ИСТИНА

The hydrogen isotope exchange reactions arouse special interest, as they are used in nuclear isotope enrichment and thermonuclear fusion techniques. Catalytic properties towards reactions involving hydrogen are inherent in transition d-metals in which the presence of vacant d-orbitals gives rise to the ability to adsorb hydrogen. Metals that complete the transition metal series, Ni, Pd, and Pt, are known to exhibit especially high activities towards H2-D2 exchange and towards hydrogenation of organic compounds. However, the neighboring metals, Cu, Ag, and Au, which have completely filled d-shells, are absolutely inactive at low temperature. Meanwhile, as we have noted, when taken in the nano-sized state, chemically inert gold does show activity towards hydrogen isotope exchange. The H2-D2 exchange can be considered as a model for investigation of organic reactions that involve hydrogen and are catalyzed by gold nanoparticles, as the isotope exchange is always preceded by atomization of the hydrogen molecule. Previously, Н2 + D2 isotope exchange catalyzed by systems containing gold nanoparticles has almost not been studied. The aim of this work was to systematically investigate the effect of the size of gold nanoparticles on their catalytic activity towards hydrogen isotope exchange and to elucidate the relationship between the “size effect” and structural inhomogeneity of the particle surface. For this purpose, gold particles with a wide size variation from 0.7 nm and up to 40 nm were synthesized. The study demonstrated with certainty that increasing the size of γ-Al2O3-supported particles induces a 750-800-fold decrease in the specific catalytic activity at 77 K. The method of preparation of gold particles does not affect the catalytic properties. The nanoparticle catalytic activity was found to be correlated with the presence of low-coordinated gold atoms on their surface.