A synergistic effect between ZnO/CdS S-scheme heterojunction and GO cocatalyst for boosting photocatalytic performance

ZnO nanosheets, 2D/1D ZnO/CdS hybrid and ternary ZnO/CdS/GO S-scheme heterojunction photocatalyst were fabricated by a low-temperature hydrothermal technique. As expected, by investigating the degradation efficiency of rhodamine B under simulated sunlight, with the assistance of CdS and GO, the ternary heterostructure showed superior photocatalytic activity. The test results display that the dye degradation rate constant of ZnO/CdS/GO is about 1.75 × 10−2 min−1, which is 3.6 times higher than that of bare ZnO. SEM results prove the finding that the content of CdS can regulate the size and distribution of ZnO NSs, increasing the specific surface area of the sample. Besides, the results of ultraviolet–visible (UV–vis) absorbance spectra revealed that the addition of CdS and GO significantly synergistically increased the visible light absorption of ZnO, and also shortened the band gap of ZnO. Photoluminescence (PL) spectra, electrochemical impedance spectroscopy (EIS) and transient photocurrent response (TPR) results show that the presence of CdS and GO synergistically promotes the rapid separation of photoexcited carriers in ZnO. Notably, the GO also further speeds up the transmission rate of electrons and improves the photoelectric stability of the ZnO/CdS heterogeneous photocatalyst. The above changes can effectively promote the photocatalytic performance of photocatalysts. Moreover, a reasonable S-scheme carriers migration mechanism was proposed with the assistance of Mott-Schottky (MS) test, VB-XPS and sacrificial agent experiments. Through comprehensive analysis and discussion, it can be concluded that ZnO/CdS S-scheme heterojunction and GO synergistically promote the photocatalytic performance of ZnO. Therefore, this thesis may provide a deeper insight into developing the practical application of ZnO-based heterojunction photocatalysts in pollutant degradation.