Facile Synthesis, Characterization, Catalytic and Photocatalytic Activity of Multiferroic BiFeO3 Perovskite Nanoparticles

We report the synthesis of multiferroic BiFeO3 perovskite nanoparticles using the microwave combustion technique. Phase evolution is investigated by X-ray diffraction (XRD), which confirms that the formation of a secondary α-Bi2O3 phase with a monoclinic structure along with the existing rhombohedral (BiFeO3) structure. The average crystalline size has been found at 50 nm. The optical band gap was calculated from the Tauc’s plot it has been found 2.18 eV, as measured by diffuse reflectance spectroscopy (DRS). The appearances of Fourier transform infrared spectroscopy (FT-IR) absorption bands at 550 and 444 cm-1 were correlated to the rhombohedral stretching modes of bismuth ferrite nanostructure. The morphology observations using scanning electron microscopy (SEM) showed the formation of nanosized grains with pores. Energy-dispersive X-ray analysis (EDX) was done to confirm the extent of Bi3+, Fe3+, and O2- in the samples. The magnetization-Field (M-H) hysteresis curves recorded from the vibrating sample magnetometer (VSM) revealed the appearance of ferrimagnetic behavior at room temperature. The specific surface area characterized by N2 adsorption-desorption isotherm is found 44.86 m2 g-1 using Brunauer-Emmett-Teller (BET) technique. The as-fabricated BiFeO3 perovskite nanoparticles were investigated for their superior catalytic activity in two applications, which include (i) the conversion of glycerol to formic acid in a selective liquid phase batch reactor at atmospheric pressure. This bismuth-based nanoparticles exhibit as an efficient multifunctional catalyst with high conversion and selectivity efficiency around 99.2% and 98.5%, respectively, (ii) the photocatalytic degradation of rhodamine B under visible light irradiation is found maximum efficiency (99.9%), when a small amount of H2O2 was added during photocatalysis, indicating the samples possessed photo-Fenton like catalytic activity. Finally, we concluded that the BiFeO3 perovskite nanoparticles' high performance in future multifunctional devices is demonstrated by the simultaneous enhancement of catalytic and photocatalytic activities.

Peroxydisulfate activation by LaNiO3 nanoparticles with different morphologies for the degradation of organic pollutants

A series of LaNiO3 perovskite nanoparticles with different morphologies, such as spheres, rods and cubes, were prepared through co-precipitation and hydrothermal methods, and used as the catalysts for peroxydisulfate (PDS) activation. The physical and chemical characteristics of LaNiO3 perovskites were performed, including X-ray diffraction (XRD), scanning electron microscopy (SEM), nitrogen isotherm absorption (BET), electrochemical impedance spectroscopy (EIS), and X-ray photoelectron spectroscopy (XPS). The LaNiO3 with different shape showed different activities in Acid Orange 7 (AO7) degradation. Spheres-like LaNiO3 exhibited the highest catalytic activity, which is probably due to the largest specific surface area, higher proportion of reductive Ni2+ and the higher electron transfer ability. The radical scavenging experiments and electron paramagnetic resonance (EPR) revealed the production of massive sulfate radicals (SO4•−) and hydroxyl radicals (•OH) during the oxidation. Finally, the possible mechanisms of PDS activation and AO7 degradation were proposed. The prepared LaNiO3 perovskites also showed excellent reusability and stability.