CO₂ Hydrogenationto Methanol over Ni/In₂O₃: Effects of In₂O₃ Morphology

Abstract

CO₂ to methanol is an important reaction that reduces the concentration of CO₂ in the atmosphere. Ni/In₂O₃ catalysts with three different In₂O₃ morphologies, i.e. cube (c), hollow tube (h), and plate (p), were synthesized by an impregnation method and studied for CO₂ hydrogenation to methanol. It was found that the performance of the catalysts is closely related to the morphology of In₂O₃. At 300 °C, 2 MPa, and 16 L·g^–1·h^–1, the Ni/In₂O₃-h catalyst showed the highest space time yield of methanol of 18.73 mmol·g^–1·h^–1. The morphology of In₂O₃ affects the state of Ni species on its surface, and highly dispersed Ni species, rather than single-atom Ni species or aggregated Ni species, are considered as active sites in CO₂ hydrogenation to methanol. The appropriate quantity of oxygen vacancies is also an important factor affecting the performance of the catalysts. In-situ diffuse reflectance infrared Fourier-transform spectroscopy measurements suggest that hydrogenation of CO₂ to methanol may follow the formate pathway on the Ni/In₂O₃ catalysts.