Mechanism investigation of A-site doping on modulating electronic band structure and photocatalytic performance towards CO₂ reduction of LaFeO₃ perovskite

Three kinds of metal atoms with different valence electronic configurations, Bi (6s²6p³), Y (4d¹5s²), and Ce (4f¹5d¹6s²), were selected to investigate the effect of A-site (La³⁺) doping on electronic band structure, photoelectric properties, and photocatalytic performance of LaFeO₃ perovskite. It was identified that the Bi doped LaFeO₃ presented significantly improved photocatalytic activity towards the reduction of CO₂, while the Y or Ce doped LaFeO₃ displayed decreased photocatalytic activity compared to the pristine LaFeO₃. It was revealed that doping of all the three metal atoms resulted in narrowed band gap and thus extended light absorption of LaFeO₃ by lowering its conduction band minimum (CBM). The recombination rate and mobility of the charge carriers were represented by the relative effective mass (D) between holes and electrons for pristine and A-site doped LaFeO₃. The doping of Bi resulted in increased D value, attributed to the Bi 6s electron states at the valence band maximum (VBM), and thus promoted separation and transfer of the charge carriers and improved photocatalytic activity of LaFeO₃. In contrast, the doping of Ce resulted in significantly decreased D value, induced by the highly localized Ce 4f hole states at the CBM, and thus higher recombination rate of the charge carriers and decreased photocatalytic activity of LaFeO₃. Furthermore, the Y doped LaFeO₃ with a slightly decreased D value presented slightly increased recombination rate of the charge carriers and thus decreased photocatalytic activity. Such a work provides new insights into the A-site doping in LaFeO₃ perovskite, which should be helpful for optimizing the electronic band structure and activity of perovskite-type photocatalysts at atomic level.