Flux-Assisted Synthesis of a Visible-Light-Active La2FeTiO6 Double Perovskite with Intrinsic Bifunctional Activity for Photocatalytic Water Reduction and Oxidation

Abstract

Developing visible-light-responsive materials that are intrinsically active for both the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) is crucial for cost-effective solar hydrogen production. Here, we report a novel oxide double perovskite, La2FeTiO6 (LFTO), synthesized via a flux-assisted method. LFTO shows extended absorption to ~650 nm (direct bandgap of 2.05 eV) and suitably aligned band edges for driving both water-splitting half-reactions. Theoretical simulations reveal highly dispersive CBM and VBM states that promote efficient charge separation and transfer. Remarkably, LFTO demonstrates intrinsic, cocatalyst-free photocatalytic activity for both HER and OER under visible-light irradiation (λ ≥ 420 nm), representing a rare single oxide semiconductor capable of bifunctional photocatalysis without any cocatalysts. Loading RuO2 as a cocatalyst significantly enhances OER, achieving an apparent quantum efficiency (AQE) of 4.3% at 420 nm, while Pt loading markedly improves HER performance. Charge-carrier dynamics analyses and photocatalytic stability tests confirm enhanced charge separation and transfer, together with excellent structural stability. These findings identify LFTO as a promising visible-light-active photocatalyst for sustainable solar-to-hydrogen conversion.