The purposeful construction of dual Z-scheme system to the formation of intimate interface contact and multi-channel charge flow through the system remains a huge challenge. Herein, a tandem 2D/0D/2D g-C₃N₄ nanosheets/FeOOH quantum dots/ZnIn₂S₄ nanosheets (CNFeZn) dual Z-scheme system (DZSS) has been successfully constructed using electrostatic self-assembly method. Owing to the band structure and elaborate morphology of 2D g-C₃N₄, 0D FeOOH and 2D ZnIn₂S₄ in unique designed DZSS, plenty of spatial charge transfer channels are formed between the g-C₃N₄/FeOOH and FeOOH/ZnIn₂S₄ interfaces, which greatly accelerate the charge separation and transfer. As bifunctional catalysts, CNFeZn DZSS achieves the highest H₂ evolution rate of ~436.6 μmol/h with a great promotion of ~10.6 folds and ~6.9 folds compared to pristine g-C₃N₄ and ZnIn₂S₄, respectively. Meanwhile, the H₂O₂ production rate reached ~301.19 μmol/L after 60 min irradiation, up to ~5.1 times and ~2.3 times that of pristine g-C₃N₄ and ZnIn₂S₄. Experiment and DFT calculation further confirmed that the stable double built-in electronic field can be formed owing to the electron configuration between double interfaces, and reveal that the ample atomic-level charge transfer channels were established in the strong interaction connected double interfaces, which can act as the charge migration pathway promote the separation of photogenerated charges.

Catalysts that can rapidly degrade tetracycline (TC) in water without introducing secondary ion pollution have always been challenging. Herein, a cobalt-based catalyst (CoO@P-C) is prepared so that CoO quantum particles (5–10 nm) are uniformly distributed on a linear substrate, and the outer layer is covered with a shell (P-C). The quantum particles of CoO provide many active sites for the reaction, which ensures the efficient degradation effect of the catalyst, and 30 mg/L TC can be completely degraded in only 5 min. The shell of the quantum particles' outer layer can effectively reduce ions' extravasation. The combination of the shell-like structure and the linear substrate greatly enhances the catalysis's stability and ensures that the catalyst is prepared into a film for practical application. The high catalytic activity of CoO@P-C is mainly due to the following factors: (1) Uniformly distributed ultra-small nanoparticles can provide many active sites. (2) The microenvironment formed by the core-shell structure enhances not only catalytic stability but also provides the driving force to improve the reaction rate. (3) The composite of CoO and P-C core-shell structure can accelerate electron transfer and generate many reactive oxygen species in a short time, which makes TC degrade extremely rapidly.