DYNAMIC PHASE-BEHAVIOR OF BASE-METAL NOBLE-METAL CATALYST PARTICLES .3. GRAPHITE-SUPPORTED IRON IRIDIUM

As part of a program designed to study the structure of bimetallic particle phase behavior and surface chemistry, iron-iridium particles supported on graphite were studied by true differential calorimetry, Mossbauer spectroscopy, X-ray diffraction, and transmission electron microscopy. The phase behavior of the supported particles was determined to be a complex function of the sequence of oxidation and reduction treatments. One point stands out as being of particular significance to the catalysis community: at least two chemically different reduced surfaces were produced. One reduced surface was iron-like, and the other the surface of a true iron-iridium alloy. The type of dynamic phase behavior observed is similar to the behavior of iron-rhodium particles extensively studied in earlier work.