Abstract :
The variation of surface compositions on amorphous Ni80.4W1.5P18.1 alloy by O2 oxidation and H2 reduction treatments
have been studied by XPS, UPS and ISS. It shows that addition of tungsten in the amorphous Ni–P alloy leads to dramatic
changes of the relating component distributions in the surface layers before and after these treatments. Oxidation of a
Ni80.4W1.5P18.1 amorphous alloy in 1 bar of oxygen at 513 K caused a significant segregation of nickel in different oxide
states at the surface. The subsequent reduction of the oxidized surface with 1 bar hydrogen at 553 K resulted in only a small
portion of Ni and P being reduced into elemental states, while most of them was found to combine to form a kind of nickel
phosphate compound. On the other hand, under the same conditions, the oxidation and reduction of a Ni80P20 alloy gave rise
to metallic Ni and elemental P as the predominate species on the alloy surface. The addition of W in the amorphous alloy
might act as nuclei for a favorable formation of the phosphate structure which was proposed to be an active species for
hydrogen-relating catalytic reactions. q1999 Elsevier Science B.V. All rights reserved
