Surface structure and catalytic activity of rapidly quenched amorphous iron based alloys: II. Effect of hydrochloric acid treatment

The surface structure of Fe 80B 20 and Fe 40Ni 40B 20 amorphous alloys in the as-received state and after HCI treatment was studied by X-ray photoelectron spectroscopy. The surface composition and valence state determined in depth were related to the catalytic activity and selectivity revealed in CO+H 2 reaction. It was established that on the shiny side of the Fe 80B 20 sample deep oxidation took place due to the removal of the boron oxide layer by HCI etching, while on the dull side the originally porous layer became smooth resulting in the formation of a compact oxide layer decreasing thereby the accessible metal sites. On the other hand, on the Fe 40Ni 40B 20 alloy, after removing the prevailing boron oxide and iron oxide layer, an increased number of nickel and iron sites was responsible for the enhanced catalytic activity. Accordingly, on pure iron-boron alloy the catalytic activity considerably decreased whereas on iron-nickel-boron alloy not only a six-fold activity increase was measured but the olefin selectivity was significantly diminished due to the hydrogen activating function of nickel.