Sintering studies on platinum black catalysts. Part 2.—Effect of temperature of treatment and method of preparation on the sintering process

Abstract

The sintering of a platinum black catalyst prepared by HCHO reduction of H₂PtCl₆ and Pt(NH₃)₄(OH)₂ between 0 and 60°C has been investigated under a variety of conditions. Particle sizes were studied as a function of temperature of pretreatment in a standard thermal cycle between 100 and 480°C. Increased temperature produced larger particle sizes but this process was reversed above 400°C. The effect of water vapour was investigated as were variations in the standard thermal cycle. It was concluded that hydrogen treatment cleaned the surfaces of the crystallites, that a welding process occurred, and that hydrogen may have reacted with sub-surface oxygen. The inhibition of sintering is explained in terms of carbon segregation at the surface of the platinum black.