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

Perovskite oxides (ABO(3)) are widely studied as excellent sorbing and catalytic materials for NOx 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 photo catalysts 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 (O-center dot(2)-) 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 NOx abatement under ambient conditions. (C) 2016 Elsevier B.V. All rights reserved.