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Nitrogen – doped porous carbon obtained by precipitation of acetonitrile vapors on template C–CaO nanoparticles for electrochemical applications

Shlyakhova E.V.¹, Fedoseeva Y.V.¹, Nischakova A.D.¹, Vorfolomeeva A.A.¹, Bulusheva L.G.¹, Okotrub A.V.¹

1 – Nikolaev Institute of Inorganic Chemistry, Novosibirsk, Russia

shlyakhovaev@niic.sbras.ru

Porous nitrogen-containing carbon nanomaterials are promising electrode materials for new generation electrochemical current sources due to developed pore texture, high electronic conductivity and high thermal stability. The synthesis of nitrogen-containing carbon nanomaterials was carried out in several stages: thermal decomposition of organic calcium salts of tartaric, glutaric, and adipic acids at 750 °C, subsequent CVD carbon deposition using acetonitrile as a source, and removal of template particles by treatment with an HCl solution. It has been established that as a result of the thermolysis of calcium salts, composite template particles are mainly consisting of CaO and carbon. The deposition of acetonitrile vapor on their surface leads to the formation of nitrogen-containing graphite-like layers containing 3–5 at.% nitrogen. Removal of template particles from the material leads to the formation of nanopores in the carbon material. The pore size of carbon materials varies from 3 to 30 nm, the gravimetric surface area is from 188 to 832 m²/g, and the specific pore volume is from – 0.4 to 1.6 cm³/g. The influence of the nature of calcium salts of carboxylic acids, which were the sources of template particles, on the structure and electrochemical characteristics of nitrogen-containing carbon nanomaterials was investigated.

Acknowledgement.This work was supported by the Russian Science Foundation, grant 19-73-10068.

N-doped graphene nanoflakes for catalysis and tribology

Stolbov D.N.^1,2, Chernyak S.A.¹, Usol’tseva N.V.² Savilov S.V.¹, Parfenov A.S.³

1 – Department of Chemistry, Lomonosov Moscow State University, Moscow, Russia

2 – Ivanovo State University, Nanomaterials Research Institute, Ivanovo, Russia

3 – Ivanovo State Academy of Medicine, Ivanovo, Russia

stolbovdn@gmail.com

High demand for carbon nanomaterials (CNM) can be explained by the variety of their chemical and physical properties, as well as high potential of structure modification and possibility of introduction into various matrices to obtain various composite materials [1]. Changes in electronic structure and the formation of different surface defects can be achieved by the partial replacement of carbon atoms by heteroatoms, in particular, nitrogen ones.

In this work, pristine and N-doped graphene nanoflakes (GNF and N-GNF) were synthesized by template pyrolysis and studied by set of physicochemical methods. To study the effect of doping, the samples were studied as cobalt catalyst supports for the Fischer-Tropsch process, as well as additives for industrially produced lubricants.

It was found that the introduction of nitrogen atoms increases the dispersion of the deposited metal, thereby increasing the activity of the catalyst. Also, in the model system, the largest decrease in the friction coefficient (up to 42 %) was exhibited by N-GNF at a concentration of 1.5 wt% at high loads.

Acknowledgement.This work was supported by the Russian Foundation for Basic Research (grant no. 18-29-19150_mk) and supported by the Ministry of Education and Science of the Russian Federation in the framework of the state task for Ivanovo State University (Application No FZZM2020-0006)

References:

[1] Savilov S.V., Ivanov A.S., Egorov A.V., Kirikova M.N., Arkhipova E.A., Lunin V.V. Effect of the morphology of structured carbon nanomaterials on their oxidizability. Russ. J. Phys. Chem. A N.2, V.90, 2016, 429-435

