Ruddlesden-Popper compound Sr2TiO4 co-doped with La and Fe for efficient photocatalytic hydrogen production

Doping techniques generally serve as effective means for tailoring the physicochemical properties of a target compound. In this work, we successfully co-doped La/Fe into Ruddlesden-Popper (RP) compound Sr 2 TiO 4 and performed a detailed investigation on the crystal structure, morphology, optical absorption and photocatalytic hydrogen production reactions after doping. Our findings suggest that La/Fe co-doping slightly expand the unit cell of Sr 2 TiO 4 while maintains the structure lamination. Incorporating La/Fe into Sr 2 TiO 4 efficiently reduces the band gap and the level of band gap reduction can be controlled by varying the amounts of dopants. La/Fe co-doping significantly improves the photocatalytic properties of Sr 2 TiO 4 under both full range (λ ≥ 250 nm) and visible light illumination (λ ≥ 420 nm). A fivefold enhancement in hydrogen production rate (∼106.2 μmol/h) is seen in sample Sr 1.9 La 0.1 Ti 0.9 Fe 0.1 O 4 (x = 0.1). Efficient photocatalytic hydrogen production under visible light illumination (λ ≥ 420 nm) is also achieved in sample Sr 1.7 La 0.3 Ti 0.7 Fe 0.3 O 4 (x = 0.3) with AQE as high as ∼1.18% at 420 nm. DFT calculations confirm the critical role of Fe in reducing the band gap of Sr 2 TiO 4 by forming additional spin-polarized bands (SPB). The anisotropic charge transportation in Sr 2 TiO 4 is also verified by our calculations as both conduction band minimum (CBM) and valence band maximum (VBM) are buried in TiO 6 octahedron layers. The 2D charge transportation properties are particularly useful for photocatalytic reactions since interlayer charge recombination is essentially prevented.