Preparation and Characterization of Nanocrystalline Noble Metal Films by MOCVD

摘要

Noble metals such as palladium, platinum, iridium and ruthenium were prepared in ah horizontal hot-wall MOCVD apparatus using metal-acetylacetonates as precursors. A wide range of deposition conditions (T_(dep)=250-800°C and P_(total)=0.1-500 Torr) was explored and the effects on the features of the films were investigated. Structural and morphological characteristics were found to be very sensitive to those conditions. By the use of appropriate conditions and reactive gas (H_2 or O_2), high-purity, dense and oriented films were obtained. On the other hand, films consisted of agglomerated nanocrystalline particles of pure metals or metal oxides were also possible to obtain. The size of nanoparticles varied from 15 to 100 nm depending on deposition conditions. The nanocrystalline nature of films was used for applications requiring large surface area such as electrocatalysts for electrochemical reactions of technological interest. Nanocrystalline platinum films prepared by MOCVD exhibited superior electrocatalitic activity than platinum electrocatalysts prepared by conventional methods in the hydrogen evolution reaction. In addition, iridium-ruthenium oxide films showed to be very promising for the oxygen evolution reaction.