A Density Functional Theory and Experimental Study of CO2 Photoreduction to Methanol over α-Sulfur-TiO2 Composite

CO2 reduction is an attractive way for the production of sustainable environment-friendly chemicals. Using the density functional theory employed by DMol3, we calculated the electronic properties of α-sulfur-modified surface of TiO2 (111). We report α-sulfur-TiO2 composite material for selective CO2 reduction to methanol. The α-sulfur-TiO2 catalyst showed higher adsorption for CO2 molecule (reactant) and lower adsorption for methanol (product) as compared to TiO2 catalyst. The introduction of the α-sulfur molecule in the TiO2 catalyst leads to redistribution of the lowest unoccupied molecular orbital (LUMO) and the highest occupied molecular orbital (HOMO). The DFT studies showed that the α-sulfur-TiO2 catalyst reduced the band gap to 2.06 eV from 2.88 (α-sulfur) and 3.2 eV (TiO2). The experimental study was done using photoelectrochemical CO2 reduction. The sulfur-TiO2 catalyst showed higher methanol production (17 mM/h) under visible light as compared to α-sulfur catalyst (8.5 mM/h).