Photocatalytic reduction of carbon dioxide with water using InNbO4 catalyst with NiO and Co3O4 cocatalysts

InNbO4 was prepared by the solid-state reaction method. Various cocatalysts were added on InNbO4 by the incipient-wetness impregnation method. The effects of co-catalyst and pretreatment conditions on the photocatalytic activity of InNbO4 for photoreduction of carbon dioxide were investigated. NiO–InNbO4 and Co3O4–InNbO4 were pretreated by reduction at 500 °C for 2 h and subsequent oxidation at 200 °C for 1 h. The catalysts were characterized by X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy, and UV–vis diffuse reflectance spectroscopy. The characterization results of NiO–InNbO4 catalysts after pretreatment showed the presence of highly crystalline NiO and monoclinic Nb2O5. NiO–InNbO4 with reduction–oxidation pretreatment exhibited the highest activity due to the presence of core–shell type Ni0 and NiO on the surface and the presence of a small amount of Nb2O5 as a promoter.

► NiO–InNbO4 and Co3O4–InNbO4 were more active than InNbO4 for photoreduction of CO2 under visible light irradiation.
► The activity of Co3O4–InNbO4 was lower than that of NiO–InNbO4 catalyst, due to the redox property of cobalt cations.
► NiO–InNbO4 exhibited high activity due to the presence of core–shell type Ni0 and NiO and Nb2O5.