A novel integration of 3D-printed skeleton, surface nanoscale heterojunctions and intrinsic ferroelectric fields in the BixOyIz/TiO2 photocatalysts: insights into adsorption-photocatalysis synergistic behavior and mechanism

An economically viable solution to balance photocatalytic efficiency with material recyclability is urgently needed. Z-scheme heterojunction Bi x O y I z /TiO 2 photocatalysts were prepared by in-situ growing Bi x O y I z (BiOI/Bi 4 O 5 I 2 ) nanosheets with tunable ferroelectric built-in electric fields on low-cost three-dimensional printing（3DP） self-supporting hierarchical porous TiO 2 skeletons (TiO 2 -3D). The synergistic adsorption-degradation behavior and underlying mechanisms for tetracycline hydrochloride (TC) were systematically investigated. Results demonstrate that the hierarchical porous structure of the skeletons endowed the composite materials exceptional TC adsorption efficiency (96.2% at 420   min), with performance strongly dependent on pH conditions. The dark adsorption amount is parabolic correlated with the photocatalytic degradation efficiency. The ferroelectric electric field within the Bi x O y I z crystal and the Z-scheme heterojunction electric field synergistically promote the directional separation and transfer of photogenerated carriers. Under visible light, Bi 4 O 5 I 2 /TiO 2 achieves 96.9% TC degradation, featuring a rate constant (20.65×10 -3 min -1 ) double that of TiO 2 -3D. After 5 cycles, the composite material still maintains more than 96% of the initial degradation efficiency and the crystal structure remains stable. This work highlights the crucial synergistic effect of optimizing carrier transfer and adsorption-degradation kinetics to enhance the performance of 3D photocatalysts, providing a new strategy for the design of efficient, stable and economical 3D photocatalytic materials.