oa The Oxidation of Rhodium-Platinum

The oxidation behaviour of platinum and its alloys at high temperatures is of fundamental importance to its application as both a structural material and a catalyst in a wide range of industrial processes. One of the principal factors determining the efficiency of a catalyst is its surface condition and this in turn depends upon both the initial surface preparation and the changes in surface structure and composition that take place during use. During the manufacture of nitric acid from ammonia a rhodium-platinum catalyst gauze is employed, and under the reaction conditions the surface of the catalyst is altered. The processes involved in this change are not yet fully known, but a study undertaken to provide a more detailed characterisation of the oxide layer formed upon the surface of rhodium-platinum is now reported and may have relevance both to its use as a catalyst in ammonia oxidation and as a structural material.