Constructing nanoflower-like semiconductor–insulator SrCO3/SrTiO3 heterojunction photocatalyst for the efficient removal of TC by the synergistic effect of adsorption and photocatalysis

A combination of adsorption and photocatalysis is a promising method to degrade organic pollutants. Herein, the work adopts SrTiO₃ semiconductor coupled with insulator SrCO₃ via an in-situ solvent method to construct a heterojunction with built-in electric field (IEF) photocatalyst, which improves excellently the electrons-holes (h⁺-e^-) separation and adsorption performance on SrTiO₃. The close heterojunction and the IEF formed at the heterojunction interface enhance the transfer and separation of photogenerated carriers, generating more active substances. Meanwhile, the unique nanoflower structure of SrCO₃/SrTiO₃ and the introduction of SrCO₃ provide more adsorption sites and active centers, which is conducive to the adsorption and activation of TC. Thus, the maximum adsorption capacity of SrCO₃/SrTiO₃ could be up to 47.15 mg/g^-1 within 30 min. Compared with pure SrTiO₃, SrCO₃/SrTiO₃ exhibited the excellent removal of tetracycline hydrochloride (TC) (120 min, 90.5 %) via the synergistic effect of adsorption and photocatalysis under visible light, and its photocatalytic reaction rate was 24.79 and 3 times higher than SrCO₃ and SrTO₃, individually. h⁺and •O₂^– played a pivotal role in TC degradation. Additionally, the adsorption behavior of TC on SrCO₃/SrTiO₃ composite and the photocatalytic degradation mechanism of SrCO₃/SrTiO₃ were investigated in detail. This work provides a new idea for improving the photocatalytic performance of SrTiO₃ and the application of insulators in photocatalysis.