Copper-decorated TiO2 nanorod thin films in optofluidic planar reactors for efficient photocatalytic reduction of CO2

As the global warming which is mainly caused by atmospheric CO2 and the depletion of fossil fuels becomes more and more serious, the method for reducing CO2 with high efficiency and low energy consumption is urgently needed. In this letter, an effective photocatalytic reduction of CO2 by using Cu2+TiO2 nanorod thin films photocatalyst in optofluidic planar reactors under UV light was studied. Cu2+ -deposited TiO2 nanorod thin films were fabricated by using the combination of hydrothermal method and ultrasonic-assisted sequential cation adsorption method. The samples were characterized by X-ray diffraction (XRD), UV–vis diffuse reflectance spectra (DRS), scanning electron microscope (SEM), energy dispersive spectroscopy (EDS) and transmission electron microscope (TEM). Their photocatalytic activities were evaluated by reduction of gas-phase CO2, and the main products were methanol and ethanol. The experiment results showed that when the doped concentration of Cu2+ was 0.02 M, the reaction product yield reached the maximum, and the methanol and ethanol yields were 36.18 μmol/g-cat h and 79.13 μmol/g-cat h at a flow rate of 2 mL/min and under the reaction system temperature of 80 °C. The highly efficient photocatalytic activities of Cu2+TiO2 nanorod thin films in the reduction process of CO2 were attributed to the incorporation of Cu2+ ions and one-dimensional (1D) nanostructure which improved the limitations of photon transfer. In addition, the photocatalytic mechanism was discussed to understand the experimental results over the Cu2+ modified TiO2 nanorod thin films.