SO2 adsorption and desorption kinetics on Pt(111)

Abstract SO 2 /Pt(111) adsorption and desorption kinetics in the temperature range 160–300 K were investigated by molecular beam technique and TDMS measurements. The initial sticking probability s 0 SO 2 turns out to be unity independent of surface temperature, and the S SO 2 (θ) curves indicate the operation of a precursor mechanism. The TDMS spectra of SO 2 could be analysed by means of second order desorption kinetics indicating that SO 2 seems to be adsorbed dissociatively even at low temperatures (at least for small coverages). The resulting kinetic parameters are interpreted as values determining the recombination process (SO) ad + O ad → (SO 2 ) ad , assuming the SO 2 molecule to desorb directly. Combining these results with those on SO dissociation and recombination recently obtained by us, it was possible to complete our proposed potential energy diagram for sulfur-oxygen reactions on Pt(111).