X-ray photoelectron spectroscopic studies of unsupported and supported rhenium using argon-ion bombardment

Identification of 4f binding energies of rhenium in various valencies has been attempted using X-ray photoelectron spectroscopy in conjunction with successive in situ reduction by means of argon-ion bombardment. For the first time a valency state attributable to oxidic ReIII has been identified. Ion bombardment has also proved useful in probing catalyst–support interaction and the effects of catalyst promoters. The iron oxide support interacted strongly with part of the supported rhenium of several valencies, making it difficult to reduce the rhenium by ion bombardment, while the weakly interacting rhenium was easily reduced. When potassium ion was present in the Re/iron oxide system, rhenium interacting strongly with the support was mainly in the 7+ valence state.