Adsorption and decomposition of 2-chloroethyl ethyl sulfide on Pt(111): A temperature programmed desorption and laser-induced thermal desorption/Fourier transform mass spectrometry study

Abstract

Using temperature programmed desorption and laser-induced thermal desorption/Fourier transform mass spectrometry, we have investigated the adsorption and thermal decomposition of 2-chloroethyl ethyl sulfide, a simulant for mustard gas, on Pt(111). At 90 K, sulfide adsorption, through the sulfur atom, is molecular and very strong. Molecular desorption does not occur at low coverages, but at high coverages, the multilayer desorbs at 180 K and a small fraction (15%) of the chemisorbed monolayer desorbs between 220 and 380 K. Decomposition, a major reaction channel (85%) for the chemisorbed monolayer, occurs between 280 and 380 K, producing surface ethylidyne (CCH3) and sulfur, and gaseous HCl, H2 , and C2H4 at low coverages and, in addition, C2H6 and S(C2H5)2 at high coverages. The CCH3 decomposes, releasing H2 , between 450 and 700 K. The remaining surface carbon and sulfur poison the surface for further decomposition of the sulfide. We discuss the decomposition mechanism and the effect of adsorbed atomic O on decomposition.