The chemisorption of organophosphorus compounds at an Al(111) surface

The reactive chemisorption of three organophosphorus compounds have been investigated at clean and oxidised Al(1 1 1) surfaces using X-ray photoelectron spectroscopy (XPS). Phosphoric acid, trimethyl ester (or trimethylphosphate, TMP, O=P(OCH3)(3)), and methyl phosphonic acid and dimethyl ester (or dimethylmethylphosphate, DMMP, O=P(CH3)(OCH3)(2,)) were adsorbed from the gas phase, but this approach proved unsuccessful for methyl phosphonic acid (MPA, O=P(CH3)(OH)2) due to decomposition in the gas phase. NIPA was therefore adsorbed from either an aqueous or an ether solution placed onto the aluminium. sample in a helium atmosphere. Core binding energies for the P-OCH3, P-CH3, P-O and P=O groups are reported and the decomposition pathways for the three compounds discussed, The P-CH3 bond is stable at both clean and oxidised aluminium surfaces up to temperatures of 570 K, whereas the P-OCH3 bond can be broken even at room temperature. Decomposition of all three molecules requires clean aluminium sites and is hindered by high concentrations of adsorbed species. (C) 2001 Elsevier Science B.V. All rights reserved.