Bi₂WO₆-based heterojunction photocatalyst for antibiotic degradation has been a research hotspot, but its photocatalytic performance needs to be further improved. Therefore, 2D/2D P-doped g-C₃N₄/Bi₂WO₆ direct Z-scheme heterojunction photocatalysts with different composition ratios were prepared through three strategies of phosphorus (P) element doping, morphology regulation, and heterojunction, and the efficiency of its degradation of tetracycline hydrochloride (TC-HCl) under visible light was studied. Their structural, optical, and electronic properties were evaluated, and their photocatalytic efficiency for TC-HCl degradation was explored with a detailed assessment of the active species, degradation pathways, and effects of humic acid, different anions and cations, and water sources. The 30% P-doped g-C₃N₄/Bi₂WO₆ had the best photocatalytic performance for TC-HCl degradation. Its photocatalytic rate was 4.5-, 2.2-, and 1.9-times greater than that of g-C₃N₄, P-doped g-C₃N₄, and Bi₂WO₆, respectively. The improved photocatalytic efficiency was attributed to the synergistic effect of P doping and 2D/2D direct Z-scheme heterojunction construction. The stability and reusability of the 30% P-doped C₃N₄/Bi₂WO₆ were confirmed by cyclic degradation experiments. Radical scavenging experiments and electron spin resonance spectroscopy showed that the main active species were •O₂⁻ and h⁺. This work provides a new strategy for the preparation of direct Z-scheme heterojunction catalysts with high catalytic performance.

In this study, nanoporous TiO₂ with hierarchical micro/nanostructures was synthesized on a large scale by a facile one-step solvothermal method at a low temperature. A series of characterizations was performed and carried out on the as-prepared photocatalysts, which were applied to the degradation of the antibiotic tetracycline (TC). The results demonstrated that nanoporous TiO₂ obtained at a solvothermal temperature of 100 °C had a spherical morphology with high crystallinity and a relatively large specific surface area, composed of a large number of nanospheres. The nanoporous TiO₂ with hierarchical micro/nanostructures exhibited excellent photocatalytic degradation activity for TC under simulated sunlight. The degradation rate was close to 100% after 30 min of UV light irradiation, and reached 79% only after 60 min of visible light irradiation, which was much better than the photodegradation performance of commercial TiO₂ (only 29%). Moreover, the possible intermediates formed during the photocatalytic degradation of TC were explored by the density functional theory calculations and HPLC-MS spectra. Furthermore, two possible degradation routes were proposed, which provided experimental and theoretical support for the photocatalytic degradation of TC. In this study, we provide a new approach for the hierarchical micro/nanostructure of nanoporous TiO₂, which can be applied in industrial manufacturing fields.

In this study, nitrogen-doped TiO₂ heterojunction materials were successfully synthesized via a facile one-step solvothermal approach. A range of advanced characterization techniques were employed to thoroughly analyze the structural and compositional properties of the synthesized photocatalysts, and their application potential for tetracycline (TC) degradation under visible light was studied. The results indicated that N-doped TiO₂ exhibited a well-defined hierarchical micro/nanostructure and formed an efficient anatase/rutile homogeneous heterojunction. The photocatalytic performance of N-TiO₂ for TC degradation under visible light was significantly enhanced, achieving a degradation efficiency of up to 87% after 60 min of irradiation. This improvement could be attributed to the synergistic effects of optimal nitrogen doping, heterojunction formation, and the hierarchical micro/nanostructure, which collectively reduced the bandgap energy and suppressed the recombination rate of photogenerated carriers. Furthermore, density functional theory (DFT) calculations were conducted to systematically explore the impacts of substitutional and interstitial nitrogen doping on the energy band structure of TiO₂.