International project
20-52-76018 ERA_t
Ion-implanted two-dimensional materials for single-site catalysis
The development of catalysts for many chemical processes was aimed at reducing the particle size of the catalytically active elements. The lower limit of this trend can be called the fixation of individual catalytically active atoms on the surface of various substrates. Such single site catalysts (SCC) can be considered as the limiting case of heterogeneous catalysts, when the size of active metal nanoparticles traditionally used in heterogeneous catalysis is reduced to the size of one atom. BCC research is one of the most innovative and rapidly developing areas of materials science. Despite some progress made, the further development of the field is hampered by the shortcomings of the existing chemical methods traditionally used for the production of relevant materials, for example, the agglomeration of atoms and particles on the surface, as well as their penetration into the volume of the substrate material. At the same time, recent advances in the synthesis of various high surface-to-volume nanostructures that are ideal substrates for BCC, as well as advances in controlled low-energy ion implantation (AI), are opening up unique new possibilities in the field of catalysis_cc781905-5cde-3194- bb3b-136bad5cf58d_ for further development and production of inexpensive and highly efficient hybrid nanocatalysts. h-BN is one of the most advanced nanostructured materials with a high specific surface area. The development of highly efficient BCCs based on them with the use of transition metals opens up wide opportunities for the study and development of one of the most innovative areas at the intersection of materials science and catalysis in recent years - single-center catalysis on nanostructures. Within the framework of this project, using an interdisciplinary approach that involves the use of advanced physical and chemical methods, as well as modern theoretical modeling, the development and comprehensive study of new BCCs is proposed. To this end, two-dimensional nanostructures based on boron nitride will be synthesized, methods for their functionalization by hydrogenation, chlorination, fluorination, as well as control of the defect structure in order to control the sorption characteristics of the substrates, will be developed. The most efficient schemes for the synthesis of bcc based on modified h-BN will be determined and a comprehensive assessment of their catalytic characteristics in reactions of great fundamental and practical importance will be carried out: carbon monoxide oxidation and methane reforming. Theoretical modeling methods will be used to study the features of the electronic structure of bcc, their adsorption properties, as well as energy barriers in the studied chemical reactions.
The main results of the project will be the development of technologies for obtaining new types of nanomaterials, the improvement of the low-energy AI process, a fundamental understanding of the relationship between the atomic and electronic structures of the material and its catalytic properties, theoretical modeling and experimental search for the most effective metals and methods for their activation for specific catalytic reactions.
Project participants
Prof. Stefan Fachko
Institute of Ion Beam Physics and Materials Research, Center im. Helmholtz Dresden-Rossendorf
GERMANY
d.ph.m.s., leading researcher Pavel Sorokin
National Research Technological University "MISiS"
RUSSIA
Prof. Konstantinos Triantafillidis
Aristotle University of Thessaloniki
GREECE
Brief report of the work on the project for the first year of execution
Methods for the synthesis of 2D h-BN and h-BNxOy using the boron oxide CVD technology, plasma-chemical synthesis from BCl3 and NH3, and the direct reaction of boric acid with ammonia have been studied. The efficiency of synthesis of nanocrystalline h-BN with a crystallite size of 6-10 nm in the reduction of boric acid in ammonia is shown. Abstract—The functionalization of the surface of boron nitride by hydrogen atoms in a hydrogen microwave plasma has been studied. It is shown that such treatment leads to an increase in the interplanar spacing along the c axis by 6–7%, which is associated with the hydrogenation of boron nitride. Abstract—The functionalization of the surface of boron nitride by chlorine and fluorine atoms during its high-temperature treatment with ammonium chloride and fluoride has been studied. A method for the functionalization of boron nitride in a hydrofluoric acid solution has been developed, which makes it possible to create structural defects on the surface of boron nitride.
The efficiency of the method of catalytic etching of h-BN powder particles with silver nanoparticles in order to form a defect structure is shown. As a result of the action of silver nanoparticles at a high temperature (950°C), pores are formed on the surface of the h-BN plate to a depth of several atomic layers. A similar heat treatment without Ag nanoparticles leads to the formation of pores only in the h-BN surface layer. The use of a powder consisting of defective h-BN particles as a substrate makes it possible to form transition metal nanoparticles with a size of less than 1 nm on their surface.
Catalysts Me/h-BNxOy (where Me = Cu, Ni, Pt) were synthesized and their catalytic activity was studied. It is shown that the replacement of nitrogen with oxygen in boron nitride leads to an increase in its catalytic activity. It has been established that the presence of oxygen centers leads to an increase in the catalytic activity of platinum, but inhibits the activity of copper and nickel, which is associated with a different redistribution of electron density in these metals.
The possibility of using phthalocyanine complexes as precursors of iron-based monatomic catalysts is shown. The deposition of iron phthalocyanine on the surface of h-BN leads to the formation of single atoms, while the oxidation of the organic framework does not significantly affect the metal content. The resulting Fe1/h-BN systems showed activity in the CO oxidation reaction with a conversion start temperature of 150°C.
To study the possibility of implantation of metals into the near-surface layers of boron nitride, modeling was carried out using the molecular dynamics method with the energies of metal atoms ~ 10^1 eV. The energy at which the fraction of metal atoms lying between the first and second h-BN layers is maximum was estimated. Then, within the framework of the electron density functional theory, a theoretical study of the catalytic activity of the h-BN system with an implanted metal atom was carried out. As an h-BN model with a defect, we considered a two-layer film with a boron vacancy located in the upper layer. The transition metal atom was placed under the vacancy between the layers on the assumption that such a defect was formed as a result of irradiation of h-BN with metal ions. The change in the total energy of the system in the density functional theory during the dissociative adsorption of methane on a defect is used as the activity index of the described center. Of all metals, the atoms of the end of the periods of transition metals, starting with Ni, are active. In this case, only for Cu and Ag, a significant magnetization of the edge nitrogen atoms of the vacancy defect was observed. Obviously, this circumstance plays a decisive role in the activity of this center in the radical mechanism of hydrogen abstraction from methane.