Synergistic conversion of CO₂ into C1 and C2 gases using hybrid in-doped TiO₂ and g-C₃N₄ photocatalysts

Achieving high-efficiency photocatalytic conversion of CO₂ into value-added chemicals remains a challenge. This study synthesizes In-doped TiO₂ and g-C₃N₄ composites (In-TiO₂/g-C₃N₄) via a facile and reliable method. The as-synthesized In-TiO₂/g-C₃N₄ produces CO, CH₄, and C₂H₄ under UV, and CO and CH₄ under visible light from gaseous CO₂ and H₂O vapor. A prolonged photocatalysis results in the continuous production of the same set of carbonaceous compounds over 30 h, with a photonic yield of ∼ 40%. The yield of C₂H₄ with In-TiO₂/g-C₃N₄ is ∼ 11-times greater than the sum of In-TiO₂ and g-C₃N₄. The CO₂ adsorption isotherms show that In-TiO₂ acts as a CO₂ adsorbent and photocatalyst whereas g-C₃N₄ mainly works as a photocatalyst. In-situ FTIR study reveals the formation of CH₄ and C₂H₄ on In-TiO₂/g-C₃N₄. Time-resolved photoluminescence indicate that In-doping facilitates charge transfer and a strongly coupled g-C₃N₄ induces cascaded charge transfer. This leads to inhibited charge recombination and long-lived charge carriers.