Preparation of Pd–Au/TiO2–WO3 to enhance photoreduction of CO2 to CH4 and CO

In this study, Pd–Au/TiO2–WO3 nanoparticles were successfully prepared using a hydrothermal and sol-gel route and applied to the photoreduction of CO2 under UV visible-light irradiation. The synthesized Pd–Au/TiO2–WO3 nanoparticles were characterized using X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy, Brunauer–Emmett–Teller surface area measurement, ultraviolet–visible absorption spectrophotometry, and photoluminescence analysis. The experimental results showed that Pd–Au/TiO2–WO3 nanoparticles with the appropriate amounts of Pd and Au achieved the highest activity for CO2 photoreduction. Among the synthesized Pd–Au/TiO2-WO3 nanoparticles, the highest production rates of CH4 and CO, 39.1 μmol g−1 h−1 and 271.3 μmol g−1 h−1, respectively, were observed with 0.5 wt%Pd-0.1 wt%Au/TiO2-WO3, manifesting a significant 247-fold enhancement of CO yield over TiO2. Moreover, 0.5 wt%Pd-0.1 wt%Au/TiO2-WO3 exhibited a 43-fold higher CH4 production rate than did TiO2 alone. This might be attributed to the increased specific surface area (72.9 m2 g−1) and the low recombination rate of photogenerated electron-hole pairs. Based on the results, a plausible mechanism for CO2 photoreduction that uses synthesized Pd–Au/TiO2–WO3 is discussed in this paper. This study demonstrated that Pd–Au/TiO2–WO3 is a promising candidate for the development of an efficient photocatalyst for CO2 photoreduction under solar light irradiation.