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.