The modifying effect of added metals on the surface of platinum catalyst used for ammonia oxidation

Abstract

The surface of Pt-10%Rh catalyst has been coated by vacuum evaporation with Al, Mg, Zr, and Pd layers of a thickness of 1–25 nm, and long-term laboratory investigations have been carried out on its activity, catalytic etching, and mass losses during ammonia oxidation. The composition of the surface was examined by Auger electron spectroscopy and by an X-ray microprobe. It was found that contamination of the catalyst by the above metals decreases its catalytic properties, speeds up the etching of its surface, and increases platinum losses. The results obtained are in agreement with the oxide mechanism for the etching process and for the explanation of platinum losses.