Structural and catalytic properties of supported Ni-Ir alloy catalysts for H2 generation via hydrous hydrazine decomposition

Iridium modified Ni/Al2O3 catalysts were prepared using Ni-Al hydrotalcite as precursor and tested in the selective decomposition of hydrous hydrazine for H-2 generation. Compared to Ni/Al2O3, NiIr/Al2O3 catalysts exhibited an increase of the reaction rate up to 6-fold and the H-2 selectivity from 93% to above 99%. The XRD and EXAFS analysis confirmed that Ir and Ni were present in the form of Ni-Ir alloy; and the H-2 differential heat of adsorption is appreciably lowered with increasing the amount of Ir in Ni-Ir alloy. High-temperature reduction, e.g. 700 degrees C, induced the migration of Ir atoms into the Ni bulk and produced a Ni-skin surface. This structural modification is associated with a strongly decrease of activity and selectivity. EXAFS measurements were also performed on different noble metals (NM, Ir, Pt, and Au) modified Ni/Al2O3 catalysts in order to verify the extent of NM-Ni bimetallic bond formation, which was found to correlate with the catalytic performance. (C) 2013 Elsevier B.V. All rights reserved.