THERMAL GENERATION OF CH3(G) FROM CH3OH ADSORBED ON OXYGEN-COVERED MO(110) - C-O BOND STRENGTH CONSIDERATIONS FROM MOLECULAR-ORBITAL THEORY

By use of the atom superposition and electron delocalization molecular orbital theory and a surface cluster model, it is found that O atoms (formally O2-) and CH3O bind most strongly on the highest coordination site of Mo(110). Compared to the 3.7-eV strong C-O bond in methanol formed by binding CH3. and OH., the forming of a methoxy anion by binding CH3. to O2- on the Mo surface generates an electron that is promoted to the surface conduction band, and this promotion weakens the C-O bond strength to about 1.4 eV. This explains the thermal desorption results of Serafin and Friend, who observed CH3.(g) formation on heating a Mo(110) surface with adsorbed methoxy to 590 K.