Reusable BiOI-Modified CuWO4 Heterojunction Films and Their Excellent Photocatalytic Oxidation Activity of Nanoplastics and Methylene Blue

CuWO₄ films were prepared on FTO glass substrates by the hydrothermal method. To improve their photocatalytic activity, the CuWO₄ films were further modified with BiOI using the successive ionic layer adsorption and reaction (SILAR) method. Characterization results indicate that BiOI and CuWO₄ achieved nanoscale mixing and formed a Type II <i>p</i>-<i>n</i> heterojunction. The heterojunction formation not only extends the light absorption threshold of CuWO₄ from 530 nm to 660 nm but also enhances the light absorption capacity across the entire solar spectrum. More importantly, the heterojunction formation facilitates the separation and transfer of photogenerated carriers and inhibits the recombination of photogenerated electrons and holes, which is evidenced by the results of PL spectra, photocurrent density, and EIS spectra. Compared with individual CuWO₄ films, the photocatalytic activity of BiOI/CuWO₄ heterojunction films in degrading the organic dye MB is increased by up to 1.17 times. Additionally, BiOI/CuWO₄ heterojunction films exhibit certain activity in the photocatalytic degradation of polystyrene (PS) nanoplastics and are capable of reducing the average particle size of nanoplastics from 425 nm to 325 nm within 80 h.