CO2 reduction over NaNbO3 and NaTaO3 perovskite photocatalysts

The activity of NaNbO 3 and NaTaO 3 perovskites for the photocatalytic reduction of CO 2 is studied in this work. For this purpose, sodium niobate and tantalate have been prepared using solid-state reactions, extensively characterised by means of powder X-ray diffraction, UV-vis, photoluminescence and Raman spectroscopies and N 2 adsorption isotherms, and tested in the gas-phase reduction of CO 2 under UV light in a continuous flow photoreactor. NaNbO 3 is constituted of an orthorhombically distorted perovskite structure, while a ca . 4.5 : 1 combination of the orthorhombic and monoclinic modifications is found in the tantalate. Both catalysts exhibit interesting intrinsic activities, with the tantalate material giving rise to a slightly higher performance. This is attributed to a compromise situation between electron-hole recombination and the reducing potential of conduction band electrons. In addition, a decrease in the competition of water protons for photogenerated electrons is observed with both catalysts with respect to TiO 2 . Both NaNbO 3 and NaTaO 3 exhibit interesting intrinsic photocatalytic activities for CO 2 reduction in terms of conversion and selectivity.