Synthesis, characterization, and photoreduction performance evaluation of gold/titanium oxide/calcium carbonate photocatalysts for carbon dioxide reduction

Abstract

Abstract Titanium oxide (TiO2)-based photocatalysts are one of the most promising materials that can reduce carbon dioxide (CO2) by utilizing sunlight, thus reducing CO2 concentration in the air. In this study, we develop a simple and practical one-pot synthesis method to prepare photocatalysts with Au nanoparticles (AuNPs) supported on mixtures of titanium oxide and calcium carbonate (CaCO3). By synthesizing a lot of smaller AuNPs and supporting them on the surface of the photocatalyst, it is possible to enhance the surface area of AuNPs, improving the photocatalytic performance of carbon dioxide reduction. The synthesized photocatalysts with fixed TiO2 content and varied CaCO3 fractions between 0 and 200 wt% are characterized through X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and ultraviolet–visible spectroscopy. The size of AuNPs in the photocatalyst with CaCO3 is smaller than that in the photocatalyst without CaCO3, and the density of AuNPs per catalyst area in the photocatalyst with 40 wt% CaCO3 is approximately 200 times higher than that of the photocatalyst without CaCO3. With the addition of CaCO3, the yields of CO and CH4 increase by 2.9–4.0 and 1.3–2.1 times, respectively. Article highlights Photocatalysts using Au nanoparticles supported on TiO2 and CaCO3 are prepared using a simple one-pot synthesis method. The ratio of CaCO3 to TiO2 is changed and specific Au nanoparticles with a small size and a large number are synthesized when 40 wt% of CaCO3 was added. Photocatalysts with smaller Au nanoparticles and larger Au surface area produce more CO and CH4.

Keywords

• Titanium oxide
• Calcium carbonate
• Gold nanoparticle
• Photoreduction
• Carbon monoxide
• Methane