Effects of Mo doping on the structure, adsorption performance, and photocatalytic activity of LaFeO3 nanoparticles: Experimental and DFT studies

In this study, a series of Mo-doped LaFeO3 composite photocatalyst nanoparticles (x-LFMO, x = 0.33, 0.5, 0.67) were synthesized by ultrasonic-assisted sol-gel method under controlled Mo doping. X-ray diffraction (XRD) analyses indicate that Mo substitutes one-third of the Fe atoms in the B site of the LaFeO3 to form orthogonal perovskite structures LaFe0.67Mo0.33O3, which is the only pure phase crystal formed at stoichiometric Fe to Mo ratios of 2:1, 1:1, and 1:2, respectively. SEM and N-2 adsorption/desorption revealed significantly smaller particle sizes (30-50 nm) and the formation of rich channels after Mo doping, thus enriching the specific surface area and pore size dispersion. DRS confirmed that the Mo-doped LFO composites exhibit significantly enhanced absorption in the visible region. This can be further explained by DFT theoretical calculations of energy band structures and density of states, which demonstrate that the effective mass of the electrons in LaFe0.67Mo0.33O3 is reduced and the off-domain properties of the electrons are enhanced, facilitating the excitation and transport of the photogenerated electrons. Kinetic studies showed that Mo-doped composite nanoparticles exhibit excellent adsorption capacity for quinoline, indole, and pyridine, and the pure phase LaFe0.67Mo0.33O3 and 0.5-LFMO performed well for them with removal efficiencies (>98 %) under visible light irradiation. Based on experimental observations and theoretical insights, it is suggested that the higher quantum yield and photocatalytic reactivity of x-LFMO composites are attributed to the bulk oxygen mobility and surface oxygen reactivity promoted by the octahedral distortion of BO6 in LaFe0.67Mo0.33O3 and the heterogeneous structure formed at the interface of the two phases.