10BaF₂:NaF, Na₃AlF₆/TiO₂ composite as a novel visible-light-driven photocatalyst based on upconversion emission

A rare-earth free upconversion luminescent material, 10BaF₂:NaF, Na₃AlF₆/TiO₂, is synthesized by a hydrothermal method. The study of fluorescent spectrum indicates that it can convert visible light (550 nm-610 nm) into ultraviolet light (290 nm-350 nm), and two emission peaks at 304 nm and 324 nm are observed under the excitation of 583 nm at room temperature. Subsequently, 10BaF₂:NaF, Na₃AlF₆/TiO₂ composite photocatalyst is prepared and its catalytic activity is evaluated by the photocatalytic reduction of CO₂ under visible light irradiation (\lambda>515nm). The results show that 10BaF₂:NaF, Na₃AlF₆/TiO₂ is a more effective photocatalyst for CO₂ reduction than pure TiO₂, their corresponding methanol yields are 179 and 0 \mumol/g-cat under the same conditions. Additionally, the mechanism of photocatalytic reduction of CO₂ on 10BaF₂:NaF, Na₃AlF₆/TiO₂ is proposed.