Non-metal fluorine doping in Ruddlesden–Popper perovskite oxide enables high-efficiency photocatalytic water splitting for hydrogen production

Perovskite oxides have been extensively investigated as catalysts for solar water splitting to generate hydrogen (H₂) due to the easily tuned band gap, distinct optical/chemical properties and superior structural/compositional flexibility. Cation doping is widely used to boost the photocatalytic activity of perovskite oxides while the anion doping into the oxygen (O)-site of perovskite oxides is less investigated. Herein, we present a non-metal fluorine (F⁻) doping strategy to improve the photocatalytic activity of Ruddlesden–Popper Sr₂TiO₄ perovskites for H₂ evolution reaction (HER). By optimizing the F⁻ doping amount in Sr₂TiO_4−xF_x, the highest H₂ generation rate of 282 μmol/h/g is achieved by Sr₂TiO_3.97F_0.03 under full-range sunlight illumination (λ ≥ 250 nm), which is 44% larger than that of Sr₂TiO₄ (195 μmol/h/g). Such enhancement in the photocatalytic HER activity of Sr₂TiO_3.97F_0.03 can be assigned to the increased surface oxygen vacancy amount, suppressed charge carrier recombination, more negative conduction band position as well as well-balanced band gap energy, particle size, and specific surface area induced by the F⁻ doping. Our current study presents a facile and effective strategy for the future design of highly efficient catalysts for solar water splitting.