Effect of water vapor and hydrogen treatments on the surface structure of Ni 3 Al foil

Abstract

Abstract We have developed a water vapor treatment followed by hydrogen reduction to modify the surface structure of Ni 3 Al foils in order to obtain high catalytic activity. The Ni 3 Al foils were heat treated in water vapor at 873 K for 1 h followed by H 2 reduction at 873 K for 1 h. The effects of the water vapor treatment and the H 2 reduction on the surface structure of the Ni 3 Al foils were investigated by means of scanning electron microscopy and synchrotron radiation X-ray photoemission spectroscopy. Both Ni and Al in the surface layer of the Ni 3 Al foil were oxidized during the water vapor treatment; fine NiO particles with a high density were formed on the outermost surface, accompanied by the formation of oxide layers of Al(OH) 3 and NiAl 2 O 4 /Al 2 O 3 beneath the NiO particles. The NiO particles were reduced to metallic Ni and the Al(OH) 3 was decomposed to Al 2 O 3 , whereas the NiAl 2 O 4 and Al 2 O 3 remained unchanged during the subsequent H 2 reduction, forming a Ni-enriched porous structure on the surface layer of NiAl 2 O 4 /Al 2 O 3 .