Low-Temperature Oxidation of Methane on Rutile TiO(2)(110): Identifying the Role of Surface Oxygen Species.

Understanding the microkinetic mechanism underlying photocatalytic oxidative methane (CH(4)) conversion is of significant importance for the successful design of efficient catalysts. Herein, CH(4) photooxidation has been systematically investigated on oxidized rutile(R)-TiO(2)(110) at 60 K. Under 355 nm irradiation, the C-H bond activation of CH(4) is accomplished by the hole-trapped dangling O(Ti)(-) center rather than the hole-trapped O(b)(-) center via the Eley-Rideal reaction pathway, producing movable CH(3)(•) radicals. Subsequently, movable CH(3)(•) radicals encounter an O/OH species to form CH(3)O/CH(3)OH species, which could further dissociate into CH(2)O under irradiation. However, the majority of the CH(3)(•) radical intermediate is ejected into a vacuum, which may induce radical-mediated reactions under ambient conditions. The result not only advances our knowledge about inert C-H bond activation but also provides a deep insight into the mechanism of photocatalytic CH(4) conversion, which will be helpful for the successful design of efficient catalysts.