Highly selective photocatalytic oxidation of methane to methyl hydroperoxide

Partial oxidation of methane into primary oxidation products with high value remains a challenge. In this work, photocatalytic oxidation of methane (CH 4 ) with high methyl hydroperoxide (CH 3 OOH) selectivity is achieved using pure titanium oxide (TiO 2 ) without any cocatalyst at room temperature and atmospheric pressure. The CH 3 OOH production rate can reach up to 2050 ± 88 µmol·g −1 ·h −1 at pH ≈ 7.0 with 100% selectivity in the liquid product. The stable reaction cycle can reach more than 30 times. This low-cost system achieves superior CH 4 conversion activity and selectivity compared with similar work. The energy of hydrogen peroxide (H 2 O 2 ) to adsorbed hydroperoxyl radical (⋆OOH) has a significantly lower reaction energy than conversion to adsorbed hydroxyl radical (⋆OH) on the (210) surface of the TiO 2 . The ⋆OOH preferentially combines with methyl radical (·CH 3 ) to form the most energetically favorable CH 3 OOH. The mild oxidative environment of this system prevents the reduction of CH 3 OOH to CH 3 OH or over-oxidation of CH 4 , which ensures the final CH 3 OOH with high selectivity and stability. This work provided a low-cost but highly efficient method to achieve partial oxidation with superior selectivity, i.e., to convert CH 4 into high-value chemicals.