of forced convection cooling. In this study, to partially recover presently lost exergy in such situations in the form of electric power, we integrate thermo-electrochemical conversion, which has been mostly studied for stationary conditions, into forced convection cooling. The proposed concept is graphically illustrated in Fig. 1.
To investigate this concept, we design a test cell (Fig. 2a) in which an electrolyte liquid is forced through a channel formed between two parallel electrodes (Fig. 2b) and the hot-side electrode simulates an object to be cooled. We use cobalt redox couple CoII/III(bpy)3(NTf2)2/3 (Fig. 2c) dissolved in an ionic liquid as the coolant (electrolyte) for this purpose.
Our experimental investigations show that the narrower interelectrode channels afford higher cooling and power generation performances. The mass transfer resistance is the most dominant type of resistance for all the conditions tested and the charge transfer kinetics is controlled by electrolyte viscosity. The dependence of the generated power on the flow rate is caused by the change in the diffusion coefficient of redox species with temperature. As an evaluation measure for such forced-flow thermo-electrochemical cells, the “gain”—defined as the ratio of the generated power to the hydrodynamic pumping work required to force the liquid through the cell—is introduced. The gain is found to be above unity in a certain flow rate region. This demonstrates that such a system can generate more electric power than the hydrodynamic pump work required to drive the liquid through the cell, supporting our concept to address aforementioned unresolved issue in the situations of forced-convection cooling.
Reference:
Ikeda, K. Fukui, and Y. Murakami, Phys. Chem. Chem. Phys., 2019, in press, DOI: 10.1039/c9cp05028k; arxiv.org/abs/1908.08646.

Figure 1
Effect of the Electron Transport Layer on the Photovoltaic Properties of Hybrid Organic Inorganic Perovskites Solar Cells: Cross-Section of Optics, Morphology, Composition and Quality
Authors: Demopoulos George P. , Yekani Rana , Yasin Amrita , Dagdeviren Omur , Dragomir Vlad , Leonelli Richard , Grutter Peter 
Published: May 2020

Ever since their dawn in 2009 1, hybrid organic–inorganic perovskite materials have been experiencing an ever increase in research investment to finally emerge as a strong alternative for high power conversion efficiency (PCE) photovoltaic devices at low costs. One of the main challenges that is currently impeding the upscaling of these solar cells is the phenomenon of hysteresis on their j–V response that has been correlated with slow ion migration which, in turn, affects their photovoltaic properties. Although hysteresis has been described to some extent of detail, the precise role of the external contacts remains under debate. Furthermore, there has been a great deal of focus on materials and interface design while less attention has been given to optical aspects of these cells. Our work highlights the role of electron transport layer (ETL) of different compositions and synthesized through various routes on the hysteresis response of these systems. We show that there’s a clear correlation between thickness, morphology and composition of the ETL on the photovoltaic response these systems. To better elucidate such a response, we have utilized photoluminescence, electroluminescence, absorption and kelvin probe force microscopy to get a substantial grasp of the optoelectronic phenomena occurring at the interfaces in perovskite solar cells.
Acknowledgments: This research was supported by a Hydro-Quebec/NSERC CRD grant and the McGill Sustainability Systems Initiative (MSSI).
1- Kojima, A., Teshima, K., Shirai, Y. and Miyasaka, T., 2009. Organometal halide perovskites as visible-light sensitizers for photovoltaic cells. Journal of the American Chemical Society, 131(17), pp.6050-6051.
(Invited) Oxygen Reduction Reactivity at Fe- and Cu-Codoped Carbon Nanostructures
Authors: Yagi Ichizo , Fujibayashi Natsuki , Abe Daiki , Yasuda Satoshi , Kato Masaru 
Published: May 2020

Polymer electrolyte fuel cells (PEFCs), which can efficiently convert hydrogen into electricity without using fossil fuels, are a promising energy conversion device. At the cathodes of PEFCs, oxygen reduction reaction (ORR) occurs via 4-electrons' and 4-protons' transfer. Due to its low reaction rate limiting the performance of PEFCs, the electrocatalysts are necessary and the platinum-based electrocatalysts for ORR are mainly used because of its highest electrocatalystic activity in the metals. Since platinum metal is expensive and rare, there is a need to develop non-platinum-based electricatalysts based on iron and/or copper with high ORR activity1,2,3,4).
A cytochrome c oxidase (CcO), which is a metalloenzyme and contains iron and copper metal ions, catalyzes the ORR efficiently to produce ATP in mitochondria5) and its activity is higher than that of artificial platinum-based electrocatalysts6). Metalloenzymes are not practical because of their stability, size, and difficulty to isolate and purify.
In this study, iron and copper co-doped carbon electrocatalysts, synthesized from the mixtures of Fe and/or Cu complexes and carbon nanotubes in heat treatment inspired by the CcO’s active center, were developed. Synthetic conditions of Fe : Cu metal ratios and heating temperatures were optimized. The ORR activity was evaluated by hydrodynamic voltammetry using a rotating ring disk electrode in 0.05 M sulfuric acid aqueous solution saturated with oxygen. The activity of Fe/Cu/CNT catalyst was compared with two catalysts: iron-doped carbon carbon catalyst (Fe/CNT) and copper-doped carbon catalyst (Cu/CNT). The Fe/Cu/CNT catalyst showed more positive onset potential for the oxygen reduction in acidic media than Fe/CNT and Cu/CNT, indicating that Fe/Cu/CNT is more active, and we figure out that the coexistence of iron and copper in CNTs contributes to the improvement of ORR activity.

