X-ray photoelectron spectroscopic study for the adsorption of acetic acid and ethylenediamine on iron and nickel

Abstract

The interaction of acetic acid and ethylenediamine with vapor deposited and oxygen precovered iron and nickel was investigated by means of X-ray photoelectron spectroscopy. Acetic acid dissociates proton of -OH group on iron and nickel at 300 K to give acetate, CH 3COO _. The coexistence of acetyl group, CH 3CO, is suggested from the O 1s/C 1s intensity ratio and the spectral features. The interaction of the acid with oxygen precovered surfaces also gives acetate as a result of acid-base reaction with surface oxygen as base forming water. Adsorption of ethylenediamine on the metals at 300 K gives the anion, NH 2CH 2CH 2NH _, by losing proton which produces, probably, the dianion, N̄HCH 2CH 2N̄H, during heating to ≈ 340 K. On the preoxidized surfaces where the oxygen coverage, θ, is less than one monolayer, the surface oxygen on nickel is removed as water by the interaction with ethylenediamine while that on iron is not. In cases of θ 62 1, the adsorption is predominantly molecular.