PHOTOCHEMICAL C-H BOND ACTIVATION OF METHANE ON A PT(111) SURFACE

Methane adsorbed on a Pt(111) surface simply desorbs at almost-equal-to 70 K. However, after the methane-precovered surface is irradiated with 193 nm photons, the intensity of the thermal desorption peak decreases and a new peak of methane at almost-equal-to 260 K grows with the accumulated number of photons. This new desorption peak is attributed to recombination of CH3 and H on Pt (111). It clearly indicates that methane on Pt(111) is photodissociated to yield a chemisorbed CH3 radical and an adsorbed H atom as products. The total cross section of photochemical processes is estimated to be 1. 5 x 10(-19) cm2.