Visible light photoreduction of CO$_{2}$ using CdSe/Pt/TiO$_{2}$ heterostructured catalysts

A series of CdSe quantum dot (QD) sensitized TiO$_{2}$ heterostructures have been synthesized, characterized, and tested for the photocatalytic reduction of CO$_{2 }$in the presence of H$_{2}$O. ~Our results show that these heterostructured materials are capable of catalyzing the photoreduction of CO$_{2}$ using visible light illumination ($\lambda \quad >$ 420 nm) only. The effect of removing surfactant caps from the CdSe QDs by annealing and using a hydrazine chemical treatment have also been investigated. The photocatalytic reduction process is followed using infrared spectroscopy to probe the gas phase reactants and gas chromatography to detect the products. Gas chromatographic analysis shows that the primary reaction product is CH$_{4}$, with CH$_{3}$OH, H$_{2}$, and CO observed as secondary products. Typical yields of the gas phase products after visible light illumination ($\lambda \quad >$ 420 nm) were 48 ppm g$^{-1}$ h$^{-1}$ of CH$_{4}$, 3.3 ppm g$^{-1}$ h$^{-1}$ of CH$_{3}$OH (vapor), and trace amounts of CO and H$_{2}$.