Zn-Cu promoted TiO2 photocatalyst for CO2 reduction with H2O under UV light

The photocatalytic reduction of CO2 has been studied aiming to find a useful application for such low cost and abundant raw material. Besides reducing CO2 in the atmosphere, the process can contribute for the generation of high energy products (CH4 and CH3OH). The reaction was performed in liquid phase, batch, at 25 °C, with the photocatalyst (1 g/L) maintained in suspension. UVC lamp (18 W, 254 nm) was chosen as the radiation source. Photocatalysts were prepared using oxides of titanium, copper and zinc. Commercial TiO2 (P-25, Degussa) was utilized as reference. Techniques such as N2 adsorption, XRF, SEM-EDS, XRD, XPS, DRS UV–vis and TPD-CO2 were used for photocatalysts characterization. Catalysts having specific area ranging from 36 to 52 m2/g and bandgap energies varying from 3.0 to 3.3 eV were obtained. TPD-CO2 results showed different strengths of CO2 adsorption for each photocatalyst. In the performance tests, CH4 production achieved the range of 126–184 μmol/gcat after a 24 h-irradiation period. Regarding the photocatalysts tested, it was observed increased CH4 formation in the following order: TiO2 (P-25) ∼ TiO2 < 2%CuO/TiO2 < 2%CuO–19%ZnO/TiO2. Results indicate that the interaction between CO2 and the photocatalyst influences the photocatalytic activity.