Visible light-driven metal-oxide photocatalytic CO2 conversion

Abstract

In this work, nine photocatalysts were prepared by a conventional solid-state reaction method. The samples were characterized by X-ray diffraction, UV–Vis diffuse reflectance spectroscopy, surface area measurements based on the Brunauer–Emmett–Teller theory, and scanning electron microscopy. The tested materials (BaBiO3, Bi2WO6, SrTiO3, KNbO3, NaNbO3, Sr4Nb2O9, YInO3, CaIn2O4, and YFeO3) showed great potential for use as photocatalysts in the efficient reduction of CO2 into a renewable hydrocarbon fuel as well as in water splitting. Our results showed that among the nine tested photocatalysts, three could generate CH4. In particular, it was observed that KNbO3, as a result of its high surface area and the suitable band gap, showed the highest CH4 generation, (86.842 ppm g−1 h−1). Some of the tested photocatalysts could generate H2 and O2 at a very promising rate; Sr4Nb2O9 and NaNbO3 were the best two photocatalysts, with an average O2 production rate of 69.476 ppm g−1 h−1 and 57.928 ppm g−1 h−1, respectively. Further, NaNbO3 showed the highest H2 production average with a rate of 220.128 ppm g−1 h−1. The photocatalysts presented herein represent a significant improvement because of the reactor type and the preparation techniques implemented in this study.