— A nanostructured gold–nickel coating has been synthesized on the surface of pyrolytic graphite. Its physicochemical properties have been studied by scanning tunneling microscopy and spectroscopy, Auger spectroscopy, mass spectrometry, and other methods. It has been found that the coating consists of clusters formed by gold and nickel nanoparticles. It has been shown that an electric field can inhibit or stimulate the adsorption of hydrogen on gold and the reduction of the oxidized surface of nickel nanoparticles with carbon monoxide. The mechanisms of the influence of the field on the chemical processes involving H 2 and CO are different. Quantum-chemical simulation has made it possible to determine the values of the energy barriers for CO adsorption on nickel nanoparticles.

Measurements are reported of the increase in catalytic CO oxidation rate on gold nanocoatings obtained by applying a positive or negative electrical voltage of variable magnitude to a coating. In experiments on an initial mixture of 1.8

Экспериментально определено увеличение скорости каталитического окисления СО на покрытиях из наночастиц золота при подаче на них электрического напряжения различной полярности и величины от внешнего источника. В условиях эксперимента при 430 °С, атмосферном давлении, начальном составе смеси 1.8% СО + 10.2% О 2 + Ar и начальном размере частиц покрытия 0.2–3 нм последовательное увеличение подаваемого положительного напряжения U вначале приводит к росту скорости окисления СО на 28% при U = +10 В, плавно снижающемуся до 20% при U = +30 В. Подача отрицательного напряжения менее эффективна: вначале скорость окисления растет на 12% при U = –10 В, а затем снижается до 7% при U = –30 В. Выполнены квантовохимические расчеты теплот ассоциации СО и О 2 с простейшим электронейтральным или электрически заряженным кластером золота Au 3 , а также теплот реакций Au 3 CO + O → Au 3 CO 2 и Au 3 CO 2 → Au 3 + CO 2 для различных зарядов Au 3 -содержащих комплексов. По результатам расчетов предложено объяснение увеличения скорости каталитического окисления СО на покрытиях из наночастиц золота, электрически заряженных с помощью внешнего источника напряжения.

The interaction of CO and H-2 with single clusters of gold and copper-based nanoparticles in the presence of an electric field has been studied. It is shown that depending on the direction of the electric field vector, the adsorption of molecules from the gas phase is stimulated or inhibited. Mechanisms of influence of the field on chemical processes are proposed.

The possibility of increasing the catalytic activity of a coating of gold nanoparticles during the oxidation of carbon monoxide (CO) by applying a positive electric voltage to the coating is experimentally established for the first time. Applying voltage U = +10 V to the coating increases the rate of CO oxidation by 28% at 430°C and atmospheric pressure for the initial mixture of 1.8% CO + 10.2% O2 + Ar.

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 influence of the electric field on the interaction of CO with oxidized copper-nickel nanoparticles is studied. It is established that the restoration of the surface of nanoparticles is possible at potentials of φ ≤ +5 V applied to the sample relative to the ground potential, and at φ ≥ +5 V it is difficult. The most probable mechanism of the influence of the electric field on the reduction rate of the surface oxide is related to the spatial orientation of CO molecules.

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 possibility of increasing the catalytic activity of a coating of palladium nanoparticles during CO oxidation by applying a positive electric voltage to it is experimentally established. Applying U = +10 V on a coating leads to an increase in the rate of CO oxidation by 14% at 330°С, atmospheric pressure, and with the initial composition of the mixture of 1.8% CO + 10.2% О 2 + Ar.

The increase in the rate of catalytic oxidation of CO on palladium nanosized coatings is measured when electric voltages of different polarities and magnitudes are applied to the coatings from an external source. Under the experimental conditions at 330°С, atmospheric pressure, and the initial composition of the mixture of 1.8% CO + 10.2% О2 + an Ar application of a positive voltage of +10 or +30 V to the coating leads to the CO oxidation rate increasing by 14 or 42%, respectively. Applying a negative voltage of –10 or –30 V results in less acceleration of oxidation by 4 or 12%. It is shown that the effect of the voltage supply does not depend on the particle size in the coating and increases linearly with increasing voltage. The quantum-chemical calculations of the heat of the association of CO and O2 with the simplest neutral or electrically charged palladium Pd2 clusters are calculated. It is found that the creation on Pd2 of a positive charge leads to a decrease in the difference between the heat of association of CO and O2 by 16.7 kcal/mol, while the creation on Pd2 of a negative charge leads to a smaller effect: a decrease in the specified difference by 10.6 kcal/mol. Based on the results of the calculations, an explanation is proposed for the increase in the rate of catalytic oxidation of CO on palladium electrically charged using an external voltage source is proposed.

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.

The paper presents the results of studies of coatings formed by gold, copper, nickel, and palladium nanoparticles in various combinations on the surface of highly oriented pyrolytic graphite. It was shown that the structure of the bimetallic coatings and the adsorption of hydrogen, oxygen, and carbon monoxide on them are affected by interactions between dissimilar nanoparticles.

This paper presents the results of quantum chemical modeling of hydrogen atom adsorption on AuNi, AuCu, and CuNi bimetallic nanoparticles. It is established that changes in the electronic structure of these clusters depend both on the transformation of the atomic structure of the cluster and on charge transfer. The effect of charge transfer manifests itself most noticeably in clusters consisting of atoms with slightly different lattice constants Cu and Ni. With strong differences in this parameter, changes in adsorption properties will be determined to a greater extent by the transformation of the atomic structure.

It has been experimentally shown that the catalytic activity of a platinum nanocoating in CO oxidation can be improved via the application of a positive electric potential to the coating. A potential of +10 V leads to an 18% increase in the CO oxidation rate at 250°C, atmospheric pressure, and the initial mixture composition of 1.8% CO + 10.2% O2 + Ar.