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.