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.