Nanoconstructing ZnWO4/sulfur-doped polyimide Z-scheme heterojunction with improved charges transfer for enhanced solar photocatalysis

In this study, ZnWO₄ nanorods were effectively anchored onto the surface of sulfur-doped π-conjugated polyimide (SPI) by an in situ crystallization growth method. Thus a Z-type heterostructure of ZnWO₄/SPI (ZWO/SPI) composite material was constructed as a solar photocatalyst. The obtained SPI, ZnWO₄, and ZWO/SPI composites were systematically characterized and analyzed by various techniques, such as XRD, SEM, TEM, FTIR, XPS, BET, DRS, UV–vis spectroscopy, Motschottky, PL, EIS, photocurrent, and ESR. It was found that ZnWO₄ nanorods with a diameter of about 30 nm and regular morphology grown on the surface of SPI. The photoelectrochemical analysis indicates that incorporating ZnWO₄ nanorods notably boosts the photocurrent of ZWO/SPI, thereby significantly enhancing the transport efficiency of photogenerated charge. The highest solar photocatalytic degradation of 78.54% for both orange methyl (MO) and 96.04% for methylene blue (MB) was achieved with 5ZWO/SPI. The enhancement of the activity is mainly attributed to ZnWO₄ nanorods as the conductor of photogenerated charges and the nano-construction of the Z-type heterojunction between ZWO and SPI. The obtained band positions and ESR signals of ·O₂^– and ·OH radicals displayed the charge mobility mechanism of the Z-Scheme across the heterojunction. This work presents a method for designing polymer photocatalysts enhanced by surface nanomodification for efficient degradation of organic contaminants.