Using the density functional theory (DFT) simulation of the adsorption of atomic oxygen and hydrogen on the surface of nickel and platinum nanoparticles on graphite substrates with various defects, we calculate the binding energies of adatoms and changes in the density of states of metal atoms upon interaction with adatoms. It is found that the density of states decreases more when oxygen is adsorbed at the top of a metal cluster than when oxygen is adsorbed at the interface between the metal cluster and the graphite substrate. For hydrogen adsorption, no such dependences are found. It is shown that the effect of monatomic defects of the substrate is insignificant in the case of adsorption of both types of adatoms.

The quantum-chemical modeling of copper nanoparticles on graphite substrates with various defects shows a stronger decrease in the density of the states of copper atoms during hydrogen adsorption near the interface compared to similar adsorption far from it. It is also found that, in general, the effect of the substrate on the atomic and electronic structures of the copper nanoscale system is less pronounced than that of the gold nanoscale system.

The morphologies and local electronic structures of titanium coatings deposited on the surfaces of highly oriented pyrolytic graphite were determined. Chemical compositions of the oxides formed on the coating surfaces were established. A theoretical model was developed describing the changes in the TiO_x oxides (1.75 < x < 2) band gap depending on the duration and temperature of the titanium film annealing procedure in oxygen. The effective activation energy of oxygen diffusion in TiO_x (1.75 < x < 2) was determined, and the pre-exponential factor of the diffusion coefficient was estimated.

Using the method of quantum-chemical modeling of a system of gold nanoparticles on a graphite substrate with various defects, a decrease in the density of states of gold atoms during the adsorption of hydrogen near the interface is shown. Substrate defects, such as vacancies and cutoffs of the graphene plane, contribute to a decrease in the density of states during the adsorption of hydrogen atoms.

An experimental study of molecular hydrogen adsorption on single gold nanoparticles of various sizes deposited on the surface of highly oriented pyrolytic graphite (HOPG) was carried out by means of scanning tunneling microscopy and spectroscopy. The effect of size on the HOPG/Au system was established. Hydrogen was dissociatively chemisorbed on the surface of gold nanoparticles with an average size of 5–6 nanometers. An increase in the size of nanoparticles to 10 nm or more led to hydrogen chemisorption being inhibited and unable to be detected.

The features of deuterium adsorption on the surface of gold nanoparticles deposited on highly oriented pyrolytic graphite (HOPG) were determined. The results showed that deuterium adsorption on gold nanoparticles takes place at room temperature. The results also showed that the filling of the nanoparticles’ surfaces with the adsorbate occurs from the graphite–gold interface until the entire surface is covered by deuterium. The results of quantum chemical simulations are used to explain the experimental data. A simple model of the observed effects is proposed.