Engineering a ZnO/Ag2CO3/Ag2O Ternary Heterojunction: Dual Z-Scheme Photocatalytic Pathway for Enhanced Pollutants Degradation

As the widespread discharge of antibiotics, pesticides, and dyes exacerbates water pollution, the development of efficient photocatalytic materials has become crucial for addressing this challenge. In this study, a new paradigm of n-p-p ternary heterojunction photocatalyst composed of ZnO nanospindle, Ag₂CO₃, and Ag₂O nanoparticles was synthesized via a hydrothermal and coprecipitation method followed by calcination. By adjusting the calcination time, the phase transition from Ag₂CO₃ to Ag₂O was precisely controlled, leading to enhanced charge separation, transition, and improved light absorption properties. The prepared ZnO/Ag₂CO₃/Ag₂O (Z/AC/A) photocatalyst exhibited outstanding photocatalytic performance for the degradation of typical water pollutants, including 2,4-dichlorophenol (2,4-D), tetracycline (TC), and malachite green (MG) under simulated sunlight irradiation. And the photocatalytic efficiencies reached 90.8, 94.8, and 97.4%, respectively, with the ZnO/Ag₂CO₃/Ag₂O photocatalyst, which was calcined at 195 °C for 12 min, abbreviated as Z/AC/A-3, demonstrating the highest activity. Radical scavenging experiments and electron spin resonance (ESR) tests revealed that superoxide radicals (•O₂^-) serve as the dominant active species, while holes (h⁺) and hydroxyl radicals (•OH) play secondary roles in the photocatalytic process. Additionally, the photocatalytic degradation mechanism was confirmed to follow a dual Z-scheme charge transfer pathway, which effectively enhanced the charge separation and photocatalytic performance. The photocatalyst also exhibited excellent structural stability and reusability over five consecutive cycles. These results suggest that the Z/AC/A n-p-p ternary heterojunction holds promising potential for practical photocatalytic applications in environmental remediation.