Construction of AgI/PCN-224 Z-scheme heterojunction for efficient photocatalytic degradation of tetracycline hydrochloride: Pathways, mechanism and theoretical calculations

Abstract

The construction of heterojunction structures is pivotal in enhancing carrier separation and photocatalytic activity. Hence, AgI/PCN-224 (APN-x composites) Z-scheme heterojunctions were successfully synthesised using an in-situ precipitation method. The direction of electron migration and the band structures of APN-x were comprehensively investigated using a combination of experimental approaches and density functional theory (DFT) calculations. Owing to the extensive visible-light absorption capabilities of PCN-224 and the high efficiency of photogenerated carrier separation in the Z-scheme heterojunction, the optimally developed APN-3 photocatalyst demonstrated exceptional photodegradation efficiency for tetracycline hydrochloride (TCH). The removal rate of TCH by APN-3 within 120 min reached 91.56%, approximately 4.64 times higher than that achieved by pure AgI. The photocatalytic degradation mechanism was explored using free radical trapping experiments, electron spin resonance (ESR) technology and band structure analysis. Degradation pathways and intermediate products were investigated using liquid chromatography–tandem mass spectrometry (LC–MS).