Adsorption of hydrazine and ammonia on aluminium

Abstract

The adsorption and decomposition of hydrazine and ammonia by clean polycrystalline aluminium surfaces have been studied by X-ray photoelectron spectroscopy. At 85 K both ammonia and hydrazine are adsorbed molecularly, with N(1 s) peaks at 400.5 eV. At 290 K hydrazine is initially adsorbed to give an N(1 s) peak at about 399 eV, but with time (and further exposure) the position of the peak maximum drift to lower N(1 s) values, finally approaching 397 eV after heating the ad-layer to 390 K. These observations are interpreted in terms of a slow dissociative chemisorption process: N 2H 4(a) → NH 2(a) → NH(a) → N(a). There is no doubt that the NN bond in hydrazine is broken and that hydrogen ad-atoms formed inhibit the subsequent adsorption of N 2H 4 at 290 K. Ammonia dissociates more slowly than hydrazine to give mainly amine (NH 2) species at 290 K.