Boosting photocatalytic oxidation by integrating an ultra-thin oil layer at the water-catalyst interface.

The interfacial microenvironment plays a decisive role in reaction performance. Introducing a layer of inert oils that are immiscible with water at a conventional liquid (aqueous solution)-solid (catalyst) two-phase interface to form a novel liquid (water)-liquid (oil)-solid (catalyst) three-phase system could improve catalytic reactions involving gaseous reactants, as many oils exhibit an impressive ability to dissolve substantial volumes of gas. However, the construction and regulation of such liquid-liquid-solid three-phase systems remain challenging. Here, by combining catalyst structure optimization and reaction interface regulation, we designed a liquid-liquid-solid three-phase system featuring an ultra-thin oil layer (L-L(UTO)-S) based on ordered TiO2 porous films. The ordered porous films possess a large surface area and high surface roughness, facilitating the deposition of an ultra-thin oil layer on their surfaces. We investigated its interfacial properties and catalytic performance in a visible-light-driven photooxidation reaction. The ultra-thin oil layer (<1 nm) in this L-L(UTO)-S system synergistically enriches O2 and organic molecules at the reaction interface without substantially inhibiting electron transfer efficiency, thereby markedly enhancing photocatalytic performance compared to the liquid (water)-solid (catalyst) two-phase system. Further studies on the influence of oil thickness in the L-L-S system indicated that the ultra-thin oil layer effectively minimizes the adverse impact on interfacial electron transfer arising from the insulating properties of oil. These findings highlight the importance of rational interface architecture design, and the as-fabricated L-L(UTO)-S system provides a promising route for the further development of high-performance photocatalytic systems.