193Ir and 57Fe Mössbauer characterisation of iridium/iron bimetallic catalysts for methanol synthesis

Fe-Ir/MgO catalysts derived from the [Et4N]2[Fe2Ir2(CO)12] cluster precursor, which exhibit a high activity in the synthesis of methanol from CO and H2, were studied by 193Ir and 57Fe Mössbauer spectroscopy. The study extends from the precursors via the fresh to the aged catalysts. The presence of iridium in the metallic state as well as the presence of trivalent, divalent and alloyed iron is detected. The different structural features of catalysts prepared from mixed-metal cluster compounds and from inorganic salt precursors are discussed.