Highly efficient photocatalytic conversion of CO2 to hydrocarbons using visible-active co-doped TiO2/ PDMS nanocomposite

Considering the rising emission of the carbon dioxide (CO2) and its detrimental effects on the environment, conversion of CO2 into value-added products has emerged as a critical area of research. In particular, the photocatalytic reduction of CO2 into fuels using solar energy has recently attracted significant attention. In this study, a nanocomposite of co-doped titanium dioxide (TiO2) nanoparticles with polydimethylsiloxane (PDMS) is utilized for photocatalytic reduction of CO2. Photo, chemical, and thermal-stable PDMS serves as a transparent flexible binder for photocatalyst nanoparticles, facilitating their usage and recycling. To make TiO2 photocatalysts visible-active, reduce the charge recombination rate, and improve the charge transport and lifetime, they are co-doped using nonmetal nitrogen (N) and metal silver (Ag) with different concentrations. Following the optical, morphological, and structural analysis of the photocatalysts, their photocatalytic performance is evaluated in a fixed gas bed photoreactor. The TiO2 photocatalyst shows the lowest yield for methane (3.2 μmol/g catalyst) and ethane (0.42 μmol/g catalyst). While, the yield for methane and ethane using Ag-N-TiO2 photocatalyst reaches 34.42 and 1.01 μmol/g catalyst, respectively. Remarkably, when the PDMS-Ag-N-TiO2 nanocomposite is employed, the highest methane and ethane yield of 122.21 and 10.22 μmol/g catalyst are achieved, respectively. Thus, in the presence of PDMS polymer, instantaneous quadrupolar interactions occur between its siloxane groups and carbon dioxide molecules. This promotes the adsorption of greater amounts of CO2, making it more available for the photocatalytic reduction reaction and thereby enhancing hydrocarbon production.