Synthesis of bismuth ferrite by sol-gel auto combustion method: Impact of citric acid concentration on its physicochemical properties

In this study, pure phase BiFeO3 was prepared via a facile sol-gel auto-ignition route using water as a solvent. The influence of citric acid to metal nitrates molar ratio on physicochemical properties of BiFeO3 was also investigated through FTIR, XRD, PL, UV, SEM, and BET analysis. The XRD of the prepared samples revealed the rhombohedral perovskite structures belong to space group R3c. In addition, the BFO2:1 sample showed the smallest crystallite size (42 nm) with the highest purity and recombination rate; while the BFO1:2 sample showed the lowest purity and electron charge recombination rate. The surface areas of the BFO1:1, BFO1:2, and BFO2:1 samples were 1.63, 2.13, and 1.84 m2/g, respectively. Moreover, the bandgaps were found to be 2.17, 2.11, and 2.21 eV for the prepared BFO1:1, BFO1:2, and BFO2:1, respectively. In addition, the appearance of a near-IR band around 814 cm−1 confirms the presence of Bi2Fe4O9 byproduct in the BFO1:2 sample. Finally, SEM revealed that BFO2:1 sample was well-distributed and exhibited uniform morphology, referring to citric acid's ability to stabilize and disperse bismuth ferrite NPs. Furthermore, BFO1:2 sample showed enhanced photocatalytic activity in CR dye degradation than BFO1:1 and BFO2:1 samples, attributed by the increase in the surface area and minimized electron-hole recombination. This strategy eliminates the use of conventional organic solvents and provides an effortless and efficient way to prepare pure BiFeO3 and BiFeO3/Bi2Fe4O9 heterojunction nanocomposite that are potentially applicable for photocatalyst and in solar cell production.