Photocatalytic reduction of carbon dioxide with water using InNbO ₄ catalyst with NiO and Co ₃O ₄ cocatalysts

InNbO ₄ was prepared by the solid-state reaction method. Various cocatalysts were added on InNbO ₄ by the incipient-wetness impregnation method. The effects of co-catalyst and pretreatment conditions on the photocatalytic activity of InNbO ₄ for photoreduction of carbon dioxide were investigated. NiOInNbO ₄ and Co ₃O ₄InNbO ₄ 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 UVvis diffuse reflectance spectroscopy. The characterization results of NiOInNbO ₄ catalysts after pretreatment showed the presence of highly crystalline NiO and monoclinic Nb ₂O ₅. NiOInNbO ₄ with reductionoxidation pretreatment exhibited the highest activity due to the presence of coreshell type Ni ⁰ and NiO on the surface and the presence of a small amount of Nb ₂O ₅ as a promoter.