Self-reducing CaFe1-xCuxO3-δ perovskite for photocatalysis: The synergistic role of Cu doping and O–H groups

Pure and Cu-doped (1 wt%, 4 wt%, and 10 wt%) CaFeO_3-δ perovskite nanopowders were synthesized via a citric acid-assisted sol–gel method. In order to ensure the preservation of hydroxyl (O–H) groups, the precursors were hermetically sealed with semipermeable Parafilm during synthesis and drying. Subsequent calcination at 900 °C for 6 h yielded a well-crystallized, predominantly orthorhombic CaFeO_3-δ phase, along with minor residual Fe_2−δH_δO₃ and Ca(OH)₂ phases rich in hydroxyl groups. The synthesized materials exhibited exceptional photocatalytic activity for methylene blue (MB) degradation under visible-light irradiation. This enhanced performance is attributed to the synergistic interplay between copper doping and the hydroxyl network, which acts as an electrolyte-like medium to facilitate charge transport. It is noteworthy that 1 wt% Cu-doping demonstrated optimal efficiency, achieving 91.21 % MB degradation within 80 min. The charge carriers generated by Cu doping, coupled with efficient charge separation enabled by the hydroxyl electrolyte, are responsible for the remarkable catalytic activity. Notably, the Cu-doped CaFeO_3-δ perovskite functions as a self-sustaining catalyst, utilizing its intrinsic hydroxyl network to degrade MB with high efficiency and stability.