Thermal shock as a new approach for the synthesis of porous MoS₂

Stolyarova.S.G.¹, Kotsun A.A.², A. V. Okotrub,¹ L. G. Bulusheva¹

1 – Nikolaev Institute of Inorganic Chemistry SB RAS, Novosibirsk, Russia

2 – Novosibirsk State University, Novosibirsk, Russia

stolyarova@niic.nsc.ru

The development of technology and user needs requires more powerful devices, energy sources, and materials. Metal ion batteries are widely used now and they can be easily modified by changing electrode materials. MoS₂ is actively explored as a promising anode material. Theoretical specific capacity of MoS₂ provided by the intercalation and conversion reactions is 669 mAh g^-1, which is 2 times higher than the corresponding value for graphite. The main disadvantage of bulk MoS₂ as an anode material is the short battery life. The MoS₂-based material can be stabilized by using a carbon component, but an alternative approach is to obtain nanostructured MoS₂. In this case, decreased size and formation of defects and pores contribute to a high capacity and decreased resistance of the material and increased diffusion rate of lithium ions. Traditionally, nanostructured porous sulfides are synthesized by self-assembling in solution or with use of templates.

We offer a simple synthesis of porous nanostructured MoS₂ materials by decomposition of ammonium tetrathiomolybdate (NH₄)₂MoS₄ aerogel in thermal shock conditions in an inert atmosphere at different temperatures. The obtained MoS₂ materials possess a three-level architecture: thin carbon skin/expanded MoS₂ layers/internal intertwined MoS₂ nanosheets. The presence of pores was confirmed by the nitrogen adsorption-desorption method and their size was 2-35 nm. Increasing the temperature leads to the creation of the extended MoS₂ layers at the plate surfaces. The lateral size and the number of adjacent layers on the surface and inside were also grown. The resulting materials were tested in lithium-ion half-cells. The porous MoS₂ synthesized at 700 °C showed superior rate capability 817 mAh g^-1 at a current density of 2 A g^-1 and 1139 mAh g^-1 during cycling at 0.1 A g^-1.

Acknowledgment.This work was supported by the Russian Science Foundation, grant 19-73-10068.

References:

[1] T.Stephenson, Z. Li and D. Mitlin, D. Energy Environmental Science, 7, 209 (2014).

Polarons In Two-dimensional Pnictogens: DFT Study

Vasilchenko V.¹, Gonze X.^1,2, Levchenko S.¹, Perebeinos V.³, Zhugayevych A.¹

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

2 – Université Catholique de Louvain, Louvain-la-Neuve, Belgium

3 – University at Buffalo, NY, United States

vasilii.vasilchenko@skoltech.ru

Present work is dedicated to the study of small polarons in emerging semiconductors: two-dimensional pnictogens. They are great candidates for application in electronics and the work done will allow for better understanding of the nature of charge carriers in these materials. Up to this point, no information on their polaronic character has been provided and generally they were considered as free electrons and holes. First-principles cluster calculations and finite-size scaling show stability of a small hole polaron in blue phosphorene and arsenene. It is localized on a phosphorus atom, leading to the contraction of the bonds around it. Commonly used hybrids including PBE0, HSE06, B3LYP show consistent results with the adiabatic polaron relaxation energy slightly below 0.1 eV for phosphorene and 0.15 eV for arsenene. The adiabatic barriers for motion of the polaron are small compared to the frequency of strongly coupled phonons implying barrierless motion of the polaron.

Multifunctional Brownmillerites for Efficient Energy Harvesting and Storage Applications

Durga Sankar Vavilapalli¹, M. S. Ramachandra Rao², Shubra Singh¹

1-Crystal Growth Centre, Anna University, Chennai – 600025, Tamil Nadu, India.

2-Nano Functional Materials Technology Centre, Department of Physics, Indian Institute of Technology Madras, Chennai 600036, India

v.durgasankar@yahoo.com

In search of new and advanced materials for energy harvesting and storage applications, we come across certain brownmillerite (A₂B₂O₅) multiferroic compounds, which are also called oxygen deficient perovskites (ABO₃). Oxygen vacancies and magnetic ordering in these compounds lead to possess smaller bandgap (less than 2eV) compared to regular perovskites. These materials are promising candidates for Ferroelectric photovoltaic (PV) applications, as it enhances the optical and electrical properties. A well-known multiferroic material, BiFeO₃, featuring relatively low solar cell efficiency (~ 7 %) due to the relatively large band gap (2.6 eV), has attracted much attention. In the present case we have developed several multifunctional brownmillerite compounds and these are promising materials for PV, photocatalytic and energy storage application. The optical and catalytic properties of these compounds make them potential photocatalysts for waste water treatment². Co-existence of transition metal-oxide active sites and oxygen vacancies in these brownmillerites is useful for efficient energy storage application. These studies point towards the role of multifunctional brownmillerites in the field of energy and environmental applications. The results will be presented in detail.

