Performance analysis of externally reflected photoreactor for CO₂ conversion to methanol using f-C₃N₄/ZnV₂O₆ S-scheme photocatalyst

In this study, a novel externally reflected photoreactor was compared with a solar photoreactor for photocatalytic CO₂ conversion in liquid phase using proton-rich functionalized carbon nitride (f-C₃N₄) modified ZnV ₂O₆ nanosheets. Effects of operating parameters such as reaction medium and catalyst loading were investigated to maximize yield rates. The performance of photoreactor for CO₂ photoconversion was higher in the presence of NaOH solution as a reducing agent than H₂O and KHCO₃ solution. ZnV₂O₆ modified with f-C₃N₄ (1:1) ratio registered the highest CH₃OH yield. In an externally reflected photoreactor, the maximum yield rate of CH₃OH over ZnV₂O₆/f-C₃N₄ (1:1) nanosheets was 4665.6 μmole g-cat ⁻¹; 1.25 folds higher than solar photoreactor (3742.1 μmole g-cat⁻¹). The externally reflected photoreactor was found very efficient for photocatalytic CO₂ conversion due to its higher light harvesting efficiency compared to the solar photoreactor. The increased yield rates in externally reflected photoreactor were because the reflector provides greater photon flux for dynamic CO₂ reduction. Possible reaction mechanisms for photoconversion of CO₂ over ZnV₂O₆/f-C₃N₄ S-scheme photocatalyst were proposed in order to understand the function of the reflector and the movement of electrons and holes.