SrCO3-modified brookite/anatase TiO2 heterophase junctions with enhanced activity and selectivity of CO2 photoreduction to CH4

Abstract Utilizing the abundant solar energy to chemically convert CO 2 into high-energy chemical fuels such as CO, CH 4 or CH 3 OH offers a way to address the serious concerns about the increasing atmospheric CO 2 levels and the depletion of fossil fuels. Herein, a series of SrCO 3 -modified TiO 2 composites have been synthesized by adding SrCl 2 into a TiCl 4 hydrothermal reaction solution. It is found that brookite TiO 2 quasi nanocubes with high phase purity (denoted as pristine TiO 2 ) can be derived from the TiCl 4 reaction solution, and the additive Sr 2+ ions lead to the formation of SrCO 3 -modified TiO 2 heterophase junctions (HPJs) containing brookite nanorods and anatase nanoparticles. When used the SrCO 3 -modified TiO 2 HPJs (hereafter denoted as SrCO 3 /HPJs) as photocatalyst for CO 2 photoreduction, significantly enhanced activity and selectivity for CO 2 photoreduction to CH 4 can be achieved as compared to the pristine TiO 2 . Especially, 1.0% SrCO 3 /HPJs composite shows CH 4 /CO production activities of 19.66/2.64 μmol g −1  h −1 with an overall photoactivity of 162.6 μmol g −1  h −1 , which is 12.3 times of the pristine TiO 2 that shows an overall photoactivity of 13.2 μmol g −1  h −1 with CH 4 /CO production activities of 0.79/3.46 μmol g −1  h −1 . The brookite/anatase TiO 2 HPJs can effectively promote the photogenerated charge separation and restrain the interfacial charge recombination, and the SrCO 3 species on the TiO 2 HPJs can act as an efficient synergistic catalyst to improve the CO 2 adsorption and activation abilities, and thus cause the enhanced activity and selectivity for CO 2 photoreduction to CH 4 . This work represents the first example of coupling TiO 2 HPJs with alkaline earth metal carbonates for efficient CO 2 photoreduction.