Nonstoichiometric perovskite CaMnO3-δ nanomaterial for photocatalytic reduction of CO2

Abstract

Nanostructured perovskite oxides have emerged as a class of high-performance photocatalytic materials. In this study, the nonstoichiometric perovskite CaMnO3-δ nanomaterial is reported as a potential photocatalyst under IR and visible irradiation. The as-prepared sample was characterized by Brunauer−Emmett−Teller (BET) method and the diffuse reflectance spectroscopy (DRS). The CO2 photoreduction and methanol yield over CaMnO3-δ under both infrared and visible light irradiation as a function of irradiation time and photocatalyst concentration were investigated by chemical titration and the gas chromatographic analysis (GC-FID). The first and second harmonics of Nd:YAG laser with wavelengths of 1064 and 532 nm were used as the excitation source. After 20 min of 532 nm irradiation, the methanol yield for catalyst concentration of 0.6 g/lit exhibited the highest value (1138 μmol/g), while the methanol started to degrade with the increase of irradiation time. We have shown that under visible and IR irradiations, the electron photoexcitation from the hybridized O-2p and Mn-3d eg↑1 valance band to the Mn-3d eg↑2 conduction band provided CO2•δ− anion radicals which are required for CO2 photoreduction to methanol. This study makes the nonstoichiometric CaMnO3−δ a promising active catalytic material for CO2 photoreduction to methanol under IR and visible light irradiation.