Enhanced Effect of Metal Sulfide Doping (MgS-TiO 2 ) Nanostructure Catalyst on Photocatalytic Reduction of CO 2 to Methanol

The conversion of CO 2 gas from the global emission to methanol can be a route to look at in addressing greenhouse gas (GHG) issues. Photocatalysis has been attracting attention in the conversion of CO 2 to methanol, as it is seen to be one of the most viable, economic, and sustainable strategies. The biggest hindrance to the use of metal oxide photocatalysts was the poisoning by sulfur content in the CO 2 gas feedstock. Therefore, in the development of photocatalysts using metal oxide-based additives, the metal needs to be in the form of metal sulfides to avoid catalyst poisoning due to the presence of H 2 S. The magnesium sulfide-based TiO 2 (MgS-TiO 2 ) photocatalyst has not been synthesized and studied for its photocatalytic potential. In this study, a novel MgS-TiO 2 photocatalyst was synthesized using a combination of wet impregnation and hydrothermal method and characterized to determine the physical and chemical properties of the photocatalyst. Characterization results have shown the presence of MgS on the native TiO 2 photocatalyst. The optimization of MgS-TiO 2 formulation was conducted, wherein the MgS and TiO 2 ratio of 0.5 wt % has been shown to give the highest methanol yield of 229.1 μmol/g·h. The photocatalytic parameter optimization results showed that temperature and catalyst loading were the most important factors that impacted the photocatalytic process. In contrast, reaction time had the least significant effect on the CO 2 photocatalytic reduction to methanol. This concludes that the MgS-TiO 2 photocatalyst has potential and can be used for the photocatalytic reduction of CO 2 to methanol.