The high activation barrier of the C-H bond in methane, combined with the high propensity of methanol and other liquid oxygenates toward overoxidation to CO2, have historically posed significant scientific and industrial challenges to converting methane directly and selectively to energy-dense fuels and chemical feedstocks. Here, we report a unique photocatalyst architecture, silica encapsulated titania decorated with AuPd nanoparticles (TiO2@SiO2-AuPd), that prevents methanol overoxidation on its surface and possesses high selectivity and yield of oxygenates even at high UV intensity. This room-temperature approach achieves high selectivity for oxygenates (94.5%) with oxygenate yield of 15.4 mmol/gcat·h at 9.65 bar total pressure of CH4 and O2. The underlying working principles of the photocatalyst system were further elucidated by tracking the photogenerated radicals and systematically varying the reaction conditions. The catalyst design principle was demonstrated to be generalizable for selective oxidation of other alkanes.
Materials and Methods, Supplementary Text