The heat of adsorption of methanol on clean and oxygen pre-covered Pt(111) surfaces was measured in the temperature range of 100 to 160 K using Single Crystal Adsorption Calorimetry (SCAC). Our ultrahigh vacuum calorimeter, which also includes capabilities for AES, LEED and ISS, routinely achieves pulse-to-pulse standard deviations in heat measurements of 0.5 kJ/mol using methanol pulses containing only 0.02 ML. Averaging 8 runs reduces this to below 0.2 kJ/mol. These measurements provide the heat of formation of methoxy, an important intermediate in several catalytic reactions, including methanol reforming for highly pure H2. Above 125K, methanol is known to react with pre adsorbed oxygen adatoms to form methoxy and co-adsorbed OH (Akhter et. al., Surf. Sci.,167, 1986, 101):

CH3OH(g)+Oads-->CH3Oads+OHads, at 125K< T <160 K.

 

Recently our group experimentally determined the heat of formation of OHads on Pt(111) to be -226.8 kJ/mol, using this value we have determined the heat of formation of adsorbed methoxy and compared this value to theoretical DFT work. Heats of adsorption of methanol were also measured on clean Pt(111) at 100K, as well as on the amorphous methanol multilayer, and compared to prior TPD measurements.