Influences of A- and B-site cations on the physicochemical properties of perovskite-structured A(In_1/3Nb_1/3B_1/3)O₃ (A = Sr, Ba; B = Sn, Pb) photocatalysts

We have investigated the effects of A- and B-site cation substitution on the physicochemical properties of perovskite-structured A(In_1/3Nb_1/3B_1/3)O₃ (A = Sr, Ba; B = Sn, Pb) photocatalysts. X-ray diffraction, X-ray absorption and diffuse UV-vis spectroscopic analyses reveal that tetravalent Pb^IV or Sn^IV ions can be successfully incorporated into the octahedral B-site of the perovskite lattice, leading to a narrowing of bandgap energy (E_g). The substitution of such electronegative cations gives rise to the enhancement of photocatalytic activity to effectively decompose organic molecules. Interestingly, alkaline earth metal ions in the dodecahedral A-site with ionic bonding environment also affect significantly the band structure and photoefficiency of the perovskite compounds; a larger cation is beneficial for creating visible light driven photocatalytic activity through a decrease of E_g. This observation could be understood in terms of the weakening of transition metal-oxygen bond upon the expansion of unit cell. The present relationship between the chemical bonding nature of substituent cation and the band structure provides an efficient tool for designing and developing new efficient visible light active photocatalysts.