ENHANCEMENT OF SELECTIVE DECOMPOSITION - ADSORPTION AND REACTION OF METHANETHIOL ON CARBON-COVERED W(001)

Selective decomposition of methanethiol (CH3SH) on carbon-covered W(00 1) to produce methane is enhanced by 75% compared to the clean surface . The maximum enhancement requires only 0.25 monolayers (ML) of preads orbed C. On a surface percovered with 0.8 ML of C, the methane desorbs in peaks at 460 and 550 K compared to 360 K on the clean surface, sug gesting a greater stability in the C-S and C-H bonds. Increased intram olecular bond stability is confirmed by the temperature dependence of the S 2p and C 1s soft X-ray photoemission. Methyl thiolate, CH3S, for ms upon adsorption at 100 K. Chemisorbed methanethiol, which is not st able on the clean surface, is also observed between 100 and 300 K. The chemisorbed thiol decomposes to form additional thiolate. The thiolat e reacts along three competing pathways. It undergoes rehydrogenation and desorbs as methanethiol, it selectively decomposes to form desorbe d methane and adsorbed S, or it totally decomposes to form S, C, and d esorbed H-2.