Tandem photo-oxidation of methane to methanol at room temperature and pressure over Pt/TiO_(2)

In the process of methane(CH_(4))oxidation to methanol(CH3OH),CH3OH is more easily oxidized than CH_(4),resulting in inevitable peroxide phenomenon.In this work,we innovatively proposed a tandem reaction pathway to obtain a photocatalytic oxidation process of CH_(4) with high activity and selectivity.This work confirms that the methyl hydrogen peroxide(CH3OOH),the first product of CH_(4) oxidation by H_(2)O_(2),is then completely reduced to CH3OH in an electron-rich environment.Under irradiation,H_(2)O_(2) was excited into hydroxyl radicals(·OH)and hydroperoxyl radicals(·OOH)on brookite TiO_(2) photocatalyst.The·OH oxidized CH_(4) to form methyl radicals(·CH3),which then reacted with·OOH to form CH3OOH.CH3OOH gained electrons on Pt nanoparticles(NPs)and was reduced to CH3OH.At this point,low concentration of·OH was difficult to further oxidize CH3OH,so that it can exist stably.Under the conditions of room temperature(25°C)and atmospheric pressure,the productivity of CH3OH was 883μmol/(g·h),which was 4 times more than the reported photocatalytic CH_(4) oxidation system with the same reaction conditions,and the selectivity was 100%in liquid products(98.77%for all products).The photocatalyst showed excellent stability and maintained>85%product activity after 9 catalytic cycles.This work contributed to the development of highly efficient and selective CH_(4) photooxidation system under mild conditions.