Photoinduced structural transformation of SrFeO3 and Ca2Fe2O5 during photodegradation of methyl orange

Photodegradation of methyl orange solution under UV light irradiation have been studied over photocatalyst perovskite SrFeO3 and brownmillerite Ca2Fe2O5. XRD and FTIR analysis show that both SrFeO3 and Ca2Fe2O5 transform to carbonates during the photodegradation process of methyl orange. This result indicates that UV light irradiation induce a photochemical reaction between photocatalysts and CO2 released from the photodegradation of methyl orange. The photochemical reaction between photocatalysts and CO2 is responsible for the transformation of the structures. The fact that SrFeO3 has better photocatalytic property and endures serious transformation than Ca2Fe2O5 is due to existence of unstable Fe (IV) in the perovskite structure of SrFeO3. Such kind of Fe (IV) makes perovskite structure unstable and sensitive to ambient (especially sensitive to UV light irradiation).