Interaction of acetic acid with ethylenediamine on a Ni(111) surface studied by XPS

Abstract

The interaction of ethylenediamine with a Ni(111) surface was investigated in the temperature range 170–420 K by means of X-ray photoelectron spectroscopy. Molecularly absorbed species were predominant below 290 K giving the C1s and the N 1s peaks at 286.4 and 399.9 eV (at 250 K) and at 286.0 and 399.7 eV (at 290 K), respectively. The amount dehydrogenated species increased during heating up to 420 K resulting in a variation of the N 1s binding energy as 399.7 → 397.7 → 397.5 → 397.7 eV. The variation was correlated with successive dehydrogenation reactions such as ▪ The interaction of acetic acid with molecularly absorbed ethylenediamine below 200 K brought about the appearance of the N 1s peak at 401.9 eV assignable to the ammonium form of nitrogen at the expense of the N 1s peak at 400.1 eV. The remaining N 1s peak is located at 399.6 eV. Ethylenediamine absorbed at 290 K, showing the N 1s peak at 399.7 eV, gave no ammonium form even after interaction with acetic acid at 220 K. These results indicate that a part of ethylenediamine was unidentate and the rest was bidentate (chelating) on the Ni(111) surface at 250 K and all of the molecules were bidentate at 290 K. When acetic acid was adsorbed on a clean Ni(111) surface at 165 K, formation of an acetyl group was indicated besides acetate.