CO2 photoreduction using TiO2 nanoflower /UiO-66 composite under UV light irradiation

In the present study, new photocatalysts of TiO2 nanoflower (TNF) with UiO-66 composites (denoted as TNF@ xU) were synthesized and investigated for CO2 photoreduction process. The as-synthesized composites were characterized through XRD, TEM, BET, FTIR, EDS, FE-SEM, PL, EIS, photocurrent response and UV–Vis DRS techniques. It was found that the TNF@ 25%U has the highest activity towards fuel production. The excellent photocatalytic activity of TNF@ xU may be related to its high tendency to adsorb CO2 and improving the separation of electrons and holes due to the strong binding between TNF and UiO-66. In addition, the petal-like structure of TNF creates an additional path for transfer of excited electrons to the surface. The effects of different parameters such as partial pressure of CO2 (PCO2), temperature, partial pressure of H2O (PH2O) and light power for CH4 and CH3OH production were evaluated using response surface methodology (RSM). Examining the effects of temperature and lamp power on the CO2 photoreduction showed that the production of CH4 and CH3OH increased with increasing temperature and lamp power. Also, the production of CH4 and CH3OH increased and then decreased with the increase of the PH2O and PCO2. Moreover, results showed that under optimum conditions (338.15 K, 150 W, PCO2 =70 kPa and PH2O =9 kPa), the maximum CH4 and CH3OH production rate were 41.81 and 1.58 µmol gcat-1 h -1, respectively. Finally, electron-hole transfer mechanism of type I heterojunction was proposed for TNF@ 25%U composite.