Perovskite LaFeO₃-SrTiO₃ composite for synergistically enhanced NO removal under visible light excitation

Perovskite oxides (ABO₃) are widely studied as excellent sorbing and catalytic materials for NO_x abatement in automobile or stationary depollution processes, and recently they have attracted significant interest in solar conversion reactions due to the flexible composition, facile optical and electronic tuning properties. In this work, perovskite LaFeO₃ microspheres were synthesized and employed as photocatalysts to remove parts-per-billion level NO, and it is found that the photocatalytic efficiency was dramatically improved by coupling with SrTiO₃ nanocubes. The LaFeO₃-SrTiO₃ composite with proper mass ratio (0.3–1) displayed 3.1 and 4.5 fold enhancement in NO removal rate as compared to the pristine LaFeO₃ and SrTiO₃, respectively. Moreover, the LaFeO₃-SrTiO₃ composite exhibited decreased NO₂ yield possibly due to the basic surface property of strontium sites. The synergistically improved activity was due to broad visible light harvest, enlarged surface area, and most importantly, the depressed surface charge recombination originating from the perfectly matched LaFeO₃-SrTiO₃ interface and facile charge transfer along the staggered band alignment. The temperature programmed desorption (TPD) analysis revealed that the composite had efficient chemisorption for NO. Further, the electron spin resonance (ESR) combined with the radical scavenger tests and density functional theory (DFT) calculations suggested that the photocatalytic NO oxidation via superoxide radicals ([rad]O₂⁻) from SrTiO₃ and direct hole (h⁺) transfer from LaFeO₃ might be the predominant routes. We believe that this study provides some new insights into perovskite nanomaterials as photocatalyst for NO_x abatement under ambient conditions.