Triphase Photocatalytic CO2 Reduction over Silver‐Decorated Titanium Oxide at a Gas–Water Boundary

Photocatalytic CO2 reduction reaction (CO2 RR) is an attractive process to convert CO2 into valuable chemicals. But this reaction is often restricted by the poor mass transfer of CO2 in the liquid phase. Here, we have developed a triphase photocatalytic CO2 RR system by supporting Ag-decorated TiO2 nanoparticles at a gas-water boundary with hydrophobic-hydrophilic abrupt interfacial wettability. Such a triphase system allows the rapid delivery of gas-phase CO2 to the surface of photocatalysts while maintaining an efficient water supply and uncovered active sites. Ag-TiO2 supported at the gas-water boundary showed a CO2 reduction rate of 305.7 μmol g-1 h-1 , without hole scavengers, approximately 8 times higher than the nanoparticles dispersed in the liquid phase. Even using diluted CO2 (10 %) as the reactant, the CO2 RR activity was superior to most reported Ag-TiO2 based photocatalysts using pure CO2 . The findings provide a general strategy to promote the interfacial CO2 mass transfer to improve photoactivity and selectivity.