Improving artificial photosynthesis over carbon nitride by gas–liquid–solid interface management for full light-induced CO₂ reduction to C₁ and C₂ Fuels and O₂

The activity and selectivity of simple photocatalysts for CO₂ reduction remain limited by the insufficient photophysics of the catalysts, as well as the low solubility and slow mass transport of gas molecules in/through aqueous solution. In this study, these limitations are overcome by constructing a triphasic photocatalytic system, in which polymeric carbon nitride (CN) is immobilized onto a hydrophobic substrate, and the photocatalytic reduction reaction occurs at a gas–liquid–solid (CO₂–water–catalyst) triple interface. CN anchored onto the surface of a hydrophobic substrate exhibits an approximately 7.2-fold enhancement in total CO₂ conversion, with a rate of 415.50 μmol m⁻² h⁻¹ under simulated solar light irradiation. This value corresponds to an overall photosynthetic efficiency for full water–CO₂ conversion of 0.33 %, which is very close to biological systems. A remarkable enhancement of direct C2 hydrocarbon production and a high CO₂ conversion selectivity of 97.7 % are observed. Going from water oxidation to phosphate oxidation, the quantum yield is increased to 1.28 %.