Facile synthesis of multi-shelled AgI/ZnO composite as Z-scheme photocatalyst for efficient ciprofloxacin degradation and H2 production

Overcoming defects through effective modification methods have become the main method for material performance optimization. In this paper, AgI nanoparticles were loaded on the hollow multi-shell ZnO microspheres through a chemical precipitation method, and the composites with a hollow multi-shell structure were successfully constructed. The formation of heterojunctions between these two semiconductors alleviates the photo-corrosion phenomenon for ZnO, and then the composite exhibits higher photocatalytic stability. On the other hand, the introduction of narrow band-gap AgI effectively reduces the optical band gap of ZnO. The photocatalytic performance of the composite was evaluated through the ciprofloxacin (CIP) photodegradation and H2 evolution under simulated solar irradiation. The results show that when the ratio of AgI was controlled 7%, the AgI/ZnO composite shows the best CIP photodegradation performance with an apparent rate constant of 0.0463 min−1 (5.26 times as the rate of ZnO), and the photocatalytic H2 production rate reaches 2.725 mmol/g/h. The structure and photoelectric property characterization indicate that the boost of the photocatalytic property for AgI/ZnO composites is major due to improve light absorption region, strengthen of e−/h+ separation, and promotion of the electron transfer efficiency. Combined with free radical capture experiments and theoretical calculations, the possible catalytic mechanism of heterojunction catalysts is proposed. Moreover, this work provides a direction in building multi-shelled ZnO heterojunction photocatalysts with silver halides modification and investigating the mechanism of photocatalytic activity enhancement.