Photo-response range extension of Z-scheme ZnO/CdS for LED-light-driven photo-active catalyst

• Published in: Renewable and Sustainable Energy Reviews
• Main Author: Sinar Mashuri S.I.; Kasim M.F.; Mohd Kaus N.H.; Tan Y.H.; Islam A.; Rashid U.; Asikin-Mijan N.; Andas J.; Taufiq-Yap Y.H.; Yaakob M.K.; Wan Ismail W.I.N.; Ibrahim M.L.
• Format: Article
• Language: English
• Published: Elsevier Ltd 2023
• Online Access: https://www.scopus.com/inward/record.uri?eid=2-s2.0-85166298763&doi=10.1016%2fj.rser.2023.113602&partnerID=40&md5=91b93d489a93f3f367604d2433864631

Zinc oxide (ZnO) photocatalysts are suitable for wastewater treatment via photocatalytic processes. However, they are hindered by fast e− and h+ recombination, a large bandgap, and the need for a high-energy light source for activation. Thus, this study was aimed to synthesize a photocatalyst that operates under a low-energy consumption. We introduced cadmium sulphide (CdS) heterojunction to ZnO photocatalyst, and successfully reducing their bandgap from 3.30 eV to 2.46 eV. This modification allows activation with a 21-Watt light-emitting diode (LED) visible light source. The surface structure characteristics of the ZnO/CdS photocatalyst was analyzed using XRD, HRTEM, FESEM, and N2 adsorption-desorption isotherms. UV-NIR was used for bandgap analysis and the DFT simulation method to compute the atomic properties of the materials. Catalytic evaluation showed that the ZnO/CdS photocatalyst completely degraded the model dye solution (100%) using 0.5 g of Z3C1 (3:1 M ratio) of 100 mg L−1 MB solution at pH 9 within only 90 min. A scavenger test confirmed that the hydroxyl OH• and superoxide •O2− radicals proved were the major active species responsible for degradation process. The reusability of Z3C1 was demonstrated over 4 reaction cycles, proving that CdS significantly enhances visible light absorption by extending the photo-response range and promoting superior formation of e− and h+. This delays their recombination due to the Z-scheme type, making it highly potential for wastewater treatment. © 2023 Elsevier Ltd