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Название: First virtual Bilateral Conference on Functional Materials (BiC-FM)

Автор: Сборник статей

Издательство: Aegitas

Жанр: Техническая литература

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isbn: 9780369404497

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СКАЧАТЬ style="font-size:15px;">      Oxygen evolution reaction on pristine and defective nitrogen-doped carbon nanotubes and graphene

      Murdachaew G.1, and Laasonen K.1

      1) Aalto University, Department of Chemistry and Materials Science, Finland

      [email protected]

      Hydrogen obtained by electrochemical water splitting on a suitable catalyst has raised a lot of interest. The ideal catalyst should be efficient, stable under operating conditions, and composed of earth-abundant elements. Density functional theory simulations within a simple thermodynamic model of the more difficult half-reaction, the anodic oxygen evolution reaction (OER), with a single-walled carbon nanotube as a catalyst, showed that the presence of < 1 % nitrogen reduces the required OER overpotential significantly. We performed an extensive exploration of systems and active sites with various nitrogen functionalities [1] (graphitic, pyridinic, or pyrrolic) obtained by introducing nitrogen and simple lattice defects (atomic substitutions, vacancies, or Stone-Wales rotations). The lowest predicted overpotentials were about 0.4 V, close to what has been measured experimentally for the best-performing nitrogen-doped nanocarbon catalysts. The lowest predicted overpotential of 0.39 V was obtained for a model system with a Stone-Wales defect in combination with pyrrolic nitrogen doping. The most OER-active sites/systems were carbon atoms in the vicinity of Stone-Wales pyrrolic nitrogen, followed by graphitic nitrogen. For the majority of the nanotube-based systems, the third step of the four-step OER mechanism, the formation of attached OOH, is the potential-determining step of the reaction. The nanotube radius and chirality effects were examined by considering OER in the limit of large radius by studying graphene as a model system. They exhibited trends similar to those of the nanotube-based systems but often with reduced reactivity due to weaker attachment of the OER intermediate molecules.

      References:

      [1] G. Murdachaew and K. Laasonen J. Phys. Chem. C, 2018, 122, 25882, https://doi.org/10.1021/acs.jpcc.8b08519

      Kari Laasonen is a professor of physical chemistry in Aalto University (from 2010). He did his M.Sc. in University of Helsinki 1988, PhD. in 1991 in TKK (physics). Before Aalto he worked in EPFL (Lausanne), IBM Research Laboratory (Zurich), University of Pennsylvania (Philadelphia) and University of Oulu. He has specialized to computational chemistry and especially on modelling surfaces and electrochemical reactions. He has also long expertise of modelling reaction in solutions. He has published more 150 papers and these papers have been cited more than 10.000 times.

      Starfish-like phosphorus carbide nanotubes

      Kistanov A. A.1, Shcherbinin S. A.2, Huttula M.1, Cao W.1

      1 – Nano and Molecular Systems Research Unit, University of Oulu, Oulu, Finland

      2 – Southern Federal University, Rostov-on-Don, Russia

      [email protected]

      Recently several allotropes of a novel two-dimensional material, phosphorus carbide (PC), have been predicted theoretically and some of them have already been successfully fabricated [1]. For one of these PC allotropes, α-PC, the possibility of its rolling to a PC nanotube (PCNT) at room temperature under compressive strain has been found [2]. These PCNTs of different sizes exhibit high thermal stability and possess well tunable band gap. In this work, PCNT obtained by the rippling of β0-PC and β1-PC monolayers along their armchair (APCNT) and zigzag (ZPCNT) directions are investigated in the framework of density functional theory.

      It has been found that most of created β-PCNTs possess starfish-like structure (see Figure 1a). The dynamical stability of these β-PCNTs has been verified using ab initio molecular dynamics calculations conducted at 300 K. It is also found that β-PCNTs of the smallest/biggest size consist of 12/44 atoms. According to electronic band structure calculations, β-PCNTs can be semiconductors, semimetals or metals depending on their size and form (see Figure 1b). Therefore, due to their extraordinary form and highly tunable band structure, β-PCNTs may find the application in straintronic, optical and photovoltaic devices.

      Figure 1. (a) Atomic structure and (b) band gap size as a function of size of β0– and β1-APCNT and β0– and β1-ZPCNT.

      Acknowledgement.A.A.K. M.H. and W.C. acknowledges the financial support by the Academy of Finland (grant No. 311934). S.A.Sh. acknowledges the financial support by the Ministry of Education and Science of the Russian Federation (state task in the field of scientific activity, Southern Federal University), theme N BAS0110/20-3-08IF.

      References:

      [1] X. Huang, Y. Cai, X. Feng, W. C. Tan, D. Md. N. Hasan, L. Chen, N. Chen, L. Wang, L. Huang, T. J. Duffin, C. A. Nijhuis, Y. W. Zhang, C. Lee and K. W. Ang, ACS Photonics, 5(8), 3116–3123 (2018)

      [2] S. A. Shcherbinin, K. Zhou, S. V. Dmitriev, E. A. Korznikova, A. R. Davletshin and A. A. Kistanov, J. Phys. Chem. C, 124(18), 10235-10243 (2020)

      Computational search for new high-TC superconductors with subsequent synthesis

      A.G. Kvashnin1, I.A. Kruglov2,3, D.V. Semenok1, A.R. Oganov1,

      1 – Skolkovo Institute of Science and Technology, Moscow, Russia

      2 – Moscow Institute of Physics and Technology, Dolgoprudny, Russia

      3 – Dukhov Research Institute of Automatics (VNIIA), Moscow, Russia

      [email protected]

      Hydrogen-rich hydrides attract great attention due to recent theoretical [1] and then experimental discovery of record high-temperature superconductivity in H3S (TC = 203 K at 155 GPa [2]).

      Here we perform a systematic evolutionary search for new phases in the Fe-H [3], Th-H [4], U-H [5] and other numerous systems under pressure [6] in order to predict new materials which are unique high-temperature superconductors.

      We predict new hydride phases at various pressures using the variable-composition search as implemented in evolutionary algorithm USPEX [7–9]. Among the Fe-H system two potentially high-TC FeH5 and FeH6 phases in the pressure range from 150 to 300 GPa were predicted and were found to be superconducting within Bardeen-Cooper-Schrieffer theory, with TC values of up to 46 K. Several new thorium hydrides were predicted to be stable under pressure using evolutionary algorithm USPEX, including ThH3, Th3H10, ThH4, ThH6, ThH7 and ThH10. Fcc-ThH10 was found to be the highest-temperature superconductor with TC in the range 221–305 K at 100 GPa. Actinide hydrides show, i.e. AcH16 was predicted to be stable at 110 GPa with TC of 241 K.

      To continue this theoretical study, we performed an experimental synthesis of Th-H phases at high-pressures including ThH10. Obteined results can be found in Ref. [10].

      Acknowledgement.This work was supported by RFBR foundation № 19-03-00100 and facie foundation, grant UMNIK № 13408GU/2018.

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