Sustained, photocatalytic CO₂ reduction to CH₄ in a continuous flow reactor by earth-abundant materials: Reduced titania-Cu₂O Z-scheme heterostructures

Photocatalytic conversion of CO₂ and water vapor to hydrocarbon fuels is a promising approach for storing solar energy while reducing greenhouse gas emissions. However, still certain issues including low product yields, limited photocatalyst stability and relatively high cost have hampered practical implementation of this technology. In the present work, a unique strategy is adopted to synthesize a stable, and inexpensive photocatalyst comprised of earth-abundant materials: a reduced titania-Cu₂O Z-scheme heterostructure. Under illumination for 6 h, the optimized reduced titania-Cu₂O photocatalyst enables 0.13 % photoreduction of highly diluted CO₂ with water vapors to 462nmol g⁻¹ of CH₄ while showing excellent stability over seven testing cycles (42 h). Our studies show the Z-scheme inhibits Cu₂O photocorrosion, while its synergistic effects with reduced titania result in sustained CH₄ formation in a continuous flow photoreactor. To the best of our knowledge stability exhibited by the reduced titania-Cu₂O Z-scheme is the highest for any Cu-based photocatalyst.