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.