It's highly desired to design and fabricate an effective Z-scheme photo-catalyst with excellent charge transfer and separation, and a more negative conduction band edge (ECB) than O2/·O2− (−0.33 eV) and a more positive valence band edge (EVB) than ·OH/OH− (+2.27 eV) which provides high-energy redox radicals. Herein, we firstly designed and synthesized a core–shell-heterojunction-structured Z-scheme system BaTiO3@In2S3 (BT@IS, labelled as BTIS) through a hydrothermal method, where commercial BT was used as the core and In(NO3)3·xH2O together with thioacetamide as the precursor of IS was utilized as the shell material. In this system, the shell IS possesses a ECB of −0.76 eV and visible-light-response Eg of 1.92 eV, while the core BT possesses a EVB of 3.38 eV, which is well suited for a Z-scheme. It was found that the as-prepared BTIS possesses a higher photocatalytic degradation ability for methyl orange (MO) than commercial BT and the as-prepared IS fabricated by the same processing parameters as those of BTIS. Holes (h+) and superoxide radicals (·O2−) were found to be the dominant active species for BTIS. In this work, the core–shell structure has inhibited the production of ·OH because the shell IS has shielded the OH− from h+. It is assumed that if the structure of BTIS is a composite, not a core–shell structure, ·OH could be produced during photocatalysis, and therefore a higher photocatalytic efficiency would be obtained. This current work opens a new pathway for designing Z-scheme photocatalysts and offers new insight into the Z-scheme mechanism for applications in the field of photocatalysis.
Doxycycline hydrochloride (DH), a persistent antibiotic frequently detected in aquatic environments, remains challenging to eliminate because conventional photocatalysts often suffer from limited visible-light utilization and rapid charge recombination, which suppress reactive oxygen species generation and slow DH transformation. Herein, we develop a visible-light-responsive BaTiO3–In2S3 photocatalyst by constructing an S-scheme heterojunction that steers oxygen-mediated electron transfer for accelerated photocatalytic degradation of DH. Ferroelectric BaTiO3 provides a polarization-associated driving force for carrier separation, whereas In2S3 broadens light harvesting and supplies reductive electrons for oxygen activation. Their work-function mismatch establishes an interfacial electric field that promotes directional carrier migration and suppresses interfacial charge recombination, as evidenced by ex situ/in situ XPS analysis and further supported by DFT analysis. As a result, the BaTiO3–In2S3 heterojunction delivers 59.1% DH conversion with a pseudo-first-order rate constant of 0.02606 min–1, 2.15 times higher than pristine BaTiO3. Quenching and EPR experiments identify ·O2– and h+ as the dominant reactive species, consistent with an S-scheme charge-transfer pathway that preserves high-energy electrons in In2S3 and oxidative holes in BaTiO3. LC-MS analysis suggests three feasible degradation routes, and ECOSAR prediction indicates an overall reduction in aquatic toxicity for several low-molecular-weight intermediates.
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