Formal Quantum Efficiencies for the Photocatalytic Reduction of CO2 in a Gas Phase Batch Reactor

The photocatalytic reduction of CO ₂ to fuels, or useful products, is an area of active research. In this work, nanoengineering and surface modification of titania were investigated as approaches for improving the CO ₂ reduction efficiency in a fixed-bed gas phase batch photoreactor under UV–vis irradiation. Titania nanotubes were prepared by a hydrothermal method, and TiO ₂ (P25) was surface modified with copper clusters. Unmodified TiO ₂ (P25) was used as the bench-mark comparison. The titania nanotubes and Cu-TiO ₂ materials showed higher efficiency for the photocatalytic reduction of CO ₂ to yield CH ₄ as compared to P25. Carbon monoxide yields were similar for all photocatalysts tested. The photocatalytic reduction of CO ₂ was observed on all photocatalyst tested, with the nanotubes proving to be the most efficient for the production of CH ₄ . The product yields per mass of catalyst observed in this work are similar to those reported in the literature (with similar reactor parameters) but the calculated formal quantum efficiencies for CO ₂ reduction are very low (4.41 × 10 ⁻⁵ to 5.95 × 10 ^-4 ).