Egg white-mediated synthesis of BiFeO3 cubes and their enhanced photocatalytic degradation properties under solar irradiation

Herein, the egg white-mediated synthesis of BiFeO3 (BFO) cubes has been demonstrated using it as metal complex-forming agent during the sol-gel process. The BiFeO3 phase is confirmed using XRD technique, while the XPS spectra confirmed the native oxidation state of the elements and chemical composition. The XPS studies also showed that synthesized BFO particles via conventional sol-gel method possess oxygen vacancies, while no such defect is observed in BFO cubes. The cubic morphology with average size of 150 nm is observed from their FESEM images, while irregular particles of size around 300 nm is observed for BFO synthesized via conventional sol-gel process. The bandgap energy of particles and cubes is estimated to be around 2.32 and 2.36 eV, respectively, and the observed reduced bandgap energy could be due to the defects induced new energy level in BFO particles, while the increased bandgap energy of BFO cubes is attributed to their discrete band energy structure due to their uniform cubic morphology. The solar-driven photocatalytic efficiency toward degradation of methylene blue (MB) dye is found to be enhanced for BFO cubes (99.6%) as compared to particles (73.2%) at the end of 3 h, which attributed to the existence of improved charge separation, recombination resistance, rich surface-active sites, and suitable redox potential in BFO cubes as corroborated from their XPS, PL, and scavenger studies. The photocatalytic recyclability tests up to 5 cycles indicated that BFO cubes is photochemically stable and can be employed for durable photocatalytic degradation applications.