Investigation of the physico-chemical properties of Sr2FeNb1−x W x O6 (0.0 ≤ x ≤ 0.1) for visible-light photocatalytic water-splitting applications

Abstract

Incorporation of the pentavalent W-ion has been investigated in Sr2FeNb1−x W x O6 for 0.0 ≤ x < 0.15. The synthesized double perovskite system was used to study its structural and optical properties. The optical, as well as structural, properties were found to change with the varying Nb:W stoichiometric ratio. The Sr2FeNb1−x W x O6 samples with 0.0 ≤ x < 0.1 were further investigated for visible-light photocatalytic water splitting. At an optimized value of ∼0.01, i.e., Sr2FeNb0.99W0.01O6, the perovskite lattice yielded an efficient photocatalyst, it displayed a moderately-altered direct band-gap of 2.17 eV, and gave twice the higher quantum yield for photosplitting in a H2O-CH3OH mixture compared to that for x ∼0 under visible light (λ ≥ 420 nm). For x > 0.1, the Sr2FeNb1−x W x O6 showed no change in the optical properties but crystal structure was drastically affected, exhibiting impurity phases and a disordered structure, thus yielding a degraded photocatalytic behavior. The higher absorption coefficient in the Sr2FeNb0.99W0.01O6 and a higher electron-density acquired by n-type lattice doping seems to be responsible for the better efficient charge separation in Sr2FeNb1−x W x O6 (0.01 ≤ x ≤ 0.20) and consequently the higher photocatalytic activity in co-catalyst loaded photocatalysts.