References:

1. Durga Sankar Vavilapalli et al. "Nitrogen Incorporated Photoactive Brownmillerite Ca₂Fe₂O₅ for Energy and Environmental Applications" Scientific Reports 10 (1), 2713 (2020).

1. Durga Sankar Vavilapalli et al. "Multifunctional brownmillerite KBiFe₂O₅: Structural, magneto-dielectric, optical, photoelectrochemical studies and enhanced photocatalytic activity over perovskite BiFeO₃" Solar Energy Materials and Solar Cells 200, 109940 (2019).

1. Durga Sankar Vavilapalli et al. "Photoactive Brownmillerite Multiferroic KBiFe₂O₅ and Its Potential Application in Sunlight-Driven Photocatalysis" ACS Omega 3 (12), 16643-16650 (2018).

The influence of chlorine and chloroauric acid treatment on electromechanical properties of SWCNT fibers

Vershinina A.I., Gordaya O.R., Lomakin M.V., Shandakov S.D.

Kemerovo State University, Kemerovo, Russia

annaver89@mail.ru

The effects of mechanical deformation on the electrical properties of carbon nanotubes are of interest in electromechanical devices. Single-walled carbon nanotubes (SWCNTs) doping with chloroauric acid (HAuCl₄) and treatment in gaseous chlorine (Cl₂) are effective methods for improving their electrical properties [1,2]. In this work, we study the electromechanical behavior of SWCNT fibers functionalized in chloroauric acid and chlorine.

The fibers have been fabricated from SWCNT films which were synthesized by floating catalyst (aerosol) CVD [3,4]. A part of the SWCNT films was treated in gaseous chlorine and then we prepared fibers using a recently developed wet pulling technique (WP) [5] with ethanol (C₂H₅OH), acetone (C₃H₆O), dimethyl sulfoxide (DMSO) (C₂H₆OS), and tetrahydrofuran (THF) (C₄H₈O) as solvents. We also obtained fibers from the pristine SWCNT films by WP technique using ethanol as solvent. These fibers were treated with a 0.1 M aqueous solution of HAuCl₄ diluted with ethanol to form 10 mM solution. The fibers' length were 10 mm. The electromechanical properties of the fibers were investigated using a tensile stage on the base of a microscrew and a stepper motor.

The study by a two-contact method employing the NI ELVIS II workstation showed the change of the SWCNT fibers' electrical resistance after the treatment in HAuCl₄ and Cl₂. The gauge factor (GF) of the fibers exhibited monotonic increase with deformation after the treatment by chloroauric acid, and the maximum GF value was found to be about 2. The GF of the samples treated in chlorine using ethanol, acetone, and THF as solvent had maximum value of about 3, while for the fibers prepared with DMSO, the value of GF reached ~4.

Acknowledgement.This work was supported by the Russian Foundation for Basic Research (project no. 18-29-19169) and by the Ministry of Science and Higher Education of the Russian Federation (project no. FZSR-2020-0007 in the framework of the state assignment no. 075-03-2020-097).

