Efficient Photocatalytic Conversion of Methane into Ethanol over P-Doped g-C3N4 under Ambient Conditions

Photocatalytic conversion of methane with water and oxygen into ethanol was achieved over P-doped g-C3N4 (CNP) under ambient conditions. The optimized photocatalyst exhibited an ethanol production rate of 51 mu mol g(-1) h(-1) at 25 degrees C, 1 atm. A systematic study showed that the superior photocatalytic activity over CNP could be attributed to its enhanced light absorption and charge carrier separation and migration. To clarify the mechanism of the methane conversion process, intermediates in the reaction were studied by electron spin resonance spectroscopy and in situ diffuse reflectance infrared Fourier transform spectroscopy. In the reaction, a boosted activity of oxygen reduction reaction was achieved over CNP, generating H2O2. Hydroxyl radicals that originated from H2O2 were confirmed to be key species to activate methane, enabling the direct conversion of methane into ethanol under ambient conditions. Monodentate methoxy was also detected, and a possible mechanism of ethanol formation was proposed. This system provided a promising way to activate methane and convert it into highly value-added chemicals under mild conditions.