Copper modified TiO2 and g-C3N4 catalysts for photoreduction of CO2 to methanol using different reaction mediums

Abstract

In this study, Cu/TiO₂ and Cu/g-C₃N₄ catalysts were tested for CO₂ reduction to methanol. The catalysts were prepared by the wet impregnation method and, characterized by XRD and FESEM. The product identification and yield were determined using a GC with FID. The CO₂ photoreduction process was performed in each of the following reaction mediums: H₂O, NaOH, KOH, Na₂CO₃, K₂CO₃, NaHCO₃ and KHCO₃. The efficiency was studied by comparing the methanol yield for each. A slurry type photoreactor with a UV lamp of 365 nm wavelength was used. CO₂ photoreduction to methanol using NaOH as the reaction medium registered the highest yield of 431.65 μmole/g-cat•hr. This is due to the higher solubility of CO₂ in the alkali as compared to that of the other reaction mediums, the ability of NaOH to serve as a hole scavenger owing to the formation of OH•ions and the higher selectivity of NaOH solution for CO₂ photoreduction to methanol. It was obvious the choice of reaction medium affected the photoreduction of CO₂ to methanol. The trend of results indicated the use of NaOH as a reaction medium improved the efficiency of the photoreduction process. The findings from this research could promote research in the field of photocatalysis by improving the yield which will encourage the support for methanol economy.