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 (CH₄) with high methyl hydroperoxide (CH₃OOH) selectivity is achieved using pure titanium oxide (TiO₂) without any cocatalyst at room temperature and atmospheric pressure. The CH₃OOH 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 CH₄ conversion activity and selectivity compared with similar work. The energy of hydrogen peroxide (H₂O₂) to adsorbed hydroperoxyl radical (*OOH) has a significantly lower reaction energy than conversion to adsorbed hydroxyl radical (*OH) on the (210) surface of the TiO₂. The *OOH preferentially combines with methyl radical (·CH₃) to form the most energetically favorable CH₃OOH. The mild oxidative environment of this system prevents the reduction of CH₃OOH to CH₃OH or over-oxidation of CH₄, which ensures the final CH₃OOH 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 CH₄ into high-value chemicals.