Enhancing photocatalytic methane oxidation by coupling Pt-mediated charge transfer with hydrophobic triphase interface regulation

The low solubility of methane in water and the resulting gas–liquid–solid mass-transfer limitation severely restrict the efficiency of photocatalytic selective methane oxidation. Herein, Pt-In 2 O 3 catalysts were constructed and further modified with triethoxy-n-octylsilane (OTES) to achieve the synergistic enhancement of charge transfer and triphase mass transport. Pt loading and OTES grafting preserved the bulk crystal phase of In 2 O 3 , while establishing a Pt/In 2 O 3 heterointerface and a hydrophobic surface layer. Pt mainly promoted photogenerated charge separation and interfacial electron transfer, whereas OTES had only a minor effect on the electronic process. Among the catalysts examined, the optimized catalyst showed the best performance, giving a total productivity of 4659.1 μmol g −1  h −1 , a liquid-phase productivity of 4116.7 μmol g −1  h −1 , and a liquid-product selectivity of 88.4%, with the liquid-phase productivity being 1.44 times that of the corresponding catalyst without OTES modification. The activity showed a volcano-type dependence on OTES dosage, indicating an optimal hydrophobic range. Trapping experiments, electron paramagnetic resonance (EPR), and chemical-probe analyses identified ·OH and ·O 2 − /·OOH as the key reactive species involved in the reaction. This work demonstrates that tuning interfacial wettability is an effective strategy for enhancing photocatalytic methane oxidation in water.