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Effects of pH on Au-Deposited TiO₂ for Catalytic Photoreduction of CO₂ with H₂O



Author(s)

Y. Y. Maruo, T. Kondoh and Y. Nakagawa

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DOI:10.17265/2161-6213/2018.9-10.006

Faculty of Engineering, Tohoku Institute of Technology, Sendaishi, Miyagi 982-8577, Japan

The photoreduction of CO₂ to hydrocarbons is a sustainable energy technology that not only reduces emissions but also the need for alternative fuels. In this study, Au nanoparticles were deposited on anatase TiO₂ using various pH controlled Au ion solutions (from pH = 6 to 9). Photoreduction experiments were performed in an FT-IR gas reactor using CO₂ gas with 50% relative humidity as the reactant for the four Au/TiO₂ samples. CH4 was mainly detected as the CO₂ reduction product, along with a small amount of CO. The amounts of CH₄ produced normalised by Au weight were 437 ppm (pH 6), 664 ppm (pH 7), 1,040 ppm (pH 8) and 2,356 ppm (pH 9). Therefore, the pH of the solution used in Au nanoparticle deposition strongly influenced the amount of CH4 produced. The highest production efficiency was obtained when the pH of the solution was 9. Considering the experimental results, we performed X-ray photoelectron spectroscopy and transmission electron microscope measurements and found that Au particle size was influenced by the pH of the solution with the size at pH 9 being smaller than that at pH 6. It was also found that there were Au-O states at the interface of Au nanoparticles and anatase TiO₂.

Au nanoparticle, Au/TiO2, photoreduction, CO2, methane.