XPS studies on surface electronic characteristics of Ni-B and Ni-P amorphous alloy and its correlation to their catalytic properties

The Ni-B, Ni-P, Ni-B/SiO2 and Ni-P/SiO2 amorphous alloy samples were prepared by chemical reduction with BH4- or H2PO2-. Their amorphous structures were verified by X-ray diffraction (XRD) and extended X-ray absorption fine structure (EXAFS). Transmission electron microscopy (TEM) was used to determine their morphology and particle size. XPS experiments have been carefully designed to characterize the surface electronic state of the as-prepared samples. By comparing with electron binding energies of the pure Ni, B and P, the XPS spectra demonstrated that boron donated electron to nickel in Ni-B alloy, resulting in electron-enrichment of elemental Ni, while no significant electron transfer between Ni and P in Ni-P alloy was observed. Those results seem reasonable to elucidate the different catalytic behaviors of Ni-P and Ni-B amorphous alloy catalysts, such as the hydrogenation activity and sulfur resistance ability. (C) 1999 Elsevier Science B.V. All rights reserved.