ELECTRON TRANSFER REACTIONS AT THE INTERPHASE BOUNDARY OF THE SURFACE OF A SOLID-MELTING DURING THE SYNTHESIS OF NANOMATERIALS UNDER THE CONDITIONS OF CATIONIC CATALYSIS

Abstract

In order to compare the experimental and theoretically obtained characteristics, an analysis of the interaction of the diamond surface with carbonate- and boron-containing melts was carried out. It is shown that the Fermi level on the surface of a pure diamond crystal is located closer to the boundary of the conduction band, while pure diamond behaves like a classical dielectric. It was established that the adsorption of carbon dioxide on the diamond surface leads to a significant polarization of the surface cluster to the side of the conduction zone. The width of the band gap decreases, but the dielectric character of the cluster does not change, there is no overlapping of zones, that is, the diamond does not acquire the semiconducting and semimetallic character of conductivity. At that time, the adsorption of BO2– on the diamond surface leads to a strong polarization of the surface cluster towards the valence band. At the same time, the width of the band gap decreases slightly, less than in the case of carbon dioxide. Thus, the presence of ВО2– also does not lead to the semiconducting nature of conductivity. The conditions for the occurrence of oxidation-reduction processes at the interface of the electrode/salt melt, where the adsorption of melt ions occurs, are proposed, which leads to the appearance of significant induced dipole moments in the adsorbate particles due to the redistribution of electron density between the adsorbent and the adsorbate. As a result of such redistribution, the position of the Fermi level changes and, as a result, it approaches the bottom of the conduction band (or the border of the valence band), which leads to the transition of the surface layer of the dielectric to the conductive state. Changing the cation-anion composition of the melt allows you to control the rate of redox reactions at the dielectric/melt interface. Obviously, this leads to the fact that in some melts the dielectric begins to exhibit an electrode function and, as a result, acts as an active substrate in high-temperature electrochemical synthesis. The calculation of the cathodic exchange current during one-electron charge transfer through the conduction zone of a solid was carried out using the chosen model of the dependence of the density of electron levels on the energy.