Optimum molar ratio of H₂ and H₂O to reduce CO₂ using Pd/TiO₂

This study investigated the optimum moral ratio of CO2 and reductants H2O and H2 to obtain high CO2 reduction performance of Pd/TiO2 photocatalyst. The Pd/TiO2 film photocatalyst is prepared by sol-gel and dip-coating process to form TiO2 film and by pulse arc plasma method to dope Pd. The prepared Pd/TiO2 film was characterized by SEM, EPMA and EELS. The impact of overlapping two Pd/TiO2 films on CO2 reduction performance was also investigated to utilize the light and prepared photocatalyst more effectively. Moreover, this study investigated the characteristics of Pd/TiO2 film to reduce CO2 under the illumination condition of Xe lamp with or without ultraviolet (UV) light. It is found when the moral ratio of CO2/H2/H2O is set at 1:0.5:0.5, the best CO2 reduction performance has been obtained under the illumination conditions of Xe lamp with and without UV light. It is revealed that the moral quantity of CH4 per weight of photocatalyst for overlapped Pd/TiO2 film is 8.14 μmol/g for the moral ratio of CO2/H2/H2O of 1:0.5:0.5 under the illumination condition of Xe lamp with UV light, which is approximately 1.1 times larger than that for one Pd/TiO2 film. It can be concluded that the optimum moral ratio of CO2/H2/H2O, for the CO2 reduction reaction, is 1:0.5:0.5.