Kinetics of the photocatalytic degradation of methylene blue under natural sunlight irradiation using nanocatalysts Ce³⁺ and Mg²⁺ co-doped CaFeO_3−δ

Nanoparticles of pure and co-doped according to the formula Ca_1−yCe_yFe_1−xMg_xO_3−δ (x = y = 0.0, y = 0.1; x = 0.0, 0.1, 0.2) have been successfully synthesized through a wet chemical sol–gel method using citric acid as a chelating agent. So, the prepared materials after calcination at 800 °C for 6 h were examined for structural, optical, and photocatalytic properties using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (IRTF), and ultraviolet–visible spectrophotometer (UV–Vis). The X-ray diffraction measurements of all the compositions confirm the formation of a single-phase orthorhombic perovskite-related structure, with a Pcmn space group without any other heterogeneity or structural transition. The crystallite size is found to decrease with increasing Mg²⁺ doping in Ca_0.9Ce_0.1Fe_1−xMg_xO_3−δ. The results of the FTIR analysis confirmed the presence of the typical band characteristics of metal oxygen bonds, which are features of FeO₆ octaedra in the oxide perovskite materials. UV–Vis optical spectra revealed that the band gap of pure CaFeO_3−δ observed in the visible range was tuned by doping Ce³⁺ and Mg²⁺, which has improved the photodegradation efficiency and kinetic degradation rates of methylene blue under sunlight irradiation. The possible mechanism of the photocatalytic activity is also proposed in this contribution.