Z-Scheme Heterojunction-Enabled Superoxide Radical Dominance in BiO2-x-Bi2O2CO3 Photocatalyst for Efficient Organic Pollutant Degradation

Heterojunction photocatalysis holds great significance for low-cost and efficient environmental remediation processes, particularly for addressing persistent antibiotic contamination. Here, BiO 2-X -Bi 2 O 2 CO 3 heterojunction photocatalysts are fabricated via a low-temperature solvothermal epitaxial growth method. The intimate interfacial contact between the BiO 2-X nanoparticles and the epitaxially grown Bi 2 O 2 CO 3 nanosheets was detected, which endows the heterostructure with significantly enhanced visible-light activity. The photocatalytic properties of the optimized composite, BiO 2-X -Bi 2 O 2 CO 3 -20, are investigated in detail toward tetracycline (TC) degradation. The superior charge carrier dynamics is confirmed to be vital to enhanced performance, as evidenced by PL spectroscopy and transient photocurrent analysis, which collectively indicate that the heterojunction effectively suppresses electron-hole recombination and promotes charge transfer. Mechanistic studies, including ESR and radical trapping experiments, validated a Z-scheme charge transfer pathway, which ensures the preservation of the strong reducing (e - at -0.75 eV) and oxidizing (h + at 2.51 eV) potentials. This preserved high energy (∼3.26 eV) promotes the generation of the superoxide radical (·O 2 - ), conclusively identified as the dominant active species responsible for the high efficiency. This work introduces a robust Z-scheme method for Bi-based photocatalysts, which is ready to extend to other heterogeneous systems and offers a new option to design high-performance catalysts for efficient antibiotic-contaminated wastewater treatment under visible light. The BiO 2-X -Bi 2 O 2 CO 3 heterojunction with built-in internal electric field (IEF) efficiently separates photogenerated charge carriers under visible light, generating ·O 2 - and ·OH radicals for significantly enhanced photocatalytic degradation of organic pollutants. • Epitaxial BiO 2-x -Bi 2 O 2 CO 3 synthesis boosts interface charge transfer. • Z-scheme validated by Mott-Schottky and ESR spectroscopy. • 15 times faster tetracycline degradation than pure Bi 2 O 2 CO 3 component. • Preserved 3.26 eV potential maximizes ·O 2 - generation. • Robust Z-scheme resolves Bi-catalyst light/power trade-off constraint.