DYNAMICS OF CATALYTIC CORROSION OF THE SURFACE OF A PLATINUM CATALYST IN AMMONIA OXIDATION REACTION

The dynamics of intensive rearrangement of the surface of a platinum catalyst in the course of ammonia oxidation is investigated using electronic microscopy. It is shown that the process has two stages differing in the type of the structures formed and in the rates of their growth. The first stage involves the formation of parallel grooves (''facets''); the second step comprises the accumulation of separate crystals with regular cut, which grow significantly faster than the facets. In the second stage, an induction period can be observed. It is concluded that the gas phase transfer of platinum vapor, formed because of nonequilibrium sublimation from the catalyst surface due to recuperation of the energy of chemical acts in the crystal lattice of the catalyst, plays a dominant role in this process.