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

Abstract

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.