References:

[1] A.P. Tsapenko, A.E. Goldt, E. Shulga, et al. Carbon, 130, 448–457 (2018)

[2] A.I. Vershinina, M.V. Lomakin, D.M. Russakov, et al. Russian Physics Journal, 61, 1185–1186 (2018)

[3] A. Moisala, A.G. Nasibulin, D.P. Brown, et al. Chemical Engineering Science, 61, 4393–4402 (2006)

[4] A. Moisala, A.G. Nasibulin, S.D. Shandakov, H. Jiang, E.I. Kauppinen, Carbon, 43, 2066–2074 (2005)

[5] M.A. Zhilyaeva, E.V. Shulga, S.D. Shandakov, et al. Carbon, 150, 69–75 (2019)

Preparation of functional carbon coatings on the surface of hollandite-like ceramics with composition of K_1.53(Сu_0.76Ti_7.24)O₁₆

Vikulova M.A.¹, Tsiganov A.R.¹, Artyukhov D.I.¹, Gorshkov N.V.^1,2

1 – Yuri Gagarin State Technical University of Saratov, Saratov, Russia

2 – N.N. Semenov Federal Research Center for Chemical Physics RAS, Moscow, Russia

vikulovama@yandex.ru

Carbon-ceramic composite materials based on potassium titanate with hollandite structure are of great research interest due to the possibility of their application in potassium ion energy storage devices and as fillers in polymer matrices for elements of modern electronics producing. The advantages of using carbon are that it can be easily adapted to suit your needs. Carbon materials provide high surface area as well as good electronic and ionic conductivity. The use of carbon coatings makes it possible to compensate for the low electrical conductivity of potassium titanate with hollandite structure, which will increase the specific energy of electrode materials based on them.

However, obtaining carbon coatings on the surface of titanate ceramics is a difficult task. This may be partly due to the incompatibility of C with the TiO₂ lattice, along with the high temperature and pressure requirements for such materials production. Commonly used methods for preparing TiO₂-C composites include flame pyrolysis, high-temperature sintering, hydrothermal or sol-gel technology. In addition, it is usually required an external carbon source with little or no control over the degree or arrangement of the С atoms. Hence, another popular approach is to modify the TiO₂ surface with C nanostructures such as carbon nanotubes, graphene, reduced graphene oxide, and carbon nitride.

In this regard, the aim of this work is to study the possibility of obtaining hollandite-like ceramics K_1.53(Cu_0.76Ti_7.24)O₁₆ with a carbon-modified surface by various methods.

Acknowledgement.This work was supported by the Russian Science Foundation, grant 19-73-10133.

Phosphorus-filled single-walled carbon nanotubes: synthesis, characterization and electrochemical properties

Vorfolomeeva A.A.¹, Stolyarova S.G.¹, Bulusheva L.G.¹, Okotrub A.V.¹

1 – Nikolaev Institute of Inorganic Chemistry, SB RAS, Novosibirsk, Russia

vorfolomeeva@niic.nsc.ru

Single-walled carbon nanotubes (SWCNTs) can fill with various inorganic compounds changing the electronic structure and chemical activity of the material [1]. Phosphorus can penetrate the cavity of a nanotube, forming various chain structures and nanoclusters, or be embedded in the graphene lattice with the formation of a phosphorus-carbon bond. SWCNTs have good conductivity and provide mechanical and chemical stability during electrochemical cycling. However, their theoretical capacity in the lithium-ion batteries (LIBs) does not exceed 600 mAh g^-1, which is not enough for use in new high-capacity devices. Phosphorus has a high theoretical specific capacity 2595 mAh g^-1 [2]. Combination of SWCNTs as a conductive base and phosphorus in the internal cavity can allow the creating an effective electrode material for LIB LIBs.

One of the most effective and simple methods of synthesis of filled SWNTs is the ampoule method of synthesis. The filling was carried out in an H-shaped ampoule, in one part of which phosphorus was placed, and in another – SWCNTs. By varying such parameters as the ratio of reagents, synthesis time, and synthesis temperature, we achieve 8 at.% of phosphorus content according to XPS. To increase the degree of filling of nanotubes, the synthesis conditions were modified and ultrasonic treatment was introduced. Ultrasonic treatment was carried out at different stages of obtaining materials, due to which it was possible to increase the phosphorus content to 15 at.% according to XPS.