References:

1. Kato et al., Chem. Lett.
45, 1213–1215 (2016).
2. Kato et al., ACS Appl. Energy Mater. 1, 2358–2364 (2018).
3. Chung et al., Science
357, 479–484 (2017).
4. Yasuda et al., Adv. Funct. Mater. 26, 738–744 (2016).
5. Sakamoto et al., PNAS
108, 12271–12276 (2011).
6. Kjaergaard et al., Inorg. Chem. 49, 3567–3572 (2010).
Functionalized Carbon Nanotubes for Lithium-Organic Batteries
Authors: Kamaleddine Hanine , Charrier Gaëlle , Jousselme Bruno , Cornut Renaud , Gutel Thibaut , Barchasz Céline , Campidelli Stephane 
Published: May 2020

Lithium batteries are among the most promising systems for electrochemical energy storage. However, their capacity and cost-efficiency have to be improved for further applications.1 Lithium/organic batteries offer an interesting alternative to the classical Li-ion systems due to the low molecular weight of organic materials, their potential low cost and recyclability. However, two major roadblocks currently prevent the industrial development in these kind of batteries: (i) the progressive dissolution of the active material in the electrolyte, which hinders the cyclability of the devices and (ii) the electrical insulating nature of organic materials.2

Here, we develop a new positive electrode material avoiding the dissolution of the active material in the electrolyte upon cycling, by grafting new diazonium derivatives containing active groups onto multi-walled carbon nanotubes (MWNTs) at different ratios between the carbon nanotubes and the active material.3 The MWNTs insure a well distributed electronic conductivity inside the positive electrode and serve as a support for a covalent immobilization of the organic active species.

References

[1] Cheng, F., Liang, J., Tao, Z., and Chen, J. Adv. Mater, 2011, 23, 1695-1715.
[2] C. Barchasz, F. Mesguich, J. Dijon, J.-C. Leprêtre, S. Patoux and F. Alloin, J. Power Sources. 2012, 211, 19-26.
[3] G. Charrier, H. Kamaleddine, C. Barchasz, R. Cornut, B. Jousselme and S. Campidelli, ChemElectroChem. 2018, 5, 1732-1737.
(Invited) Beta, Beta-Functionalized Push-Pull Opp-Dibenzoporphyrins As Sensitizers for Dye-Sensitized Solar Cells: The Role of the Phenylethynyl Bridge and the Tertiary Amine Push Group
Authors: Wang Hong , Hu Yi , Thomas Michael , Alsaleh Ajyal , D'Souza Francis 
Published: May 2020

Significant progress has been made on dye-sensitized solar cells sensitized by push-pull porphyrins in recent years.1-3 An effective way to significantly enhance power conversion efficiencies of porphyrin dyes is through installation of push (electron-donating) and pull (electron-withdrawing) groups at porphyrin meso-positions.4-6 In this presentation, we present a different strategy to install push and pull groups at porphyrin b-positions. Three series of novel opp-dibenzoporphyrins were prepared using this strategy. Our studies show significant push-pull effects for these porphyrins.7 DFT calculations suggest that the inclusion of ethynylphenyl bridge between the donating group and the porphyrin core significantly segregate the frontier orbitals, which is a much-favored feature for sensitizers in DSSC. It has also been found that dimethylaminophenyl group cause dye decomposition on solar cells. To solve the dye degradation problem, porphyrin dyes with tertiary arylamine groups serving as the donor groups were prepared. Our studies show that tertiary arylamine groups are able to stabilize the dyes adsorbed on the solar cells. The electronic and optical properties of these p-extended porphyrins were measured using UV-Vis spectroscopy, life-time and steady state fluorescence spectroscopy, cyclic voltammetry and transient spectroscopy. Their photovoltaic performances were tested in dye-sensitized solar cells.

Reference

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3. L. L. Li and E. W. Diau, Chem. Soc. Rev., 2013, 42, 291-304.
4. A. Yella, H.-W. Lee, H. N. Tsao, C. Yi, A. K. Chandiran, M. K. Nazeeruddin, E. W.-G. Diau, C.-Y. Yeh, S. M. Zakeeruddin and M. Grätzel, Science, 2011, 334, 629-634.
5. S. Mathew, A. Yella, P. Gao, R. Humphry-Baker, B. F. Curchod, N. Ashari-Astani, I. Tavernelli, U. Rothlisberger, M. K. Nazeeruddin and M. Gratzel, Nat. Chem., 2014, 6, 242-247.
6. G. Di Carlo, A. O. Biroli, F. Tessore, S. Caramori and M. Pizzotti, Coord. Chem. Rev., 2018, 358, 153-177.
7. Y. Hu, S. Yellappa, M. B. Thomas, R. G. W. Jinadasa, A. Matus, M. Shulman, F. D'Souza and H. Wang, Chem Asian J, 2017, 12,