Visible light responsive CdS sensitized TiO2 nanorod array films for efficient photocatalytic reduction of gas phase CO2

In this letter, an effective photocatalytic reduction of CO2 by using CdS-Cu2+/TiO2 nanorod array films photocatalyst under visible light was studied. TiO2 nanorod array films were prepared by the hydrothermal method, after which Cu2+ ions and CdS quantum dots (QDs) were deposited on the TiO2 nanorod arrays using the ultrasonic-assisted sequential cation adsorption method and successive ionic layer adsorption and reaction (SILAR) method respectively. The composition, morphology and optical property of the samples were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), X-ray photoelectric spectroscopy (XPS) and UV-vis diffuse reflectance spectra (DRS). The loading amount of CdS QDs was regulated by controlling the deposition cycles which demonstrates correspondingly optical behaviors. Their photocatalytic activities were evaluated by reduction of gas-phase CO2 to estimate the ethanol yield under various operating parameters, including the CdS QDs concentration, CO2 flow rate and reaction temperature. The experiment results showed that when the SILAR method cycle deposition was two, the reaction product yield reached the maximum, and the ethanol yield was 109.12 mu mol/g-cat h at a flow rate of 4 mL/min and under the reaction system temperature of 80 degrees C. The highly efficient photocatalytic activities of CdS-Cu2+/TiO2 nanorod array films in the reduction process of CO2 were attributed to the combination of one-dimensional (1D) nanostructure with decorating Cu2+ ions and CdS QDs, which restrain recombination of the electron hole pairs and broaden the visible-light response. In addition, the photocatalytic mechanism was discussed to understand the experimental results over the CdS-Cu2+/TiO2 nanorod array films.