Oxalic acid modified hexagonal ZnIn2S4 combined with bismuth oxychloride to fabricate a hierarchical dual Z-scheme heterojunction: Accelerating charge transfer to improve photocatalytic activity

Multivariate organic acids can modify the structure and morphology of materials to some extent. In this work, the addition of oxalic acid can make the morphology of ZnIn2S4 become uniform, the crystal structure of ZnIn2S4 can change from cubic to hexagonal, and the photocatalytic activity was improved. The dual Z-scheme ZnIn2S4/BiOCl heterojunction was successfully fabricated by a two-step hydrothermal-hydrolytic method. The concept of green chemistry was used to make full use of thiourea, and the rapid decomposition of Rh B and TC was realized by ZIS/BOC-8 under visible light in a shorter period time than other photocatalysts in this system. In order to investigate the relationship between the structure and properties of the catalyst, XRD, FT-IR, SEM, HRTEM, UV–vis DRS, XPS and other characterization technologies were used to analyze the structure, morphology, optical properties of the samples, showing that ZnIn2S4/BiOCl have been successfully synthesized indicates the existence of Z-scheme heterojunction structure. PL, TRPL and EIS analysis showed that the Z-scheme heterostructures could rapidly promote the separation of holes and photo-induced electron carriers, enhancing the photocatalytic performance and stability. The photocatalytic degradation results showed that the degradation rate of Rh B and TC by ZIS/BOC-8 were more than 92% within 30 min, comparing with other catalyst, ZIS/BOC-8 showed preferable visible light catalytic degradation activity, and the order of catalytic activity was as follows: ZIS/BOC-8 > BiOCl-S > BiOCl, ZnIn2S4. Moreover, the degradation pathway of Rh B was discussed by 3D-EEM and LC-MS, and the photocatalytic mechanism of the system was proposed, especially the mechanism of photocatalytic degradation of Rh B by ZIS/BOC under visible light.