The resulting series of samples were studied as an anode material in LIBs. The best characteristics were demonstrated by a sample with a phosphorus content of 15 at.% and showed a specific capacity of 760 mAh g^-1 at a current density of 0.1 A g^-1, which is three times higher than the capacity of the initial SWCNTs (245 mAh g^-1 at a current density of 0.1 A g^-1). This effect is associated with the reversible reaction of the interaction of lithium with phosphorus with the formation of intermediates of various compositions Li_xP and with the reaction of lithium intercalation between bundles of nanotubes.

References:

[1] J.C.Zheng, M.C.Payne, Y.P.Feng, and A.T.L.Lim, Physical Review B, 67, 15 (2003)

[2] W.Liu, H.Zhi and X.Yu, Energy Storage Materials, 16 (2019)

Deagglomeration of carbon nanotubes via rapid expansion of supercritical suspensions

Zuev Ya. I.¹, Vorobei A. M.¹, Novikov I. V. ², Fedorov F. S. ², Goldt A. E. ², Krasnikov D. V. ², Parenago O.O. ¹, Nasibulin A.G. ²

1 – Kurnakov Institute of General and Inorganic Chemistry of Russian Academy of Sciences, Moscow, Russia

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

vorobei@supercritical.ru

The main difficulty in the preparation of carbon nanotubes (CNTs) composites is the agglomeration of CNTs due to huge intermolecular attraction forces between them. The commonly used method for CNT de-aggregation is ultrasonication which sometimes can be harmful to CNT structure. In this work, we use a RESS (the Rapid Expansion of Supercritical Suspensions) method as an additional tool for CNTs de-bundling. In the RESS process, CNTs are suspended in a supercritical fluid (SCF) in a high-pressure vessel. After storing the suspension for the required amount of time at high pressure, it is rapidly sprayed into the precipitation chamber at atmospheric pressure. Following the spraying, the fluid rapidly expands behind the nozzle and undergoes a transition from supercritical to a gas phase. The microstructure of the dispersed material changes, mainly due to the rapid and non-uniform pressure drop.

It was shown that RESS treatment leads to a significant increase in CNT bulk volume (up to 11 times). Usage of supercritical nitrogen instead of carbon dioxide is more promising since due to a very low nitrogen critical temperature value there is no risk of the formation of a two-phase liquid-vapour system during fluid rapid expansion, which could bring up capillary effects detrimental to highly disperse materials. It is demonstrated that the dispersion of CNTs strongly depends on nanotubes type. For CNTs obtained from different manufacturers, the value of the increase in specific volume may differ in 10 times.

Moreover, RESS-processed CNTs were used preparation of polyurethane composites. The conductivity of such composites was several orders of magnitude higher than those synthesized without additional treatment. The use of RESS technology also gives a possibility to obtain composites with a percolation threshold of ca. 0.01 %-wt. which is 50 times lower when compared with unprocessed CNTs composites.

Acknowledgement.This work was supported by the Russian Foundation for Basic Research, grant 18-29-06071

Electrocatalytic Activities of Nitrogen Doped Carbon Nanostructures

Ram Manohar Yadav^#*

^#Department of Materials Science and Nano Engineering, Rice University, Houston -77005, USA ^*Department of Physics, VSSD College Kanpur, INDIA-208002

rmanohar28@gmail.com

The conversion of CO₂ into fuels or commodity chemicals, incorporated with intermittent renewable energy sources like solar and wind, is an attractive venture that could offer an alternative solution to both the contemporary energy crisis and environmental issues. Elaborating highly active electrocatalysts for carbon dioxide reduction, oxygen reduction and oxygen evolution reactions are among the most promising areas of materials research. In this regards, chemically modified carbon nanostructures have emerged as a new metal-free electrocatalysts for these reactions due to their low cost, high activity and excellent durability. We have studied nitrogen doped carbon nanostructures (NCNTs, N Graphene etc) as electrocatalysts for oxygen reduction, carbon dioxide reduction and oxygen evolution reactions. The details about the work will be presented in the conference.