Photocatalytic reduction of carbon dioxide on NiO/InTaO4 under visible light irradiation

Developing a photocatalyst system for the conversion of solar energy to electric energy or chemical energy is a topic of great interest with fundamental and practical importance. The semiconductor catalysts, such as InTaO4, have been extensively used for water splitting under visible light irradiation. However, it has not been used for photoreduction of carbon dioxide with water. InTaO4 was synthesized by solid-state reaction. NiO was added by incipient-wetness impregnation method as the cocatalysts. The catalysts were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), ultraviolet–visible spectroscopy (UV–Vis) and X-ray photoelectron spectroscopy (XPS). The photocatalytic reduction was carried out in a Pyrex reactor under visible light illumination using 500 W halogen light as the light source. The band gap of InTaO4 was estimated, from UV–Vis spectrum, to be 2.6 eV, showing that these catalysts have ability to reduce CO2 into methanol. The effects of the NiO cocatalyst and pretreatment process on the photocatalytic reduction of the catalyst to methanol were investigated. The methanol yield increased with the amount of NiO cocatalyst. The reduction–oxidation pretreatment had a positive effect on the catalyst.