Catalysis by amorphous metal alloys. Part 2.—Effects of oxygen pretreatment on the catalytic activity of amorphous and crystallised Ni–P alloys

Abstract

The effects of pretreatments for activation of amorphous Ni–P alloy, especially the role of treatment with oxygen, have been studied by estimating the numbers of surface nickels by temperature-programmed reduction of the oxidised species and recording the ESCA spectra of the surface layers. Oxygen treatment followed by reduction with hydrogen creates surface nickels that interact with phosphorus and oxidised nickel and phosphorus species. The number of surface nickels and the strength of the interaction increases with the temperature of the oxygen treatment and are correlated with the catalytic activity. The decrease in the catalytic activity caused by over-oxidation and crystallisation is due to the disappearance of the homogeneity of the amorphous alloy and reconstruction of the structure involving the aggregation of nickel species.