ESR EVIDENCE OF HYDROGEN MIGRATION ON SUPPORTED METAL CATALYSTS

The ESR investigation has provided evidence that the resonance at g = 2.10, developed upon heating of noble-metal-supported catalysts in hydrogen, results from the reduction of iron oxide to metallic iron also present on the supported catalyst. The mechanism of the oxide reduction evidently occurs by a sequence of events including hydrogen chemisorption on a metal such as palladium, hydrogen atom transfer to the support and then to iron oxide sites, and subsequent coalescing of iron to form ferromagnetic domains. The relative effectiveness of iron oxide reduction resulting from the presence of various supported metals and supports appears to depend on the relative heats of hydrogen atom sorption compared with the activation energy required for the atom transfer from the metal to the support. © 1968.